How Bold and Friendly Fish Judge Group Sizes

Greg Howard
3rd March, 2024

Image Source: Natural Science News, 2024

Key Findings

In a study of 10 freshwater fish species, bolder fish were better at choosing the right shoal size
Fish with very high or low sociability were not as good at shoal size discrimination
The ability to judge shoal sizes was not affected by the numerical contrast ratio in bolder fish

Understanding the connection between an animal's personality and its cognitive abilities is a fascinating area of research that can provide insights into how different species adapt and thrive in their environments. A recent study conducted by researchers from Chongqing Normal University has shed new light on this relationship by examining how personality traits are linked to cognitive performance in a variety of freshwater fish species^[1]. The study focused on a specific cognitive task that has direct implications for the survival and fitness of these fish: the ability to discriminate between different shoal sizes. Shoaling, or the behavior of fish swimming in groups, is a common phenomenon in aquatic environments, and the ability to choose the right shoal can be crucial for an individual fish's protection from predators and success in foraging. Researchers discovered that bolder fish species—those that exhibit more 'shuttle' behavior, which involves actively moving back and forth to gather information—tended to perform better in tasks requiring them to distinguish between shoal sizes. These high-performing (HP) species were adept at making these distinctions without being influenced by the numerical contrast ratio, which refers to the relative difference in size between two shoals. On the other hand, shyer species demonstrated lower performance (LP) in the same task. Interestingly, the study found that species with either very high or very low sociability also showed LP in shoal size discrimination. For highly sociable species, the frequent need to discern shoal sizes might not be as pressing, possibly due to their tendency to form large, stable groups. In contrast, species with low sociability might lack the motivation or willingness to join and maintain their presence in shoals, which could explain their lower performance. The findings of this study align with previous research that has shown a link between personality and cognitive ability within species. For instance, a study on wild-caught zebrafish found that bolder individuals were better learners, although they showed poorer memory retention^[2]. This suggests that personality traits such as boldness can influence learning and memory, which are key aspects of cognitive ability. Additionally, the role of parasites in shaping behavior within host populations has been highlighted, with evidence suggesting that parasite load can affect animal personality traits and that these differences may be maintained by the parasites themselves^[3]. While the current study did not directly address the impact of parasites on shoal size discrimination, it adds to the understanding of how various factors can influence cognitive performance and behavior. Moreover, the study's findings complement research on numerical discrimination abilities in fish. Previous work has shown that zebrafish can discriminate between numbers and that this ability compares favorably with other vertebrates^[4]. The current research extends these insights by demonstrating that numerical abilities and personality traits are interconnected across different fish species. The study also resonates with research on the producer-scrounger game in birds, where cognition was found to influence foraging tactics^[5]. Although the current study did not involve birds, it underscores the broader principle that cognitive traits can play a crucial role in the foraging strategies of animals across different taxa. In conclusion, the study from Chongqing Normal University provides compelling evidence for an evolutionary link between numerical abilities and behavior across fish species. By demonstrating that bolder species are generally better at discriminating shoal sizes, the research suggests that personality traits can have a significant impact on cognitive performance. This has important implications for our understanding of how different species have adapted their cognitive abilities to meet the demands of their respective environments. The study not only advances our knowledge of animal cognition and personality but also highlights the complex interplay between behavior, learning, and ecological factors.

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