A mind cleared by walnut oil: The effects of polyunsaturated and saturated fat on extinction learning.

The treatment of anxiety-based psychopathology often hinges upon extinction learning. Research in nutritional neuroscience has observed that the regular consumption of perilla oil (50% alpha-linolenic acid (ALA)) facilitates extinction learning in rats (Yamamoto et al., 1988). However, acute facilitation of extinction learning by oils rich in ALA has not been reported for rats or humans, though the acute consumption of rapeseed oil (10% ALA) has been observed to improve cognitive processing speed in humans (Jones, Sünram-Lea, & Wesnes, 2012). For this reason, the present laboratory work examined the effects of adding walnut oil (12% ALA) to a chocolate milkshake on the acquisition, generalization, and extinction of a fear-based prediction in young adults. It compared performance between subjects. The other participants consumed a similar milkshake with either an equicaloric amount of cream (saturated fat), or with no added fat (control). Acquisition and generalization of the fear-based prediction were similar for all groups. However, those who consumed walnut oil extinguished most rapidly and profoundly. Implications for extinction learning are discussed.

How Dog Behavior Influences Pet Owner's Perceptions of Dog Preference for Dental Chews.

American pet owners spend billions of dollars on food and treats so it is important to understand what products they want and what they think their dog would enjoy. This study analyzed video recordings of dogs engaging in dental chews in their home environment and compared the observed appetitive behaviors to owner preference and owner-reported dog preference. Overall, appetitive behavior differed significantly between some dental chews. Owner preference for the chews correlated significantly with dog appetitive behavior, but the effect was small (r (702) = 0.22, p = 0.001), whereas owner-reported dog preference correlated significantly with dog appetitive behavior and showed a moderate effect size (r (702) = 0.43, p = 0.001)-similar in magnitude to findings when parents are asked to report on their children's behavior. By merging objective behavioral observation of owner-recorded videos with their survey responses, we were able to preliminarily parse out what factors owners may use to assess preference and encourage the future use of in-home video recordings to better understand dog and owner engagement and interaction with pet products.

Decision making by humans in a behavioral task: do humans, like pigeons, show suboptimal choice?

Consistent with human gambling behavior but contrary to optimal foraging theory, pigeons show a strong preference for an alternative with low probability and high payoff (a gambling-like alternative) over an alternative with a greater net payoff (Zentall & Stagner, Proceedings of the Royal Society B, 278, 1203-1208, 2011). In the present research, we asked whether humans would show suboptimal choice on a task involving choices with probabilities similar to those for pigeons. In Experiment 1, when we selected participants on the basis of their self-reported gambling activities, we found a significantly greater choice of the alternative involving low probability and high payoff (gambling-like alternative) than for a group that reported an absence of gambling activity. In Experiment 2, we found that when the inhibiting abilities of typical humans were impaired by a self-regulatory depletion manipulation, they were more likely to choose the gambling-like alternative. Taken together, the results suggest that this task is suitable for the comparative study of suboptimal decision-making behavior and the mechanisms that underlie it.

Self-control without a "self"?: common self-control processes in humans and dogs.

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.

Object permanence in dogs: invisible displacement in a rotation task.

Dogs were tested for object permanence using an invisible displacement in which an object was hidden in one of two containers at either end of a beam and the beam was rotated. Consistent with earlier research, when the beam was rotated 180 degrees , the dogs failed to find the object. However, when the beam was rotated only 90 degrees , they were successful. Furthermore, when the dogs were led either 90 degrees or 180 degrees around the apparatus, they were also successful. In a control condition, when the dogs could not see the direction of the 90 degrees rotation, they failed to find the object. The results suggest that the 180 degrees rotation may produce an interfering context that can be reduced by rotating the apparatus only 90 degrees or by changing the dogs' perspective. Once the conflict is eliminated, dogs show evidence of object permanence that includes invisibly displaced objects.

Matching-to-sample by pigeons: the dissociation of comparison choice frequency from the probability of reinforcement.

