Active explorers show low learning performance in a social insect

Abstract

An intriguing question in behavioral biology is whether consistent individual differences (called animal personalities) relate to variation in cognitive performance because commonly measured personality traits may be associated with risk-reward trade-offs. Social insects, whose learning abilities have been extensively characterized, show consistent behavioral variability, both at colony and at individual level. We investigated the possible link between personality traits and learning performance in the carpenter ant Camponotus aethiops. Exploratory activity, sociability, and aggression were assessed twice in ant foragers. Behaviors differed among individuals, they were partly repeatable across time and exploratory activity correlated positively with aggression. Learning abilities were quantified by differential conditioning of the maxilla-labium extension response, a task that requires cue perception and information storage. We found that exploratory activity of individual ants significantly predicted learning performance: "active-explorers" were slower in learning the task than "inactive-explorers". The results suggest for the first time a link between a personality trait and cognitive performance in eusocial insects, and that the underlying individual variability could affect colony performance and success.

Keywords: ants; associative learning; cognition; exploratory activity; personality.

Figure 1.

Learning curves of conditioned stimuli (CS+, dark line and CS−, gray line) along trials, expressed in percentage of maxilla-labium extension responses (%MaLER). The two stimuli were discriminated along trials (GLMM: χ²=26.01; df = 1; P < 0.001). MaLER significantly increased during the CS+ trials (GLMM: χ²=69.03; df = 1; P < 0.001) but remained low during CS− trials (GLMM: χ²=2.71; df = 1; P = 0.10).

Figure 2.

Relationship between exploratory activity and learning performance (acquisition score, AS+; mean ± SD = 6.489 ± 3.195); colonies (C1, C2, C3) are depicted by different symbols. Exploratory activity is expressed as the average of the two repeats. The solid line represents the regression line.