Daniel Mills

Left gaze bias in humans, rhesus monkeys and domestic dogs

While viewing faces, human adults often demonstrate a natural gaze bias towards the left visual field, that is, the right side of the viewee’s face is often inspected first and for longer periods. Using a preferential looking paradigm, we demonstrate that this bias is neither uniquely human nor limited to primates, and provide evidence to help elucidate its biological function within a broader social cognitive framework. We observed that 6-month-old infants showed a wider tendency for left gaze preference towards objects and faces of different species and orientation, while in adults the bias appears only towards upright human faces. Rhesus monkeys showed a left gaze bias towards upright human and monkey faces, but not towards inverted faces. Domestic dogs, however, only demonstrated a left gaze bias towards human faces, but not towards monkey or dog faces, nor to inanimate object images. Our findings suggest that face- and species-sensitive gaze asymmetry is more widespread in the animal kingdom than previously recognised, is not constrained by attentional or scanning bias, and could be shaped by experience to develop adaptive behavioural significance.

Clever hounds: social cognition in the domestic dog (Canis familiaris)

This paper reviews the reasons why domestic dogs make good models to investigate cognitive processes related to social living and describes experimental approaches that can be adopted to investigate such processes in dogs. Domestic dogs are suitable models for investigating social cognition skills for three broad reasons. First, dogs originated from wolves, social animals that engage in a number of co-operative behaviours, such as hunting and that may have evolved cognitive abilities that help them predict and interpret the actions of other animals. Second, during domestication dogs are likely to have been selected for mental adaptations for their roles in human society such as herding or companionship. Third, domestic dogs live in a human world and “enculturation” may facilitate the development of relevant mental skills in dogs. Studies of social cognition in animals commonly use experimental paradigms originally developed for pre-verbal human infants. Preferential gaze, for example, can be used as a measure of attention or “surprise” in studies using expectancy violation. This approach has been used to demonstrate simple numerical competence in dogs. Dogs also readily use both conspecific and human social signals (e.g. looking or pointing) as information sources to locate hidden rewards such as food or favourite toys. Such abilities make dogs particularly good models for investigating perspective-taking tasks, where animals are required to discriminate between apparently knowledgeable and apparently ignorant informants.

Discrimination of human and dog faces and inversion responses in domestic dogs (Canis familiaris)

Although domestic dogs can respond to many facial cues displayed by other dogs and humans, it remains unclear whether they can differentiate individual dogs or humans based on facial cues alone and, if so, whether they would demonstrate the face inversion effect, a behavioural hallmark commonly used in primates to differentiate face processing from object processing. In this study, we first established the applicability of the visual paired comparison (VPC or preferential looking) procedure for dogs using a simple object discrimination task with 2D pictures. The animals demonstrated a clear looking preference for novel objects when simultaneously presented with prior-exposed familiar objects. We then adopted this VPC procedure to assess their face discrimination and inversion responses. Dogs showed a deviation from random behaviour, indicating discrimination capability when inspecting upright dog faces, human faces and object images; but the pattern of viewing preference was dependent upon image category. They directed longer viewing time at novel (vs. familiar) human faces and objects, but not at dog faces, instead, a longer viewing time at familiar (vs. novel) dog faces was observed. No significant looking preference was detected for inverted images regardless of image category. Our results indicate that domestic dogs can use facial cues alone to differentiate individual dogs and humans and that they exhibit a non-specific inversion response. In addition, the discrimination response by dogs of human and dog faces appears to differ with the type of face involved.

Reading faces: differential lateral gaze bias in processing canine and human facial expressions in dogs and 4-year-old children.

Sensitivity to the emotions of others provides clear biological advantages. However, in the case of heterospecific relationships, such as that existing between dogs and humans, there are additional challenges since some elements of the expression of emotions are species-specific. Given that faces provide important visual cues for communicating emotional state in both humans and dogs, and that processing of emotions is subject to brain lateralisation, we investigated lateral gaze bias in adult dogs when presented with pictures of expressive human and dog faces. Our analysis revealed clear differences in laterality of eye movements in dogs towards conspecific faces according to the emotional valence of the expressions. Differences were also found towards human faces, but to a lesser extent. For comparative purpose, a similar experiment was also run with 4-year-old children and it was observed that they showed differential processing of facial expressions compared to dogs, suggesting a species-dependent engagement of the right or left hemisphere in processing emotions.

Medical paradigms for the study of problem behaviour: a critical review

Abstract The study of animal behaviour problems is an area of increasing interest in applied ethology. As with the study of abnormal behaviour in humans, there are two broad approaches to this subject, one emphasising the role of the environment and biology of the species in shaping behaviour and other the importance of pathological processes within the individual. The latter is based on a medical model as is the tradition in human psychiatry. Blind adherence to a medical model causes serious problems when it comes to the scientific investigation of problem behaviour. These stem from the way problems are categorised, the emphasis that is frequently given to the results of drug trials and the perception that the animal is malfunctioning. This paper argues that primary emphasis needs to be given to the study of the regulation of normal behaviour using psychobiological models, which provide construct validity for the processes observed. This shifts emphasis away from specific defining signs and towards an analysis of the ultimate functional value of the behaviour seen as a problem. This approach also allows the parsimonious explanation of the effects of a range of therapeutic interventions, whose effects might otherwise be poorly predictable.

