A reversed-reward contingency task reveals causal knowledge in chimpanzees (Pan troglodytes)

In the reversed-reward contingency task, subjects are required to choose the less preferred of two options in order to obtain the more preferred one. Usually, this task is used to measure inhibitory skills, but it could also be used to measure how strong the subjects’ preferences are. We presented chimpanzees with support tasks where only one of two paper strips could physically bring food into reach. Subjects were rewarded for choosing the non-functional strip. In Experiment 1, subjects failed to pick the non-baited strip. In Experiment 2, subjects failed to pick the broken strip. Chimpanzees performed worse in these tasks than in other similar tasks where instead of paper strips, there were similar shapes painted on a platform. The fact that subjects found the reversed-reward contingency task based on causality more difficult to solve than a perceptually similar task with no causality involved (i.e., arbitrary) suggests that they did not treat real strips as an arbitrary task. Instead, they must have had some causal knowledge of the support problem that made them prefer functional over non-functional strips despite the contrary reward regime.     

Intuitive optics: what great apes infer from mirrors and shadows

There is ongoing debate about the extent to which nonhuman animals, like humans, can go beyond first-order perceptual information to abstract structural information from their environment. To provide more empirical evidence regarding this question, we examined what type of information great apes (chimpanzees, bonobos, and orangutans) gain from optical effects such as shadows and mirror images. In an initial experiment, we investigated whether apes would use mirror images and shadows to locate hidden food. We found that all examined ape species used these cues to find the food. Follow-up experiments showed that apes neither confused these optical effects with the food rewards nor did they merely associate cues with food. First, naïve chimpanzees used the shadow of the hidden food to locate it but they did not learn within the same number of trials to use a perceptually similar rubber patch as indicator of the hidden food reward. Second, apes made use of the mirror images to estimate the distance of the hidden food from their own body. Depending on the distance, apes either pointed into the direction of the food or tried to access the hidden food directly. Third, apes showed some sensitivity to the geometrical relation between mirror orientation and mirrored objects when searching hidden food. Fourth, apes tended to interpret mirror images and pictures of these mirror images differently depending on their prior knowledge. Together, these findings suggest that apes are sensitive to the optical relation between mirror images and shadows and their physical referents.     

Token Economies: Using Basic Experimental Research to Guide Practical Applications

This paper highlights the applicability of patterns seen within basic experimental research in relation to contemporary application of token economies. Token economies are one of the most widely used interventions to promote behavior change, and this procedure has evolved to be effective across many settings, behaviors, and individuals. Due to this widespread use, casual implementation of the token economy might result in inconsistencies in responding and therefore an overall skepticism in the procedure itself. We present multiple barriers that encumber practical application of token economies, including insufficient conditioning and pairing of tokens, determining quality of backup reinforcers, unforeseen effects of motivating operations, teaching the token exchange, effects of higher-order reinforcement schedules, ratio strain, and use of response cost procedures. To assist practitioners in implementing more effective treatments, for each barrier we revisit the often overlooked basic research involving features of conditioned reinforcement and reinforcement schedules. It is important to translate the often complex implications of basic research so that practitioners can use this information to improve their own practice as well as their confidence in disseminating use of this evidence-based treatment. To further guide practitioners in using this knowledge in everyday settings, we also provide recommendations specific to each barrier as well as relevant applied research and practical examples.     

Intuitions about gravity and solidity in great apes: the tubes task

We investigated whether great apes, like human infants, monkeys and dogs, are subject to a strong gravity bias when tested with the tubes task, and – in case of mastery – what the source of competence on the tubes task is. We presented 22 apes with three versions of the tubes task, in which an object is dropped down a tube connected to one of three potential hiding places and the subject is required to locate the object. In two versions, apes were confronted with a causal tube that varied in the amount of perceptual information it provided (i.e. presence or absence of acoustic cues). The third version was a non‐causal adaptation of the task in which a painted line ‘connected’ dropping and hiding places. Results indicate that apes neither have a reliable gravity bias when tested with the tubes, nor understand the causal function of the tube. Even though there is evidence that they can integrate tube‐related causal information to localize the object, they seem to depend mainly on non‐causal inferences when searching for an invisibly displaced object.     

Representing Space and Objects in Monkeys and Apes

Primate foraging can be construed as a set of interconnected problems that include finding food, selecting efficient travel routes, anticipating the positions of moving prey, and manipulating, and occasionally, extracting food items using tools. The evidence reviewed in this paper strongly suggests that both monkeys and apes use three types of representation (i.e., static, dynamic, and relational) to solve various problems. Static representations involve recalling certain features of the environment, dynamic representations involve imagining changes in the trajectories of moving objects, and relational representations involve encoding the properties of objects in relation to other objects. Contrary to previous claims, no clear differences were found between the representational skills of monkeys and apes. Current evidence also suggests that primates may be better at representing general compared to specific problem features. Finally, we have characterized the domains of space and objects as complementary and indicated future lines of research in these domains.