It has been proposed that comparison choice in matching-to-sample should depend on two factors, the relative probability of reinforcement associated with each of the comparison stimuli and the conditional probability of each comparison stimulus being correct given presentation of one of the samples. DiGian and Zentall [DiGian, K.A., Zentall, T.R., 2007. Matching-to-sample in pigeons: in the absence of sample memory, sample frequency is a better predictor of comparison choice than the probability of reinforcement for comparison choice. Learn Behav. 35, 242-261] have shown that sample frequency together with the probability of choosing each of the comparison stimuli in training can influence comparison choice when delays are introduced, when the number of reinforcements associated with each of the comparison stimuli is equated. Furthermore, Zentall and Clement [Zentall, T.R., Clement, T.S., 2002. Memory mechanisms in pigeons: Evidence of base-rate neglect. J. Exp. Psych.: Anim. Behav. Proc. 28, 111-115] have found that sample frequency can affect comparison choice when delays are introduced independently of the number of choices of each of the comparison stimuli in training and the number of reinforcements associated with each of the comparison stimuli is equated. In the present experiment we found that the probability of choosing each of the comparison stimuli in training can affect comparison choice when delays are introduced, independently of sample frequency and when the number of reinforcements associated with each of the comparison stimuli is equated. Together, these experiments suggest that when the sample is not available, there is a partial dissociation between comparison choice and the probability of reinforcement associated with each of the comparison stimuli.

Self-regulatory depletion in dogs: insulin release is not necessary for the replenishment of persistence.

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 a placebo) is administered following initial inhibition. The mechanism for replenishment by glucose is currently unknown. Energy transfer is not necessary, although 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 it 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.

There is no sweet escape from social pain: glucose does not attenuate the effects of ostracism.

Ostracism causes social pain and is known to activate regions of the brain that are involved in the representation of physical pain. Previous research has observed that acetominophen (a common pain reliever) can reduce the pain of exclusion. The taste and consumption of glucose can also relieve physical pain, and the purpose of the current study was to examine whether it might also reduce the negative emotional effects of ostracism. In an appropriately powered experiment, participants were given 25g of glucose or a sucralose placebo before being ostracized while playing Cyberball. Strong effects of ostracism were observed, however, there was no effect of glucose on immediate or delayed self-reported needs or mood. These results are discussed in reference to the possibility that social pain is unlike physical pain since the latter is affected by glucose, which is believed to lessen pain by increasing endogenous opioid activity.

Can you enhance executive control without glucose? The effects of fructose on problem solving.

The consumption of glucose can enhance executive control by increasing blood glucose and providing energy for brain processes. However, a glucose mouth rinse also positively affects executive control in the absence of an effect on blood glucose. This observation suggests that glucose can enhance executive control via another mechanism, perhaps by increasing cortical activation in motivational reward pathways. This hypothesis was examined in the current study by having participants consume fructose, glucose or a placebo 10 minutes before solving word anagrams. Fructose was used because it does not affect blood glucose levels, inhibits cortical responding, and cannot entrain a taste preference post-ingestion. The latter evidences that fructose differs from glucose in its ability to elicit activation in motivational reward pathways. It was observed that consuming fructose and glucose resulted in the resolution of more anagrams than the placebo. These results suggest that at least some of the effects of glucose and fructose on problem solving operate through a common peripheral mechanism that is independent of motivational reward pathways.

The impact of facial emotional expressions and sex on interpersonal distancing as evaluated in a computerized stop-distance task.

This study utilizes a novel computerized stop-distance task to examine social space preferences of young adult female and male participants (18-23 years old) who envisioned being approached by others of both sexes who were displaying different facial emotional expressions. The results showed that those displaying anger were kept furthest away, followed by those displaying fear, then sadness, and then neutral expressions, leaving those displaying happiness closest to the participant. It was observed that female participants maintained greater distance from approachers than male participants, and that female approachers were allowed to come nearer than male approachers. These sex differences were observed for most of the emotional facial expressions.

Guilt by association and honor by association: the role of acquired equivalence.

Guilt by association and honor by association are two types of judgments that suggest that a negative or positive quality of a person or object can transfer to another person or object, merely by co-occurrence. Most examples have been demonstrated under conditions of direct associations. Here, we provide experimental evidence of guilt by association and honor by association via indirect associations. We show that participants may treat two individuals alike if they have been separately paired with a common event using an acquired-equivalence paradigm. Our findings suggest that association fallacies can be examined using a paradigm originally developed for research with nonhuman animals and based on a representation mediation account.

Spatial integration of boundaries in a 3D virtual environment.

