Arousal and temporal factors imprinting in mallards.
A number of factors affecting the learning processes in laboratory imprinting were examined. Two factors alone explained the degree to which young ducklings learn the characteristics of a given model: the length of exposure to the model, and the endogenous arousal state of the duckling. A third, the effect of muscular exertion is not warranted. The characteristics of some models are more rapidly learned than others, and the significance of this fact for biochemical studies of learning is discussed. In this study ease of learning coincided with innate preference; this suggests the presence of a neural filtering mechanism in the duckling which alters the assimilation of information into the CNS and hence controls both innate preference and learnability.