underlying mechanisms. For instance, insulin- like growth factors are believed to infl u- ence body growth at the same time as infl uencing neural growth. It is also assumed that
environmental factors, such as maternal smoking during pregnancy, may also explain part of the association between height and cognition. In comparing twins, Black, Dev-
ereux, and Salvanes 2007 found a connection between birthweight on the one hand, and IQ test scores and height in late adolescence on the other, again underscoring the
importance of the intrauterine environment for adult height as well as cognitive ability.
Based on the basic presumption that an individual’s endowment affects both cogni- tive and height development, Case and Paxson 2008a postulate that cognitive ability
and the onset of the growth spurt in adolescence should be correlated, which is indeed what they fi nd in their data.
5
For boys, cognitive test scores at age 11 are positively associated with height gain in the subsequent fi ve years and negatively associated with
height gain from age 16 onwards. Though boys entering their growth spurt late may catch up in height, they will still lag behind cognitively as the relative position, when
it comes to intelligence, is rather fi rmly established early in life. This fact may explain why height in adolescence is a stronger predictor of adult earnings than adult height.
Hence, the association between height and cognition has primarily been attributed to common underlying factors, and not to any causal relation between the two. From
this respect, cognitive ability should be regarded as a control variable when estimating the height premium.
6
B. Noncognitive Skills
Noncognitive skills are commonly referred to in the literature as personal character traits such as motivation, persistence, charm, and leadership abilities. In the labor eco-
nomics literature, the term essentially describes a complexity of personal characteris- tics connected to the aspects of one’s persona apart from pure cognition, potentially
affecting productivity.
It seems uncontroversial to presume that noncognitive abilities are valued by em- ployers, co- workers and potential customers in almost any kind of occupation. Indeed,
a recent body of research has shown that noncognitive skills are important predictors of various adult socioeconomic outcomes. See, for example, Heckman and Rubin-
stein 2001; Heckman, Stixrud, and Urzua 2006; Borghans et al. 2008; Lindqvist and Vestman 2011. If height in adolescence is related to the development of noncognitive
skills, it is therefore straightforward to formulate a hypothesis where part of the height premium refl ects the returns to noncognitive skills, as in Persico, Postlewaite, and
Silverman 2004.
Whereas the linkage between cognition and height has been attributed mainly to biological processes early in life, the connection between noncognitive skills and
5. Endowments are defi ned as environmental conditions such as health and nutrition, biological factors, genetic factors, and gene- environment interactions.
6. Though we will adopt this consensus view in our analyses, we note that there may be alternative mecha- nisms operating as well. For instance, one cannot completely rule out the possibility that the development of
cognitive skill may also be infl uenced by a person’s height if taller children are subjected to greater intellec- tual challenges, expectations and opportunities. Moreover, Cunha and Heckman 2008 argue that cognitive
and noncognitive skills may well be complementary in the sense that they promote the acquisition of each other, yielding interdependence between the two.
height has commonly been attributed to social processes, in which taller individuals are treated differently than shorter ones. For instance, a common theory in social psy-
chology postulates that taller people are more successful for reasons of interpersonal dominance. See, for example, Frieze, Olson, and Good 1990. It then follows that if
being tall is an advantage in different competitive situations, this may facilitate the building of self- esteem and social skills in relatively taller individuals. Moreover,
children may face different expectations from parents, teachers, other adults, and peers depending on their height. If children react to expectations by complying, such
expectations may become self- fulfi lling. For instance, if taller children are perceived and treated as being more mature, when it comes to temperance, responsibility, and
planning, they may well be fostered into developing such traits.
As discussed by Persico, Postlewaite, and Silverman 2004, another explanation emphasizes the role of self- esteem, but from a different perspective. Here, the height
premium stems from the greater self- image that is achieved through a comparison with a socially determined notion of ideal height. It is then argued that a greater self-
image leads to higher achievement through noncognitive factors such as perseverance and social skills. This is related to the fi ndings of Persico, Postlewaite, and Silver-
man 2004, where teen height is found to explain a large part of the relationship between height and earnings, and where the premium is reduced when controlling
for participation in high school sports and clubs. The latter fi nding causes the authors to conclude that such participation shapes noncognitive skills. This is well in line with
Kuhn and Weinberger 2005 who, controlling for cognitive ability, found that self- perceived leadership skills as well as exposure to leadership positions in high school,
was positively related to earnings later in life. Moreover, Lindqvist 2012 fi nds that height is positively related to leadership skills, as measured at the Swedish enlistment.
In sum, existing explanations for the association between height and noncognitive skills in general focus on how height may affect the development of noncognitive
skills, rather than both being determined by some third, underlying factor. From these respects, noncognitive skill is a mediating factor in explaining the height premium.
7
C. Muscular Strength
