Relationships between people that are characterized by loving, caring, commitment, and intimacy, such as those between adult friends, dating partners, lovers, and married couples, are known as close relationships.

Our close relationships make us happy and healthy. We experience higher self-efficacy, self-esteem, and positive mood when we believe that our friends and partners are responding to us supportively and with a concern for our needs and our welfare.

When we say that we like or love someone, we are experiencing interpersonal attraction. People are strongly influenced by the physical attractiveness of their partners in initial encounters. On average, we find younger people more attractive than older people, we are more attracted to faces that are more symmetrical in comparison with those that are less symmetrical, and we prefer faces that are more, rather than less, average. Although the preferences for youth, symmetry, and averageness appear to be universal, there is evidence that at least some differences in perceived attractiveness are due to social and cultural factors.

Overall, both men and women value physical attractiveness. However, for men, the physical attractiveness of women is more important than it is for women judging men, whereas women are relatively more interested in the social status of men. These gender differences may have evolutionary origins. The tendency to perceive attractive people as having positive characteristics, such as sociability and competence, is known as the what is beautiful is good stereotype.

Relationships are more likely to develop and be maintained to the extent that the partners share values and beliefs. The basic principles of social exchange and equity dictate that there will be general similarity in status among people in close relationships. And we tend to prefer people who seem to like us about as much as we like them.

Simply being around another person also increases our liking for that individual. The tendency to prefer stimuli (including, but not limited to, people) that we have seen more frequently is known as mere exposure.

We tend to like people more when we are in a good mood and to like them less when we are in a bad mood. And it has been found that arousal polarizes our liking of others. The strong feelings that we experience toward another person that are accompanied by increases in arousal are called passion, and the emotionally intense love that is based on arousal and sexual attraction is known as passionate love.

As partners stay together over time, cognition becomes relatively more important than passion, and close relationships are more likely to be based on companionate love than on passionate love. As a relationship progresses, the partners in the relationship come to know each other more fully and care about each other to a greater degree—they become closer to each other. Intimacy is marked in large part by reciprocal self-disclosure—that is, the tendency to communicate frequently and openly.

The partners in close relationships increasingly turn to each other for social support and for other needs. The members of a close relationship are highly interdependent and rely to a great degree on effective social exchange. When partners are attentive to the needs of the other person, and when they help the other meet his or her needs without explicitly keeping track of what they are giving or expecting to get in return, we say that the partners have a communal relationship.

In relationships in which a positive rapport between the partners is developed and maintained over a period of time, the partners are naturally happy with the relationship and they become committed to it.

The triangular model of love proposes that there are different types of love, each made up of different combinations of the basic components of passion, intimacy, and commitment.

Children have been found to develop either a secure or insecure attachment style with their caregivers, and individual differences in these styles remain somewhat stable into adulthood. People with secure attachment styles may make better partners. Attachment styles, though, do show some diversity across different cultural and age groups. They can also shift somewhat, even during adulthood, and so people who are currently showing insecure attachment can move toward being more securely attached in their relationships.