Interest in fish cognition has increased dramatically in recent decades and many fish have become 'mainstream' models for research (Patton Triki et al., 2025). Another benefit is the diversity: as the most species rich group of vertebrates, fish together encompass a vast array of ecological niches and offer an impressive array of models to address a variety of questions (Braasch et al., 2015; Newport, 2021; Rétaux Schartl, 2014). This diversity is one of the most compelling reasons for studying fish cognition, perhaps most importantly for disentangling the evolution of cognition through comparative frameworks (Bshary et al., 2001; Bshary Triki et al., 2025). A range of exciting questions promise that interest in fish cognition will remain high (Bshary Healy Miller, 2017; Salena et al., 2021; Vila Pouca Sarter, 2004), a stress response (Brydges et al., 2009), a response to an unintended cue we cannot even perceive. Biases due to sensory differences between researcher and animals is a common issue (Nagel, 1974), and fishes employ some relatively exotic senses, such as the mechanosensory lateral line system (Dijkgraaf, 1963) and electroreception (Schuster Schubiger et al., 2020). Howevere, these challenges are perhaps most acute in studies of fish cognition where, apart from zebrafish and a handful of other species (Brown Salvanes et al., 2013; Závorka et al., 2022). These issues with task relevance and testing conditions complicate interpretation and hinder cross-species comparisons. They can also affect reproducibility (Paull et al., 2024; Webster Utne-Palm when stimulus shoals were separated by larger distances (45 or 60 cm) this preference was not seen (Swaney et al., 2024). Likewise, the dimensions of the setup used for a detour task to study inhibitory control and risk-taking in mosquitofish (Gambusia affinis) were found to be a potential reason for the inability of this species to exhibit the expected differences across experimental conditions with different levels of microplastic pollutants (Irwin et al., 2024). These studies underscore the importance of the dimensions of experimental setups when interpreting results. Dellinger et al. (2024) explore a relatively unstudied species in cognitive fields, the Arctic charr (Salvelinus alpinus). They describe several factors which hindered the ability of char to perform a spatial learning task and suggest solutions worth considering for researchers exploring other less common species. Primarily, they propose the integration of arenas into housing aquaria and acclimation times to increase the proportion of individuals that participate in trials, reinforcing previous recommendations in this vein (Salena et al., 2021). As cognitive research predominantly relies on well-established model species, these methodological insights are especially valuable for broadening taxonomic representation in the field. At a more general level, Munson and DePasquale (2024) have developed a comprehensive guide for the use of mazes in fish cognition. Building on recent work examining how maze design and assay protocols affect zebrafish performance (Benvenutti et al., 2021), their review extends these findings to other species and synthesizes critical factors to consider when designing spatial cognition assays for fishes. This resource will be invaluable for researchers developing maze-based methodologies in the future. In addition to species-level differences in cognitive abilities, variation within populations also influences assay outcomes. Individual sex, size and age can all affect behaviour, with important implications for experimental design and test arena configuration. Here Yin and Horzmann (2024) detail an empirical exploration of performance in mazes across sex and age using the classic zebrafish model. Males and older fish (more than 3 years old) learnt more slowly and made more errors than fish from younger age groups, with fish under 1 year old performing best across all metrics in a T-maze study. Exploring a more nuanced social factor of male presence and the potential of coercive mating, Ernst et al. (2024) found that there was no impact on female spatial navigation learning in porthole livebearers (Poeciliopsis gracilis). This was despite the consequences of male presence, with reduced body condition and slower growth of focal females exposed to males and the expectation and ample evidence that coercive mating impacts the female brain and behaviour in previous work. This highlights the complex and potentially species-specific nature of social influences on cognitive performance. A major area of research where fish can be useful is exploring 'swarm intelligence' or collective cognition. Understanding how groups coordinate and make decisions is an exciting area of research, but developing empirical assays that can unravel the mechanisms behind such decision making can be a challenge (Ioannou, 2017), for example water depth in such studies is kept shallow to better track fish, but limit behavioural responses and cause artefacts. Similarly, training protocols and appropriate cues to initiate responses vary across individuals, species and test setups. In this vein, Lecheval and Theraulaz (2024) proposed and successfully tested aversive conditioning for use in a schooling species, the rummy-nose tetra (Hemigrammus rhodostomus). They showed that they can use aversive stimuli to effectively trigger collective escape responses that propagate rapidly through small schools. A major goal for some fields is to develop high-throughput protocols and fully automate testing systems. By reducing human involvement, such approaches are aimed at minimizing biases and human observation errors, while also reducing welfare costs for fish. However, current automated tracking methods face challenges themselves. Low-cost systems that are easily adapted to multiple species or research questions are still limited. As a partial solution, Lucks et al. (2024) detail a low-cost, versatile Raspberry Pi-based system for gate opening (that removes the need for human manipulation of in-tank gates) that can be customized to fit a variety of experimental setups for testing spatial orientation and navigation. The authors illustrate the validity of their protocols with a