Reinforcer effectiveness in dogs—The influence of quantity and quality

Exploring breed differences in discrimination, reversal learning, and resistance to extinction in the domestic dog (Canis familiaris)

Learning is crucial for shaping domestic dogs' behaviour through life experiences, yet not all breeds exhibit the same learning aptitude towards a particular task. The current study's objective was to identify differences in behaviour and learning performance across and within five breed clades and elucidate the underlying factors contributing into these variations. Dogs (n = 111) from five breed clades (UK Rural, Retrievers, Asian Spitz, European Mastiff, and New World) participated in a virtual learning task with their owners. Owners completed validated questionnaires of Impulsivity and Reward Responsiveness. The learning task comprised of reinforcing an arbitrary behaviour (hand-touch) through multiple sessions of Acquisition (reinforcing the hand-touch), Discrimination (reinforcing the hand-touch on one of two hands) and Reversal Learning (reinforcing the hand-touch on the opposite hand), followed by a single session of Extinction (hand-touch not reinforced). Results showed notable differences across the studied breed clades in certain learning and behavioural components. However, the observed disparities may not be entirely attributed to inherent cognitive differences among the breed clades but rather potentially influenced by contextual factors such as the human-dog communication dynamics associated with breeds' cooperativity. Furthermore, breed clades differed in the contributing factors predicting individual learning performances, which could highlight the potential effect of breeds' historical function.

What if the reward is not as yummy? Study of the effects of Successive Negative Contrast in domestic dogs in two different tasks

Successive Negative Contrast (SNC) occurs when there is a reduction in the quantity or quality of a reward that is expected according to the presence of contextual cues. This induces an emotional response of frustration that is similar to stress. While this phenomenon has been observed in several mammal species, findings in domestic dogs have been inconsistent, although this issue has strong relevance in dog training. The aim of this study was to assess the effects of Successive Negative Contrast in two responses that had already been studied in this species, but with an increase in the methodological rigor and variations in the experimental conditions to examine the generalizability of the phenomenon. To this end, experimental dogs experienced a pre-shift phase in which they received a high-value reward (liver), followed by a post-shift phase in which they obtained a low-value reward (dry dog food), and then a re-shift phase in which the high-value reward was available again. Control dogs received dry food in all phases. The results show a contrast effect on the behavior of following human pointing to obtain food (Study 1). On the contrary, there were no differences in problem solving behavior after the de- and re-evaluation of the reward during a non-social task (Study 2). The results support that Successive Negative Contrast is not a consistent phenomenon in pet dogs. It is possible that certain characteristics of dogs such as the great availability of high-value rewards in their daily lives could attenuate the effects of a reduction in incentive value.

Impact of Training Discipline and Experience on Inhibitory Control and Cognitive Performance in Pet Dogs

Training experience has been shown to enhance a dog's cognitive performance when comparing highly trained working or sporting dogs with untrained dogs. However, whether the type or level of training a pet dog receives can alter their performance in cognitive tasks requiring inhibitory control has not been assessed. Here, we tested whether pet dogs trained in scent work, agility, and obedience differ in cognitive performance. The impact of primary training discipline and combined training experience was assessed using two well-defined tasks that require inhibitory control: (1) the A-not-B task, in which dogs must inhibit a previously learned response in favour of an alternative response; and (2) the detour task, in which dogs must inhibit a direct approach to food to gain a reward. Dogs trained in scent work demonstrated higher levels of inhibitory control and persistence across the two tasks, but this did not affect individual task performance. Increased combined training experience improved learning in the A-not-B task training phase, but did not alter performance during the test phase, whereas it had no effect on success in the detour task. Overall, dogs that performed better in the A-not-B task were also more likely to succeed in the detour task, showing a relationship in the cognitive ability underpinning performance in the two tasks. The effect of the primary discipline on the behavioural phenotype shows that this should be accounted for in future studies, rather than applying the practice of partitioning dogs into highly trained vs. untrained groups.

