Abstract
This
study compares the behaviour of the mule (Equus asinus x Equus
caballus) with that of its parent species to assess the effects of
hybridization on cognition. Six mules, six ponies (E. caballus) and six
donkeys (E. asinus) were given a two choice visual discrimination
learning task. Each session consisted of 12 trials and pass level was
reached when subjects chose the correct stimulus for at least 9 out of
the 12 trials in three consecutive sessions. A record was made of how
many pairs each subject learnt over 25 sessions. The mules' performance
was significantly better than that of either of the parent species
(Kruskal-Wallis: H(x) = 8.11, P = 0.017). They were also the only group
to learn enough pairs to be able to show a successive reduction in the
number of sessions required to reach criterion level. This study
provides the first empirical evidence that the improved characteristics
of mules may be extended from physical attributes to cognitive function.
