The role of line-of-sight in operant experiments using food reinforcers in guinea pigs

The guinea pig (Cavia porcellus) is a species utilized as a model in laboratory science and is a popular companion animal. The study aimed to assess the role of line-of-sight with a food reinforcer in the ramp climbing behaviour of guinea pigs. Ten guinea pigs climbed a ramp of increasing slopes to gain a reinforcer in two conditions. The experimental condition provided constant line-of-sight with the food reinforcer at any angle, via a mirror placed at the top of the ramp. The control condition did not have a mirror. The results showed that guinea pigs had shorter climbing durations and reached ramp heights of up to 63 centimetres, when line-of-sight with the food was maintained. In comparison, ramp climbing was initially faster, but guinea pigs did not climb beyond a height of 18 centimetres in the control condition. The findings highlight the importance of ensuring visual access to reinforcers in behavioural studies and to inform husbandry practices such as providing guidance when ramps are used to enhance enclosures.