How chimpanzees (Pan troglodytes) perform in a modified emotional Stroop task

Evaluating Self-Directed Behaviours and Their Association with Emotional Arousal across Two Cognitive Tasks in Bonobos (Pan paniscus)

Self-directed behaviours (SDBs) are widely used as markers of emotional arousal in primates, and are commonly linked to negative arousal, or are used as indicators of stress or poor welfare. However, recent studies suggest that not all SDBs have the same function. Moreover, lateralisation in the production of these behaviours has been suggested to be associated with emotional processing. Hence, a better understanding of the production and the asymmetry of these displacement behaviours is needed in a wider range of species in order to confirm their reliability as indicators of emotional arousal. In the current study, we experimentally evaluated the production and asymmetry of SDBs in zoo-housed bonobos during two cognitive touchscreen tasks. Overall, nose wipes were most commonly observed, followed by gentle self-scratches, and rough self-scratches. The rates of nose wipes and rough self-scratches increased with incorrect responses, suggesting that these behaviours indicate arousal and possibly frustration. Rough self-scratching was additionally more directed towards the left hemispace after incorrect responses. In contrast, gentle self-scratching increased after correct responses in one study, possibly linking it with positive arousal. We also tested if left-handed bonobos showed greater behavioural reactivity towards incorrect responses, but found no evidence to confirm this hypothesis. Our results shed light on potential different mechanisms behind separate SDBs. We therefore provide nuance to the use of SDBs as indicator of emotional arousal in bonobos.

Apex and ApeTouch: Development of a Portable Touchscreen System and Software for Primates at Zoos

Simple Summary

Zoos are increasingly looking at technology-based enrichment as a way to improve the welfare of primates in their care. Touchscreen tasks are an option that have a long and established history of usage by primates in research settings as well as a history in zoos. However, the barrier-to-entry is high for new zoos interested in adopting the primate touchscreen method. There are no pre-built and zoo-specific hardware and software options available, so zoos must assemble touchscreen systems on their own and write their own software or use pre-existing research-based software that is not ideally suited to zoo settings and applications. To remedy this, we developed a pre-built portable touchscreen system named Apex along with easy-to-operate primate software named ApeTouch; both are available for zoos to acquire. Our system and software offer enrichment, research, and husbandry applications. To illustrate the utility of these tools, we report on a training study with four species of zoo-housed macaques using the Apex machine and ApeTouch software.

Abstract

We report on the development and testing of a portable touchscreen apparatus and accompanying software program for primate enrichment, cognitive research, and husbandry applications. For zoos considering using technology to bolster scientific efforts or enhance the welfare of primates in their care, touchscreen activities offer a solution that has a long and proven record of primate use in laboratory settings as well as a history of usage in the zoo world. We review the options that are available for zoos to build their own touchscreen systems and we offer as an alternative our pre-built apparatus, Apex, and primate software suite, ApeTouch, both of which are tailored for use in a zoo setting. The efficacy and utility of these tools are demonstrated in a training study with four macaque groups of different species that were previously naïve to touchscreens. All of the groups in the study learned to use the device and displayed a consistent engagement with the touchscreen tasks over 95 daily sessions of exposure. In the final stage of the training, two of the four groups displayed an above-chance level performance on a numerical sequencing task.

Chimpanzees (Pan troglodytes) navigate to find hidden fruit in a virtual environment

Almost all animals navigate their environment to find food, shelter, and mates. Spatial cognition of nonhuman primates in large-scale environments is notoriously difficult to study. Field research is ecologically valid, but controlling confounding variables can be difficult. Captive research enables experimental control, but space restrictions can limit generalizability. Virtual reality technology combines the best of both worlds by creating large-scale, controllable environments. We presented six chimpanzees with a seminaturalistic virtual environment, using a custom touch screen application. The chimpanzees exhibited signature behaviors reminiscent of real-life navigation: They learned to approach a landmark associated with the presence of fruit, improving efficiency over time; they located this landmark from novel starting locations and approached a different landmark when necessary. We conclude that virtual environments can allow for standardized testing with higher ecological validity than traditional tests in captivity and harbor great potential to contribute to longstanding questions in primate navigation, e.g., the use of landmarks, Euclidean maps, or spatial frames of reference.

