The effects of physical luminance on colour discrimination in dogs: A cautionary tale

Canine Special Senses: Considerations in Olfaction, Vision, and Audition

Canine companions have learned to aid in performing tasks and conducting work for decades. Areas where unique capabilities of working dogs are harnessed are growing. This expansion, alongside efforts to increase domestic purpose-bred stock and awareness of the important role working dogs play in society, is increasing the role veterinarians provide. This article provides a brief overview of 3 key sensory systems in working dogs and highlights considerations for care related to each olfaction, audition, and vision.

2D or not 2D? An fMRI study of how dogs visually process objects

Given humans' habitual use of screens, they rarely consider potential differences when viewing two-dimensional (2D) stimuli and real-world versions of dimensional stimuli. Dogs also have access to many forms of screens and touchpads, with owners even subscribing to dog-directed content. Humans understand that 2D stimuli are representations of real-world objects, but do dogs? In canine cognition studies, 2D stimuli are almost always used to study what is normally 3D, like faces, and may assume that both 2D and 3D stimuli are represented in the brain the same way. Here, we used awake fMRI in 15 dogs to examine the neural mechanisms underlying dogs' perception of two- and three-dimensional objects after the dogs were trained on either two- or three-dimensional versions of the objects. Activation within reward processing regions and parietal cortex of the dog brain to 2D and 3D versions of objects was determined by their training experience, as dogs trained on one dimensionality showed greater differential activation within the dimension on which they were trained. These results show that dogs do not automatically generalize between two- and three-dimensional versions of object stimuli and suggest that future research consider the implicit assumptions when using pictures or videos.

Dogs accurately track a moving object on a screen and anticipate its destination

The prediction of upcoming events is of importance not only to humans and non-human primates but also to other animals that live in complex environments with lurking threats or moving prey. In this study, we examined motion tracking and anticipatory looking in dogs in two eye-tracking experiments. In Experiment 1, we presented pet dogs (N = 14) with a video depicting how two players threw a Frisbee back and forth multiple times. The horizontal movement of the Frisbee explained a substantial amount of variance of the dogs' horizontal eye movements. With increasing duration of the video, the dogs looked at the catcher before the Frisbee arrived. In Experiment 2, we showed the dogs (N = 12) the same video recording. This time, however, we froze and rewound parts of the video to examine how the dogs would react to surprising events (i.e., the Frisbee hovering in midair and reversing its direction). The Frisbee again captured the dogs' attention, particularly when the video was frozen and rewound for the first time. Additionally, the dogs looked faster at the catcher when the video moved forward compared to when it was rewound. We conclude that motion tracking and anticipatory looking paradigms provide promising tools for future cognitive research with canids.

Methodological Considerations in Canine Olfactory Detection Research

Dogs are increasingly used in a wide range of detection tasks including explosives, narcotics, medical, and wildlife detection. Research on detection dog performance is important to understand olfactory capabilities, behavioral characteristics, improve training, expand deployment practices, and advance applied canine technologies. As such, it is important to understand the influence of specific variables on the quantification of detection dog performance such as test design, experimental controls, odor characteristics, and statistical analysis. Methods for testing canine scent detection vary influencing the outcome metrics of performance and the validity of results. Operators, management teams, policy makers, and law enforcement rely on scientific data to make decisions, design policies, and advance canine technologies. A lack of scientific information and standardized protocols in the detector dog industry adds difficulty and inaccuracies when making informed decisions about capability, vulnerability, and risk analysis. Therefore, the aim of this review is to highlight important methodological issues and expand on considerations for conducting scientifically valid detection dog research.

Depths and limits of spontaneous categorization in a family dog

Categorization has been tested in non-human animals after extensive training procedures under laboratory conditions and it is assumed that in non-primate species categorization relies on perceptual similarity. We report evidence of the ability to categorize objects in absence of specific training in a family dog with vocabulary knowledge of multiple toys, including exemplars of 4 categories. Our experimental design was devised to test categorization in absence of specific training and based on the spontaneously learned vocal labels of the categories, a condition that mirrors human studies more than previous experiments on non-human animals. We also observed that the dog’s categorization skills were more accurate when, prior to the categorization test, she was given the opportunity to play with the novel exemplars, suggesting that category representations arise not only from physical resemblance, but also from objects’ affordances (function).

Illusory contour perception in domestic dogs

One way to better understand how animals visually perceive their environment is to assess the way in which visual information is interpreted and adapted based on preconceptions. Domestic dogs represent a unique species in which to evaluate visual perception as recent findings suggest they may differ from humans and other animal species in terms of their susceptibility to geometric visual illusions. Dogs have demonstrated human-like, reversed, and null susceptibility depending on the type of illusion. To further evaluate how dogs perceive their environment, it is necessary to perform additional assessments of visual perception. One such assessment is the perceptual filling-in of figures, which may be invoked when presented with illusory contours. Six dogs were assessed on their perception of the Ehrenstein illusory contour illusion in a two-choice size-discrimination task. Dogs, as a group, demonstrated equivocal perception of illusory contours. Some individual dogs, however, demonstrated human-like perception of the subjective contours, providing preliminary evidence that this species is capable of perceiving illusory contour illusions, thereby improving the current understanding of canine visual perception capabilities. Additional assessments using alternative illusory contour illusions are needed to clarify these results and identify features that underpin the individual differences observed.