Ethan Watters in the Pacific Standard:
The human brain is genetically comparable around the globe, it was agreed, so human hardwiring for much behavior, perception, and cognition should be similarly universal. No need, in that case, to look beyond the convenient population of undergraduates for test subjects. A 2008 survey of the top six psychology journals dramatically shows how common that assumption was: more than 96 percent of the subjects tested in psychological studies from 2003 to 2007 were Westerners—with nearly 70 percent from the United States alone.
The article explains that by many psychological criteria, Westerners in general (and Americans in particular) are not representative of humanity, but instead exist near an extreme. This means that, looking back, a hell of a lot of studies have suffered from severe selection bias.
The entire article is interesting, but this passage caught my eye:
As Norenzayan sees it, the last few generations of psychologists have suffered from “physics envy,” and they need to get over it. The job, experimental psychologists often assumed, was to push past the content of people’s thoughts and see the underlying universal hardware at work. “This is a deeply flawed way of studying human nature,” Norenzayan told me, “because the content of our thoughts and their process are intertwined.” In other words, if human cognition is shaped by cultural ideas and behavior, it can’t be studied without taking into account what those ideas and behaviors are and how they are different from place to place.
To me this doesn’t necessarily mean that there is no “underlying universal hardware”; it just means that the hardware layer is further down than we thought.