Testing for the “Blues”: Using the Modified Emotional Stroop Task to Assess the Emotional Response of Gorillas

Simple Summary

We presented three adult male zoo-housed gorillas (Gorilla gorilla gorilla) with a modified emotional Stroop task on a computer touchscreen as a way to assess gorillas’ attentional shift for positively versus negatively valenced items. The gorillas learned to respond to a blue border and to withhold responding to a yellow border. Images of items assumed to have a positive or negative valence for the gorillas were placed within the borders. As predicted, gorillas touched the reinforced blue border more slowly when ‘negative’ images appeared within the blue border, compared to when ‘positive’ images appeared within the yellow border. However, gorillas’ accuracy did not vary as a function of which images appeared within the blue border, possibly because of the high levels of performance on all trials. These results validate the procedure to some degree for assessing the emotional valence of familiar stimuli.

Abstract

We adapted the emotional Stroop task developed for primates to test whether gorillas would show response slowing for images of ‘negative’ compared to images of ‘positive’ items placed within previously reinforced borders. Three zoo-housed male gorillas participated in six phases of an emotional Stroop paradigm. In Phase One, they learned to select blue borders over yellow borders in a forced choice task presented on the touchscreen. In Phase Two, neutral yellow or blue two-dimensional shapes were placed within the borders. On congruent trials, blue images were presented within both blue and yellow borders. On incongruent trials, yellow images were placed within both blue and yellow borders. We continued to use these trials as control trials in subsequent phases. We predicted that response latencies would be slower and accuracy would be lower on incongruent trials. Although the gorillas responded more quickly to incongruent trials, in contrast to predictions, they were more accurate on congruent trials, consistent with predictions. Therefore, we proceeded with Phase Three in which photographs of images assumed to have positive and negative valences for the gorillas were placed within the borders. On test trials, the same positive or negative image was placed within both borders. In Phase Four, a positive image was paired with a negative image on each trial and the positive image appeared in either the blue (congruent trials) or yellow border (incongruent trials). Phases Five and Six replicated Phases Three and Four with images of novel positive and negative items. The gorillas responded more quickly on congruent trials compared to incongruent trials on test trials but not on control trials throughout Phases 3–6. These findings provide some validation for the emotional Stroop task to test attentional shift with emotionally valenced items.

Familiarity mediates apes' attentional biases toward human faces

In zoos, primates experience markedly different interactions with familiar humans, such as the zookeepers who care for them, compared with those with unfamiliar humans, such as the large volume of zoo visitors to whom they are regularly exposed. While the behaviour of zoo-housed primates in the presence of unfamiliar, and to a lesser extent familiar, humans has received considerable attention, if and how they spontaneously distinguish familiar from unfamiliar people, and the cognitive mechanisms underlying the relationships they form with familiar and unfamiliar humans, remain poorly understood. Using a dot-probe paradigm, we assessed whether primates (chimpanzees and gorillas) show an attentional bias toward the faces of familiar humans, with whom the apes presumably had a positive relationship. Contrary to our predictions, all subjects showed a significant attentional bias toward unfamiliar people's faces compared with familiar people's faces when the faces showed a neutral expression, both with and without a surgical face mask on, but no significant attentional bias when the faces showed a surprised expression. These results demonstrate that apes can spontaneously categorize humans based on familiarity and we argue that the attentional biases the apes showed for unfamiliar human faces reflect a novelty effect.

Validation of a battery of inhibitory control tasks reveals a multifaceted structure in non-human primates

Inhibitory control, the ability to override an inappropriate prepotent response, is crucial in many aspects of everyday life. However, the various paradigms designed to measure inhibitory control often suffer from a lack of systematic validation and have yielded mixed results. Thus the nature of this ability remains unclear, is it a general construct or a family of distinct sub-components? Therefore, the aim of this study was first to demonstrate the content validity and the temporal repeatability of a battery of inhibitory control tasks. Then we wanted to assess the contextual consistency of performances between these tasks to better understand the structure of inhibitory control. We tested 21 rhesus macaques (Macaca mulatta, 12 males, nine females) in a battery of touchscreen tasks assessing three main components of inhibitory control: inhibition of a distraction (using a Distraction task), inhibition of an impulsive action (using a Go/No-go task) and inhibition of a cognitive set (using a Reversal learning task). All tasks were reliable and effective at measuring the inhibition of a prepotent response. However, while there was consistency of performance between the inhibition of a distraction and the inhibition of an action, representing a response-driven basic form of inhibition, this was not found for the inhibition of a cognitive set. We argue that the inhibition of a cognitive set is a more cognitively demanding form of inhibition. This study gives a new insight in the multifaceted structure of inhibitory control and highlights the importance of a systematic validation of cognitive tasks in animal cognition.

