Perspectives: The Looking Time Experimental Paradigm in Studies of Animal Visual Perception and Cognition

Experiments are the foundation of empirical science, and experimental paradigms that are broadly applicable across settings and species are particularly useful for comparative research. Originally developed to address questions related to perception and cognition of pre-verbal human infants, the looking time experimental paradigm has been increasingly used to study animal behavior and cognition, particularly in non-human primates. Looking time experiments are based on the assumption that animals direct eye gaze toward objects or scenes based on their degree of interest, and use looking behavior to infer perceptual or cognitive characteristics of subjects. This paradigm can be used in a variety of contexts and is not based on species-typical behaviors, allowing for intra- and interspecific comparisons. Here, we describe the history of use of looking time measures, provide an overview of the problems and controversies related to this method, and offer recommendations on how to implement looking time tasks, focusing on the preparation of stimuli, experimental procedures, and data analysis. Our overview focuses on non-human primates, where most work has been carried out, but the issues discussed should be applicable to a wide range of species. We conclude that despite pertinent criticism, looking time tasks are practical when executed and interpreted properly. The further implementation of these methods in studies of animal behavior and cognition is likely to be fruitful.