Laterality enhances numerical skills in the guppy, Poecilia reticulata

Abstract

It has been hypothesized that cerebral lateralization can significantly enhance cognition and that this was one of the primary selective forces shaping its wide-spread evolution amongst vertebrate taxa. Here, we tested this hypothesis by examining the link between cerebral lateralization and numerical discrimination. Guppies, Poecilia reticulata, were sorted into left, right and non-lateralized groups using a standard mirror test and their numerical discrimination abilities tested in both natural shoal choice and abstract contexts. Our results show that strongly lateralized guppies have enhanced numerical abilities compared to non-lateralized guppies irrespective of context. These data provide further credence to the notion that cerebral lateralization can enhance cognitive efficiency.

Individual guppies differ in quantity discrimination performance across antipredator and foraging contexts

“…Apparatus The apparatus consisted of three independent tanks (Dadda et al 2015;). The 'subject tank' was a 60 × 40 × 35 cm glass tank with the bottom and long walls covered with green plastic material; two 60 × 40 × 35 cm glass tanks for the stimuli, with gravel bottoms, were displaced continuously to the short wall of the subject tank.…”

“…We tracked the position of the subject to measure shoaling preference. We considered the subject to have chosen a shoal only when it was in a choice area within a distance of 11 cm from the glass facing the stimulus tank (Dadda et al 2015) and we analysed the time spent by the subjects in the two choice areas. As a measure of the performance, we then calculated a preference index for the larger shoal: (time spent in the sector near the larger shoal / (time spent near the larger shoal + time spent near the smaller shoal)) × 100 (Dadda et al 2015).…”

“…We considered the subject to have chosen a shoal only when it was in a choice area within a distance of 11 cm from the glass facing the stimulus tank (Dadda et al 2015) and we analysed the time spent by the subjects in the two choice areas. As a measure of the performance, we then calculated a preference index for the larger shoal: (time spent in the sector near the larger shoal / (time spent near the larger shoal + time spent near the smaller shoal)) × 100 (Dadda et al 2015). We also calculated the overall percentage of time spent in the two choice areas as a measure of the willingness to shoal with conspecifics (Brown and Irving 2014;.…”

Sex Differences in Discrimination of Shoal Size in the Guppy (Poecilia reticulata)

“…One possible confound in our experiments is that the subject may freeze or notice only one stimulus; to exclude this possibility, we only included subjects that moved at least twice between the two choice areas during the trial (Dadda et al 2015;. The time spent in the two choice areas during the 28 min of experiments was computed by an experimenter na€ ıve to the purpose of the study using computer software (Ciclic Timer) that produces output data divided into seven blocks of 4 min each.…”

“…As a measure of coping with the stress of the experimental manipulation, we also recorded whether the subjects performed freezing behaviour (more than 5 s motionless) in the first 8 min of experiment 1. One possible confound in our experiments is that the subject may freeze or notice only one stimulus; to exclude this possibility, we only included subjects that moved at least twice between the two choice areas during the trial (Dadda et al 2015;. This selection was made before scoring the performance by looking at the recordings at 169 speed.…”