in-group members whereas low attitude-similarity would lead to diversity among in-group members, promoting social attraction and achieving high group performance in different tasks. Although attitude similarity and attraction are linearly related, attraction may not contribute significantly to attitude change. Other social and cultural aspects Byrne, Clore and Worchel (1966) suggested that people with similar economic status are likely to be attracted to each other. Buss & Barnes (1986) also found that people prefer their romantic partners to be similar in certain demographic characteristics, including religious background, political orientation and socio-economic status. Researchers have shown that interpersonal attraction was positively correlated to personality similarity. People are inclined to desire romantic partners who are similar to themselves on agreeableness, conscientiousness, extroversion, emotional stability, openness to experience, and attachment style. Activity similarity was especially predictive of liking judgments, which affects the judgments of attraction. According to the post-conversation measures of social attraction, tactical similarity was positively correlated with partner satisfaction and global competence ratings, but was uncorrelated with the opinion change and perceived persuasiveness measures. When checking similar variables they were also seen as more similar on a number of personality characteristics. This study found that the length of the average relationship was related to perceptions of similarity; the couples who were together longer were seen as more equal. This effect can be attributed to the fact that when time passes by couples become more alike through shared experiences, or that couples that are alike stay together longer. Similarity has effects on starting a relationship by initial attraction to know each other. It is shown that high attitude similarity resulted in a significant increase in initial attraction to the target person and high attitude dissimilarity resulted in a decrease of initial attraction. Similarity also promotes relationship commitment. Study on heterosexual dating couples found that similarity in intrinsic values of the couple was linked to relationship commitment and stability. Social homogamy refers to "passive, indirect effects on spousal similarity". The result showed that age and education level are crucial in affecting the mate preference. Because people with similar age study and interact more in the same form of the school, propinquity effect (i.e., the tendency of people to meet and spend time with those who share the common characteristics) plays a significant impact in spousal similarity. Convergence refers to an increasing similarity with time. Although the previous research showed that there is a greater