A Methodological Review of Personality-Related Studies in Fish: Focus on the Shy-Bold Axis of Behavior

Personality research has begun to take hold in the animal kingdom as psychologists turn to animal models to investigate various aspects of personality. Similarly, behavioral ecologists and related fields have begun to explore the idea that individual variation in behavior is more than just noise around an average for a given population or group of interest. As a result, many have begun to turn to personality-related questions to explain individual differences in animal behavior. Collectively, psychologists, ecologists and related fields have created a boom in animal personality-related research. This interest has expanded to a variety of fish species, with many studies focused on an important axis of behavior in humans: the shy-bold axis. Unfortunately, there has been very little consideration for the methodology employed. We review both the experimental and statistical methodology found in a body of research on fish species, for which personality-related research has been conducted. Our aim is to shed light on many important considerations that are often overlooked in order to facilitate research concerned with the reliability and validity of the many methods used. The classic approach to behavioral and evolutionary ecology seeks answers based on averaged behavior and fails to consider unique variation between individuals and the functional importance of such variability (Mather, 1998; Slater, 1981). The importance of finer scale investigations at the level of the individual is only beginning to emerge as researchers have begun explore Darwin’s less accepted views that evolution acts on the individual and may not be limited to only physical traits (Darwin, 1998; Gosling, 2001). This burgeoning interest has given rise to research in areas of animal personality and temperament in a wide range of taxa and has led to recent recognition of the potential implications in ecological studies of animal behavior. If something similar to personality is found in animals and individual differences in behavior reflect more than just noise around an average, then traditional approaches to behavioral ecology, behavioral biology and how we approach questions about evolution may be challenged. The boom of interest in these new directions combined with the fear of anthropomorphism seems to have placed the search for “individual differences” at the forefront of investigations with little regard to ensuring adequate measures and methodology. In a complex and controversial topic such as animal personality, these considerations are vital to research in this area. This article aims to present some inconsistencies and considerations by reviewing a subset of studies focused on an important shy-bold axis, which has been a growing focus in research with many species of fish.