What's not to like about Likert? Developing a nonverbal animal preference scale (NAPS)

Rating scales, such as Likert scales, are incredibly flexible and intuitive tools for measuring individuals' rating of agreement with or relative preference for many types of stimuli. For humans, this typically involves ratings of agreement between end points representing distinct attitudes or beliefs; For example, strongly disagree to strongly agree. Nonverbal versions of Likert scales have also been presented to children, allowing them to indicate their degree of preference, pain, or happiness. However, before the current study, no known efforts had been made to develop a nonverbal rating scale for use with nonhuman animals. Such a scale would be a useful welfare tool, allowing nonverbal individuals to indicate not just relative preferences between pairs of items but their degree of liking for individual items. I present an outline of the steps taken to create such a scale for use with three zoo-housed gorillas. Two gorillas succeeded in associating preferred and less preferred foods with different response buttons but none of the gorillas were able to effectively use the neutral response button. It is possible that limits in gorillas' capacity for conditional discriminations and/or conceptualization of constructs as abstract as "liking" impeded training. These data are relevant for understanding gorilla cognition and can inform continued efforts to create a tool for nonhumans to communicate their preferences to human caregivers in a more nuanced way than is currently possible.

Heterogeneity of performances in several inhibitory control tasks: male rhesus macaques are more easily distracted than females

Inhibitory control, the ability to override a dominant response, is crucial in many aspects of everyday life. In animal studies, striking individual variations are often largely ignored and their causes rarely considered. Hence, our aims were to systematically investigate individual variability in inhibitory control, to replicate the most common causes of individual variation (age, sex and rank) and to determine if these factors had a consistent effect on three main components of inhibitory control (inhibition of a distraction, inhibition of an action, inhibition of a cognitive set). We tested 21 rhesus macaques (Macaca mulatta) in a battery of validated touchscreen tasks. We first found individual variations in all inhibitory control performances. We then demonstrated that males had poorer performances to inhibit a distraction and that middle-aged individuals exhibited poorer performance in the inhibition of a cognitive set. Hence, the factors of age and sex were not consistently associated with the main components of inhibitory control, suggesting a multi-faceted structure. The rank of the subjects did not influence any inhibitory control performances. This study adopts a novel approach for animal behaviour studies and gives new insight into the individual variability of inhibitory control which is crucial to understand its evolutionary underpinnings.

A Kiosk Station for the Assessment of Multiple Cognitive Domains and Cognitive Enrichment of Monkeys

Nonhuman primates (NHP's) are self-motivated to perform cognitive tasks on touchscreens in their animal housing setting. To leverage this ability, fully integrated hardware and software solutions are needed that work within housing and husbandry routines while also spanning cognitive task constructs of the Research Domain Criteria (RDoC). Here, we detail such an integrated robust hardware and software solution for running cognitive tasks in cage-housed NHP's with a cage-mounted Kiosk Station (KS-1). KS-1 consists of a frame for mounting flexibly on housing cages, a touchscreen animal interface with mounts for receptables, reward pumps, and cameras, and a compact computer cabinet with an interface for controlling behavior. Behavioral control is achieved with a Unity3D program that is virtual-reality capable, allowing semi-naturalistic visual tasks to assess multiple cognitive domains.KS-1 is fully integrated into the regular housing routines of monkeys. A single person can operate multiple KS-1's. Monkeys engage with KS-1 at high motivation and cognitive performance levels at high intra-individual consistency. KS-1 is optimized for flexible mounting onto standard apartment cage systems and provides a new design variation complementing existing cage-mounted touchscreen systems. KS-1 has a robust animal interface with options for gaze/reach monitoring. It has an integrated user interface for controlling multiple cognitive tasks using a common naturalistic object space designed to enhance task engagement. All custom KS-1 components are open-sourced.In summary, KS-1 is a versatile new tool for cognitive profiling and cognitive enrichment of cage-housed monkeys. It reliably measures multiple cognitive domains which promises to advance our understanding of animal cognition, inter-individual differences, and underlying neurobiology in refined, ethologically meaningful behavioral foraging contexts.