Prior research, using two- and three-dimensional environments, has found that when both human and nonhuman animals independently acquire two associations between landmarks with a common landmark (e.g., LM1-LM2 and LM2-LM3), each with its own spatial relationship, they behave as if the two unique LMs have a known spatial relationship despite their never having been paired. Seemingly, they have integrated the two associations to create a third association with its own spatial relationship (LM1-LM3). Using sensory preconditioning (Experiment 1) and second-order conditioning (Experiment 2) procedures, we found that human participants integrated information about the boundaries of pathways to locate a goal within a three-dimensional virtual environment in the absence of any relevant landmarks. Spatial integration depended on the participant experiencing a common boundary feature with which to link the pathways. These results suggest that the principles of associative learning also apply to the boundaries of an environment.

The breakfast effect: dogs (Canis familiaris) search more accurately when they are less hungry.

We investigated whether the consumption of a morning meal (breakfast) by dogs (Canis familiaris) would affect search accuracy on a working memory task following the exertion of self-control. Dogs were tested either 30 or 90 min after consuming half of their daily resting energy requirements (RER). During testing dogs were initially required to sit still for 10 min before searching for hidden food in a visible displacement task. We found that 30 min following the consumption of breakfast, and 10 min after the behavioral inhibition task, dogs searched more accurately than they did in a fasted state. Similar differences were not observed when dogs were tested 90 min after meal consumption. This pattern of behavior suggests that breakfast enhanced search accuracy following a behavioral inhibition task by providing energy for cognitive processes, and that search accuracy decreased as a function of energy depletion.

Too dog tired to avoid danger: self-control depletion in canines increases behavioral approach toward an aggressive threat.

This study investigated whether initial self-control exertion by dogs would affect behavioral approach toward an aggressive threat. Dogs were initially required to exert self-control (sit still for 10 min) or not (caged for 10 min) before they were walked into a room in which a barking, growling dog was caged. Subject dogs spent 4 min in this room but were free to choose where in the room they spent their time. Approaching the unfamiliar conspecific was the predisposed response, but it was also the riskier choice (Lindsay, 2005). We found that following the exertion of self-control (in comparison with the control condition), dogs spent greater time in proximity to the aggressor. This pattern of behavior suggests that initial self-control exertion results in riskier and more impulsive decision making by dogs.

Acquired equivalence between stimuli trained in the same context.

The role of context was examined in human acquired equivalence. Participants were trained on two conditional discriminations. In the first conditional discrimination, if sample A1 was presented, choice of comparison B1, but not B2, was correct, and if sample A2 was presented, choice of comparison B2, but not B1, was correct. In the second conditional discrimination, if sample X1 was presented, choice of comparison Y1, but not Y2, was correct, and if sample X2 was presented, choice of comparison Y2, but not Y1, was correct. In each conditional discrimination, one of the conditional relations was trained in context 1 (e.g., A1 → B1 and X1 → Y1) and the other was trained in context 2 (i.e., A2 → B2 and X2 → Y2). On test trials, when conditional stimuli from the two conditional discriminations were interchanged (e.g., sample A1 was presented with comparisons Y1 and Y2) and were presented in a neutral context, positive transfer resulted. That is, in the absence of the training context, stimuli that shared a common context on different trials in training came to be treated as equivalent.

The case of the disappearing bone: dogs' understanding of the physical properties of objects.

To assess dogs' memory for an occluded object, a gaze duration procedure was used similar to one often used with nonverbal infants. A bone shaped dog biscuit was placed behind a solid screen that then rotated in the depth plane through an arc front to back. Dogs were shown either of the two test events. In one event (the possible event), the screen rotated until it reached the point at which it would have reached the bone and then stopped (about 120°); in the other event (the impossible event), the screen rotated through a full 180° arc, as though it had passed through the bone. The dogs looked significantly longer at the impossible event. To control for the differential time it took for the screen to move, for a control group, a bone was placed behind the screen and the screen was rotated either 60° or 120° (both possible events). No difference in looking time was found. To control for the movement of the screen through 120° or 180° when both were possible, for a second control group, the bone was placed to the side of the screen rather than behind the screen and the screen was moved 120° or 180°. Again, no significant difference in looking time was found. Results suggest that much like young children, dogs understand the physical properties of an occluded object. That is they appear to understand that an object (such as a screen) should not be able to pass through another object (such as dog bone).

"Counting" by pigeons: discrimination of the number of biologically relevant sequential events.