worked example where weakly electric fish navigate through a test system. Step-by-step protocols and codes for the gate control are included for other researchers to use in their own projects. Similarly, Ajuwon, Cruz, Giske et al., 2025), these are exciting technological advances that will have a large impact on cognitive studies of fish both in the laboratory and in the wild. While the preceding sections argue for more accurate and comparative science though standardization and careful consideration of constraints, it is important to pause and consider whether these rules are actually useful: do they help or obscure our search for answers to all questions in the field? Schuster (2024) draws on decades of experience and examples from the literature to raise the point that following methods too rigidly can cause problems. His article poses five 'golden rules' commonly used in cognitive and behavioural studies, and then challenges them, and us, to consider when it might be worthwhile to bend or break them. While we strive to improve our understanding of fish cognition, Schuster cautions us to bear in mind that there is no one-size-fits-all test. The search for the cognitive abilities of an animal requires experience and knowledge of that species, and sometimes substantial luck, which no amount of careful design or acclimation protocols can replace. The diversity of fish species and their natural variation in behaviour and ecology represents a fascinating source for investigating how cognitive abilities arise and how variation is maintained and affected by environmental factors. Studies of fish cognition explore a broad range of domains, from processing social information and learning (Brown Dewenter et al., 2017; Laland et al., 2011), to how fish perceive and navigate through environments (Nava et al., 2011; Santacà et al., 2022; Sibeaux et al., 2022, 2025), and recognition (de Waal, 2019; Kohda et al., 2019, 2023; Newport et al., 2016, 2018; Vail et al., 2013) and understanding the emergence and coordination of collective behaviour (Bshary et al., 2006; Jolles et al., 2020; Munson et al., 2021) As this field expands into new species and environmental contexts, including how cognitive processes respond to anthropogenic stressors (Breedveld et al., 2025; Newport et al., 2021), establishing robust methodological foundations becomes increasingly critical. The methodological insights presented in this special issue provide essential groundwork for ensuring that our understanding of cognitive diversity keeps pace with the remarkable biological diversity we seek to comprehend. Incorporating the ecological significance of cognition is essential for understanding how cognitive abilities arise and persist. In situ observations of 'wild cognition' through the use of adapting methodology and technology is increasingly favoured (Bshary Griebling et al., 2022; Mourier et al., 2025; Pritchard et al., 2016), but field studies face specific challenges that are inherent to working in a less controlled environment. A major obstacle here is tracking and identifying individual fish, which is typically more difficult than in captivity (Jungwirth et al., 2019). Here, rapid technological advances have seen the development of systems that overcome these challenges (Francisco et al., 2020). Affordable open-source Radio Frequency Identification platforms for animal identification (Bridge et al., 2019), computer vision AI tools for analysing video recordings in natural settings (Martinez-Alpiste et al., 2024; Weinstein, 2018) and innovative experimental designs for cognitive testing in the wild (Vila-Pouca et al., 2025) now offer unprecedented opportunities to study fish cognition at scale in their natural environment. The methodological considerations highlighted in this special issue, when combined with technological advances and forays into wild cognition, provide a roadmap for more robust and ecologically meaningful studies of fish cognition. Negative results and pilot studies are crucial tools for identifying issues and refining experimental methods, but often represent wasted effort when their insights remain unpublished. Pilots are essential for determining suitable cues and experimental procedures that work with fish subjects. For example, Braithwaite and Salvanes (2005) conducted several pilots to discover that using pairs of fish yielded optimal engagement because solitary fish would not interact with test stimuli at all. Despite their extensive use in laboratories, such pilots are rarely published or even mentioned in manuscripts. Similarly negative results are often unpublished because isolating any methodological reasons for the lack of expected effects often requires further work and less immediate impact. However, while there are practical difficulties in developing such studies or small pilots into full outputs, we argue that developing such work into standalone studies would be worthwhile to reduce the continual 'reinvention of the wheel' by making procedures and designs available to all. Similar arguments have been made before (Bespalov et al., 2019), but bear repeating. Moreover, we suggest that methodological studies of negative results and expansions of pilots provide useful avenues for guidance for research students on their first forays into relatively simple empirical projects. As a final note, we would like to thank the contributors to the issue and the many reviewers whose diligent work made this possible. The methodological insights presented in this special issue, from acclimation protocols and apparatus design to tracking innovations and species-specific considerations, represent important steps toward the goal of advancing rigorous fish cognition research. By building on these foundations and continuing to prioritize methodological transparency, the fish cognition community can ensure that our understanding of cognitive diversity keeps pace with the remarkable biological diversity we seek to understand. Nick A. R. Jones wrote the first draft, all co-authors edited and contributed to the writing of the final manuscript. Data sharing not applicable to this article as no datasets were generated or analysed during the current study.
Jones et al. (Sun,) studied this question.