<P> It has been proposed that negative, withdrawal - associated emotions are processed predominantly by the right hemisphere, whereas the left hemisphere is largely responsible for processing positive, approach - related emotions . This has been called the "laterality - valence hypothesis". </P> <P> One sub-set of laterality in animals is limb dominance . Preferential limb use for specific tasks has been shown in species including chimpanzees, mice, bats, wallabies, parrots, chickens and toads . </P> <P> Another form of laterality is hemispheric dominance for processing conspecific vocalizations, reported for chimpanzees, sea lions, dogs, zebra finches and Bengalese finches . </P> <P> Domestic horses (Equus ferus caballus) exhibit laterality in at least two areas of neural organization, i.e. sensory and motor . In thoroughbreds, the strength of motor laterality increases with age . Horses under 4 years old have a preference to initially use the right nostril during olfaction . Along with olfaction, French horses have an eye laterality when looking at novel objects . There is a correlation between their score on an emotional index and eye preference; horses with higher emotionality are more likely to look with their left eye . The less emotive French saddlebreds glance at novel objects using the right eye, however, this tendency is absent in the trotters, although the emotive index is the same for both breeds . Racehorses exhibit laterality in stride patterns as well . They use their preferred stride pattern at all times whether racing or not, unless they are forced to change it while turning, injured, or fatigued . </P>

Handedness the preference for using one hand over the other