Two Key Studies of Evolutionary Explanations for Behaviour: Buss et al. (1989) & Clarke & Hatfield (1989) (SL IB Psychology)

Aim: To investigate evolutionary explanations for partner preferences using a cross-cultural large-scale survey

Participants: A total of 10,047 participants from 33 countries and 5 islands aged from 19.96 years to 28.71 years (mean age = 23.05 years). A range of sampling techniques were used including:

• systematic sampling (e.g. in Venezuela every 5th household in one neighbourhood was sampled);
• self-selecting sampling (e.g. in West Germany participants were obtained via a newspaper advert);
• opportunity sampling (e.g. high school students who attended 3 schools in New Zealand)

Procedure: Self-reports were conducted either via a written questionnaire or having questions read aloud by a researcher (some rural populations were unable to read or write). The questions dealt with attitudes towards partner preference e.g. preferred age of partner, how important chastity or fidelity was; the importance of marriage and children. 
The participants were also asked to rank a list of characteristics that they would look for in a partner.

Results: 

• 97% of the females in the sample valued ‘good financial prospects’ which (apart from Spain) was higher than the males in the sample
• 92% of the females valued ‘ambition and industriousness’ more than men (but not in Spain, Columbia or the Zulu sample)
• Males across all of the sample stated a preference for a younger partner with an average preferred age difference of 2.66 years; females showed a preference for an older partner and to be married at a younger age than males preferred (25.39 years as opposed to 27.49 years)
• Males across the sample rated ‘good looks’ higher than females did and 62% of males rated chastity as a desirable quality in a partner (this was particularly true in China, Iran and India)
• The majority of Western, individualistic samples thought that chastity was ‘irrelevant’

Conclusion: Females value financial security and an older partner more than males do; males value physical appearance and youth more than females do; both males and females appear to value partners who will give them a selective advantage in terms of reproduction; there are distinct cultural differences in partner preference

Evaluation of Buss (1989)

Strengths

• The use of a large sample representing so many countries and cultures guarantees good external validity which means that the results can be easily generalised
• The questionnaires for each country were translated using three translators (to translate from English; to translate to English; to resolve discrepancies and ensure all terms were gender neutral) which increases reliability as it ensures consistency across the measure

Weaknesses

• The limited age range of the sample does not represent the views and attitudes of older people so it is only partially insightful
• Some of the responses may have been due to social desirability bias, particularly in cultures where men must appear to be ‘macho’ i.e. the responses may not actually match the true feelings of all of the participants, which decreases the validity of the findings

Key terms:

• Evolutionary
• Partner preference
• Selective advantage 

Aim: To investigate the difference in choosiness between males and females when sex is offered by a stranger

Participants: An opportunity sample of 48 females and 48 males from Florida University. The study was conducted in 1978 and again in 1982 using the same number and gender balance of participants

Procedure: The researchers recruited 5 female and 4 male confederate who were similar in age to the participants (around 22 years old) and who were deemed to be attractive. Each confederate was placed at one of 5 predetermined locations around the university campus. Their instructions were to select a student of the opposite sex (whom they found genuinely attractive and at random ask them one of the following questions:

• “I’ve watched you around campus, I find you very attractive” followed by either:
  • “Would you go out with me tonight?” or
  • “Would you come over to my apartment tonight?” or
  • “Would you go to bed with me tonight?”

Results: 

• The first request (“would you go out with me tonight?”) resulted in around 50% ‘yes’ responses from both males and females
• The second request (“would you come over to my apartment”) resulted in a ‘yes’ response from 69% of the males but only 0-6% of the females across both studies
• The third request (“would you go to bed with me”) resulted in a ‘yes’ response from 72% of the males across both studies but 0% of the females across both studies responded with a ‘yes’
• Some of the females who were asked this third question responded with comments such as ‘What is wrong with you?’, ‘Leave me alone!’ 

Conclusion: There does appear to be a difference in choosiness when it comes to being propositioned sexually, with females demonstrating much more caution than males 

Evaluation of Clarke & Hatfield (1989)

Strengths

• The use of a field experiment using naive participants increases the ecological validity of the study
• The agreement in the responses of both male and female participants across both increases the study’s reliability as it shows consistency over time 

Weaknesses

• The complete absence of female ‘yes’ responses to having sex with a stranger may have more to do with women being conditioned to fear predatory males than from an evolutionary mechanism which favours choosiness
• There are some ethical issues with this study: the confederates were able to act on any ‘yes’ responses they received which could have put some of them in a difficult position plus they may have embarrassed some of the participants with their request for sex

Key terms:

• Choosiness
• Confederates
• Naïve participants