Rat boredom-like behaviour in a monotonous versus a varied foraging task: effects of sensory variation

Abstract

Evidence increasingly reveals that non-human animals in monotonous situations can show boredom-like states, distinctively manifesting as increases in both arousal-seeking, restless behaviour and low arousal, drowsy behaviour. However, task related boredom has been little investigated in animals, but could have implications for animal training efficacy, for animal welfare, and for modelling human task fatigue. We investigated whether varied sensory stimuli helped prevent boredom-like behaviour in a repetitive foraging scenario, compared with a monotonous equivalent. In a cross-over design, 20 rats searched pairs of containers for a small reward hidden within a digging material, with a new pair of containers presented every 2 min during a 20 min session. Multisensory cues distinguished the rewarded vs. non-rewarded containers. We hypothesized that, if rats became bored by sensory monotony, rats in a monotonous version of the scenario would show more arousal-seeking (e.g. exit-directed behaviour, jumping) and drowsy behaviour (e.g. standing still, yawning, task disengagement) than in a varied version. In the Monotony treatment, the digging material, reward flavour, and features of the cues remained constant in each presentation, whereas these changed throughout the Variety treatment. Behaviour was observed blind to treatment in a randomised order. Monotony significantly increased exit-directed behaviour compared with Variety, but no other treatment effects reached significance. Possible reasons for the relative lack of findings are discussed, including suggestions for future research. Here, sensory monotony during the task did not induce the full range of behaviours characterizing boredom, but it is of interest that it did increase exit-directed behaviour.

Keywords: Animal welfare; Boredom; Cognitive engagement; Sensory stimulation; Task fatigue.

Fig. 1

Overview of the arena used in the experiment. Two glass ramekins containing a digging material were placed at one end of the arena. In front of each was either a stone or a tile, which – during the experimental sessions – acted as discriminative stimuli that indicated which one of the two ramekins contained a reward within the digging material. At the other end of the arena was an upturned box, which served as an exit platform from which rats would be lifted and returned to the homecage. The dotted lines represent imaginary lines delineating different rat locations within the arena, whereby line A separated the front from the middle area and line B separated the middle from the rear area

Fig. 2

Photographs of stimuli used in three trials of the Varied and Monotonous treatments. Within one session, rats were presented with ten stimulus sets, each lasting 2 min per trial. Three example trials are shown here (i-iii), with column (A) showing the Varied treatment and (B) the Monotonous treatment. Each stimulus set comprised two glass ramekins containing a digging material, one of which also contained a reward buried within the digging material (here the reward is on the surface for illustrative purposes). The stimulus set also included a stone and a tile in front of the two ramekins to potentially act as predictive cues indicating which ramekin contained the reward; in these photographs, the tile indicates the reward location in both treatments, but whether the stone or the tile was the positive cue was balanced across individual rats. The left versus right hand side location of the reward was randomised across trials. In the Varied treatment, the colour and flavour of the reward, the type of digging material, and the precise stone and tile presented to the rat differed on every trial. In the Monotonous treatment, each rat experienced an identical stimulus set on every trial, with trials differing only in whether the reward and positive predictive cue was presented on the left versus right hand side