Anticipatory behaviour over prolonged durations between conditioned and unconditioned stimuli in lambs (#10)
Most studies of anticipatory behaviours in animals fail to show how such behaviours are affected by an increase in duration between the conditioned stimuli (CS) and unconditioned stimuli (US), but only present results when looking at the CS-US duration as a whole. The aim of this study was to investigate how anticipatory behaviours in lambs vary over time. Twelve pairs of male lambs experienced a gradual increase between CS-US (green light and food reward, respectively) over nine days reaching three minutes on a final session. At CS-US durations of one, two and three minutes, lambs’ behaviours were observed using instantaneous sampling (four seconds). Comparing different minutes (i.e. a CS-US duration of three minutes resulted in three separate minutes), time showed to have a significant effect (X2=40.57(5), p<0.0001) on the proportion of the time lambs were observing the area where CS and US were presented (A). Lambs observed A the most when the CS-US duration was one minute (0.53 [0.47-0.67], median of proportion of registrations [Q1-Q3]) and the least during the final two minutes when the CS-US duration was three minutes (0.27 [0.07-0.47] and 0.07 [0.0-0.4] respectively). Time also had an effect on whether the lambs stayed in the half of the pen closest or farthest from A (X2=17.43(5), p=0.0038). Lambs spent more time close rather than far away from A in all minutes, and spent the least time close to A during the initial (0.67 [0.2-1.0]) and final (0.67 [0.0-1.0]) minute when the CS-US duration was three minutes. These result shows that certain anticipatory behaviours are affected by the duration between CS and US, and not addressing this important factor may result in overlooking issues with e.g. habituation to CS or the strength of the CS-US contingency.