The nature of human perception is a topic fraught with complexity and shared mystery.
A landmark study conducted in 1956 by social scientists Donald Campbell and Melville Herskovits from Northwestern University, along with Marshall Segall from Syracuse University, set out to explore whether individuals perceive the world identically across different cultures.
The researchers traversed various societies, examining perceptions in diverse settings, including a gold mine in Johannesburg, forager communities in the Kalahari Desert, and a college campus in Evanston, Illinois.
Central to their investigation was the Müller-Lyer illusion, a well-known visual trick where identical horizontal lines appear unequal due to arrowheads pointing inward or outward.
In America, the line with inward-facing arrows typically seems longer, but the researchers sought to determine if this held true in other cultures.
Upon concluding their study in 1961, the results were startling: not every culture succumbed to this illusion with the same intensity.
While American students predominantly perceived the upper line as longer, the Zulu pastoralists of South Africa showed a diminished response, and the San foragers of the Kalahari interpreted the lines as equal, seemingly unaffected by the illusion.
These findings prompted profound questions about the universality of human perception.
As psychology aims to unveil fundamental truths about the human mind, concerns have been raised regarding the generalizability of findings predominantly based on narrow, WEIRD test groups—Western, Educated, Industrialized, Rich, and Democratic populations.
This focus has spurred a wave of researchers to expand their studies beyond familiar subjects to gain a broader understanding of human psychology.
Nevertheless, the question remains: which psychological principles differ across groups, and which ones underscore a shared human experience?
The initial findings sparked intrigue and debate, leading to the Cultural Byproduct Hypothesis, which posits that perceptions like the Müller-Lyer illusion arise from the structured environments in which people are raised.
According to this view, exposure to straight lines and angles seen in urban settings shapes how individuals interpret visual illusions.
However, the authors of a new paper contend otherwise, revisiting over a century of perception research with evidence suggesting that such illusions and many perceptual aspects may be deeply seated within our biology, rather than merely cultural artifacts.
They raise several alarm bells regarding the Cultural Byproduct Hypothesis, citing the fact that many nonhuman animals, including guppies, horses, and monkeys, are also susceptible to the Müller-Lyer illusion.
These animals perceive the illusion in much the same way as humans, prompting skepticism about the idea that culture shapes perception exclusively.
Furthermore, the Müller-Lyer illusion’s effectiveness does not hinge solely on straight lines; alternative versions of the illusion exist that utilize curves, dots, or even human faces, challenging the initial assumption tied to carpentry influences.
An even more compelling insight comes from recent surgical interventions in North India, where children with congenital cataracts received corrective surgery.
Astoundingly, those children, having never experienced visual stimuli prior to the surgery, exhibited the same inclination toward the Müller-Lyer illusion mere hours after the procedure.
This suggests that the mechanisms underlying such perceptions might transcend individual cultural exposure, hinting at a more universal biological framework.
Although the initial cross-cultural studies found variations in responses to the Müller-Lyer illusion, past research reveals inconsistencies, with some populations unexpectedly demonstrating stronger effects than others.
For instance, in earlier studies from the 20th century, one Indian jungle-dwelling group exhibited more pronounced illusions compared to pastoralists from the same region, while a rural South African community showed stronger illusions than urban counterparts.
The original researchers’ findings also contained notable contradictions, such as miners subjected to a highly structured environment displaying minimal illusion effects, contradicting the Culture Byproduct Hypothesis.
A closer examination of these studies exposes potential methodological flaws, as translation issues and experimenter biases creep into the research.
Experimenters’ expectations about how respondents should answer could skew results, with some admitting to feeling the impulse to correct respondents when their answers deviated from anticipated outcomes.
In some cases, data demonstrating strong illusions may have been omitted, obscuring findings that could have contradicted the prevailing narrative.
As we reflect on these insights, it becomes evident that while diversifying psychological research to capture the breadth of human experience is imperative, certain perceptual experiences may indeed be universal.
By challenging established assumptions about cultural influences on perception, researchers can deepen our understanding of the intricate workings of the human mind.
Ultimately, while cultural context undoubtedly shapes various aspects of our lives, the core of our perceptual system may reveal shared characteristics among all humans, regardless of background or upbringing.
image source from：slate
