Pigeons can reliably discriminate pictures of cars from pictures of chairs.This best illustrates their capacity to develop

A) concepts.
B) mental sets.
C) heuristics.
D) algorithms.

Pigeons' ability to reliably discriminate between pictures of cars and pictures of chairs suggests that they have formed a conceptual category for each of these objects, which allows them to distinguish one from the other. Mental sets refer to a tendency to approach a problem in a particular way, heuristics are problem-solving strategies that may not always lead to a correct solution, and algorithms are step-by-step procedures for solving a problem. While some of these concepts may also apply to pigeon behavior, none of them specifically address their ability to form categories.