From Visual Discrimination to Violation of Expectation: Developing a visual discrimination task in domestic chicks (Gallus gallus)

Violation of expectation (VoE) research so far has primarily focused on corvids and mammals, but other animal models should be investigated as well. The research conducted with domestic chicks (Gallus gallus) has scarcely employed the violation of expectation paradigm (VoE), and not ever in combination with a perceptual discrimination task. Hence for conducting an experiment like this it was necessary to develop and validate a reliable discrimination task procedure. Previous literature provides some evidence of young chickens’ perceptual preferences (circular shapes and orange colours) and discrimination abilities (shape, colour and orientation). However these findings do not necessarily generalise to a novel experimental set-up that would be designed for use specifically within a VoE paradigm. During the development of the experimental procedure we had to account for the subjects’ inherent perceptual preferences, spatial bias, difficulties discriminating stimuli, and occasional loss of motivation. This work illustrates the importance of preparatory studies by reviewing the methodological refinement process that resulted in a functional experimental set-up. We describe and discuss here various experimental apparatuses, stimuli sets, reward systems and procedures that were tested, with their strengths and limitations. The procedure presented here has subsequently been tested on a larger sample, validated and adopted for future violation of expectation experiments.