{"id":3576,"date":"2017-02-02T18:57:02","date_gmt":"2017-02-02T18:57:02","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/waymaker-psychology\/?post_type=chapter&#038;p=3576"},"modified":"2017-05-23T04:03:53","modified_gmt":"2017-05-23T04:03:53","slug":"illusions-in-the-real-world","status":"web-only","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-fmcc-intropsych\/chapter\/illusions-in-the-real-world\/","title":{"raw":"Illusions","rendered":"Illusions"},"content":{"raw":"<div class=\"textbox learning-objectives\">\r\n<h3>Learning Objectives<\/h3>\r\n<ul>\r\n \t<li>Explain how and why psychologists use illusions<\/li>\r\n<\/ul>\r\n<\/div>\r\n<h2>Why Illusions?<\/h2>\r\nPsychologists have analyzed perceptual systems for more than a century. Vision and hearing have received the most attention by far, but other perceptual systems, like those for smell taste movement, balance, touch, and pain, have also been studied extensively. Perception scientists use a variety of approaches to study these systems\u2014they design experiments, study neurological patients with damaged brain regions, and create perceptual illusions that toy with the brain's efforts to interpret the sensory world.\r\n\r\n[caption id=\"attachment_3721\" align=\"alignright\" width=\"512\"]<a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/14154724\/Horizontal_3d_graffiti_%C5%81%C3%B3d%C5%BA_Schillera_Passage.jpg\"><img class=\"wp-image-3721 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/14154724\/Horizontal_3d_graffiti_%C5%81%C3%B3d%C5%BA_Schillera_Passage.jpg\" alt=\"3D street art showing a rubix cube, deck of cards, waterfall, and blocks all on a 2D surface.\" width=\"512\" height=\"343\" \/><\/a> Figure 1. This 3-D street art demonstrates how artists utilize illusions to portray depth on a 2-D sidewalk.[\/caption]\r\n\r\nCreation and testing of perceptual illusions has been a fruitful approach to the study of perception\u2014particularly visual perception\u2014since the early days of psychology. People often think that visual illusions are simply amusing tricks that provide us with entertainment. Many illusions are fun to experience, but perception scientists create illusions based on their understanding of the perceptual system. Once they have created a successful illusion, the scientist can explore what people experience, what parts of the brain are involved in interpretation of the illusion, and what variables increase or diminish the strength of the illusion. Scientists are not alone in this interest. Visual artists have discovered and used many illusion-producing principles for centuries, allowing them to create the experience of depth, movement, light and shadow, and relative size on two-dimensional canvases.\r\n<h2>Depth\u00a0Illusions<\/h2>\r\nWhen we look at the world, we are not very good at detecting the absolute qualities of things\u2014their exact size or color or shape. What we are very good at is judging objects in the context of other objects and conditions. Let's take a look at a few illusions to see how they are based on insights about our perception. Look at Figure 2 below. Which of the two horizontal yellow lines looks wider, the top one or the bottom one?\r\n\r\n[caption id=\"attachment_3649\" align=\"aligncenter\" width=\"225\"]<a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/07210125\/Ponzo_illusion.gif\"><img class=\"wp-image-3649 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/07210125\/Ponzo_illusion.gif\" alt=\"Lines of a railroad track as they converge off into the distance. One yellow line is close to the front of the image on the tracks and another line of the same size is placed towards the back of the image along the tracks. Because of the converging lines, the yellow line in the back appears larger than the line in the foreground.\" width=\"225\" height=\"166\" \/><\/a> Figure 2. The Ponzo Illusion.[\/caption]\r\n\r\nMost people experience the top line as wider. They are both exactly the same length. This experience is called the Ponzo illusion. Even though you know that the lines are the same length, it is difficult to see them as identical. Our perceptual system takes the context into account, here using the converging \u201crailroad tracks\u201d to produce an experience of depth. Then, using some impressive mental geometry, our brain adjusts the experienced length of the top line to be consistent with the size it would have if it were that far away: if two lines are the same length on my retina, but different distances from me, the more distant line must be in reality longer. You experience a world that \u201cmakes sense\u201d rather than a world that reflects the actual objects in front of you.\r\n\r\nThere are many depth illusions. It is difficult to see the drawing on the left below as a two-dimensional figure. The converging lines and smaller square at the center seem to coax our perceptual systems into seeing depth, even though we know that the drawing is flat. This urge to see depth is probably so strong because our ability to use two-dimensional information to infer a three dimensional world is essential for allowing us to operate in the world. The picture on the right below is a driving tunnel, something you would need to process at high speed if you were in a car going through it. Your quick and detailed use of converging lines and other cues allows you to make sense of this 3-D world.\r\n\r\n[caption id=\"attachment_3650\" align=\"aligncenter\" width=\"514\"]<a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/07210639\/Screen-Shot-2017-02-07-at-3.04.55-PM.png\"><img class=\"wp-image-3650 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/07210639\/Screen-Shot-2017-02-07-at-3.04.55-PM.png\" alt=\"The drawing on the left shows a large square with a smaller square on the inside and lines connecting the corners of the inner and outer square. The secong image shows the inside of a tunnel.\" width=\"514\" height=\"222\" \/><\/a> Figure 3. Understanding depth enables us to function in a 3-dimensional world.[\/caption]\r\n<h2>Light and Size Illusions<\/h2>\r\nDepth is not the only quality in the world that shows how we adjust what we experience to fit the surrounding world. Look at the two gray squares in the figure below. Which one looks darker?\r\n\r\n[caption id=\"attachment_3654\" align=\"aligncenter\" width=\"557\"]<a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/07211928\/Simultaneous_Contrast.jpg\"><img class=\"wp-image-3654\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/07211928\/Simultaneous_Contrast.jpg\" alt=\"A dark black square with a gray square in the center next to a white square with a gray square in the middle. The black surrounding the gray makes the gray appear lighter than with the white background.\" width=\"557\" height=\"278\" \/><\/a> Figure 4. Which gray square appears darker?[\/caption]\r\n\r\nMost people experience the square on the right as the darker of the two gray squares. You\u2019ve probably already guessed that the squares are actually identical in shade, but the surrounding area\u2014black on the left and white on the right\u2014influence how our perceptual systems interpret the gray area. In this case, the greater difference in shading between the white surrounding area and the gray square on the right results in the experience of a darker square.\r\n\r\nHere is another example below. The two triangular figures are identical in shade, but the triangle on the left looks lighter against the dark background of the cross when compared to the triangle in the white area on the right.\r\n\r\n[caption id=\"attachment_3655\" align=\"aligncenter\" width=\"300\"]<a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/07212941\/569px-Benary_Cross.svg_.png\"><img class=\"wp-image-3655 size-medium\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/07212941\/569px-Benary_Cross.svg_-300x300.png\" alt=\"Gray cross with a lighter gray triangle inside of the cross arm, and another outside of the arm of the cross. The triangle outside of the cross arm appears darker with its greater contrast against the white background.\" width=\"300\" height=\"300\" \/><\/a> Figure 5. Benary Cross[\/caption]\r\n\r\nOur visual systems work with more than simple contrast. They also use our knowledge of how the world works to adjust our perceptual experience. Look at the checkerboard below. There are two squares with letters in them, one marked \u201cA\u201d and the other \u201cB\u201d. Which one of those two squares is darker?\r\n\r\n[caption id=\"attachment_3656\" align=\"aligncenter\" width=\"300\"]<a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/07213735\/Optical.greysquares.arp_.jpg\"><img class=\"wp-image-3656 size-medium\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/07213735\/Optical.greysquares.arp_-300x242.jpg\" alt=\"A checkerboard with a large green cylinder on top of the gameboard, casting a shadow on the board. The shadow makes the pieces appear darker, so much so that the lighter &quot;B&quot; piece is actually the same color as the darker &quot;A&quot; piece.\" width=\"300\" height=\"242\" \/><\/a> Figure 6. Which looks darker, A or B?