Numerical competence has been studied in animals under a variety of conditions, but only a few experiments have reported animals' ability to detect absolute number. Capaldi and Miller (1988) tested rats' ability to detect absolute number by using biologically important events--the number of reinforced runs followed by a nonreinforced run--and found that the rats ran significantly slower on the nonreinforced run. In the present experiments, we used a similar procedure. Pigeons were given a sequence of trials in which responding on the first three trials ended in reinforcement but responding on the fourth trial did not (RRRN). When the response requirement on each trial was a single peck (Experiment 1), we found no significant increase in latency to peck on the fourth trial. When the response requirement was increased to 10 pecks (Experiment 2), however, the time to complete the peck requirement was significantly longer on the nonreinforced trial than on the reinforced trials. Tests for control by time, number of responses, and amount of food consumed indicated that the pigeons were using primarily the number of reinforcements obtained in each sequence as a cue for nonreinforcement. This procedure represents a sensitive and efficient method for studying numerical competence in animals.

Imitation and emulation by dogs using a bidirectional control procedure.

A successful procedure for studying imitative behavior in non-humans is the bidirectional control procedure in which observers are exposed to a demonstrator that responds by moving a manipulandum in one of two different directions (e.g., left vs. right). Imitative learning is demonstrated when observers make the response in the direction that they observed it being made. This procedure controls for socially mediated effects (the mere presence of a demonstrator), stimulus enhancement (attention drawn to a manipulandum by its movement), and if an appropriate control is included, emulation (learning how the environment works). Recent research with dogs has found that dogs may not demonstrate imitative learning when the demonstrator is human. In the present research, we found that when odors were controlled for, dogs imitated the direction of a screen-push demonstrated by another dog more than in a control condition in which they observed the screen move independently while another dog was present. Furthermore, we found that dogs would match the direction of screen-push demonstrated by a human and they were equally likely to match the direction in which the screen moved independently while a human was present.

A differential-outcomes effect using hedonically nondifferential outcomes with delayed matching to sample by pigeons.

When differential outcomes follow correct responses to each of two comparison stimuli in matching to sample, relative to the appropriate control condition, higher matching accuracy is typically found, especially when there is a delay between the sample and the comparison stimuli. In two experiments, we examined whether this differential-outcomes effect depends on using outcomes that differ in hedonic value (e.g., food vs. water). In Experiment 1, we found facilitated retention when a blue houselight followed correct responses to one comparison stimulus and a white houselight followed correct responses to the other, prior to nondifferential presentations of food. In Experiment 2, we found facilitated retention again when a blue houselight followed correct responses to one comparison stimulus and a tone followed correct responses to the other, prior to nondifferential presentations of food. The results of both experiments indicate that the differential-outcomes effect does not depend on a difference in hedonic value of the differential outcomes, and they suggest that outcome anticipations consisting of relatively arbitrary but differential stimulus representations can serve as cues for comparison choice.

What do dogs know about hidden objects?

Previous research has found that dogs will search accurately for an invisibly displaced object when the task is simplified and contextual ambiguity is eliminated [Doré, F.Y., Fiset, S., Goulet, S., Dumas, M.-C., Gagnon, S., 1996. Search behavior in cats and dogs: interspecific differences in working memory and spatial cognition. Animal Learning & Behavior 24, 142-149; Miller, H., Gipson, C., Vaughan, A., Rayburn-Reeves, R., Zentall, T.R., 2009. Object permanence in dogs: invisible displacement in a rotation task. Psychonomic Bulletin & Review 16 (1), 150-155]. For example, when an object is placed inside an occluder, one of which was attached to each end of a beam that could be rotated 90 degrees , dogs search inside of the appropriate occluder. The current research confirmed this finding and tested the possibility that the dogs were using a perceptual/conditioning mechanism (i.e., their gaze was drawn to the occluder as the object was placed inside and they continued looking at it as it rotated). The test was done by introducing a delay between the displacement of the object and the initiation of the dogs' search. In Experiment 1, during the delay, a barrier was placed between the dog and the apparatus. In Experiment 2, the lights were turned off during the delay. The search accuracy for some dogs was strongly affected by the delay, however, search accuracy for other dogs was not affected. These results suggest that although a perceptual/conditioning mechanism may be involved for some dogs, it cannot account for the performance of others. It is likely that these other dogs showed true object permanence.