Conservatism and “copy-if-better” in chimpanzees (<Emphasis Type="Italic">Pan troglodytes</Emphasis>)

Social learning is predicted to evolve in socially living animals provided the learning process is not random but biased by certain socio-ecological factors. One bias of particular interest for the emergence of (cumulative) culture is the tendency to forgo personal behaviour in favour of relatively better variants observed in others, also known as the “copy-if-better” strategy. We investigated whether chimpanzees employ copy-if-better in a simple token-exchange paradigm controlling for individual and random social learning. After being trained on one token-type, subjects were confronted with a conspecific demonstrator who either received the same food reward as the subject (control condition) or a higher value food reward than the subject (test condition) for exchanging another token-type. In general, the chimpanzees persisted in exchanging the token-type they were trained on individually, indicating a form of conservatism consistent with previous studies. However, the chimpanzees were more inclined to copy the demonstrator in the test compared to the control condition, indicating a tendency to employ a copy-if-better strategy. We discuss the validity of our results by considering alternative explanations and relate our findings to the emergence of cumulative culture.     

Chimpanzee problem-solving: contrasting the use of causal and arbitrary cues

Humans are able to benefit from a causally structured problem-solving context rather than arbitrarily structured situations. In order to better understand nonhuman causal cognition, it is therefore important to isolate crucial factors that might differentiate between events that follow a purely spatial and temporal contingency and those that hold a “true” causal relationship. In the first of two experiments, chimpanzee subjects were required to detect a bottle containing juice from five opaque bottles of equal shape and size. In the causal condition, the juice bottle looked identical to the other four bottles, only it was much heavier than the others. In the arbitrary condition, the weight of all five bottles was identical, but the juice bottle was color-marked differently. Since bottle opening was made difficult (and therefore costly), the question was whether subject’s manipulative behavior would be random or somehow influenced by the nature of the provided information. Our results show that subjects detected and opened the juice bottle significantly faster when weight was the discriminating feature (causal condition) compared to situations in which the discrimination was necessarily based on a color-cue (arbitrary condition). Experiment 2 ruled out the possibility of a general learning bias toward tactile rather than visual information in chimpanzees. When tested in a simple exchange paradigm that prevented any use of causal information, no predominance of a tactile cue (weight) over a visual cue (color) could be found. Furthermore—and in contrast to the causal condition in Experiment 1—no learning occurred during the course of Experiment 2, neither in the weight nor in the color condition. We therefore conclude that chimpanzees can more easily determine the content of an object based on its causal properties compared to situations in which the only available information is a pure arbitrary regularity. This supports the view that chimpanzees’ causal cognition does not rely on mere perceptual information but also on structural abstraction about their physical environment.     

Relative quantity judgments in South American sea lions (<Emphasis Type="Italic">Otaria flavescens</Emphasis>)

There is accumulating evidence that a variety of species possess quantitative abilities although their cognitive substrate is still unclear. This study is the first to investigate whether sea lions (Otaria flavescens), in the absence of training, are able to assess and select the larger of two sets of quantities. In Experiment 1, the two sets of quantities were presented simultaneously as whole sets, that is, the subjects could compare them directly. In Experiment 2, the two sets of quantities were presented item-by-item, and the totality of items was never visually available at the time of choice. For each type of presentation, we analysed the effect of the ratio between quantities, the difference between quantities and the total number of items presented. The results showed that (1) sea lions can make relative quantity judgments successfully and (2) there is a predominant influence of the ratio between quantities on the subjects’ performance. The latter supports the idea that an analogue representational mechanism is responsible for sea lions’ relative quantities judgments. These findings are consistent with previous reports of relative quantities judgments in other species such as monkeys and apes and suggest that sea lions might share a similar mechanism to compare and represent quantities.     

36‐month‐olds conceal visual and auditory information from others

By three years of age, children are skilled at assessing under which circumstances others can see things. However, nothing is known about whether they can use this knowledge to guide their own deceptive behaviour. Here we investigated 3‐year‐olds’ ability to strategically inhibit or conceal forbidden actions that a nearby adult experimenter could see or hear. In the first experiment, children were more likely to disobey the adult when she did not have visual access to their activities than they were when she was looking at them. In the second experiment, in which the adult could never see the child, children refrained from making noise when engaging in a prohibited action that the adult might hear. These results suggest that by three years of age children use their knowledge of others’ perceptual states to decide whether it is safe to commit a transgression and, moreover, actively conceal perceptual cues that could reveal to others their ongoing transgression.     

Task constraints mask great apes' ability to solve the trap-table task

Researchers have investigated animals' causal knowledge with a task requiring subjects to use a tool to bring a reward within reach whilst avoiding a trap. Previous studies have suggested limitations in the ability of several species to avoid traps in tubes or tables. However, certain features may have inflated task difficulty. We tested 20 chimpanzees (Pan troglodytes), 7 orangutans (Pongo pygmaeus), 5 bonobos (Pan paniscus), and 5 gorillas (Gorilla gorilla) in the trap-table--a task in which subjects have to pull one of two rakes prepositioned behind two rewards on a flat surface. One of the rewards is in front of a trap into which it will fall. We investigated the effect of trap type, tool type, the number of available tools, and reinforcement regime on performance. We replicated previous findings showing that apes failed to choose the correct rake above chance. However, when they could instead choose where to insert a single tool, around 80% of the apes solved the trap-table task in the first trial, revealing an important effect of task constraints on their performance.     