Representation of rewards differing in their hedonic valence in the caudate nucleus correlates with the performance in a problem-solving task in dogs (Canis familiaris)

We have investigated dogs' (Canis familiaris) abilities in associating different sounds with appetitive stimuli of different incentive values. The association's establishment was first tested on family dogs (n = 20) in a problem-solving behavioural paradigm (experiment 1), then in a problem-solving behavioural paradigm as well as an fMRI study on specially trained family dogs (n = 20) (experiment 2). The aim was to show behavioural and parallel neural effects of the association formed between the two sounds and two different associated appetitive stimuli. The latency of solving the problem was considered an indicator of the motivational state. In our first experiment, where only behaviour was studied, we found that dogs were quicker in solving a problem upon hearing the sound associated with food higher in reward value, suggesting that they have successfully associated the sounds with the corresponding food value. In our second experiment, this behaviour difference was not significant. In the fMRI study, the cerebral response to the two sounds was compared both before and after the associative training. Two bilateral regions of interest were explored: the caudate nucleus and the amygdala. After the associative training, the response in the caudate nucleus was higher to the sound related to a higher reward value food than to the sound related to a lower reward value food, which difference was not present before the associative training. We found an increase in the amygdala response to both sounds after the training. In a whole-brain representational similarity analysis, we found that cerebral patterns in the caudate nucleus to the two sounds were different only after the training. Moreover, we found a positive correlation between the dissimilarity index in the caudate nucleus for activation responses to the two sounds and the difference in latencies (i.e. high reward value associated sound condition latency-low reward value associated sound condition latency) to solve the behavioural task: the bigger the difference between the conditions in latency to solve the task, the greater the difference in the neural representation of the two sounds was. In summary, family dogs' brain activation patterns reflected their expectations based on what they learned about the relationship between two sounds and their associated appetitive stimuli.

Owner-implemented paired-stimulus food preference assessments for companion dogs

Behavioral interventions for animals typically require the inclusion of programmed reinforcers. Although pet owners and human caregivers can often identify items that the animal will consume, preference assessments can more accurately determine relative preference rankings between various stimuli, which is important given that higher preferred items tend to function as more effective reinforcers than lower preferred items. Preference assessments have been developed to identify rankings for a variety of stimuli across species, including the domesticated dog (Canis lupus familiaris). However, previous preference assessments for dogs were developed for laboratory use and could be challenging for dog owners to perform alone. The purpose of this study was to modify existing dog preference assessment methods to produce a valid and feasible preference assessment for dog owners. Results suggest that the preference assessment identified preference rankings for individual dogs. Owners were able to implement the protocol with high integrity and found the protocol acceptable.

Activity patterns are associated with fractional lifespan, memory, and gait speed in aged dogs

Maintaining an active lifestyle is considered a hallmark of successful aging. Physical activity significantly reduces the risk of cognitive decline and Alzheimer's disease in humans. However, pain and lack of motivation are important barriers to exercise. Dogs are a remarkable model for translational studies in aging and cognition as they are prone to Canine Cognitive Dysfunction syndrome, which has many similarities with Alzheimer's disease. According to owner reports, changes in activity levels are characteristic of this syndrome, with decreased daytime activity, but also excessive pacing, especially at sleep time. We used physical activity monitors to record the activity of 27 senior dogs and evaluated the association between activity level and age, fractional lifespan, cognitive status measured by an owner questionnaire and cognitive tests. We also assessed the relationship between activity and joint/spinal pain, and the off/on leash gait speed ratio (a potential marker of gait speed reserve and motivation). We found that activity patterns in dogs are associated with fractional lifespan and working memory. Additionally, dogs with higher on/off leash gait speed are more active in the afternoon of weekdays. These results encourage future studies evaluating how physical activity can improve or delay cognitive impairment in senior dogs.

Evaluating the accuracy of facial expressions as emotion indicators across contexts in dogs

Facial expressions potentially serve as indicators of animal emotions if they are consistently present across situations that (likely) elicit the same emotional state. In a previous study, we used the Dog Facial Action Coding System (DogFACS) to identify facial expressions in dogs associated with conditions presumably eliciting positive anticipation (expectation of a food reward) and frustration (prevention of access to the food). Our first aim here was to identify facial expressions of positive anticipation and frustration in dogs that are context-independent (and thus have potential as emotion indicators) and to distinguish them from expressions that are reward-specific (and thus might relate to a motivational state associated with the expected reward). Therefore, we tested a new sample of 28 dogs with a similar set-up designed to induce positive anticipation (positive condition) and frustration (negative condition) in two reward contexts: food and toys. The previous results were replicated: Ears adductor was associated with the positive condition and Ears flattener, Blink, Lips part, Jaw drop, and Nose lick with the negative condition. Four additional facial actions were also more common in the negative condition. All actions except the Upper lip raiser were independent of reward type. Our second aim was to assess basic measures of diagnostic accuracy for the potential emotion indicators. Ears flattener and Ears downward had relatively high sensitivity but low specificity, whereas the opposite was the case for the other negative correlates. Ears adductor had excellent specificity but low sensitivity. If the identified facial expressions were to be used individually as diagnostic indicators, none would allow consistent correct classifications of the associated emotion. Diagnostic accuracy measures are an essential feature for validity assessments of potential indicators of animal emotion.

