Self-control constitutes a fundamental aspect of human nature. Yet there is reason to believe that human and nonhuman self-control processes rely on the same biological mechanism--the availability of glucose in the bloodstream. Two experiments tested this hypothesis by examining the effect of available blood glucose on the ability of dogs to exert self-control. Experiment 1 showed that dogs that were required to exert self-control on an initial task persisted for a shorter time on a subsequent unsolvable task than did dogs that were not previously required to exert self-control. Experiment 2 demonstrated that providing dogs with a boost of glucose eliminated the negative effects of prior exertion of self-control on persistence; this finding parallels a similar effect in humans. These findings provide the first evidence that self-control relies on the same limited energy resource among humans and nonhumans. Our results have broad implications for the study of self-control processes in human and nonhuman species.
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"Regardless, the account can only explain species differences in perseverative errors, and thus, a second mechanism must be at play, such as timing. Although it was hypothesized that dogs' superior selfcontrol would result in optimal performance, much selfcontrol research is conducted with tasks that require waiting rather than choice (e.g., Miller et al. 2010). In choice tasks, such as the mid-session reversal task, dogs may be more impulsive than pigeons. "
[Show abstract][Hide abstract] ABSTRACT: Pigeons given a simultaneous spatial discrimination reversal, in which a single reversal occurs at the midpoint of each session, consistently show anticipation prior to the reversal as well as perseveration after the reversal, suggesting that they use a less effective cue (time or trial number into the session) than what would be optimal to maximize reinforcement (local feedback from the most recent trials). In contrast, rats (Rattus norvegicus) and humans show near-optimal reversal learning on this task. To determine whether this is a general characteristic of mammals, in the present research, pigeons (Columba livia) and dogs (Canis familiaris) were tested with a simultaneous spatial discrimination mid-session reversal. Overall, dogs performed the task more poorly than pigeons. Interestingly, both pigeons and dogs employed what resembled a timing strategy. However, dogs showed greater perseverative errors, suggesting that they may have relatively poorer working memory and inhibitory control with this task. The greater efficiency shown by pigeons with this task suggests they are better able to time and use the feedback from their preceding choice as the basis of their future choice, highlighting what may be a qualitative difference between the species.
"A limitation of the present study is the small sample size. Given an a priori power calculation using the observed effect size from Miller et al. (2010), we started with a sufficient sample size. However , we lost three subjects during the execution of this project and were unable to readily replace them. "
[Show abstract][Hide abstract] ABSTRACT: It has been hypothesized that self-control is constrained by a limited energy resource that can be depleted through exertion. Once depleted, this resource can be replenished by the consumption or even the taste of glucose. For example, the need to inhibit reduces subsequent persistence at problem solving by humans and dogs, an effect that is not observed when a glucose drink (but not placebo) is administered following initial inhibition. The mechanism for replenishment by glucose is currently unknown. Energy transfer is not necessary, though insulin secretion may be involved. This possibility was investigated in the current study by having dogs exert self-control (sit–stay) and subsequently giving them (1) glucose that causes the release of insulin, (2) fructose that does not result in the release of insulin nor does it affect glucose levels (but is a carbohydrate), or (3) a calorie-free drink. Persistence measures indicated that both glucose and fructose replenished canine persistence, whereas the calorie-free drink did not. These results indicate that insulin release is probably not necessary for the replenishment that is presumed to be responsible for the increase in persistence. This article is part of a Special Issue entitled: Canine Behavior.
"Interestingly, studies on inhibitory control in dogs have revealed parallels to inhibitory control in humans: difficulties in inhibiting an action were more pronounced in aged individuals (Tapp et al. 2003), and exercising self-control on one task led to decreased motivation to exert inhibitory control on a subsequent task that could be prevented by intake or a taste of glucose (Miller et al. 2010; Molden et al. 2012). These findings suggest that inhibitory control in humans and dogs, and thus likely other non-human animals, might rely on similar mechanisms (Miller et al. 2010). Therefore, effects that have been found to facilitate inhibitory control in humans, such as training of self-control on one task that increases the subsequent performance on a different task (Oaten and Cheng 2006a, b), might present an interesting issue to take into account in future studies on cooperative problem-solving abilities of dogs. "
[Show abstract][Hide abstract] ABSTRACT: The process of domestication has arguably provided dogs (Canis familiaris) with decreased emotional reactivity (reduced fear and aggression) and increased socio-cognitive skills adaptive for living with humans. It has been suggested that dogs are uniquely equipped with abilities that have been identified as crucial in cooperative problem-solving, namely social tolerance and the ability to attend to other individuals’ behaviour. Accordingly, dogs might be hypothesised to perform well in tasks in which they have to work together with a human partner. Recently, researchers have found that dogs successfully solved a simple cooperative task with another dog. Due to the simplicity of the task, this study was, however, unable to provide clear evidence as to whether the dogs’ successful performance was based on the cognitive ability of behavioural coordination, namely the capacity to link task requirements to the necessity of adjusting one’s actions to the partner’s behaviour. Here, we tested dogs with the most commonly used cooperative task, appropriate to test behavioural coordination. In addition, we paired dogs with both a conspecific and a human partner. Although dogs had difficulties in inhibiting the necessary action when required to wait for their partner, they successfully attended to the two cues that predicted a successful outcome, namely their partner’s behaviour and the incremental movement of rewards towards themselves. This behavioural coordination was shown with both a conspecific and a human partner, in line with the recent findings suggesting that dogs exhibit highly developed socio-cognitive skills in interactions with both humans and other dogs.
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The online version of this article (doi:10.1007/s10071-013-0676-1) contains supplementary material, which is available to authorized users.