[\/caption]\r\n\r\nThis seems like an easy comparison, but the truth is that squares A and B are identical in shade. Our perceptual system adjusts our experience by taking some visual information into account. First, \u201cA\u201d is one of the \u201cdark squares\u201d and \u201cB\u201d is a \u201clight square\u201d if we take the checkerboard pattern into account. Perhaps even more impressive, our visual systems notice that \u201cB\u201d is in a shadow. Object in a shadow appear darker, so our experience is adjusted to take account of effect of the shadow, resulting in perceiving square B as being lighter than square A, which sits in the bright light. And if you really don't believe your eyes, take a look at a video showing the same color tiles <a href=\"https:\/\/www.youtube.com\/watch?v=CRvo1jRXiI8\" target=\"_blank\" rel=\"noopener noreferrer\">here<\/a>.\r\n\r\nOne final illusion takes us back to adjustment for size. Look at the two sets of circles below. Your task is to adjust the center circle on the left so it is the same actual size as the center circle on the right. The surrounding circles will not change in size, though the right of circles will expand to accommodate the size of the center circle. Use the slide bar with the label \u201cSize of left circle\u201d to make your adjustments. When you are satisfied with your adjustment, check your accuracy by clicking on the \u201cVerify Diameter\u201d button. Click \u201cReset\u201d to try again.\r\n\r\n<center><iframe src=\"https:\/\/s3-us-west-2.amazonaws.com\/oerfiles\/Psychology\/interactives\/circles1.html\" width=\"530\" height=\"380\"><\/iframe><\/center>This illusion is called the Ebbinghaus illusion, created by Hermann Ebbinghaus, one of the early founders of experimental psychology. It is shown again below.\r\n\r\n<a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/02202255\/650px-Mond-vergleich.svg_.png\"><img class=\"aligncenter wp-image-3581 \" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/02202255\/650px-Mond-vergleich.svg_.png\" alt=\"Large blue circles surrounding a small orange circle and a large (appearing) orange circle surrounded by blue circles. The center orange circles are in fact the same size.\" width=\"536\" height=\"330\" \/><\/a>\r\n\r\nIn this version of the illusion, most people see the circle on the right as larger than the one on the left. The two orange circles are exactly the same size. The Ebbinghaus illusion again illustrates the tendency of our perceptual systems to adjust our experience of the world to the surrounding context.\r\n<div class=\"textbox tryit\">\r\n<h3>Try It<\/h3>\r\nhttps:\/\/assessments.lumenlearning.com\/assessments\/2875\r\n\r\nhttps:\/\/assessments.lumenlearning.com\/assessments\/2876\r\n\r\n<\/div>\r\n<div class=\"textbox examples\">\r\n<h3>Link to Learning<\/h3>\r\nIf you want to explore more visual illusions, <a href=\"http:\/\/www.michaelbach.de\/ot\/\" target=\"_blank\" rel=\"noopener noreferrer\">here<\/a> is a great site with dozens of interesting illusions created by Michael Bach.\r\n\r\n<\/div>\r\nHow do you think a psychologist might use the Ebbinghaus\u00a0illusion to learn about mental processes or behavior (shown again below)? Read on to see an actual example from a psychologist at Colorado State University.\r\n\r\n<center><iframe src=\"https:\/\/s3-us-west-2.amazonaws.com\/oerfiles\/Psychology\/interactives\/circles1.html\" width=\"530\" height=\"430\"><\/iframe><\/center>\r\n<h2>Ebbinghaus in the Real World<\/h2>\r\nImagine that you are in a golf competition in which you are putting against someone with the same experience and skill that you have. There is one problem: Your opponent gets to putt into a hole that is 10% larger than the hole you have to use. You\u2019d probably think that the competition was unfairly biased against you.\r\n\r\n[caption id=\"attachment_3719\" align=\"alignright\" width=\"453\"]<a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/14025440\/ball-1842170_1920.jpg\"><img class=\"wp-image-3719\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/14025440\/ball-1842170_1920.jpg\" alt=\"aerial view of a golf hole and golf ball\" width=\"453\" height=\"291\" \/><\/a> Figure 1. Do you suspect that the <em>perceived<\/em> size of a golf hole will affect putting performance?[\/caption]\r\n\r\nNow imagine a somewhat different situation. You and your opponent are about equal in ability and the holes you are using are the same size, but the hole that your opponent is using <em>looks<\/em>\u00a010% larger than the one you are using. Would your opponent have an unfair advantage now?\r\n\r\nIf you read the earlier section on the Ebbinghaus effect, you have an idea how psychologists could exploit your perceptual system (and your opponent\u2019s) to test this very question. Psychologist Jessica Witt and her colleagues Sally Linkenauger and Dennis Proffitt recruited research participants with no unusual golf experience to participate in a putting task. They competed against themselves rather than against another person.\r\n\r\nThe experimenters made the task challenging by using a hole with a 2-inch diameter, which is about half the diameter of the hole you will find on a golf course. An overhead projector mounted on the ceiling of their lab allowed them to project Ebbinghaus\u2019s circles around the putting hole. Some participants saw the putting hole surrounded by circles that were smaller than the hole in the center; the other half saw surrounding black circles that were larger.\r\n\r\nParticipants putted from about 11\u00bd feet away. \u00a0They took 10 putts in one condition, and then 10 in the other condition. Half of the participants putted with the large surrounding circles first and half saw the small surrounding circles first. This procedure is called <strong>counterbalancing<\/strong>. If there is any advantage (e.g., getting better over time with practice) or disadvantage (e.g., getting tired of putting), counterbalancing assures that both conditions are equally exposed to the positive or negative effects of which task goes first or second. Failure to take account of this type of problem means that you may have a <strong>confounding variable<\/strong>\u2014practice or fatigue\u2014that influences performance. A confounding variable is something that <em>could<\/em>\u00a0influence performance, but is not part of the study. We try to <em>control<\/em>\u00a0(that is, neutralize) potentially confounding variables so they cannot be the cause of performance differences. So, for instance, if everyone did the large surrounding circles condition first and then the small surrounding circles, then differences in performance could be due to order of conditions (leading to practice or fatigue effects) rather than the size of the surrounding circles. By counterbalancing, we don\u2019t get rid of the effects of practice or fatigue for any particular person, but\u2014across all the participants\u2014practice or fatigue should affect both conditions (both types of Ebbinghaus circles) equally.\r\n\r\nThe experimenters wanted to know two things. First, did they actually produce the Ebbinghaus illusion? Remember: there is no guarantee that people see or think the way your theory says they should. So just before the participant started putting in a particular condition, he or she drew a circle using a computerized drawing tool, attempting to match the exact size of the putting hole. This is better than simply asking, \u201cdo you see the illusion?\u201d The drawing task attempts to directly measure what they perceive.\r\n\r\nSecond, the experimenters wanted to see if the perceived size of the hole influenced putting accuracy. They recorded the success or failure of each putt. Each participant could get a score of 0 to 10 successful putts in each condition.\r\n<h3>Methods Summary<\/h3>\r\nRecap the steps you've read about thus far:\r\n<ol>\r\n \t<li>The participant practices putting to get used to the task.<\/li>\r\n \t<li>The participant completes\u00a0the first condition (large surrounding circles for half of the participants and small surrounding circles for the other half).\r\n<ul>\r\n \t<li>The participant draws a circle corresponding to his or her estimation of the actual size of the putting hole. This allows\u00a0the experimenters to determine if the Ebbinghaus effect actually occurred.<\/li>\r\n \t<li>The participant putts 10 times in this condition.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li>Participant completes\u00a0the second condition (whichever condition they have not yet done).\r\n<ul>\r\n \t<li>The participant draws a circle corresponding to his or her estimation of the actual size of the putting hole.<\/li>\r\n \t<li>The participant putts 10 times in this condition.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ol>\r\n<div class=\"textbox tryit\">\r\n<h3>Try It<\/h3>\r\n<strong>Now that you know the details of Jessica Witt\u2019s experiment, see if you can answer the following questions. Click on the option you think is correct and then click the 'Show Answer' link to see if you're right.