International Journal of Comparative Psychology

The current research examined dog's ability to dsicriminate between different amounts of food. Using a two alternative forced choice procedure dogs werre 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 two alternatives. Discrimination was better when there were fewer rather than more than 4 pieces of food available on the varying alternative. Specifically, 1 was discriminated from 4 more easily than 4 was discriminated from 7 pieces of food. These results confirmed the ability of dogs to discriminate food amount on a psychophyical choice procedure.