Preference for milking parlor side was compared to facial hair whorl patterns on the forehead to determine if there was a relationship. Anecdotal reports from horse trainers indicate the hair whorl patterns on the forehead are correlated with handedness. Some horses have a very strong tendency to perform better when turning towards their preferred side. Trainers have also observed that side preference is weak in some horses and strong in others. Since hair whorls form in the fetus during the same time the brain forms, our hypothesis is that relationships between handedness and hair whorls may be similar in many mammals.
Dairy cows were used as subjects because large numbers of cows could be monitored for milking parlor side preference with a computerized identification system. Side preference data was collected at a large commercial dairy on 1379 Holstein cows for 90 milkings. They were milked three times daily in a Surge Double 24 stall parallel parlor. Both sides of the parlor were identical.
Fifty-three percent (741 head) had no side preference (P<.05; two-sided Z test). Two percent (31 head) had a very strong side preference and they chose the same side of the parlor almost 100% of the time. Eighteen of these cows chose the left side and 13 cows chose the right side (P<.05; one-sided Z test). The side preference of these 31 cows were very strong because the milkers tend to discourage side preferences by chasing cows into vacant stalls.
Twenty-seven percent (378 head) with a single hair whorl in the middle of the forehead had strong side preference (P<.03; Chi Square). Forty-five cows with two hair whorls on the forehead were significantly less sided than the rest of the population (P<.02; Chi Square). This confirms anecdotal observations from horse trainers that horses with two hair whorls are less handed.
The study of hair whorls may possible provide insight into both behavioural and neurological development.
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