Discrimination of Food Amounts by the Domestic Dog (Canis familiaris)

Abstract

The current research examined the ability of dogs to discriminate between different amounts of food. Using a two-alternative-forced-choice procedure, dogs were required to discriminate between a constant amount of 4 pieces of food and another amount that varied across a range from 1 to 7 pieces. The dogs reliably selected the larger of the two alternatives. Discrimination was better when there were fewer than rather than more than 4 pieces of food available on the varying alternative. Specifically, 1 piece was discriminated from 4 pieces more easily than 4 pieces were discriminated from 7 pieces of food. These results confirmed the ability of dogs to discriminate food amount on a psychophysical choice procedure. This research addresses a question fundamental to theories of reinforcement of why reinforcer magnitude does not always control behavior in an intuitive way. We argue that the relative difficulty of discriminating smaller from larger amounts of food is an important factor in understanding the impact of reinforcer magnitude in the development of reinforcer control over behavior