<\/strong>\r\n\r\n<!--https:\/\/assessments.lumenlearning.com\/assessments\/2877-->\r\n\r\n<strong>Question 1: What is the independent variable as described in this study?<\/strong>\r\n<ul style=\"list-style-type: none;\">\r\n \t<li><input name=\"group1\" type=\"radio\" \/> \u00a0\u00a0The size of the putting hole is the independent variable.<\/li>\r\n \t<li><input name=\"group1\" type=\"radio\" \/> \u00a0\u00a0The size of the circles surrounding the putting hole is the independent variable.<\/li>\r\n \t<li><input name=\"group1\" type=\"radio\" \/> \u00a0\u00a0The distance the person had to putt is the independent variable.<\/li>\r\n \t<li><input name=\"group1\" type=\"radio\" \/> \u00a0\u00a0There are two independent variables: the size of the putting hole and the size of the surrounding circles.<\/li>\r\n<\/ul>\r\n[reveal-answer q=\"794784\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"794784\"]\r\n\r\nAn INDEPENDENT VARIABLE is something intentionally manipulated (changed) by the experimenter. To test the effect of the Ebbinghaus illusion, the experimenters had participants putt into holes surrounded by larger circles and smaller circles. This \u201cmanipulation\u201d of the size of the surrounding holes is the independent variable.\r\n\r\n[\/hidden-answer]\r\n\r\n<!--https:\/\/assessments.lumenlearning.com\/assessments\/2878-->\r\n\r\n<strong>Question 2: What is the dependent variable in this study?<\/strong>\r\n<ul style=\"list-style-type: none;\">\r\n \t<li><input name=\"group2\" type=\"radio\" \/> \u00a0\u00a0The number of successful putts is the dependent variable.<\/li>\r\n \t<li><input name=\"group2\" type=\"radio\" \/> \u00a0\u00a0The size of the circle drawn by the participant is the dependent variable.<\/li>\r\n \t<li><input name=\"group2\" type=\"radio\" \/> \u00a0\u00a0The size of the putting hole is the dependent variable.<\/li>\r\n \t<li><input name=\"group2\" type=\"radio\" \/> \u00a0\u00a0There are two dependent variables: the number of successful putts and the size of the circle drawn by the participants are both dependent variables.<\/li>\r\n<\/ul>\r\n[reveal-answer q=\"569303\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"569303\"]\r\n\r\nA DEPENDENT VARIABLE is some behavior or thought process measured by the experimenter. This study had two dependent variables:\r\n<ul>\r\n \t<li>(a) the size of the circle drawn by the participant<\/li>\r\n \t<li>(b) the number of successful putts<\/li>\r\n<\/ul>\r\nBoth dependent variables were measured for each condition, so each participant drew 2 circles and had 0 to 10 successful putts in both the large surrounding circles condition and the small surrounding circles condition.\r\n\r\n[\/hidden-answer]\r\n\r\n<\/div>\r\nNow see if you can guess the results of this study.\r\n<div class=\"textbox tryit\">\r\n<h3>Try It<\/h3>\r\n<strong>Question 3: How did the participants perceive the holes?\u00a0<\/strong>\r\n\r\nResize\u00a0the bars below by clicking and dragging them to show your predicted results when the subjects were asked to draw the circles.\u00a0Make a general prediction based on your understanding of the experiment.\r\n\r\n<center><iframe src=\"https:\/\/s3-us-west-2.amazonaws.com\/oerfiles\/Psychology\/interactives\/bargraph4.html\" width=\"530\" height=\"450\"><\/iframe><\/center>&nbsp;\r\n\r\n<!--https:\/\/assessments.lumenlearning.com\/assessments\/2879-->\r\n\r\n[reveal-answer q=\"566454\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"566454\"]\r\n\r\nThis question tested whether or not the Ebbinghaus effect was produced in this experiment. If there is no difference between the bars, that would mean that participants didn\u2019t experience the Ebbinghaus illusion. The exact height of the bars is not important here, but the relative heights should look something like this:\r\n\r\n<a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/23070233\/bars11.png\"><img class=\"aligncenter wp-image-3793\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/23070233\/bars11-300x235.png\" alt=\"Bar graph showing larger circles drawn by participants when the hole looks large and was surrounded by the smaller circles.\" width=\"400\" height=\"314\" \/><\/a>\r\n\r\nThe taller bar on the right means that the center putting hole looks larger when it is surrounded by smaller circles than when the same hole is surrounded by large circles: The Ebbinghaus illusion.\r\n\r\nThis result was important because the reasoning behind the experiment was dependent on successfully producing the Ebbinghaus illusion. There is a technical term for a dependent variable that is used to determine if your independent variable is actually working: a <strong>manipulation check<\/strong>. Good experimenters use manipulation checks to be sure they aren\u2019t fooling themselves into believing that they have done something that really didn\u2019t work.\r\n\r\n[\/hidden-answer]\r\n\r\n<strong>Question 4: Can you guess how well the participants putted? <\/strong>\r\n\r\nResize\u00a0the bars below by clicking and dragging them to show your predicted results when the subjects putted.\r\n\r\n<center><iframe src=\"https:\/\/s3-us-west-2.amazonaws.com\/oerfiles\/Psychology\/interactives\/bargraph5.html\" width=\"530\" height=\"450\"><\/iframe><\/center><!--https:\/\/assessments.lumenlearning.com\/assessments\/2880-->\r\n\r\n[reveal-answer q=\"751987\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"751987\"]\r\n\r\nThis question lets you check out your skills as a psychologist. The description of the experiment did not include the researchers\u2019 hypothesis, so you have to decide for yourself what you think is going to happen. The three possible patterns of results are shown below. The graph you drew fit one of these patterns.\r\n\r\n<a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/23070056\/bars21.png\"><img class=\"aligncenter wp-image-3791\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/23070056\/bars21-300x135.png\" alt=\"The possible results showing possible results in a bar graph: better putting when the hole looks small, the hole size doesn't matter, or better putting when the hole looks large.\" width=\"800\" height=\"359\" \/><\/a>\r\n\r\n[\/hidden-answer]\r\n\r\n<\/div>\r\n<div class=\"textbox tryit\">\r\n<h3>Try It<\/h3>\r\nBefore we show you the actual results of the study, write our your prediction. Do you think the illusion affected putting performance? Why or why not? Explain your answer in the text box below:\r\n\r\n[practice-area rows=\"4\"][\/practice-area]\r\n[reveal-answer q=\"291461\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"291461\"]\r\n\r\nUntil now, we haven\u2019t told you exactly how the Ebbinghaus illusion was\u00a0predicted to influence putting\u2014only that the experimenters thought it would have some sort of influence. So here is what they said.\r\n\r\nThe experimenters thought that the perceived size of the hole would affect the SELF-CONFIDENCE of the person as he or she putted. If you are putting into a larger hole (or what is PERCEIVED as a larger hole) you should be more confident that you will sink your putt. Remember, this is just a prediction based on the experimenters\u2019 reasoning. Their ideas came from interviewing skilled athletes who claimed that objects seemed larger and time seemed to slow down as they gained skill. If the ball you have to catch is bigger or the person blocking you is slower, you can perform at a higher level.\r\n\r\nThe experimenters could be right or they could be wrong. Your own reasoning might be different than that of the experimenters. For instance, perhaps you thought that people would be MORE CAREFUL if they thought the hole was smaller. That would be a perfectly fine hypothesis. Interestingly, it makes the opposite prediction from the experimenters\u2019 self-confidence hypothesis. This \u201ccareful putting with smaller holes\u201d theory predicts that people should putt better when they perceive the hole as smaller (i.e., when the surrounding circles are large). The experimenters\u2019 \u201cmore confidence with larger holes\u201d hypothesis predicts that people should putt better when they perceive the hole as larger.\r\n\r\nHere are the actual results. First, the hole was perceived as larger when it was surrounded by smaller holes, so there is evidence that they successfully produced the Ebbinghaus illusion. Second, the experimenters predicted that participants would be more successful when the hole seemed larger (i.e., surrounded by smaller circles). Consistent with these predictions, the results looked like this:\r\n\r\n<a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/23070152\/bars3.png\"><img class=\"aligncenter wp-image-3792\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/23070152\/bars3-300x265.png\" alt=\"Bar graph showing better putting when the hole looks large and was surrounded by the smaller circles.