Chimpanzees (Pan troglodytes) show subtle signs of uncertainty when choices are more difficult

Humans can tell when they find a task difficult. Subtle uncertainty behaviors like changes in motor speed and muscle tension precede and affect these experiences. Theories of animal metacognition likewise stress the importance of endogenous signals of uncertainty as cues that motivate metacognitive behaviors. However, while researchers have investigated second-order behaviors like information seeking and declining difficult trials in nonhuman animals, they have devoted little attention to the behaviors that express the cognitive conflict that gives rise to such behaviors in the first place. Here we explored whether three chimpanzees would, like humans, show hand wavering more when faced with more difficult choices in a touch screen transitive inference task. While accuracy was very high across all conditions, all chimpanzees wavered more frequently in trials that were objectively more difficult, demonstrating a signature behavior which accompanies experiences of difficulty in humans. This lends plausibility to the idea that feelings of uncertainty, like other emotions, can be studied in nonhuman animals. We propose to routinely assess uncertainty behaviors to inform models of procedural metacognition in nonhuman animals.

A Comparative Perspective on Three Primate Species' Responses to a Pictorial Emotional Stroop Task

The Stroop effect describes interference in cognitive processing due to competing cognitive demands. Presenting emotionally laden stimuli creates similar Stroop-like effects that result from participants' attention being drawn to distractor stimuli. Here, we adapted the methods of a pictorial Stroop study for use with chimpanzees (N = 6), gorillas (N = 7), and Japanese macaques (N = 6). We tested all subjects via touchscreens following the same protocol. Ten of the 19 subjects passed pre-test training. Subjects who reached criterion were then tested on a standard color-interference Stroop test, which revealed differential accuracy in the primates' responses across conditions. Next, to test for an emotional Stroop effect, we presented subjects with photographs that were either positively valenced (a preferred food) or negatively valenced (snakes). In the emotional Stroop task, as predicted, the primates were less accurate in trials which presented emotionally laden stimuli as compared to control trials, but there were differences in the apes' and monkeys' response patterns. Furthermore, for both Stroop tests, while we found that subjects' accuracy rates were reduced by test stimuli, in contrast to previous research, we found no difference across trial types in the subjects' response latencies across conditions.

In or out: Response slowing across housing conditions as a measure of affect in three Western lowland gorillas (Gorilla gorilla gorilla)

Background

Individuals experiencing negative affect have shown response slowing, a longer latency to respond in relation to baseline, when presented with aversive stimuli. We assessed response slowing in three male gorillas housed in a bachelor group as a function of daytime and nighttime housing arrangements.

Methods

In both experiments, three gorillas were rewarded for touching a single image (baseline, non-threatening gorilla or threatening gorilla) on a touchscreen. In Experiment One, they completed 48 50-trial sessions across combinations of three nested daytime and three nighttime conditions. In Experiment Two, they completed eight 50-trial sessions with novel stimuli across two daytime conditions, which were nested within two nighttime conditions. Housing conditions represented different amounts of space and degree of choice. We predicted that the gorillas would show response slowing to threatening stimuli when space and choice were restricted.

Results

We did not observe response slowing in Experiment One, although daytime and nighttime conditions interacted to predict response latencies. The gorillas responded more slowly when they had access to indoors and outdoors overnight compared to when they were in their stalls or together in an indoor habitat, but only if they had been given access to both indoors and outdoors or locked in the indoor habitat the day before. In Experiment Two, the gorillas did show response slowing to threatening stimuli, but this pattern did not interact with housing conditions. Our results, although limited by a small sample, are somewhat consistent with those of a previous study that did not find significant response slowing for apes as a function of aversive testing conditions, although the procedure has been effective in identifying dysregulated fear (high fear in low threat conditions) in macaques. The utility of this paradigm for testing affect in apes awaits further evaluation.

