Fish cognition and behavior

Abstract

The field of animal cognition is the modern approach to understanding the mental capabilities of animals. The theories are largely an extension of early comparative psychology with a strong influence of behavioural ecology and ethology. Cognition has been variously defined in the literature. Some researchers confine cognition to higher order mental functions including awareness, reasoning and consciousness. However, a more general definition of cognition also includes perception, attention, memory formation and executive functions related to information processing such as learning and problem solving. The study of animal cognition has been largely confined to birds and mammals, particularly non-human primates. This bias in the literature is in part due to the approach taken in the 1950s when cognitive psychologists began to compare known human mental processes with other closely related species. This bias was reinforced by an underlying misconception that learning played little or no role in the development of behaviour in reptiles and fishes. Throughout scientific history fishes have largely been viewed as automatons. Their behaviour was thought to be almost exclusively controlled by unlearned predispositions. Ethologists characterised their behaviour as a series of fixed action patterns released on exposure to appropriate environmental cues (sign stimuli). Whilst there is no doubt that fishes are the most ancient form of vertebrates, they are only ‘primitive’ in the sense that they have been on earth for in excess of 500 million years and that all other vertebrates evolved from some common fish-like ancestor (around 360 million years ago). However, it is important to note that fishes have not been stuck in an evolutionary quagmire during this time. Their form and function have not remained stagnant over the ages. On the contrary, within this time frame they have diversified immensely to the point where there are more species of fish than all other vertebrates combined (currently over 32,000 described species) occupying nearly every imaginable aquatic niche. The erroneous view that both behavioural and neural sophistications are associated in a linear progression from fishes through reptiles and birds to mammals is largely due to a heady mix of outdated and unscientific thinking. Aristotle’s concept of Scala naturae