Question

Psychologists once believed that any stimulus (whether a taste, sight, or sound) could serve equally well as a conditioned stimulus. this belief was challenged by research demonstrating the importance of

Answer 1

Biological Constraints is the correct answer.

Biological constraints are tendencies that are develeped through evolutionary history which induce members of a species to learn some associations that are naturally adaptive more easily than others. Any stimulus (such as sight, sound or taste) are believed to serve as a conditioned stimulus.