Assessing the relative aversiveness of two stimuli: single sheep in the arena test
In the test described here, sheep are exposed to a situation of conflict between the motivation to approach other sheep and the motivation to avoid a human handler. The distance that the test sheep keep from the handler is a reflection of the relative aversiveness of this handler to
the sheep. The test itself requires only a minimum amount of handling and gives the test animals the opportunity to choose their distance from the aversive stimulus, thereby reducing stress during the test itself. The two aversive stimuli chosen for comparison were a human handler facing toward
the test arena (more aversive) or the same handler turning his back to the arena (less aversive). Ten Scottish Blackface sheep were tested individually a total of ten times, five times with each of the two stimuli in alternate tests. During the first two tests, nine of the sheep stayed further
away when the human was facing toward the arena, compared to when he was facing away; this shows that the test is able to discriminate differences in aversiveness between two stimuli as perceived by individual sheep. This difference was not apparent in the following eight tests, probably because
of the fact that the stimuli were not reinforced during the tests. Because the test is concerned with sheep's reaction to a stimulus (eg handler), the procedure associated with the stimulus itself (eg shearing, castration) does not have to be repeated in the test, which means that this method
is ideal for studying procedures which cause distress to the animals or which are difficult to repeat.