Behavioural and physiological correlates of impulsivity in the domestic dog (Canis familiaris)

Impulsivity is a trait related to inhibitory control which is expressed in a range of behaviours. Impulsive individuals show a decreased ability to tolerate delay of reinforcement, and more impulsive behaviour has been linked to decreased levels of serotonin and dopamine in a number of species. In domestic dogs, impulsivity is implicated in problem behaviours that result from a lack of self control, but currently there are no published studies that assess behavioural and physiological measures of impulsivity in relation to this trait. Impulsivity scores were calculated for 41 dogs using an owner-report assessment, the Dog Impulsivity Assessment Scale (DIAS). Twenty-three of these subjects completed an operant choice task based on a delayed reward paradigm, to assess their tolerance to delay of reinforcement. High Pressure Liquid Chromatography (HPLC) with Fluorometric Detection was used to detect levels of the metabolites of serotonin (5-HIAA) and dopamine (HVA) in the urine of 17 of the subjects. Higher impulsivity scores were found to be significantly correlated with more impulsive behaviour (reduced tolerance to delay of reinforcement) in the behaviour tests and lower levels of urinary 5-HIAA and 5-HIAA/HVA ratio. The results demonstrate convergent validity between impulsivity (as assessed by the DIAS) and behavioural and physiological parameters.

Neophilia in domestic dogs (Canis familiaris) and its implication for studies of dog cognition

This study examined novel-object preference in dogs. In a free choice test 17 dogs were presented with a novel toy in a line up with two familiar toys. The unfamiliar object was chosen first in 38 out 50 tests suggesting a strong preference for novel over familiar items. Neophilia may be an adaptive trait for domestic dogs that has helped their adaptation towards man.

A Meta-Analysis of Studies of Treatments for Feline Urine Spraying

Feline urine spraying inside the home is a common problem behaviour that owners seek advice for from veterinarians. Individual trials relating to a variety of interventions produce variable results, and to date, no consensus on the value of different treatments has emerged. This study therefore aimed to meta-analyse, current data from appropriate published clinical trials that evaluate treatments for feline urine spraying. Inclusion and exclusion criteria for study selection were predefined and methodological quality was assessed by two independent reviewers. Ten studies in nine publications that either evaluated pharmacotherapy or pheromonatherapy (the use of a synthetic analogue of the F3 facial fraction in the cat) were suitable for analysis. There was a significant (P<0.001) association between the use of any intervention and the number of cats that ceased or reduced urine spraying by at least 90%. Analysis by intervention type indicated that fluoxetine, clomipramine and pheromonatherapy may each assist in managing urine spraying beyond a placebo based intervention. This is the first time meta-analytical techniques have been used and reported to evaluate the efficacy of interventions used in veterinary behavioural medicine, and it has established confidence in the value of both conventional treatments (pharmacotherapy) and a more recently developed treatment modality (pheromonatherapy) as an adjunct to the management of this problem. It is suggested that future research into treatment efficacy for this problem uses the benchmark standard of randomised, controlled trials lasting for at least 8 weeks, with the outcome criteria of cessation of feline urine spraying or reduction by at least 90%.

Psychological factors affecting equine performance

For optimal individual performance within any equestrian discipline horses must be in peak physical condition and have the correct psychological state. This review discusses the psychological factors that affect the performance of the horse and, in turn, identifies areas within the competition horse industry where current behavioral research and established behavioral modification techniques could be applied to further enhance the performance of animals. In particular, the role of affective processes underpinning temperament, mood and emotional reaction in determining discipline-specific performance is discussed. A comparison is then made between the training and the competition environment and the review completes with a discussion on how behavioral modification techniques and general husbandry can be used advantageously from a performance perspective.

Evaluation of a novel method for delivering a synthetic analogue of feline facial pheromone to control urine spraying by cats

Twenty-two cats with a problem of urine spraying in the home were enrolled onto a double-blinded placebo-controlled study designed to evaluate the efficacy of feline facial pheromone (FFP) delivered continuously into the atmosphere in the home through an electrically heated diffuser for controlling the problem. The cats were randomly assigned to treatment or control groups according to a predetermined schedule and later analysis suggested that there were no significant differences in the demographic characteristics of the two groups. Compared with a baseline week during which no treatment was given, the mean level of spraying was significantly lower in the treated group after four weeks, but not significantly lower in the control group. The baseline level of spraying and the treatment, but not the week of treatment, were significant predictors of the amount of spraying during the trial. However, only the type of treatment given was a significant factor in the occurrence of new marks. Linear regression analysis suggested that there was a significant relationship between the amount of spraying and the duration of the use of FFP.