\" width=\"400\" height=\"353\" \/><\/a>\r\n\r\n[\/hidden-answer]\r\n\r\n<\/div>\r\nThis is not the only experiment that has used a sports context to study the effects of illusions. Other experiments have shown that people hit softballs better when the balls are perceived as larger. People score higher in darts when the board appears larger. Athletes kick field goals and return tennis balls more successfully when the goal posts or tennis balls appear larger. In all of these studies, the balls or boards or goal posts were not actually larger, but they were perceived as larger because the experimenters created illusions. Skilled athletes often report that targets appear larger or time slows down when they are \u201cin the zone\u201d, as if practice and skill create their own perceptual illusions that increase confidence and make difficult challenges feel easier.\r\n<div class=\"textbox examples\">\r\n<h3>Link to Learning<\/h3>\r\nWatch this interview with Psychologist Jessica Witt to see her talk about how her research utilizing the Ebbinghaus illusion impacts a golfer's perception and performance. You can also read about more about similar variations of her research <a href=\"http:\/\/www.apa.org\/science\/about\/psa\/2016\/12\/action-visual-perception.aspx\">here<\/a>.\r\n\r\n<iframe src=\"https:\/\/www.youtube.com\/embed\/XDNfTUOSjFw?rel=0\" width=\"853\" height=\"480\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\" data-mce-fragment=\"1\"><\/iframe>\r\n\r\n<\/div>\r\n<h2>A Final Note: Science Doesn't Always Produce Simple Results<\/h2>\r\nProfessor Witt\u2019s study had interesting results; however, they weren\u2019t quite as simple as we have made them seem. The researchers actually had two different hole sizes: 2 inches and 4 inches. The Ebbinghaus circles were adjusted to be relatively larger or smaller than the putting hole.\r\n\r\nThe Ebbinghaus illusion worked for the smaller (2 inch) putting holes, but not for the larger (4 inch) putting holes. In other words, when people drew the circles as they perceived them (the \u201cmanipulation check\u201d dependent variable), they drew different sized circles for the 2 inch holes (the Ebbinghaus illusion), but the same size circles for the 4 inch holes (no Ebbinghaus illusion).\r\n\r\nFor the larger (4 inch) putting holes, putting accuracy was the same for the two different conditions. This didn\u2019t bother the experimenters, because\u2014as we have already noted\u2014the participants did not experience the Ebbinghaus illusion with the larger holes. If the holes were perceived as the same, then self-confidence should not have been affected and, in turn, putting should not have been better in one condition than the other.\r\n\r\nIn the research paper, the experimenters suggest a few technical reasons that the larger hole might not have produced the Ebbinghaus illusion, but they admit that they have no definitive explanation. That\u2019s okay. Science often yields messy results\u2014and these can be the basis for new experiments and sometimes for really interesting discoveries. The world is not as simple as our theories try to make it seem. Happily, in science, as in many aspects of life, you learn more from your failures than your successes, so good scientists don\u2019t try to hide from results they don\u2019t expect.\r\nhttps:\/\/assessments.lumenlearning.com\/assessments\/4827","rendered":"<div class=\"textbox learning-objectives\">\n<h3>Learning Objectives<\/h3>\n<ul>\n<li>Explain how and why psychologists use illusions<\/li>\n<\/ul>\n<\/div>\n<h2>Why Illusions?<\/h2>\n<p>Psychologists have analyzed perceptual systems for more than a century. Vision and hearing have received the most attention by far, but other perceptual systems, like those for smell taste movement, balance, touch, and pain, have also been studied extensively. Perception scientists use a variety of approaches to study these systems\u2014they design experiments, study neurological patients with damaged brain regions, and create perceptual illusions that toy with the brain&#8217;s efforts to interpret the sensory world.<\/p>\n<div id=\"attachment_3721\" style=\"width: 522px\" class=\"wp-caption alignright\"><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/14154724\/Horizontal_3d_graffiti_%C5%81%C3%B3d%C5%BA_Schillera_Passage.jpg\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-3721\" class=\"wp-image-3721 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/14154724\/Horizontal_3d_graffiti_%C5%81%C3%B3d%C5%BA_Schillera_Passage.jpg\" alt=\"3D street art showing a rubix cube, deck of cards, waterfall, and blocks all on a 2D surface.\" width=\"512\" height=\"343\" \/><\/a><\/p>\n<p id=\"caption-attachment-3721\" class=\"wp-caption-text\">Figure 1. This 3-D street art demonstrates how artists utilize illusions to portray depth on a 2-D sidewalk.<\/p>\n<\/div>\n<p>Creation and testing of perceptual illusions has been a fruitful approach to the study of perception\u2014particularly visual perception\u2014since the early days of psychology. People often think that visual illusions are simply amusing tricks that provide us with entertainment. Many illusions are fun to experience, but perception scientists create illusions based on their understanding of the perceptual system. Once they have created a successful illusion, the scientist can explore what people experience, what parts of the brain are involved in interpretation of the illusion, and what variables increase or diminish the strength of the illusion. Scientists are not alone in this interest. Visual artists have discovered and used many illusion-producing principles for centuries, allowing them to create the experience of depth, movement, light and shadow, and relative size on two-dimensional canvases.<\/p>\n<h2>Depth\u00a0Illusions<\/h2>\n<p>When we look at the world, we are not very good at detecting the absolute qualities of things\u2014their exact size or color or shape. What we are very good at is judging objects in the context of other objects and conditions. Let&#8217;s take a look at a few illusions to see how they are based on insights about our perception. Look at Figure 2 below. Which of the two horizontal yellow lines looks wider, the top one or the bottom one?<\/p>\n<div id=\"attachment_3649\" style=\"width: 235px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/07210125\/Ponzo_illusion.gif\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-3649\" class=\"wp-image-3649 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/07210125\/Ponzo_illusion.gif\" alt=\"Lines of a railroad track as they converge off into the distance. One yellow line is close to the front of the image on the tracks and another line of the same size is placed towards the back of the image along the tracks. Because of the converging lines, the yellow line in the back appears larger than the line in the foreground.\" width=\"225\" height=\"166\" \/><\/a><\/p>\n<p id=\"caption-attachment-3649\" class=\"wp-caption-text\">Figure 2. The Ponzo Illusion.<\/p>\n<\/div>\n<p>Most people experience the top line as wider. They are both exactly the same length. This experience is called the Ponzo illusion. Even though you know that the lines are the same length, it is difficult to see them as identical. Our perceptual system takes the context into account, here using the converging \u201crailroad tracks\u201d to produce an experience of depth. Then, using some impressive mental geometry, our brain adjusts the experienced length of the top line to be consistent with the size it would have if it were that far away: if two lines are the same length on my retina, but different distances from me, the more distant line must be in reality longer. You experience a world that \u201cmakes sense\u201d rather than a world that reflects the actual objects in front of you.<\/p>\n<p>There are many depth illusions. It is difficult to see the drawing on the left below as a two-dimensional figure. The converging lines and smaller square at the center seem to coax our perceptual systems into seeing depth, even though we know that the drawing is flat. This urge to see depth is probably so strong because our ability to use two-dimensional information to infer a three dimensional world is essential for allowing us to operate in the world. The picture on the right below is a driving tunnel, something you would need to process at high speed if you were in a car going through it. Your quick and detailed use of converging lines and other cues allows you to make sense of this 3-D world.<\/p>\n<div id=\"attachment_3650\" style=\"width: 524px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/07210639\/Screen-Shot-2017-02-07-at-3.04.55-PM.png\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-3650\" class=\"wp-image-3650 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/07210639\/Screen-Shot-2017-02-07-at-3.04.55-PM.png\" alt=\"The drawing on the left shows a large square with a smaller square on the inside and lines connecting the corners of the inner and outer square. The secong image shows the inside of a tunnel.\" width=\"514\" height=\"222\" \/><\/a><\/p>\n<p id=\"caption-attachment-3650\" class=\"wp-caption-text\">Figure 3. Understanding depth enables us to function in a 3-dimensional world.