Complimentary language is a speech act that caters to positive face needs. Positive face, according to Brown and Levinson, is "the positive consistent self-image or 'personality' (crucially including the desire that this self-image be appreciated and approved of) claimed by interactions". Many studies examine complimentary language in relation to gender because of the noticeable differences in compliment topic, explicitness, and response depending on gender of the speaker as well as the gender of the addressee. Analysts use these studies to demonstrate their theories about inherent differences between the genders and the societal impact of gender roles. Same-gender compliments Compliment patterns appear to be quite different when the complimenter and complimentee are the same gender from when they are different genders, and differences between males and females still arise even within same-gender interactions. In data from New Zealand, it was noted that women tended to compliment each other considerably more often than men complimented each other. This statistic is reflected in further data that showed that women gave two-thirds of the recorded compliments and received three-quarters of them. Compliments between men comprised a mere 9 percent of the data. Similar patterns have been noted in studies of English speakers from other regions as well. In written discourse, too, such patterns arose, as women tended to compliment other women more often than they complimented men, and more often than men complimented either each other or women. In one study, compliments between women numbered almost 250, while compliments between men did not even reach 50. Janet Holmes suggests that the discrepancies in male-male and female-female complimentary language may be due to differences in perception concerning the purpose of compliments. The hypothesis is that women use compliments to build affiliations, while men use compliments to make evaluative judgments. Deborah Tannen attributes female linguistic behavior to the purpose of rapport-building, so, assuming compliments are being used as such a means, the data of complimentary language between women seems to suggest this tendency to create and strengthen affiliations is strongest between women. Compliments are usually classified into one of four categories, depending on what they refer to: appearance, ability and performance, possessions, or personality. In New Zealand data, it is shown that women tend to compliment each other based on appearance most often. While 61 percent of the compliments between women were found to be appearance-based, only 36 percent of the compliments between men were found