Intended for healthcare professionals


IQ in childhood and vegetarianism in adulthood: 1970 British cohort study

BMJ 2007; 334 doi: (Published 01 February 2007) Cite this as: BMJ 2007;334:245

Non-conformity: the hidden driver behind the positive relationship between IQ and vegetarianism?

As the authors already point out, the link between childhood IQ and
vegetarianism in later life [1] is perhaps not driven by a causal chain of
mechanisms related to health. We have some data supporting a different
point of view. As the frequency of vegetarians in the population is
extremely low (in their data only 4.5 %), vegetarianism could be
considered as a type of non-conformist behavior. We argue below that
acting in a non-conformist way is less threatening for highly than for
less intelligent people. Therefore, we predict a positive relationship
between non-conformist behavior and general intelligence. To give support
to our argument, we show another similar relationship between general
intelligence and another (more general) type of non-conformity, namely the
‘need for uniqueness’.

Non-conformist behavior may threaten the belongingness to a social
group, or has the potential of enlarging the psychological distance from
others. People who deviate from the group are more likely to be punished,
ridiculed, or even rejected by other group members [2]. In that light a
mechanism such as social pain (i.e. “the distressing experience arising
from the perception of actual or potential psychological distance from
close others or a social group.”[3]) that prevents someone from social
isolation situations appears as a functional characteristic. After all, in
human’s natural environment acquiring resources in isolation is more
difficult than in groups [4]. Prospects for isolated people are rather
grim. Therefore, the need to belong may reduce people’s inclination to act
in a non-conformist way, through the motivation to secure the acquisition
of resources. However, general intelligence is a strong predictor of
future resources [5, 6]. So, the more intelligent someone is, the less
dependent this person is on the group to acquire resources. This means
that highly intelligent people can afford more non-conformist behavior
because of their capacity to secure resources in isolation. Therefore, we
propose that as general intelligence increases the need to conform to
group norms decreases.

To test this hypothesis, we measured the ‘need for uniqueness’ [7]
and a raven progressive matrices measure of general intelligence [8]. The
need for uniqueness is measured by a scale with statements all indicating
a low level of conformity (e.g. “I often dress unconventionally even when
it’s likely to offend others.” and “When a style of clothing I own becomes
too commonplace, I usually quit wearing it.”). Our study (32 men, 14
women) showed a significant positive relationship between the need for
uniqueness and general intelligence (r = .35, p = .017). This relationship
was similar for both men (r = .32) and women (r = .46).

Summarized, we explain the IQ-vegeterianism findings from a
psychological point of view and show converging evidence. Moreover, we
generalize these findings to a positive relationship between general
intelligence and non-conformity in general. Our data give support to this
view as a more general type of non-conformist behavior than vegetarianism
(the need for uniqueness) is similarly related to general intelligence.

[1] Gale CR, Deary IJ, Schoon I, & Batty, D. IQ in childhood and
vegetarianism in adulthood: 1970 British cohort study. BMJ

[2] Griskevicius V, Goldstein NJ, Mortensen CR, Cialdini RB, Kenrick
DT. Going along vs. going alone: when fundamental motives facilitate
strategic (non)conformity. J Pers Soc Psych 2006;91: 281-294.

[3] Eisenberger NI, Lieberman MD. Why rejection hurts: a comon neural
alarm system for physical and social pain. Trends in Cognitive Sciences
2004;8: 294-300.

[4] Baumeister RF, Leary ML. The need to belong: Desire for
interpersonal attachments as a fundamental human motivation. Psychol Bull
1995; 117: 497-529.

[5] Gottfredson LS. Intelligence: Is it the epidemiologists’ elusive
“fundamental cause” of social class inequalities in health? J Pers Soc
Psych 2004; 86: 174-199.

[6] Kanazawa S. Why beautiful people are more intelligent.
Intelligence 2004; 32: 227-243.

[7] Tian KT, McKenzie K. The long-term predictive validity of the
consumers' need for uniqueness scale. Journal of Consumer Psychology 2001;
10: 171-193.

[8] Millet K, Dewitte S. Altruistic behavior as a costly signal of
general intelligence. Journal of Research in Personality in press.

Competing interests:
None declared

Competing interests: No competing interests

23 January 2007
Kobe Millet
PhD student, Department of Marketing and Organization Studies, KULeuven
Siegfried Dewitte
Naamsestraat 69 3000 Leuven