<\/p>\n<\/div>\n<h2>Light and Size Illusions<\/h2>\n<p>Depth is not the only quality in the world that shows how we adjust what we experience to fit the surrounding world. Look at the two gray squares in the figure below. Which one looks darker?<\/p>\n<div id=\"attachment_3654\" style=\"width: 567px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/07211928\/Simultaneous_Contrast.jpg\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-3654\" class=\"wp-image-3654\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/07211928\/Simultaneous_Contrast.jpg\" alt=\"A dark black square with a gray square in the center next to a white square with a gray square in the middle. The black surrounding the gray makes the gray appear lighter than with the white background.\" width=\"557\" height=\"278\" \/><\/a><\/p>\n<p id=\"caption-attachment-3654\" class=\"wp-caption-text\">Figure 4. Which gray square appears darker?<\/p>\n<\/div>\n<p>Most people experience the square on the right as the darker of the two gray squares. You\u2019ve probably already guessed that the squares are actually identical in shade, but the surrounding area\u2014black on the left and white on the right\u2014influence how our perceptual systems interpret the gray area. In this case, the greater difference in shading between the white surrounding area and the gray square on the right results in the experience of a darker square.<\/p>\n<p>Here is another example below. The two triangular figures are identical in shade, but the triangle on the left looks lighter against the dark background of the cross when compared to the triangle in the white area on the right.<\/p>\n<div id=\"attachment_3655\" style=\"width: 310px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/07212941\/569px-Benary_Cross.svg_.png\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-3655\" class=\"wp-image-3655 size-medium\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/07212941\/569px-Benary_Cross.svg_-300x300.png\" alt=\"Gray cross with a lighter gray triangle inside of the cross arm, and another outside of the arm of the cross. The triangle outside of the cross arm appears darker with its greater contrast against the white background.\" width=\"300\" height=\"300\" \/><\/a><\/p>\n<p id=\"caption-attachment-3655\" class=\"wp-caption-text\">Figure 5. Benary Cross<\/p>\n<\/div>\n<p>Our visual systems work with more than simple contrast. They also use our knowledge of how the world works to adjust our perceptual experience. Look at the checkerboard below. There are two squares with letters in them, one marked \u201cA\u201d and the other \u201cB\u201d. Which one of those two squares is darker?<\/p>\n<div id=\"attachment_3656\" style=\"width: 310px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/07213735\/Optical.greysquares.arp_.jpg\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-3656\" class=\"wp-image-3656 size-medium\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/07213735\/Optical.greysquares.arp_-300x242.jpg\" alt=\"A checkerboard with a large green cylinder on top of the gameboard, casting a shadow on the board. The shadow makes the pieces appear darker, so much so that the lighter &quot;B&quot; piece is actually the same color as the darker &quot;A&quot; piece.\" width=\"300\" height=\"242\" \/><\/a><\/p>\n<p id=\"caption-attachment-3656\" class=\"wp-caption-text\">Figure 6. Which looks darker, A or B?<\/p>\n<\/div>\n<p>This seems like an easy comparison, but the truth is that squares A and B are identical in shade. Our perceptual system adjusts our experience by taking some visual information into account. First, \u201cA\u201d is one of the \u201cdark squares\u201d and \u201cB\u201d is a \u201clight square\u201d if we take the checkerboard pattern into account. Perhaps even more impressive, our visual systems notice that \u201cB\u201d is in a shadow. Object in a shadow appear darker, so our experience is adjusted to take account of effect of the shadow, resulting in perceiving square B as being lighter than square A, which sits in the bright light. And if you really don&#8217;t believe your eyes, take a look at a video showing the same color tiles <a href=\"https:\/\/www.youtube.com\/watch?v=CRvo1jRXiI8\" target=\"_blank\" rel=\"noopener noreferrer\">here<\/a>.<\/p>\n<p>One final illusion takes us back to adjustment for size. Look at the two sets of circles below. Your task is to adjust the center circle on the left so it is the same actual size as the center circle on the right. The surrounding circles will not change in size, though the right of circles will expand to accommodate the size of the center circle. Use the slide bar with the label \u201cSize of left circle\u201d to make your adjustments. When you are satisfied with your adjustment, check your accuracy by clicking on the \u201cVerify Diameter\u201d button. Click \u201cReset\u201d to try again.<\/p>\n<div style=\"text-align: center;\"><iframe loading=\"lazy\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/oerfiles\/Psychology\/interactives\/circles1.html\" width=\"530\" height=\"380\"><\/iframe><\/div>\n<p>This illusion is called the Ebbinghaus illusion, created by Hermann Ebbinghaus, one of the early founders of experimental psychology. It is shown again below.<\/p>\n<p><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/02202255\/650px-Mond-vergleich.svg_.png\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-3581\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/02202255\/650px-Mond-vergleich.svg_.png\" alt=\"Large blue circles surrounding a small orange circle and a large (appearing) orange circle surrounded by blue circles. The center orange circles are in fact the same size.\" width=\"536\" height=\"330\" \/><\/a><\/p>\n<p>In this version of the illusion, most people see the circle on the right as larger than the one on the left. The two orange circles are exactly the same size. The Ebbinghaus illusion again illustrates the tendency of our perceptual systems to adjust our experience of the world to the surrounding context.<\/p>\n<div class=\"textbox tryit\">\n<h3>Try It<\/h3>\n<p>\t<iframe id=\"lumen_assessment_2875\" class=\"resizable\" src=\"https:\/\/assessments.lumenlearning.com\/assessments\/load?assessment_id=2875&#38;embed=1&#38;external_user_id=&#38;external_context_id=&#38;iframe_resize_id=lumen_assessment_2875\" frameborder=\"0\" style=\"border:none;width:100%;height:100%;min-height:400px;\"><br \/>\n\t<\/iframe><\/p>\n<p>\t<iframe id=\"lumen_assessment_2876\" class=\"resizable\" src=\"https:\/\/assessments.lumenlearning.com\/assessments\/load?assessment_id=2876&#38;embed=1&#38;external_user_id=&#38;external_context_id=&#38;iframe_resize_id=lumen_assessment_2876\" frameborder=\"0\" style=\"border:none;width:100%;height:100%;min-height:400px;\"><br \/>\n\t<\/iframe><\/p>\n<\/div>\n<div class=\"textbox examples\">\n<h3>Link to Learning<\/h3>\n<p>If you want to explore more visual illusions, <a href=\"http:\/\/www.michaelbach.de\/ot\/\" target=\"_blank\" rel=\"noopener noreferrer\">here<\/a> is a great site with dozens of interesting illusions created by Michael Bach.<\/p>\n<\/div>\n<p>How do you think a psychologist might use the Ebbinghaus\u00a0illusion to learn about mental processes or behavior (shown again below)? Read on to see an actual example from a psychologist at Colorado State University.<\/p>\n<div style=\"text-align: center;\"><iframe loading=\"lazy\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/oerfiles\/Psychology\/interactives\/circles1.html\" width=\"530\" height=\"430\"><\/iframe><\/div>\n<h2>Ebbinghaus in the Real World<\/h2>\n<p>Imagine that you are in a golf competition in which you are putting against someone with the same experience and skill that you have. There is one problem: Your opponent gets to putt into a hole that is 10% larger than the hole you have to use. You\u2019d probably think that the competition was unfairly biased against you.<\/p>\n<div id=\"attachment_3719\" style=\"width: 463px\" class=\"wp-caption alignright\"><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/14025440\/ball-1842170_1920.jpg\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-3719\" class=\"wp-image-3719\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/14025440\/ball-1842170_1920.jpg\" alt=\"aerial view of a golf hole and golf ball\" width=\"453\" height=\"291\" \/><\/a><\/p>\n<p id=\"caption-attachment-3719\" class=\"wp-caption-text\">Figure 1. Do you suspect that the <em>perceived<\/em> size of a golf hole will affect putting performance?<\/p>\n<\/div>\n<p>Now imagine a somewhat different situation. You and your opponent are about equal in ability and the holes you are using are the same size, but the hole that your opponent is using <em>looks<\/em>\u00a010% larger than the one you are using. Would your opponent have an unfair advantage now?<\/p>\n<p>If you read the earlier section on the Ebbinghaus effect, you have an idea how psychologists could exploit your perceptual system (and your opponent\u2019s) to test this very question. Psychologist Jessica Witt and her colleagues Sally Linkenauger and Dennis Proffitt recruited research participants with no unusual golf experience to participate in a putting task. They competed against themselves rather than against another person.