Replication alert: behavioural lateralization in a detour test is not repeatable in fishes

Data for: Roche DG, Amcoff M, Morgan R, Sundin J, Andreassen AH, Finnøen MH, Lawrence MJ, Henderson E, Norin T, Speers-Roesch B, Brown C, Clark TD, Bshary R, Leungt B, Jutfelt F and Binning SA (in prep) Replication alert: behavioural lateralization in a detour test is not repeatable in fishesPlease see the readme.txt file for metadata.Abstract:1. Behavioural lateralisation, defined as the asymmetric expression of cognitive functions, is reported to enhance key fitness-relevant traits such as group coordination, multitasking and predator escape performance. Therefore, studies reporting negative effects on lateralisation in fish due to environmental stressors such as ocean acidification, hypoxia, and pollutants are worrisome. However, such studies tend to use a detour test and focus on population-level measures, without validating whether lateralisation measured using this method is consistent within individuals across time.2. We conducted a multi-species, international assessment of the repeatability (R) of lateralisation in four previously studied fish species (Ctenolabrus rupestris, Danio rerio, Neopomacentrus azysron, and Pomacentrus amboinensis) using a detour test (T-maze), a common method for testing lateralisation. We also re-analysed a published dataset on guppies (Poecilia reticulata) using new statistical methods. We expected the three shoaling species to exhibit greater within-individual consistency in lateralisation than their non-shoaling counterparts given previous reports of stronger lateralisation in group-living fishes. 3. Absolute and relative lateralisation scores were highly non-repeatable in all five species (0.01R<0.08), irrespective of their shoaling status. We carefully reviewed 31 published studies in which the detour test was employed to examine lateralisation in fish and identified statistical issues in all of them. We develop and propose new statistical analyses to test for population- and individual-level lateralisation (along with open code). 4. The commonly used detour test does not appear to be an appropriate method for quantifying behavioural lateralisation in fishes, calling into question functional inferences drawn by many published studies, including our own. As a consequence, potential fitness benefits of lateralisation and anthropogenic effects on lateralisation as a proxy for adaptive brain functioning need to be assessed with alternative paradigms.