Working Dog Training for the Twenty-First Century

Dogs are trained for a variety of working roles including assistance, protection, and detection work. Many canine working roles, in their modern iterations, were developed at the turn of the 20th century and training practices have since largely been passed down from trainer to trainer. In parallel, research in psychology has advanced our understanding of animal behavior, and specifically canine learning and cognition, over the last 20 years; however, this field has had little focus or practical impact on working dog training. The aims of this narrative review are to (1) orient the reader to key advances in animal behavior that we view as having important implications for working dog training, (2) highlight where such information is already implemented, and (3) indicate areas for future collaborative research bridging the gap between research and practice. Through a selective review of research on canine learning and behavior and training of working dogs, we hope to combine advances from scientists and practitioners to lead to better, more targeted, and functional research for working dogs.

Where Do We Stand in the Domestic Dog ( Canis familiaris ) Positive-Emotion Assessment: A State-of-the-Art Review and Future Directions

Although there have been a growing number of studies focusing on dog welfare, the research field concerning dog positive-emotion assessment remains mostly unexplored. This paper aims to provide a state-of-the-art review and summary of the scattered and disperse research on dog positive-emotion assessment. The review notably details the current advancement in dog positive-emotion research, what approaches, measures, methods, and techniques have been implemented so far in emotion perception, processing, and response assessment. Moreover, we propose possible future research directions for short-term emotion as well as longer-term emotional states assessment in dogs. The review ends by identifying and addressing some methodological limitations and by pointing out further methodological research needs.

Do dogs experience frustration? New contributions on successive negative contrast in domestic dogs (Canis familiaris)

An unexpected change in reward quantity or quality frequently elicits a sharp decrease of responses as well as a negative emotional state. This phenomenon is called successive negative contrast (SNC) and, although it has been observed in numerous mammals, results in dogs have been inconsistent. The aim of this study was to evaluate SNC in dogs, comparing the effects of rewards of different qualities in a non-social task carried out in the dogs' usual environment. Dogs were separated into two experimental groups that experienced a downshift from a high quality reward (liver or sausage) to a low quality one (dry food), as well as a control group that always received dry food. The task involved a dog toy with bone shaped pieces that had to be removed to get the food hidden underneath. When the reward changed from liver to dry food, dogs picked up significantly fewer bones than the control group. However, this effect was not observed with sausage. Results show SNC in dogs in a non-social task carried out in their home environment. Additionally, the importance of the discrepancy in the hedonic value of the rewards is highlighted.

Behavioural responses to unexpected changes in reward quality

Successive negative contrast (SNC) effects are changes in anticipatory or consummatory behaviour when animals unexpectedly receive a lower value reward than they have received previously. SNC effects are often assumed to reflect frustration and appear to be influenced by background affective state. However, alternative explanations of SNC, such as the functional-search hypothesis, do not necessarily imply an aversive affective state. We tested 18 dogs in a SNC paradigm using a patch foraging task. Dogs were tested in two conditions, once with the low value reward in all of five trials (unshifted) and once when reward value was altered between high and low (shifted). Following a reward downshift, subjects showed a SNC effect by switching significantly more often between patches compared to the unshifted condition. However, approach latency, foraging time and quantity consumed did not differ between conditions, suggesting non-affective functional search behaviour rather than frustration. There was no relationship between strength of SNC and anxiety-related behaviours as measured in a novel object test and a personality questionnaire (C-BARQ). However, associations with the C-BARQ scores for Trainability and Stranger directed aggression suggest a possible link with behavioural flexibility and coping style. While reward quality clearly affects incentive motivation, the relationship between SNC, frustration and background affective state requires further exploration.

Incentive motivation in pet dogs - preference for constant vs varied food rewards

Recently, there has been a move towards positive reinforcement using food rewards in animal training. By definition, rewards function as reinforcers if they increase or maintain the frequency of behaviour that they follow. However, in operant conditioning tasks animals frequently show systematic changes in performance - in particular a reduction in responding over time. One suggested strategy to avoid such performance decrements is to provide a variety of food rewards, rather than the same food reward in all trials. The enhancement of appetitive behaviour and consumption by reward variation is referred to as 'variety effect'. We investigated whether dogs preferred a variable or a constant food reward in a concurrent two-choice test. Of 16 dogs, six subjects showed a significant preference for the varied food reward and six for the constant food reward, while four dogs exhibited no significant preference for either option. At the group level, there was a significant effect of block: preference for the varied food reward increased across six blocks of ten trials each. Thus, although some individuals may prefer a single, favourite food reward in the short term, introducing variation in reward types may maintain dogs' motivation in operant tasks over a longer time period.