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Visual categorization of natural stimuli by domestic dogs

Dog working on touch-screen

Friederike Range, Ulrike Aust, Michael Steuer, Ludwig Huber

A computer-automated touchscreen testing procedure for studying learning, social and physical cognition in the dog (Canis familiaris) is described. Generally, the dogs’ task during each trial was to touch images that are defined as positive by the experimenter with their noses. After an autoshaping procedure, in which the dogs learned to deliver the touch response to images, they were trained on two visual discrimination problems. In the first, the subjects learned to correctly choose between two simultaneously presented images; here we used simple forms (circle and square). In the second, they learned to look carefully to discriminate between two sets of stimuli, one consisting of three colour photographs of underwater scenes, the other of three arbitrary colour drawings. After successful performance on these problems, dogs were submitted to a dog-landscape visual categorization problem. They were first trained to discriminate between a large (N=60) set of dog pictures and an equally large set of landscape pictures. After reaching a criterion of 80% correct first choices, the dogs received 4 test sessions including 40 novel positive and negative stimuli. They successfully transferred their knowledge to the novel stimuli. We conclude that the touchscreen-based operant method for investigating cognition in dogs is valid and that it allows for direct comparison of cognitive abilities with other species (e.g., pigeons and monkeys).

Bayer, K., Range, F., Aust, U., Steurer, M., & Huber, L. (2009) The touch-screen method as an implement for dog experiments. Journal of Veterinary Behavior: Clinical Applications and Research 4 (2) 51.

Range, F., Aust, U., Steurer, M. & Huber, L. (2008) Visual categorization of natural stimuli in domestic dogs. Animal Cognition, 11:339-347.


Inferential reasoning by exclusion in pigeons, dogs, and humans

Ulrike Aust, Friederike Range, Michael Steuer, Ludwig Huber

Using the touch screen we compared pigeons, dogs and humans: do they make inference based on exclusion? The ability to reason by exclusion (which is defined as the selection of the correct alternative by logically excluding other potential alternatives; Call 2006, Anim. Cogn. 9:393–403) is well established in humans. Several studies have found it to be present in some nonhuman species as well, whereas it seems to be somewhat limited or even absent in others.

As inconsistent methodology might have contributed to the revealed inter-species differences, we examined reasoning by exclusion in pigeons (n = 6), dogs (n = 6), students (n = 6), and children (n = 8) under almost equal experimental conditions. After being trained in a computer-controlled two-choice procedure to discriminate between four positive (S+) and four negative (S-) photographs, the subjects were tested with displays consisting of one S- and one of four novel stimuli (S'). One pigeon, half of the dogs and almost all humans preferred S' over S-, thereby choosing either by novelty, or by avoiding S- without acquiring any knowledge about S', or by inferring positive class membership of S' by excluding S-. To decide among these strategies, the subjects that showed a preference for S' were then tested with displays consisting of one of the S', and one of four novel stimuli (S'').

Although the pigeon preferentially chose the S'' and by novelty, dogs and humans maintained their reference for S', thereby showing evidence of reasoning by exclusion. Taken together, the results of the present study suggest that none of the pigeons, but half of the dogs and almost all humans, inferred positive class membership of S' by logically excluding S-.

Aust, U., Range, F., Steurer, M. & Huber, L. (2008) Inferential reasoning by exclusion: A comparative study of pigeons, dogs, and humans. Animal Cognition, 11: 587-597.