Buss (1989) Sex differences in human mate preferences

Males and females value different characteristics in a partner. These differences reflect different selection pressures in the EEA (Environment of evolutionary adaptation) and also demonstrate the current direction of sexual selection, by letting us know who is likely to be selected as a mate.

There are three arguments that predict particular sex differences in mate preferences;

1) predictions based on parental investment and sexual selection theory

Trivers (1972) in mammals, females make a greater investment (carry the baby). Therefore they are more choosy when selecting a partner. They seek a partner with resources (food, territory, ambition) to enhance reproductive success.

2) Predictions based on fertility ad reproductive value

Symons (1979) / Williams (1975) Youthfulness is an indicator of fertility (high when 20-30 years) and reproductive value (future reproductive possibilities, highest in early adolescence). This is signalled by physical characteristics (smooth skin, shiny hair, full lips) and by behavioural indicators (high energy level). Males who fail to select females with such characteristics would, on average, leave fewer offspring. Females are less likely to use such characteristics because age and fertility are less closely associated. 

3) Prediction based on paternity probability

Males cannot be certain that their offspring are their own. Selection should favour those males who make sure that any effort is directed towards their own offspring rather than those of any other male. Preference for chastity in a potential mate is a means of increasing paternity probability. Chastity might also be imprtant for females because it would show their mate would not have to share resources between females.

Aims

Buss aimed to investigate evolutionary explanation of sex differences in human mate preferences. if such behaviours are innate we would expect them to be the same in different cultures. Therefore, Buss aimed to compare mate preferences in different cultures.

Samples

Buss analysed 37 samples from 33 countries, a total of 10,047 participants. The mean sample size was 272 participants. The age of the participants ranged from 16.96 years in New Zealand to 28.71 in West Germany. The mean age was 23.05 years.

The sampling techniques varied, in Venezuela every fifth household was sampled in a variety of neighbourhoods. In West Germany the sample wasselected throug newspaper ads. In New Zealand the sample was of high school students.

Data collection

The research data was mainly collected by native residents of each country who were unaware of the central hypotheses of the investigation.

Questionnaires

Instrument 1 - Rating - Part 1 collected biographical data.

• Part 2 - mate preferences (preferred age to marry, preferred age difference)
• Part 3 - participants had to rate 18 characteristics on a 4 point scale.

Instrument 2 - Ranking - Participants were asked to place 13 characteristics in rank order based on their desirability in someone they might want to marry. Other variables included being religious, kind and having an exciting personality.

Translations

Research collaborators employed bilingual speakers to translate the questionnaire from English to their native language and translate the answers back to English.

Good financial prospect in a mate was valued by females more than males in 97% of the samples.

• In general, Western European samples valued earning capacity less than South America, North America, Asian and African samples.

Ambition and Industriousness in a mate was valued by females more than males in 92% of the samples.

• in 78% of the samples this difference was significant at the .05 level.
• in 8% of the samples the opposite sex difference was found, however this was only significant in the South African Zulu sample, possibly because physical tasks (building houses) are considered to be women's work.
• in 22% of the samples both sexes placed a high value on this mate characteristic.

Age Differences - in all 37 samples, males preferred mates who were younger.

• The mean age difference preferred by males was 2.66 years and the mean age at which males prefer to marry is 27.49 years. Therefore this suggests an ideal age for females of 24.83 years, which is closer to peak female fertility than peak female reproductive value. 
• In all samples females preferred males who were older - mean age difference 2.42 years and mean preferred age to marry 25.39 years, therefore ideal mate is 28.81.

Age difference (continued)

• in cultures where polygyny was substantial (Nigeria and Zambia) male preference for being older was at its largest, 6.45 and 7.38 years respectively.

Good looks - in all 37 samples males rated 'good looks' in their mate more than females did,

• in 92% of all the sampls this was significant at the .05 level.

Chastity - samples varied tremendously in the value placed on this characteristic.

• in 62% of the samples males preferred chastity in their mates whereas there was no significance in the remanining samples. Chastity was reviewed as 'irrelevant or unimportant' in most Western European samples.

A validity check

Behavioural data shows that self-reported preferences accurately reflected actual preferences. The actual mean age difference was found to be 2.99 years for men and 3.03 for women, compared with mean preferred differences of 2.66 and 3.42 respectively.

Behavioural data shows that mate preferences accurately reflected actual mating decisions. The actual mean age for marriage was 28.2 years for men and 25.3 for women, compared to 27.5 and 25.4 respectively.

Five evolution-based predictions received support from the data

1) Females valued the financial capacity of potential mates more than males, supporting the hypothesis that women seek cues related to resources.

2) Females valied ambition and industriousness more than males. This again supported the hypothesis that women seek cues related to resources.

3) Males valued physical attractiveness and relative youth more than females, supporting the hypothesis that males seek cues related to high reproductive capacity. The fact that males sought partners around the age of 25 suggests they look for cues related to fertility rather than reproductive value. However, the fact that the age preference was several years beyond peak fertility suggests that other non-evolutioanry factors may also be involved.

4) Females preferred older mates. This was not predicted at the outset but supports the importance of resources because older men would probably have greater resources.

5) Males valued chastity more than females, supporting the importance of paternity probablity. This conclusion was only demonstrated in a small number of samples.

In general these findings show 1) evolutionary explanations of sex differences in human mate preferences are appropriate, 2) that mate preferencesare not just explained in terms of female choosiness since both males and females showed preferences and 3) that cultural influences matter as there were cultural differences.

Method - Questionnaire

strengths-

• it can be easily repeated so data can be collected from large numbers of people relatively cheaply and quickly.
• Respondents may feel more willing to reveal personal/confidential information when writing their own answers than in an interview.

Weakness'-

• Answers may not be truthful due to leading questions and the social desirability bias (misrepresentation)
• the sample may be biased because maybe only certain types of people fill in questionnaires such as literate individuals who are willing to spend time filling in a questionnaire and returning it.

Sampling - study involved a very wide range of cultural groups

strengths-

• observed trends were well supported.
• able to generalise as there was a range of ages, cultures, education etc

Weakness'-

• 'cultures' were dominated by 'Westernised, industrialised nations' (26 of 37) and these samples contributed to 7,749 of the whole sample (biased)
• Buss acknowledged that rural and less-educated people were under-represented

Buss reliability-
Questionnaires given once to participants, the test-retest method could have been used to check reliability of the answers, also people could perceive questions differently etc

Ethics-
Informed consent and confidentiality, the ethical 'cost' seem low and the 'benefits' of greater scientific understanding high.

Validity-
Extensive efforts were made to ensure that all respondents understood the questions (translated to local languages, and word adapted to match local customs and read to those who could not read) however, this means the questions could have been taken out of context..