Cleaner wrasse failed in early testing stages of both visual and spatial Working Memory paradigms

Working memory (WM), an attention-based short-term storage system responsible for the manipulation and integration of past knowledge with present information for goal-directed behavior, is a key executive function and a principal predictor of general intelligence. As WM has not been a major research topic in animal behavior, we first summarize key ideas from the social sciences for interested colleagues. Given that past methodological inconsistencies have led to mixed results and conclusions across various species, we designed experiments that incorporate the critical components of WM, facilitating cross-species comparisons and accounting for potential ecological influences. We present such experiments on WM in an ectothermic vertebrate, the cleaner wrasse ( Labroides dimidiatus ), which faces environmental challenges potentially requiring complex cognitive adaptations. Overcoming several experimental challenges, we consistently obtained negative results across multiple experimental paradigms. Our negative results using experiments specifically designed to test WM call into question previous studies that used other experiments and reported positive WM findings in other fish species. If the negative results in specific WM tests were to be confirmed in other ectotherm vertebrates, the absence of WM may turn out to be a key factor underlying the significant encephalization gap between ectotherm and endotherm vertebrate species.