<\/p>\n<p>The experimenters made the task challenging by using a hole with a 2-inch diameter, which is about half the diameter of the hole you will find on a golf course. An overhead projector mounted on the ceiling of their lab allowed them to project Ebbinghaus\u2019s circles around the putting hole. Some participants saw the putting hole surrounded by circles that were smaller than the hole in the center; the other half saw surrounding black circles that were larger.<\/p>\n<p>Participants putted from about 11\u00bd feet away. \u00a0They took 10 putts in one condition, and then 10 in the other condition. Half of the participants putted with the large surrounding circles first and half saw the small surrounding circles first. This procedure is called <strong>counterbalancing<\/strong>. If there is any advantage (e.g., getting better over time with practice) or disadvantage (e.g., getting tired of putting), counterbalancing assures that both conditions are equally exposed to the positive or negative effects of which task goes first or second. Failure to take account of this type of problem means that you may have a <strong>confounding variable<\/strong>\u2014practice or fatigue\u2014that influences performance. A confounding variable is something that <em>could<\/em>\u00a0influence performance, but is not part of the study. We try to <em>control<\/em>\u00a0(that is, neutralize) potentially confounding variables so they cannot be the cause of performance differences. So, for instance, if everyone did the large surrounding circles condition first and then the small surrounding circles, then differences in performance could be due to order of conditions (leading to practice or fatigue effects) rather than the size of the surrounding circles. By counterbalancing, we don\u2019t get rid of the effects of practice or fatigue for any particular person, but\u2014across all the participants\u2014practice or fatigue should affect both conditions (both types of Ebbinghaus circles) equally.<\/p>\n<p>The experimenters wanted to know two things. First, did they actually produce the Ebbinghaus illusion? Remember: there is no guarantee that people see or think the way your theory says they should. So just before the participant started putting in a particular condition, he or she drew a circle using a computerized drawing tool, attempting to match the exact size of the putting hole. This is better than simply asking, \u201cdo you see the illusion?\u201d The drawing task attempts to directly measure what they perceive.<\/p>\n<p>Second, the experimenters wanted to see if the perceived size of the hole influenced putting accuracy. They recorded the success or failure of each putt. Each participant could get a score of 0 to 10 successful putts in each condition.<\/p>\n<h3>Methods Summary<\/h3>\n<p>Recap the steps you&#8217;ve read about thus far:<\/p>\n<ol>\n<li>The participant practices putting to get used to the task.<\/li>\n<li>The participant completes\u00a0the first condition (large surrounding circles for half of the participants and small surrounding circles for the other half).\n<ul>\n<li>The participant draws a circle corresponding to his or her estimation of the actual size of the putting hole. This allows\u00a0the experimenters to determine if the Ebbinghaus effect actually occurred.<\/li>\n<li>The participant putts 10 times in this condition.<\/li>\n<\/ul>\n<\/li>\n<li>Participant completes\u00a0the second condition (whichever condition they have not yet done).\n<ul>\n<li>The participant draws a circle corresponding to his or her estimation of the actual size of the putting hole.<\/li>\n<li>The participant putts 10 times in this condition.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n<div class=\"textbox tryit\">\n<h3>Try It<\/h3>\n<p><strong>Now that you know the details of Jessica Witt\u2019s experiment, see if you can answer the following questions. Click on the option you think is correct and then click the &#8216;Show Answer&#8217; link to see if you&#8217;re right.<\/strong><\/p>\n<p><!--https:\/\/assessments.lumenlearning.com\/assessments\/2877 --><\/p>\n<p><strong>Question 1: What is the independent variable as described in this study?<\/strong><\/p>\n<ul style=\"list-style-type: none;\">\n<li><input name=\"group1\" type=\"radio\" \/> \u00a0\u00a0The size of the putting hole is the independent variable.<\/li>\n<li><input name=\"group1\" type=\"radio\" \/> \u00a0\u00a0The size of the circles surrounding the putting hole is the independent variable.<\/li>\n<li><input name=\"group1\" type=\"radio\" \/> \u00a0\u00a0The distance the person had to putt is the independent variable.<\/li>\n<li><input name=\"group1\" type=\"radio\" \/> \u00a0\u00a0There are two independent variables: the size of the putting hole and the size of the surrounding circles.<\/li>\n<\/ul>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q794784\">Show Answer<\/span><\/p>\n<div id=\"q794784\" class=\"hidden-answer\" style=\"display: none\">\n<p>An INDEPENDENT VARIABLE is something intentionally manipulated (changed) by the experimenter. To test the effect of the Ebbinghaus illusion, the experimenters had participants putt into holes surrounded by larger circles and smaller circles. This \u201cmanipulation\u201d of the size of the surrounding holes is the independent variable.<\/p>\n<\/div>\n<\/div>\n<p><!--https:\/\/assessments.lumenlearning.com\/assessments\/2878 --><\/p>\n<p><strong>Question 2: What is the dependent variable in this study?<\/strong><\/p>\n<ul style=\"list-style-type: none;\">\n<li><input name=\"group2\" type=\"radio\" \/> \u00a0\u00a0The number of successful putts is the dependent variable.<\/li>\n<li><input name=\"group2\" type=\"radio\" \/> \u00a0\u00a0The size of the circle drawn by the participant is the dependent variable.<\/li>\n<li><input name=\"group2\" type=\"radio\" \/> \u00a0\u00a0The size of the putting hole is the dependent variable.<\/li>\n<li><input name=\"group2\" type=\"radio\" \/> \u00a0\u00a0There are two dependent variables: the number of successful putts and the size of the circle drawn by the participants are both dependent variables.<\/li>\n<\/ul>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q569303\">Show Answer<\/span><\/p>\n<div id=\"q569303\" class=\"hidden-answer\" style=\"display: none\">\n<p>A DEPENDENT VARIABLE is some behavior or thought process measured by the experimenter. This study had two dependent variables:<\/p>\n<ul>\n<li>(a) the size of the circle drawn by the participant<\/li>\n<li>(b) the number of successful putts<\/li>\n<\/ul>\n<p>Both dependent variables were measured for each condition, so each participant drew 2 circles and had 0 to 10 successful putts in both the large surrounding circles condition and the small surrounding circles condition.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<p>Now see if you can guess the results of this study.<\/p>\n<div class=\"textbox tryit\">\n<h3>Try It<\/h3>\n<p><strong>Question 3: How did the participants perceive the holes?\u00a0<\/strong><\/p>\n<p>Resize\u00a0the bars below by clicking and dragging them to show your predicted results when the subjects were asked to draw the circles.\u00a0Make a general prediction based on your understanding of the experiment.<\/p>\n<div style=\"text-align: center;\"><iframe loading=\"lazy\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/oerfiles\/Psychology\/interactives\/bargraph4.html\" width=\"530\" height=\"450\"><\/iframe><\/div>\n<p>&nbsp;<\/p>\n<p><!--https:\/\/assessments.lumenlearning.com\/assessments\/2879 --><\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q566454\">Show Answer<\/span><\/p>\n<div id=\"q566454\" class=\"hidden-answer\" style=\"display: none\">\n<p>This question tested whether or not the Ebbinghaus effect was produced in this experiment. If there is no difference between the bars, that would mean that participants didn\u2019t experience the Ebbinghaus illusion. The exact height of the bars is not important here, but the relative heights should look something like this:<\/p>\n<p><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/23070233\/bars11.png\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-3793\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/23070233\/bars11-300x235.png\" alt=\"Bar graph showing larger circles drawn by participants when the hole looks large and was surrounded by the smaller circles.\" width=\"400\" height=\"314\" \/><\/a><\/p>\n<p>The taller bar on the right means that the center putting hole looks larger when it is surrounded by smaller circles than when the same hole is surrounded by large circles: The Ebbinghaus illusion.<\/p>\n<p>This result was important because the reasoning behind the experiment was dependent on successfully producing the Ebbinghaus illusion. There is a technical term for a dependent variable that is used to determine if your independent variable is actually working: a <strong>manipulation check<\/strong>. Good experimenters use manipulation checks to be sure they aren\u2019t fooling themselves into believing that they have done something that really didn\u2019t work.