Behavioral cues that great apes use to forage for hidden food

We conducted three studies to examine whether the four great ape species (chimpanzees, bonobos, gorillas, and orangutans) are able to use behavioral experimenter-given cues in an object-choice task. In the subsequent experimental conditions subjects were presented with two eggs, one of which contained food and the other did not. In Study 1 the experimenter examined both eggs by smelling or shaking them, but only made a failed attempt to open (via biting) the egg containing food. In a control condition, the experimenter examined and attempted to open both eggs, but in reverse order to control for stimulus enhancement. The apes significantly preferred the egg that was first examined and then bitten, but had no preference in a baseline condition in which there were no cues. In Study 2, we investigated whether the apes could extend this ability to cues not observed in apes so far (i.e., attempting to pull apart the egg), as well as whether they made this discrimination based on the function of the action the experimenter performed. Subjects significantly preferred eggs presented with this novel cue, but did not prefer eggs presented with a novel but functionally irrelevant action. In Study 3, apes did not interpret human actions as cues to food-location when they already knew that the eggs were empty. Thus, great apes were able to use a variety of experimenter-given cues associated with foraging actions to locate hidden food and thereby were partially sensitive to the general purpose underlying these actions.     

Chimpanzees do not take into account what others can hear in a competitive situation

Chimpanzees (Pan troglodytes) know what others can and cannot see in a competitive situation. Does this reflect a general understanding the perceptions of others? In a study by Hare et al. (2000) pairs of chimpanzees competed over two pieces of food. Subordinate individuals preferred to approach food that was behind a barrier that the dominant could not see, suggesting that chimpanzees can take the visual perspective of others. We extended this paradigm to the auditory modality to investigate whether chimpanzees are sensitive to whether a competitor can hear food rewards being hidden. Results suggested that the chimpanzees did not take what the competitor had heard into account, despite being able to locate the hiding place themselves by the noise.     

A comparative effectiveness trial of functional behavioral assessment methods

Clinicians report primarily using functional behavioral assessment (FBA) methods that do not include functional analyses. However, studies examining the correspondence between functional analyses and other types of FBAs have produced inconsistent results. In addition, although functional analyses are considered the gold standard, their contribution toward successful treatment compared with other FBA methods remains unclear. This comparative effectiveness study, conducted with 57 young children with autism spectrum disorder, evaluated the results of FBAs that did (n = 26) and did not (n = 31) include a functional analysis. Results of FBAs with and without functional analyses showed modest correspondence. All participants who completed functional communication training achieved successful outcomes regardless of the type of FBA conducted.     

Discrete quantity judgments in the great apes (Pan paniscus, Pan troglodytes, Gorilla gorilla, Pongo pygmaeus): the effect of presenting whole sets versus item-by-item

The authors examined quantity-based judgments for up to 10 items for simultaneous and sequential whole sets as well as for sequentially dropped items in chimpanzees (Pan troglodytes), gorillas (Gorilla gorilla), bonobos (Pan paniscus), and orangutans (Pongo pygmaeus). In Experiment 1, subjects had to choose the larger of 2 quantities presented in 2 separate dishes either simultaneously or 1 dish after the other. Representatives of all species were capable of selecting the larger of 2 quantities in both conditions, even when the quantities were large and the numerical distance between them was small. In Experiment 2, subjects had to select between the same food quantities sequentially dropped into 2 opaque cups so that none of the quantities were ever viewed as a whole. The authors found some evidence (albeit weaker) that subjects were able to select the larger quantity of items. Furthermore, the authors found no performance breakdown with the inclusion of certain quantities. Instead, the ratio between quantities was the best performance predictor. The authors conclude that quantity-based judgments rely on an analogical system, not a discrete object file model or perceptual estimation mechanism, such as subitizing.     

Evaluating the influence of postsession reinforcement on choice of reinforcers

Factors that influence reinforcer choice have been examined in a number of applied studies (e.g., Neef, Mace, Shea, & Shade, 1992; Shore, Iwata, DeLeon, Kahng, & Smith, 1997; Tustin, 1994). However, no applied studies have evaluated the effects of postsession reinforcement on choice between concurrently available reinforcers, even though basic findings indicate that this is an important factor to consider (Hursh, 1978; Zeiler, 1999). In this bridge investigation, we evaluated the influence of postsession reinforcement on choice of two food items when task responding was reinforced on progressive-ratio schedules. Participants were 3 children who had been diagnosed with developmental disabilities. Results indicated that response allocation shifted from one food item to the other food item under thinner schedules of reinforcement when no postsession reinforcement was provided. These findings suggest that the efficacy of instructional programs or treatments for problem behavior may be improved by restricting reinforcers outside treatment sessions.