effect on attitude and value than on personality traits, however, it is found that initial assortment (i.e., similarity within couples at the beginning of marriage) rather than convergence, plays a crucial role in explaining spousal similarity. Active assortment refers to direct effects on choosing someone similar to oneself in mating preferences. The data showed that there is a greater effect on political and religious attitudes than on personality traits. A follow-up issue on the reason of the finding was raised. The concepts of idiosyncratic (i.e. different individuals have different mate preferences) and consensual (i.e. a consensus of preference on some prospective mates to others) in mate preference. The data showed that mate preference on political and religious bases tend to be idiosyncratic, for example, a Catholic would be more likely to choose a mate who is also a Catholic, as opposed to a Buddhist. Such idiosyncratic preferences produce a high level of active assortment which plays a vital role in affecting spousal similarity. In summary, active assortment plays a large role, whereas convergence has little evidence on showing such effect. Propinquity effect The propinquity effect relies on the observation that: "The more we see and interact with a person, the more likely he or she is to become our friend or sexual partner." This effect is very similar to the mere exposure effect in that the more a person is exposed to a stimulus, the more the person likes it; however, there are exceptions. Familiarity can also occur without physical exposure. Recent studies show that relationships formed over the Internet resemble those developed face-to-face, in terms of perceived quality and depth. Exposure effect The exposure effect, also known as the familiarity principle, states that the more a person is exposed to something, the more they come to like it. This applies equally to both objects and people. A clear illustration is in a 1992 study: the researchers had four women of similar appearance attend a large college course over a semester such that each woman attended a different number of sessions (0, 5, 10, or 15). Students then rated the women for perceived familiarity, attractiveness and similarity at the end of the term. Results indicated a strong effect of exposure on attraction that was mediated by the effect of exposure on familiarity. However, exposure does not always increase attraction. For example, the social allergy effect can occur when a person