An understanding of third-party friendships in a tolerant macaque

Complex societies are shaped by social relationships between multiple individuals. The pressure to track these relationships has driven the evolution of social cognition in primates. Importantly, it can be adaptive to track not only personal relationships, but also those established between third-parties. Primates have knowledge about others’ dominance hierarchies and kinship, but we do not know to what extent they also understand friendships. In a playback experiment, Tonkean macaques were presented with simulated conflicts involving third-party female dyads who were established friends or non-friends. Hearing a conflict between friends elicited a stronger behavioural response in listeners (i.e. an increase in looking time) compared to hearing a conflict between non-friends. Conflicts between friends are likely to represent a greater disruption of the social group and structure of the network, and therefore this difference in response may represent an adaptive strategy employed by the macaques to selectively monitor important social interactions in the group. These findings provide evidence that Tonkean macaques (and potentially other primates) can classify the relationships of others based on their degree of friendship and additionally, confirms the important role friendships have within the societies of social primates.

Sound symbolic congruency detection in humans but not in great apes

Theories on the evolution of language highlight iconicity as one of the unique features of human language. One important manifestation of iconicity is sound symbolism, the intrinsic relationship between meaningless speech sounds and visual shapes, as exemplified by the famous correspondences between the pseudowords 'maluma' vs. 'takete' and abstract curved and angular shapes. Although sound symbolism has been studied extensively in humans including young children and infants, it has never been investigated in non-human primates lacking language. In the present study, we administered the classic "takete-maluma" paradigm in both humans (N = 24 and N = 31) and great apes (N = 8). In a forced choice matching task, humans but not great apes, showed crossmodal sound symbolic congruency effects, whereby effects were more pronounced for shape selections following round-sounding primes than following edgy-sounding primes. These results suggest that the ability to detect sound symbolic correspondences is the outcome of a phylogenetic process, whose underlying emerging mechanism may be relevant to symbolic ability more generally.

An assessment of touchscreens for testing primate food preferences and valuations

Typically, animals' food preferences are tested manually, which can be both time-consuming and vulnerable to experimenter biases. Given the utility of ascertaining animals' food preferences for research and husbandry protocols, developing a quick, reliable, and flexible paradigm would be valuable for expediting many research protocols. Therefore, we evaluated the efficacy of using a touchscreen interface to test nonhuman primates' food preferences and valuations, adapting previously validated manual methods. We tested a nonhuman primate subject with four foods (carrot, cucumber, grape, and turnip). Preference testing followed a pairwise forced choice protocol with pairs of food images presented on a touchscreen: The subject was rewarded with whichever food was selected. All six possible pairwise combinations were presented, with 90 trials per pairing. Second, we measured how hard the subject was willing to work to obtain each of the four foods, allowing us to generate demand curves. For this phase, a single image of a food item was presented on the touchscreen that the subject had to select in order to receive the food, and the number of selections required increased following a quarter-log scale, with ten trials per cost level (1, 2, 3, 6, 10, and 18). These methods allowed us to ascertain the subject's relative preferences and valuations of the four foods. The success of this touchscreen protocol for testing the subject's food preferences, from both a practical and a theoretical standpoint, suggests that the protocol should be further validated with other foods with this subject, with other subjects, and with other test items.

A review of zoo-based cognitive research using touchscreen interfaces

In the past few decades, there has been an increase in the number of zoo-based touchscreen studies of animal cognition around the world. Such studies have contributed to the field of comparative cognition despite the fact research has only been performed at a relatively small number of institutions and with a narrow range of species. Nonetheless, zoo-based touchscreen studies are increasingly recognized as both having the potential to be enriching for captive animals by providing them with opportunities for choice, as well as potentially being a tool with which to measure changes in welfare. Zoo-based touchscreen research on public display also has the potential to impact zoo visitors; encouraging them not only learn more about the cognitive abilities of animals, but also potentially promoting increased respect for these species. Given the lack of a comprehensive review of this scope of specialized research, and the broad potential impacts on animals and programs, here we discuss the history, implementation, and potential outcomes of touchscreen research in zoo settings.

