No evidence for general intelligence in a fish

Abstract

The average mammal or bird has a roughly ten times larger brain relative to body size than the average ectotherm vertebrate. It has been surprisingly challenging to determine how this translates into increased cognitive performance. In particular, it is unclear whether the brain size differences translate into qualitative differences in specific cognitive abilities. Here, we provide a first exploratory study to examine the possibility that the larger brains of endotherms support a different organisation of information processing, rather than specific differences in cognitive processes. In mammals, individual performance across domain‐general cognitive tasks is positively correlated, resulting in the psychometric factor g. The value of g is positively correlated with brain size. We tested wild‐caught female cleaner fish Labroides dimidiatus, known for its highly sophisticated social behaviour, in four ecologically nonrelevant cognitive tasks that have been used to varying degrees to assess g in mammals. Cleaner fish solved three of these four tasks, flexibility (reversal learning), self‐control (detour around an obstacle) and numerical competence (simultaneous two‐choice task), while also providing enough interindividual variation to test for g. They did not perform above chance levels in the fourth task, which tested for object permanence. For the three retained tasks, individual performance did not load positively on one principal component. Furthermore, all pairwise correlation coefficients were close to zero. These negative results contradict a frequent criticism of g studies, which proposes that g is a default result of how brains are designed. Rather, the results provide a first indication that endotherm and ectotherm vertebrates may process cognitive tasks in fundamentally different ways due to differences in brain organisation. Our relatively low number of experiments compared to mammalian studies enhances this hypothesis, as the probability of finding a g factor by chance would have been higher.

Social complexity affects cognitive abilities but not brain structure in a Poeciliid fish

“…The test assesses basic operant conditioning abilities, and simple cognitive processes are sufficient for forming associations ( Savage 1980 ; Bielecki et al 2023 ; Triki et al 2023a ). The task is often excluded when researchers look into complex cognitive abilities, like the “general intelligence” factor ( Damerius et al 2017 ; Aellen et al 2022 ). In sum, social complexity would unlikely impact how an individual forms basic associations, such as between a color cue and a food reward.…”

Fish can infer relations between colour cues in a non-social learning task

“…social competence [7], and non-social flexibility are affected similarly by the same physiological manipulation [38]. While previously disputed [39], this provided the first evidence of domain-general cognition in a fish [38]. We propose that our results provide further indication of domain-general cognition in fish spanning the social and non-social domain because TI in a social hierarchy context was shown to exist in the social cichlids A. burtoni and J. transcriptus [5,12], and TI in a non-social context was shown in a social cichlid in this study.…”

Inhibitory control in teleost fish: a methodological and conceptual review

“…In zebrafish, it was reported that with greater IC performance in the tube task processed social information mostly with the left hemisphere of the brain (Lucon-Xiccato et al 2020d ). In cleaner wrasse, IC measured with the detour task was negatively correlated with performance in a reversal learning task (Aellen et al 2022 ). Reversal learning is usually considered a measure of another executive function, cognitive flexibility.…”