Psychologists are routinely publishing board claims about human behaviour that are based on biased and ethnocentric samples. Many of these samples are based on WEIRD (Western, Educated, Industralised, Rich and Democratic) societies and the conclusions assume that there is little variation across human populations and that the conclusions from social science research can be generalised to all.
I often give my students an article from ‘The Psychologist’ called ‘The use and abuse of students participants‘ to read to help them consider the implications, both methodologically and in the conclusions that are made, of using limited samples in psychological research. Helping students appreciate this is an important factor in improving their evaluative, synoptic and critical thinking skills.
Henrich et al. (2010) considered that there were many ‘certainties’ social science took for granted when explaining behaviour. They suggested that members of WEIRD societies, including young children, are among the least representative populations one could ?nd for generalising about humans and that we need to be less cavalier in addressing questions of human nature on the basis of data drawn from this particularly thin, and rather unusual, slice of humanity (Henrich et al., 2010).
In his review he looks at measures of visual perception, fairness, cooperation, spatial reasoning, categorisation, moral reasoning and IQ (among others) and his findings suggest that members of WEIRD societies, including young children, are among the least representative populations a scientist could use for generalising about behaviour.
One example taken from the study is that of the visual illusion the ‘Muller-Lyer’ (see fig.1 from Henrich). He reviews Segall et al. (1966) who manipulated the length of the two lines in the Muller-Lyer illusion (Fig. 1) and estimated the magnitude of the illusion by determining the approxi- mate point at which the two lines were perceived as being of the same length. Figure 2 shows the results from 16 societies, including 14 small-scale societies. The vertical axis gives the “point of subjective equality” (PSE), which measures the extent to which segment “a” must be longer than segment “b” before the two segments are judged equal in length. PSE measures the strength of the illusion.
The results show substantial differences among populations, with American undergraduates anchoring the extreme end of the distribution, followed by the South African-European sample from Johannesburg. On average, the undergraduates required that line “a” be about a fifth longer than line “b” before the two segments were perceived as equal. At the other end, the San foragers of the Kalahari were unaffected by the so-called illusion (it is not an illusion for them). While the San’s PSE value cannot be distinguished from zero, the American undergraduates’ PSE value is significantly different from all the other societies studied.
The full article, including the commentary is worth a read, and an excellent article to stretch top-end students who want to gain more depth of knowledge of the issues surrounding biases in samples and more sophisticated debates surrounding generalising results from studies.
There is also a fun little infographic for your classroom wall or to give to students for them to consider these issues in a more accessible way and could act as a good starting point for discussion on populations in studies and the biases that these raise in generalising the results. Getting students considering issues like this must increase their awareness of the bigger debates and help them with synoptic elements of the course.
Do you have any activities that you use to raise awareness of biases in participant samples? Does it matter that a large proportion of research considers WEIRD participants?
Henrich, J., Heine, S.J., & Norenzayan, A. (2010). The weirdest people in the world? Behavioral and Brain Sciences, 33, 61-135.