Passion, intimacy, and time: passionate love as a function of change in intimacy.

To build on existing theories about love, we propose that passion is a function of change in intimacy (i.e., the first derivative of intimacy over time). Hence, passion will be low when intimacy is stable (either high or low), but rising intimacy will create a strong sense of passion. This view is able to account for a broad range of evidence, including frequency of sex in long-term relationships, intimate and sexual behavior of extraverts, gender differences in intimate behavior, gain and loss effects of communicated attraction, the biologically atypical human preference for face-to-face coitus, and patterns of distress in romantic breakups. Although this view may provide a good fit to available evidence, the totality of evidence is not yet adequate for a definitive conclusion, and suggestions for further research are offered.