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during childhood, as is shown in the present study. Hence,
this trait is rather likely to have an important genetic basis.
Our research design cannot exclude the possible role of
parental education on native immigrants, however, many
studies have found minimal evidence for the role of parental
education on personality development (Dunn & Plomin,
1991; Krueger, 2000; Turkheimer, 2000).
One framework that tries to investigate human behaviour
is the gene–environment interaction framework (O’Connor
et al., 2003; Plomin & Crabbe, 2000; Plomin et al., 1994;
Reiss et al., 2000). Penke highlighted the role of gene–
environment interactions in the study of personality (Penke
et al., 2007), that is the interactions between genetic factors
and individual flexible responses to the environment, or
phenotypic plasticity (West-Eberhard, 2003). For openness
to experience, the gene–environment interaction seems to be
the paradigm that better explains our results. Indeed, the
difference between native immigrants and native original
islanders suggests a genetic influence does exist, because
these two groups of subjects have shared the same
environment since birth, while they are likely to come from
relatively different gene pools. On the other hand, an
influence of early experience and environment on this trait
matches with the differences found in the comparisons
between native and non-native islanders; however, the fact
that native immigrants do not differ from adapted
immigrants and mainlanders, does not support this con-
clusion. Similarly, conflicting results are found for con-
scientiousness. Thus, we suggest that for these two traits a
genetic influence exists, but it might be interacting with the
effects of early experience and the individual flexible
response to the environment.
Personality Gene Flow hypothesis
We propose the Personality Gene Flow hypothesis to explain
personality differences found in small isolated populations.
The Personality Gene Flow hypothesis suggests that it is the
combined effect of a reduced and random immigration flow
associated with a strong and non-random emigration flow
that can rapidly produce personality differences in a small
population.
Our study suggested that Egadi emigrant islanders scored
higher on extraversion and openness to experience in
comparison to sedentary people who never left the islands.
More extravert and open to experience individuals seem to
have a higher propensity to emigrate: this interpretation is
supported by the results of molecular genetic studies,
affirming a correlation between extraversion and novelty-
seeking (Benjamin et al., 1996) and by results of population
studies showing that novelty seekers tend to emigrate more
(Chen, Burton, Greenberger, & Dmitrieva, 1999). If these
traits were influenced by specific alleles, then it could be that
they were progressively removed from the island population
gene pool.
A possible criticism is that emigrants could have changed
their traits after emigrating, rather than their traits having a
causal role in their emigration. However, we have confirmed
above that extraversion is a very stable endogenous
Copyright # 2010 John Wiley & Sons, Ltd.
Personality differences in small island populations 61
personality trait, and furthermore it seems that openness
to experience is also unlikely to change in adulthood. Given
that mainlanders who immigrated to the islands conserved
their original personality, we deduce that island emigrants
should also retain their traits in the new environment.
Rebollo and Broomsma (Rebollo & Boomsma, 2007)
suggested Inbreeding Depression as an alternative expla-
nation for low extraversion and openess to experience in
islanders, but as Penke (Penke et al., 2007) noted, it is
especially striking that inbreeding depression should
exclusively affect traits that can be directly associated with
migration tendencies and active niche selection (i.e. open-
ness to experience and extraversion). The worldwide
distribution of DRD4 polymorphisms suggests that carriers
of the allele, which has been associated with high sensation
seeking, are more likely to migrate (Chen et al., 1999). In our
study, the most extravert native islanders are found within
those who emigrated. The Inbreeding Depression hypoth-
esis, contrary to the Personality Gene Flow hypothesis, does
not predict different allele frequencies within a small
population. A direct genetic study of allele frequencies in the
island population will clarify this question.
Penke and colleagues assess three evolutionary genetic
mechanisms that could explain genetic variance in person-
ality within large populations (selective neutrality, mutation–
selection balance and balancing selection). Based on
evolutionary genetic theory and empirical results from
behaviour genetics and personality psychology, they suggest
that mutation–selection balance seems best able to explain
genetic variance in intelligence, while balancing selection by
environmental heterogeneity seems best able to explain
genetic variance in personality traits (Penke et al., 2007).
Camperio Ciani et al. suggested that the alleles influencing
personality might also vary their frequency between
populations due to emigration and consequent gene flow
as an additional genetic mechanism in small populations
(Camperio Ciani et al., 2007). This hypothesis would be
consistent with the interactionist perspective (Barrick &
Mount, 1991; Hettema & Kenrick, 1992; Tett, Jackson, &
Rothstein, 1991) that proposes that people with particular
personalities actively look for the best fitting environment
and are ready to displace themselves to find it, hence
removing their alleles from the original population. In a
prospective study on Finnish people and another study on US
citizens who migrated within or between states, Jokela found
that extraversion and openness to experience are both strong
predictors of migration propensity (Jokela, 2009; Jokela,
Elovainio, Kivima¨ki, & Keltikangas-Ja¨rvinen, 2008). We
suggest that extraverted and open to experience subjects tend
to leave the confined environment of the island because it
offers few perspectives and opportunities, thus decreasing
the frequency of alleles influencing extraversion. At present,
however, we can only speculate as to what induces open to
experience and extravert people to leave the islands and
future longitudinal prospective studies are needed in order to
answer this point.
Fisher’s classic work on the effect of gene flow on a small
population shows that it is not necessary for immigration to
be completely absent in order to progressively produce
Eur. J. Pers. 25: 53–64 (2011)
DOI: 10.1002/per