Are laterality effects present in novel object responses of calves?

Abstract

Many animals exhibit preferential viewing of fear-inducing stimuli with their left eyes, reflecting cerebral lateralisation in emotion processing. In novel object tests, often used to assess fear, spatial positioning of the objects relative to the animal can vary. This study aimed to investigate visual lateralisation in calves’ responses in novel object tests, evaluate its effectiveness as an indicator of fear, and examine how initial monocular presentation of fear-inducing stimuli impacts fear responses and their reliability. Thirty-six dairy calves underwent a novel object test at six weeks of age and a second at seven weeks of age using a different object, with behavioural responses towards the novel objects recorded. There was no correlation in latency to first contact with novel objects between tests. On average, proportion of time viewing novel objects with the left eye did not significantly differ from the right eye across the two tests, nor did it correlate with latency to first contact with novel objects. The probability of contact with novel objects and latency to first contact with novel objects did not differ based on initial eye with which novel objects were seen, although among calves that showed an avoidance response, they were less likely to have used the right eye for viewing than either the left eye or both eyes just before the locomotor response. Overall, fear responses in calves during repeated novel object tests were inconsistent, and this inconsistency was not clearly attributable to the random presentation of objects to different visual fields. This may suggest either a lack of cerebral lateralisation in fear processing at this age or that alternative methods may be needed to more accurately assess it.