<\/p>\n<\/div>\n<\/div>\n<p><strong>Question 4: Can you guess how well the participants putted? <\/strong><\/p>\n<p>Resize\u00a0the bars below by clicking and dragging them to show your predicted results when the subjects putted.<\/p>\n<div style=\"text-align: center;\"><iframe loading=\"lazy\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/oerfiles\/Psychology\/interactives\/bargraph5.html\" width=\"530\" height=\"450\"><\/iframe><\/div>\n<p><!--https:\/\/assessments.lumenlearning.com\/assessments\/2880 --><\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q751987\">Show Answer<\/span><\/p>\n<div id=\"q751987\" class=\"hidden-answer\" style=\"display: none\">\n<p>This question lets you check out your skills as a psychologist. The description of the experiment did not include the researchers\u2019 hypothesis, so you have to decide for yourself what you think is going to happen. The three possible patterns of results are shown below. The graph you drew fit one of these patterns.<\/p>\n<p><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/23070056\/bars21.png\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-3791\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/23070056\/bars21-300x135.png\" alt=\"The possible results showing possible results in a bar graph: better putting when the hole looks small, the hole size doesn't matter, or better putting when the hole looks large.\" width=\"800\" height=\"359\" \/><\/a><\/p>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"textbox tryit\">\n<h3>Try It<\/h3>\n<p>Before we show you the actual results of the study, write our your prediction. Do you think the illusion affected putting performance? Why or why not? Explain your answer in the text box below:<\/p>\n<p><textarea aria-label=\"Your Answer\" rows=\"4\"><\/textarea><\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q291461\">Show Answer<\/span><\/p>\n<div id=\"q291461\" class=\"hidden-answer\" style=\"display: none\">\n<p>Until now, we haven\u2019t told you exactly how the Ebbinghaus illusion was\u00a0predicted to influence putting\u2014only that the experimenters thought it would have some sort of influence. So here is what they said.<\/p>\n<p>The experimenters thought that the perceived size of the hole would affect the SELF-CONFIDENCE of the person as he or she putted. If you are putting into a larger hole (or what is PERCEIVED as a larger hole) you should be more confident that you will sink your putt. Remember, this is just a prediction based on the experimenters\u2019 reasoning. Their ideas came from interviewing skilled athletes who claimed that objects seemed larger and time seemed to slow down as they gained skill. If the ball you have to catch is bigger or the person blocking you is slower, you can perform at a higher level.<\/p>\n<p>The experimenters could be right or they could be wrong. Your own reasoning might be different than that of the experimenters. For instance, perhaps you thought that people would be MORE CAREFUL if they thought the hole was smaller. That would be a perfectly fine hypothesis. Interestingly, it makes the opposite prediction from the experimenters\u2019 self-confidence hypothesis. This \u201ccareful putting with smaller holes\u201d theory predicts that people should putt better when they perceive the hole as smaller (i.e., when the surrounding circles are large). The experimenters\u2019 \u201cmore confidence with larger holes\u201d hypothesis predicts that people should putt better when they perceive the hole as larger.<\/p>\n<p>Here are the actual results. First, the hole was perceived as larger when it was surrounded by smaller holes, so there is evidence that they successfully produced the Ebbinghaus illusion. Second, the experimenters predicted that participants would be more successful when the hole seemed larger (i.e., surrounded by smaller circles). Consistent with these predictions, the results looked like this:<\/p>\n<p><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/23070152\/bars3.png\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-3792\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2017\/02\/23070152\/bars3-300x265.png\" alt=\"Bar graph showing better putting when the hole looks large and was surrounded by the smaller circles.\" width=\"400\" height=\"353\" \/><\/a><\/p>\n<\/div>\n<\/div>\n<\/div>\n<p>This is not the only experiment that has used a sports context to study the effects of illusions. Other experiments have shown that people hit softballs better when the balls are perceived as larger. People score higher in darts when the board appears larger. Athletes kick field goals and return tennis balls more successfully when the goal posts or tennis balls appear larger. In all of these studies, the balls or boards or goal posts were not actually larger, but they were perceived as larger because the experimenters created illusions. Skilled athletes often report that targets appear larger or time slows down when they are \u201cin the zone\u201d, as if practice and skill create their own perceptual illusions that increase confidence and make difficult challenges feel easier.<\/p>\n<div class=\"textbox examples\">\n<h3>Link to Learning<\/h3>\n<p>Watch this interview with Psychologist Jessica Witt to see her talk about how her research utilizing the Ebbinghaus illusion impacts a golfer&#8217;s perception and performance. You can also read about more about similar variations of her research <a href=\"http:\/\/www.apa.org\/science\/about\/psa\/2016\/12\/action-visual-perception.aspx\">here<\/a>.<\/p>\n<p><iframe loading=\"lazy\" src=\"https:\/\/www.youtube.com\/embed\/XDNfTUOSjFw?rel=0\" width=\"853\" height=\"480\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\" data-mce-fragment=\"1\"><\/iframe><\/p>\n<\/div>\n<h2>A Final Note: Science Doesn&#8217;t Always Produce Simple Results<\/h2>\n<p>Professor Witt\u2019s study had interesting results; however, they weren\u2019t quite as simple as we have made them seem. The researchers actually had two different hole sizes: 2 inches and 4 inches. The Ebbinghaus circles were adjusted to be relatively larger or smaller than the putting hole.<\/p>\n<p>The Ebbinghaus illusion worked for the smaller (2 inch) putting holes, but not for the larger (4 inch) putting holes. In other words, when people drew the circles as they perceived them (the \u201cmanipulation check\u201d dependent variable), they drew different sized circles for the 2 inch holes (the Ebbinghaus illusion), but the same size circles for the 4 inch holes (no Ebbinghaus illusion).<\/p>\n<p>For the larger (4 inch) putting holes, putting accuracy was the same for the two different conditions. This didn\u2019t bother the experimenters, because\u2014as we have already noted\u2014the participants did not experience the Ebbinghaus illusion with the larger holes. If the holes were perceived as the same, then self-confidence should not have been affected and, in turn, putting should not have been better in one condition than the other.<\/p>\n<p>In the research paper, the experimenters suggest a few technical reasons that the larger hole might not have produced the Ebbinghaus illusion, but they admit that they have no definitive explanation. That\u2019s okay. Science often yields messy results\u2014and these can be the basis for new experiments and sometimes for really interesting discoveries. The world is not as simple as our theories try to make it seem. Happily, in science, as in many aspects of life, you learn more from your failures than your successes, so good scientists don\u2019t try to hide from results they don\u2019t expect.<br \/>\n\t<iframe id=\"lumen_assessment_4827\" class=\"resizable\" src=\"https:\/\/assessments.lumenlearning.com\/assessments\/load?assessment_id=4827&#38;embed=1&#38;external_user_id=&#38;external_context_id=&#38;iframe_resize_id=lumen_assessment_4827\" frameborder=\"0\" style=\"border:none;width:100%;height:100%;min-height:400px;\"><br \/>\n\t<\/iframe><\/p>\n\n\t\t\t <section class=\"citations-section\" role=\"contentinfo\">\n\t\t\t <h3>Candela Citations<\/h3>\n\t\t\t\t\t <div>\n\t\t\t\t\t\t <div id=\"citation-list-3576\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Original<\/div><ul class=\"citation-list\"><li>Ebbinghaus Application and Text on Illusions. <strong>Authored by<\/strong>: Patrick J Carroll. <strong>Provided by<\/strong>: Lumen Learning. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY: Attribution<\/a><\/em><\/li><\/ul><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Shared previously<\/div><ul class=\"citation-list\"><li>Mond-Vergleich image. <strong>Authored by<\/strong>: Fibonacci. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Mond-vergleich.svg\">https:\/\/commons.wikimedia.org\/wiki\/File:Mond-vergleich.svg<\/a>. <strong>Project<\/strong>: Wikimedia. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/\">CC BY-SA: Attribution-ShareAlike<\/a><\/em><\/li><li>A hole in the head: Golf and Perception. <strong>Authored by<\/strong>: sciencentral. