Learning in domestic chicks after exposure to both discriminanda.

Abstract

Bateson and Chantrey have suggested that the characteristics of complex objects may be learned by young animals by sequential exposure to parts or views of the object. The various component stimuli are said to be "classified together" as the animal learns to perceive its world. Consequently, domestic chicks given the opportunity to classify together color stimuli are subsequently less able to discriminate between them than are controls. Nine experiments were designed to investigate this phenomenon further. Chicks were exposed either to colors or to shapes and subsequently trained to discriminate between them, and their discrimination performance was compared with that of nonexposed controls. In only two experiments, one of them a near replication of Bateson and Chantrey's work, were their findings reproduced.Recent experiments by Bateson and Chantrey (1972) and Chantrey (1972 showed that young domestic chicks learn to discriminate between two colors more rapidly if the colors are unfamiliar. Specifically, chicks exposed to red and green objects during the first 5 days after hatching later learned to discriminate between red and green more slowly than chicks exposed to only blue objects. This result is the opposite of the findings of earlier experiments in which exposure to the discri-

Object Recognition and Sensitive Periods: A Computational Analysis of Visual Imprinting

“…It has been shown that chicks will blend two objects if they appear in close temporal proximity to each other (Chantrey 1974;Stewart et al 1977). This temporal dependency alone is consistent with the idea that the object recognition system uses hysteresis to develop invariant representations of objects.…”

“…By subsequently attempting to train chicks on a visual discrimination task involving the two objects he was able to demonstrate that when the objects had been presented in close temporal proximity (under 30 sec gap between them) they became blended together to some extent. This result was replicated by Stewart et al (1977) who also controlled for the total amount of exposure to the stimuli.…”

“…However, when stimuli that share many visual features are used, evidence for blending will be more difficult to detect. We propose that the difficulties in extending the Chantrey (1974) findings to other stimuli and experimental conditions (Stewart et al 1977) is due to the relative similarity of the stimuli used.…”

Visual Imprinting in Birds: Behavior, Models, and Neural Mechanisms

“…Indeed, Chantrey (1974) and Honey and Bateson (1996) found evidence for temporal blending in chicks trained with alternate serial presentation with two imprinting stimuli. However, the effect was not found with a different pair of training stimuli and different experimental conditions (Stewart et al., 1977), possibly due to conflicts implied in the simulation.…”

Is imprinting such a special case?

“…However, when the two objects were presented 30 s or less apart, the imprinted birds took longer than the control group to learn the discrimination. The effect is sometimes elusive and Stewart et al (1977) were only able to obtain it when they replicated Chantrey's experimental conditions exactly. Perhaps the fragility is less surprising than if the birds had had a simple categorization rule, which meant that arrays of features that occurred within a short time of each other were always combined into a single represen tation.…”