Do cleaner fish learn to feed against their preference in a reverse reward contingency task?

Abstract

The ability to control impulsive behaviour has been studied in animals with a standard test in which subjects need to choose the smaller of two food items in order to receive the larger one (reverse reward contingency). As a variety of mammals that have been tested so far (mostly primates) have great diYculties to solve the task, it has been proposed that it is generally cognitively demanding. However, according to an ecological approach to cognition, a species' ability to solve the task should not depend on its general cognitive abilities but on whether its ecology causes selective pressure on the ability to restrain foraging behaviour. We tested this hypothesis using the cleaner wrasse (Labroides dimidiatus), a Wsh species that feeds against its preference in nature when engaging in cleaning interactions with so called 'client Wsh'. None of the eight tested individuals learned to choose a non-preferred item after 200 trials. In a subsequent test, one subject learned to respond correctly in a large or none contingency task (only the choice of the small food was rewarded). After a short re-experience treatment, this individual learned to solve the reverse reward task after 30 trials. In conclusion, we did not Wnd support for the general idea that interactions with clients prepared cleaners to quickly solve a reverse reward test. However, the results suggest that the potential to solve a reverse reward contingency may not be restricted to mammals but could be present also in a Wsh species in which the problem of choosing a non-preferred food over a preferred one is an ever present challenge in nature.

Individual variation in foraging behavior reveals a trade-off between flexibility and performance of a top predator

“…We suggest that this represents a measure of an individual’s behavioral flexibility. Overcoming a preexperiment bias, such as for a particular color, has been used in other studies as evidence of learning and learning flexibility (Danisman et al 2010; Miller and Pawlik 2013). Therefore, in this experiment, we interpret the ability of pike to switch from the rewarded red cup (for which they have a bias) to the rewarded blue cup as behavioral flexibility and this flexibility was captured by our measure of “switch time.” Switch time for each pike measured how quickly an individual switched to the blue rewarded cup in trials where they chose the unrewarded red cup first and was averaged across all trials.…”

Duplications and domain-generality.

“…As client fish punish cleaners who feed on their mucus (Bshary & Grutter, 2002;Bshary & Schäffer, 2002), cleaner wrasse have to inhibit their tendency to feed on client mucus to avoid punishment. Danisman, Bshary, and Bergmüller (2010) asked whether this led to better domain-general inhibition in a reverse reward contingency task. In this task, subjects have to choose the smaller of two rewards to obtain the larger one.…”

Early commitment facilitates optimal choice by pigeons

“…More specifically, wrasse fish prefer to feed on the mucus of the client fish, but that requires that they bite the client and clients typically retaliate by leaving the cleaning station or by attacking the wrasse fish (Bshary & Grutter 2002;Bshary & Schäffer 2002). That this behavior may provide them with impulse control is suggested by the finding that these fish can acquire a reverse contingency task in which, given a choice between a larger and smaller amount of food, they must learn to approach the smaller amount of food to obtain the larger amount of food (Danisman, Bshary, & Bergmüller, 2010). Recall that chimpanzees have great difficulty in acquiring this task unless the choice did not lead immediately to the outcome (Boysen et al, 1997).…”