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/www.youtube.com\/watch?v=XDNfTUOSjFw\">https:\/\/www.youtube.com\/watch?v=XDNfTUOSjFw<\/a>. <strong>License<\/strong>: <em>Other<\/em>. <strong>License Terms<\/strong>: Standard YouTube License<\/li><li>golf picture. <strong>Authored by<\/strong>: coffee. <strong>Provided by<\/strong>: Pixabay. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/pixabay.com\/en\/ball-golf-golf-ball-golf-course-1842170\/\">https:\/\/pixabay.com\/en\/ball-golf-golf-ball-golf-course-1842170\/<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/about\/cc0\">CC0: No Rights Reserved<\/a><\/em><\/li><li>Ponzo Illusion. <strong>Authored by<\/strong>: Wikipedia. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Ponzo_illusion.gif\">https:\/\/commons.wikimedia.org\/wiki\/File:Ponzo_illusion.gif<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/about\/pdm\">Public Domain: No Known Copyright<\/a><\/em><\/li><li>Contrast Illusion. <strong>Authored by<\/strong>: Paaliaq. <strong>Provided by<\/strong>: Wikimedia. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/commons.wikimedia.org\/wiki\/Category:Contrast_illusions#\/media\/File:Simultaneous_Contrast.jpg\">https:\/\/commons.wikimedia.org\/wiki\/Category:Contrast_illusions#\/media\/File:Simultaneous_Contrast.jpg<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/\">CC BY-SA: Attribution-ShareAlike<\/a><\/em><\/li><li>Benary Cross Illusion. <strong>Provided by<\/strong>: Wikimedia. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/commons.wikimedia.org\/wiki\/Category:Contrast_illusions#\/media\/File:Benary_Cross.svg\">https:\/\/commons.wikimedia.org\/wiki\/Category:Contrast_illusions#\/media\/File:Benary_Cross.svg<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/about\/pdm\">Public Domain: No Known Copyright<\/a><\/em><\/li><li>Checkerboard Illusion. <strong>Authored by<\/strong>: Adrian Pingstone . <strong>Provided by<\/strong>: Wikipedia. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Optical.greysquares.arp.jpg\">https:\/\/commons.wikimedia.org\/wiki\/File:Optical.greysquares.arp.jpg<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/about\/pdm\">Public Domain: No Known Copyright<\/a><\/em><\/li><li>Horizontal 3D grafitti. <strong>Provided by<\/strong>: Wikimedia. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Horizontal_3d_graffiti,_%C5%81%C3%B3d%C5%BA_Schillera_Passage.jpg\">https:\/\/commons.wikimedia.org\/wiki\/File:Horizontal_3d_graffiti,_%C5%81%C3%B3d%C5%BA_Schillera_Passage.jpg<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/\">CC BY-SA: Attribution-ShareAlike<\/a><\/em><\/li><\/ul><div class=\"license-attribution-dropdown-subheading\">Public domain content<\/div><ul class=\"citation-list\"><li>Baltimore Harbor Tunnel. <strong>Authored by<\/strong>: ErgoSum88. <strong>Provided by<\/strong>: Wikimedia. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/commons.wikimedia.org\/wiki\/Category:Centered_tunnel_perspective#\/media\/File:Baltimore_Harbor_Tunnel_I-895_02.JPG\">https:\/\/commons.wikimedia.org\/wiki\/Category:Centered_tunnel_perspective#\/media\/File:Baltimore_Harbor_Tunnel_I-895_02.JPG<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/about\/pdm\">Public Domain: No Known Copyright<\/a><\/em><\/li><li>Simple shape square optical illusion. <strong>Provided by<\/strong>: Wikimedia. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/commons.wikimedia.org\/wiki\/Category:Optical_illusions#\/media\/File:PSM_V54_D322_Simple_shape_creating_optical_illusion_2.png\">https:\/\/commons.wikimedia.org\/wiki\/Category:Optical_illusions#\/media\/File:PSM_V54_D322_Simple_shape_creating_optical_illusion_2.png<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/about\/pdm\">Public Domain: No Known Copyright<\/a><\/em><\/li><li>Ebbinghaus Illusion. <strong>Provided by<\/strong>: Wikimedia. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/en.wikipedia.org\/wiki\/File:Mond-vergleich.svg\">https:\/\/en.wikipedia.org\/wiki\/File:Mond-vergleich.svg<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/about\/pdm\">Public Domain: No Known Copyright<\/a><\/em><\/li><\/ul><\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t <\/div>\n\t\t\t <\/section>","protected":false},"author":29,"menu_order":9,"template":"","meta":{"_candela_citation":"[{\"type\":\"cc\",\"description\":\"Mond-Vergleich image\",\"author\":\"Fibonacci\",\"organization\":\"\",\"url\":\"https:\/\/commons.wikimedia.org\/wiki\/File:Mond-vergleich.svg\",\"project\":\"Wikimedia\",\"license\":\"cc-by-sa\",\"license_terms\":\"\"},{\"type\":\"cc\",\"description\":\"A hole in the head: Golf and Perception\",\"author\":\"sciencentral\",\"organization\":\"\",\"url\":\"https:\/\/www.youtube.com\/watch?v=XDNfTUOSjFw\",\"project\":\"\",\"license\":\"other\",\"license_terms\":\"Standard YouTube License\"},{\"type\":\"original\",\"description\":\"Ebbinghaus Application and Text on Illusions\",\"author\":\"Patrick J Carroll\",\"organization\":\"Lumen Learning\",\"url\":\"\",\"project\":\"\",\"license\":\"cc-by\",\"license_terms\":\"\"},{\"type\":\"cc\",\"description\":\"golf picture\",\"author\":\"coffee\",\"organization\":\"Pixabay\",\"url\":\"https:\/\/pixabay.com\/en\/ball-golf-golf-ball-golf-course-1842170\/\",\"project\":\"\",\"license\":\"cc0\",\"license_terms\":\"\"},{\"type\":\"cc\",\"description\":\"Ponzo Illusion\",\"author\":\"Wikipedia\",\"organization\":\"\",\"url\":\"https:\/\/commons.wikimedia.org\/wiki\/File:Ponzo_illusion.gif\",\"project\":\"\",\"license\":\"pd\",\"license_terms\":\"\"},{\"type\":\"pd\",\"description\":\"Baltimore Harbor Tunnel\",\"author\":\"ErgoSum88\",\"organization\":\"Wikimedia\",\"url\":\"https:\/\/commons.wikimedia.org\/wiki\/Category:Centered_tunnel_perspective#\/media\/File:Baltimore_Harbor_Tunnel_I-895_02.JPG\",\"project\":\"\",\"license\":\"pd\",\"license_terms\":\"\"},{\"type\":\"pd\",\"description\":\"Simple shape square optical illusion\",\"author\":\"\",\"organization\":\"Wikimedia\",\"url\":\"https:\/\/commons.wikimedia.org\/wiki\/Category:Optical_illusions#\/media\/File:PSM_V54_D322_Simple_shape_creating_optical_illusion_2.png\",\"project\":\"\",\"license\":\"pd\",\"license_terms\":\"\"},{\"type\":\"cc\",\"description\":\"Contrast Illusion\",\"author\":\"Paaliaq\",\"organization\":\"Wikimedia\",\"url\":\"https:\/\/commons.wikimedia.org\/wiki\/Category:Contrast_illusions#\/media\/File:Simultaneous_Contrast.jpg\",\"project\":\"\",\"license\":\"cc-by-sa\",\"license_terms\":\"\"},{\"type\":\"cc\",\"description\":\"Benary Cross Illusion\",\"author\":\"\",\"organization\":\"Wikimedia\",\"url\":\"https:\/\/commons.wikimedia.org\/wiki\/Category:Contrast_illusions#\/media\/File:Benary_Cross.svg\",\"project\":\"\",\"license\":\"pd\",\"license_terms\":\"\"},{\"type\":\"cc\",\"description\":\"Checkerboard Illusion\",\"author\":\"Adrian Pingstone \",\"organization\":\"Wikipedia\",\"url\":\"https:\/\/commons.wikimedia.org\/wiki\/File:Optical.greysquares.arp.jpg\",\"project\":\"\",\"license\":\"pd\",\"license_terms\":\"\"},{\"type\":\"pd\",\"description\":\"Ebbinghaus Illusion\",\"author\":\"\",\"organization\":\"Wikimedia\",\"url\":\"https:\/\/en.wikipedia.org\/wiki\/File:Mond-vergleich.svg\",\"project\":\"\",\"license\":\"pd\",\"license_terms\":\"\"},{\"type\":\"cc\",\"description\":\"Horizontal 3D grafitti\",\"author\":\"\",\"organization\":\"Wikimedia\",\"url\":\"https:\/\/commons.wikimedia.org\/wiki\/File:Horizontal_3d_graffiti,_%C5%81%C3%B3d%C5%BA_Schillera_Passage.jpg\",\"project\":\"\",\"license\":\"cc-by-sa\",\"license_terms\":\"\"}]","CANDELA_OUTCOMES_GUID":"df9767ab-fe03-40dd-a133-fd1e343e24f2","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-3576","chapter","type-chapter","status-web-only","hentry"],"part":514,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/suny-fmcc-intropsych\/wp-json\/pressbooks\/v2\/chapters\/3576","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/suny-fmcc-intropsych\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/suny-fmcc-intropsych\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-fmcc-intropsych\/wp-json\/wp\/v2\/users\/29"}],"version-history":[{"count":52,"href":"https:\/\/courses.lumenlearning.com\/suny-fmcc-intropsych\/wp-json\/pressbooks\/v2\/chapters\/3576\/revisions"}],"predecessor-version":[{"id":4869,"href":"https:\/\/courses.lumenlearning.com\/suny-fmcc-intropsych\/wp-json\/pressbooks\/v2\/chapters\/3576\/revisions\/4869"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/suny-fmcc-intropsych\/wp-json\/pressbooks\/v2\/parts\/514"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/suny-fmcc-intropsych\/wp-json\/pressbooks\/v2\/chapters\/3576\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/suny-fmcc-intropsych\/wp-json\/wp\/v2\/media?parent=3576"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-fmcc-intropsych\/wp-json\/pressbooks\/v2\/chapter-type?post=3576"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-fmcc-intropsych\/wp-json\/wp\/v2\/contributor?post=3576"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-fmcc-intropsych\/wp-json\/wp\/v2\/license?post=3576"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}