Behavior Genetics of the Horse (Equus caballus) - Genetics and the Behavior of Domestic Animals - page 262

and Gong, 1973 ). The expansion of skin over the dome-like outgrowth corre-
sponds to the position of the posterior parietal whorl—this much we know
for sure. Interest by geneticists and neuroscientists in recent years focused on
associations between hair whorl direction, language dominance, and handed-
ness. The results of these studies are not mutually conclusive. Some investi-
gators found a significant association between scalp-hair whorl direction and
handedness ( Beaton and Mellor, 2007 ; Klar, 2003 ; Friedman et al., 1952 ),
others have questioned these findings ( Jansen et al., 2007; Weber et al.,
2006 ). Handedness has long been considered to result from both genetic and
environmental factors ( Corballis, 1997; Levy and Nagylaki, 1972; McManus,
1985 ). Klar (2003) was the first to report an association between handedness
and scalp-hair whorl rotation, and proposed the role of a single gene control-
ling both handedness and hair whorl orientation. Other investigators strongly
argued against a common genetic basis of handedness or language lateraliza-
tion with scalp-hair whorl direction ( Jansen et al., 2007 ), and in a more
recent report Klar (2009) found that handedness and scalp-hair whorl rotation
is random and not genetically determined.
Finding a relationship between hair whorls and behavior in humans is
complicated by the difficulty of determining hair rotation in people with
long or curly hair. In addition, most studies only focus on whorl rotation
(e.g., clockwise, counter-clockwise) and behavior—not whorl placement and
behavior. Only Schmidt et al. (2008) looked at side placement and whorl
rotation. The study revealed a significant association between whorls located
on the center of the scalp and counter-clockwise rotation in non-right handed
children. None of these studies examined a possible association between
handedness and language dominance in people with two or more hair
whorls.
Hair Whorls in Cattle
In 1993, we noticed that hair whorl patterns in cattle were similar to those in
horses. The second author (Temple Grandin) suggested that we aim our
research toward cattle. We could study large numbers of cattle with similar
genetics and experiences, a task more difficult with horses. Our first study
revealed a significant association between the height of the whorl and behav-
ioral agitation in cattle during restraint ( Grandin et al., 1995 ; see Chapter 4).
We studied behavior of 1500 cattle while restrained in a squeeze chute
during routine handling for husbandry procedures. We rated the behavior on
a scale from one to four (a cow rated “one” was calm, with no movement; a
cow rated “four” was violently and continuously shaking the squeeze chute).
Many of the cattle given a rating of four reared up in the squeeze chute,
vocalized, and violently threw their heads during restraint. Cattle with hair
whorls above the eyes were significantly more agitated during restraint when
compared to cattle with middle or low hair whorls. The next study revealed