Do lemurs know when they could be wrong? An investigation of information seeking in three species of lemur (Lemur catta, Eulemur rubriventer, and Varecia variegata)

Sixteen lemurs, including representatives from three species (Lemur catta, Eulemur rubriventer, Varecia variegata), were presented with a food seeking task where information about the rewards location, in one of two plastic tubes, was either known or not known. We evaluated whether lemurs would first look into the tube prior to making a choice. This information-seeking task aimed to assess whether subjects would display memory awareness, seeking additional information when they became aware they lacked knowledge of the rewards location. We predicted lemurs would be more likely to look into the tube when they had insufficient knowledge about the rewards position. Lemurs successfully gained the reward on most trials. However, they looked on the majority of trials regardless of whether they had all the necessary information to make a correct choice. The minimal cost to looking may have resulted in checking behaviour both to confirm what they already knew and to gain knowledge they did not have. When the cost of looking increased (elevating end of tube requiring additional energy expenditure to look inside - Experiment 2), lemurs still looked into tubes on both seen and unseen trials; however, the frequency of looking increased when opaque tubes were used (where they could not see the rewards location after baiting). This could suggest they checked more when they were less sure of their knowledge state.