Abstract
The results of behavioural experiments provide important information about the structure and information-processing abilities of the visual system. Nevertheless, if we want to infer from behavioural data how the visual system operates, it is important to know how different learning protocols affect performance and to devise protocols that minimise noise in the response of experimental subjects. The purpose of this work was to investigate how reinforcement schedule and individual variability affect the learning process in a colour discrimination task. Free-flying bumblebees were trained to discriminate between two perceptually similar colours. The target colour was associated with sucrose solution, and the distractor could be associated with water or quinine solution throughout the experiment, or with one substance during the first half of the experiment and the other during the second half. Both acquisition and final performance of the discrimination task (measured as proportion of correct choices) were determined by the choice of reinforcer during the first half of the experiment: regardless of whether bees were trained with water or quinine during the second half of the experiment, bees trained with quinine during the first half learned the task faster and performed better during the whole experiment. Our results confirm that the choice of stimuli used during training affects the rate at which colour discrimination tasks are acquired and show that early contact with a strongly aversive stimulus can be sufficient to maintain high levels of attention during several hours. On the other hand, bees which took more time to decide on which flower to alight were more likely to make correct choices than bees which made fast decisions. This result supports the existence of a trade-off between foraging speed and accuracy, and highlights the importance of measuring choice latencies during behavioural experiments focusing on cognitive abilities.
Highlights
Ever since the pioneering research of Karl von Frisch [1], bees stand among the most productive model systems in vision research [2,3]
The results of behavioural experiments inform us of some capabilities that the visual system must have, other capabilities of the visual system may remain masked behind lack of motivation and other factors increasing behavioural noise [9]
For example, if in an experiment with proper controls bees learn to search for food in flowers of one particular colour, ignoring flowers of a different colour that have no food, we can conclude that their visual system allows bees to discriminate between the two colours
Summary
Ever since the pioneering research of Karl von Frisch [1], bees stand among the most productive model systems in vision research [2,3]. [4,5]), a research approach known as reverse engineering. Some of these hypothesised properties were investigated at the anatomical or neurophysiological levels [6,7]. The focus of visual learning research has largely shifted towards the cognitive abilities of bees [2,3,8,9], the debate around the mechanisms allowing insects to perceive and discriminate colours has not been settled and reverse engineering remains a valid strategy. If we are to use behavioural experiments to learn how visual information is acquired and processed, it is of paramount importance to devise experimental protocols that minimise noise
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