Response duration is sensitive to both immediate and delayed reinforcement

We investigated the duration of lever pressing by rats when the delivery of appetitive reinforcers was contingent upon response duration. In the first experiment, response durations increased when duration requirements were imposed, and they decreased when duration requirements were removed. This effect occurred whether reinforcers were immediate or delayed by 8 s. In order to maintain the integrity of the delay intervals, reinforcer delivery was dependent upon both lever depression and release. In a second experiment, lever depression only and a response duration of at least 4 s were required for reinforcer delivery. Compared to immediate reinforcement conditions, delayed reinforcers increased both variability and the length of the maximum response durations. In a third experiment, immediate reinforcers were delivered contingent upon lever depression and release under a variety of duration requirements. Median lever‐press durations tracked the contingencies rapidly. Across all three experiments, rats emitted numerous response durations that were too short to satisfy the reinforcer requirements, and bimodal distributions similar to those produced by differential reinforcement of low rate schedules were evident for most rats. In many aspects, response duration responds to reinforcement parameters in a fashion similar to rate of discrete responding, but an examination of this continuous dimension of behavior may provide additional information about environment–behavior relationships.     

Motivated to confront: How experiencing anger affects anchoring bias

Prior research has asserted that emotions affect anchoring bias in decision making through the emotion's certainty appraisal or through the emotion's action tendencies, but these prior studies investigate the role of each component—appraisal or action tendency—without accounting for potential effects of the other one. The current research investigates whether anger exerts a significant effect on anchoring bias by activating a desire to confront a potential anchor. Importantly, the studies compare the effect of anger versus disgust, emotions that differ in their action tendency but are similar in their certainty appraisal. In Study 1, participants completed an emotion induction task and then a negotiation task where the first offer from the negotiation partner served as a potential anchor. Anger led to more deviation from the anchor compared with disgust or neutral feelings. Subsequent studies provide evidence that the angry participants are less anchored when the anchor value comes from a more confrontable source (someone else vs. themselves in Study 2 and an out‐group member vs. an in‐group member in Study 3).     

The gestural repertoire of the wild bonobo (<Emphasis Type="Italic">Pan paniscus</Emphasis>): a mutually understood communication system

In animal communication, signallers and recipients are typically different: each signal is given by one subset of individuals (members of the same age, sex, or social rank) and directed towards another. However, there is scope for signaller–recipient interchangeability in systems where most signals are potentially relevant to all age–sex groups, such as great ape gestural communication. In this study of wild bonobos (Pan paniscus), we aimed to discover whether their gestural communication is indeed a mutually understood communicative repertoire, in which all individuals can act as both signallers and recipients. While past studies have only examined the expressed repertoire, the set of gesture types that a signaller deploys, we also examined the understood repertoire, the set of gestures to which a recipient reacts in a way that satisfies the signaller. We found that most of the gestural repertoire was both expressed and understood by all age and sex groups, with few exceptions, suggesting that during their lifetimes all individuals may use and understand all gesture types. Indeed, as the number of overall gesture instances increased, so did the proportion of individuals estimated to both express and understand a gesture type. We compared the community repertoire of bonobos to that of chimpanzees, finding an 88 % overlap. Observed differences are consistent with sampling effects generated by the species’ different social systems, and it is thus possible that the repertoire of gesture types available to Pan is determined biologically.     

Temporal and causal order effects in thinking about what might have been

When people think counterfactually about what might have been different for a sequence of events, they are influenced by the order in which the events occurred. They tend to mentally undo the most recent event in a temporal sequence of two events. But they tend to mentally undo the first event in a causal sequence of four events. We report the results of two experiments that show that the temporal and causal order effects are not dependent on the number of events in the sequence. Our first experiment, with 300 participants, shows that the temporal order effect occurs for sequences with four events as well as for sequences with two events. Our second experiment, with 372 participants, shows that the causal order effect occurs for sequences with two events as well as for sequences with four events. We discuss the results in terms of the mental representations that people construct of temporal and causal sequences.     

Triadic and collaborative play by gorillas in social games with objects

Interaction with others over objects has until recently been thought lacking in the social play of non-human great apes, in contrast to that of children; even now, only bonobos have been observed to engage in social play involving objects. Human children’s triadic interactions with objects involve joint attention, showing and giving, communication that maintains interaction, and sharing of emotions and experiences. We question assertions that chimpanzees, and non-human great apes in general, lack the key characteristics of children’s collaborative play. Here, we show that zoo gorillas play games that are both triadic and collaborative. These games were videotaped at the San Francisco Zoo in five different years and involved five different pairings of gorillas. The context was in most cases playfully competitive, involving objects such as balls, bags and leather pieces as foci of joint attention; the ostensible goal in most games was to gain or keep possession of a particular object. In some episodes, roles as possessor or pursuer of an object were exchanged many times; in others, one gorilla retained possession of an object but encouraged pursuit from a partner. Through gaze and gesture, gorillas invited others to: share interest in and attention to objects; share patterns of play; and re-engage after breaks in play. Sometimes, gorillas would assist others in their efforts to engage in collaborative play: older gorillas encouraged younger partners by ‘self-handicapping’ their own actions. Collaborative games may occur later in the ontogeny of gorillas than in humans, and depend on the challenges and artifacts available in a particular group’s habitat.     

Trait anxiety,anxious mood,and threat detection

Abstract

Subjects were required to detect either an angry or a happy target face in a stimulus array of 12 photographs. It was found with neutral distractor faces that those high in trait anxiety detected angry faces faster than did low trait-anxious subjects, but the two groups did not differ in their speed of detection of happy targets. In addition, high trait-anxious subjects detected happy target faces slower than low trait-anxious subjects when the distractor faces were angry. Comparable findings were obtained whether or not there was anxious mood induction. It was concluded that high trait-anxious individuals have facilitated detection and processing of environmental threat relative to low trait-anxious subjects, which enhance performance when the target is threatening, but which impair performance when the distractors are threatening.