Affect-Driven Attention Biases as Animal Welfare Indicators: Review and Methods

Attention bias describes the differential allocation of attention towards one stimulus compared to others. In humans, this bias can be mediated by the observer's affective state and is implicated in the onset and maintenance of affective disorders such as anxiety. Affect-driven attention biases (ADABs) have also been identified in a few other species. Here, we review the literature on ADABs in animals and discuss their utility as welfare indicators. Despite a limited research effort, several studies have found that negative affective states modulate attention to negative (i.e., threatening) cues. ADABs influenced by positive-valence states have also been documented in animals. We discuss methods for measuring ADAB and conclude that looking time, dot-probe, and emotional spatial cueing paradigms are particularly promising. Research is needed to test them with a wider range of species, investigate attentional scope as an indicator of affect, and explore the possible causative role of attention biases in determining animal wellbeing. Finally, we argue that ADABs might not be best-utilized as indicators of general valence, but instead to reveal specific emotions, motivations, aversions, and preferences. Paying attention to the human literature could facilitate these advances.

Emotion-Cognition Interaction in Nonhuman Primates: Cognitive Avoidance of Negative Stimuli in Baboons (Papio papio)

It is well established that emotion and cognition interact in humans, but such an interaction has not been extensively studied in nonhuman primates. We investigated whether emotional value can affect nonhuman primates' processing of stimuli that are only mentally represented, not visually available. In a short-term memory task, baboons memorized the location of two target squares of the same color, which were presented with a distractor of a different color. Through prior long-term conditioning, one of the two colors had acquired a negative valence. Subjects were slower and less accurate on the memory task when the targets were negative than when they were neutral. In contrast, subjects were faster and more accurate when the distractors were negative than when they were neutral. Some of these effects were modulated by individual differences in emotional disposition. Overall, the results reveal a pattern of cognitive avoidance of negative stimuli, and show that emotional value alters cognitive processing in baboons even when the stimuli are not physically present. This suggests that emotional influences on cognition are deeply rooted in evolutionary continuity.

Primate cognition: attention, episodic memory, prospective memory, self-control, and metacognition as examples of cognitive control in nonhuman primates

Primate Cognition is the study of cognitive processes, which represent internal mental processes involved in discriminations, decisions, and behaviors of humans and other primate species. Cognitive control involves executive and regulatory processes that allocate attention, manipulate and evaluate available information (and, when necessary, seek additional information), remember past experiences to plan future behaviors, and deal with distraction and impulsivity when they are threats to goal achievement. Areas of research that relate to cognitive control as it is assessed across species include executive attention, episodic memory, prospective memory, metacognition, and self-control. Executive attention refers to the ability to control what sensory stimuli one attends to and how one regulates responses to those stimuli, especially in cases of conflict. Episodic memory refers to memory for personally experienced, autobiographical events. Prospective memory refers to the formation and implementation of future-intended actions, such as remembering what needs to be done later. Metacognition consists of control and monitoring processes that allow individuals to assess what information they have and what information they still need, and then if necessary to seek information. Self-control is a regulatory process whereby individuals forego more immediate or easier to obtain rewards for more delayed or harder to obtain rewards that are objectively more valuable. The behavioral complexity shown by nonhuman primates when given tests to assess these capacities indicates psychological continuities with human cognitive control capacities. However, more research is needed to clarify the proper interpretation of these behaviors with regard to possible cognitive constructs that may underlie such behaviors. WIREs Cogn Sci 2016, 7:294-316. doi: 10.1002/wcs.1397 For further resources related to this article, please visit the WIREs website.

Emotion Evaluation and Response Slowing in a Non-Human Primate: New Directions for Cognitive Bias Measures of Animal Emotion?

The cognitive bias model of animal welfare assessment is informed by studies with humans demonstrating that the interaction between emotion and cognition can be detected using laboratory tasks. A limitation of cognitive bias tasks is the amount of training required by animals prior to testing. A potential solution is to use biologically relevant stimuli that trigger innate emotional responses. Here; we develop a new method to assess emotion in rhesus macaques; informed by paradigms used with humans: emotional Stroop; visual cueing and; in particular; response slowing. In humans; performance on a simple cognitive task can become impaired when emotional distractor content is displayed. Importantly; responses become slower in anxious individuals in the presence of mild threat; a pattern not seen in non-anxious individuals; who are able to effectively process and disengage from the distractor. Here; we present a proof-of-concept study; demonstrating that rhesus macaques show slowing of responses in a simple touch-screen task when emotional content is introduced; but only when they had recently experienced a presumably stressful veterinary inspection. Our results indicate the presence of a subtle “cognitive freeze” response; the measurement of which may provide a means of identifying negative shifts in emotion in animals.