Exploring Environmental Influences on Decision Making in Pigs Using a Modified Iowa Gambling Task

Abstract

Abstract Evidence suggests that environmental conditions play a role in the etiology of various psychiatric disorders. Impaired decision-making in these psychiatric disorders has been found using the Iowa Gambling Task (IGT). In the present study, the influence of environmental conditions on decision-making in pigs was examined. The influence of the environment was determined by using a risky decision-making task modelled after the IGT. Ten replicates of two littermate boars were reared in an enriched or barren environment and trained on the task. To investigate the cognitive functions spatial learning and working memory of the enriched- and barren-housed pigs, the decision-making task was repeated after a retention interval of thirteen weeks. During both the acquisition and the retention phase, the pigs chose from two different options. The optimal strategy in the task was the same as in the IGT: to develop a preference for the smaller reward with less loss/punishment instead of the bigger reward with more loss/punishment. Because incorrect choices are generally associated with longer responses in memory tests, the speed at which advantageous and disadvantageous choices were made has also been measured during the task performances. Salivary and hair cortisol samples were taken at different moments throughout the study and body mass was weighed at the end of testing. Both groups favoured the advantageous option in the acquisition and retention phase and the proportion of advantageous choices increased with training in both phases of the study. In both phases, the pigs increased the number of advantageous choices during the course of training. However, the pigs made less advantageous choices at the start of the retention phase than at the end of the acquisition phase. Barren-housed pigs chose the advantageous options more often in the acquisition phase compared to environmentally enriched pigs. No other differences were found for the acquisition and retention phase. A significant difference was found in latencies between advantageous and disadvantageous choices, and between the acquisition and retention phase. The advantageous choices were made faster and the latencies in the retention phase were longer compared to the acquisition phase. The rearing environments affected the level of hair cortisol. The hair cortisol level was higher in the barren-housed than in the enriched-housed pigs. No other significant differences were found for salivary and hair cortisol. The environments did not differentially affect body mass. Summarising, housing conditions affected pigs’ learning abilities, memory and performances on a decision making task and cortisol level, measured in pig hair.