with this arrangement of loudspeakers and response keys , squirrel monkeys quickly learn to respond on the key near the source of the sound stimulus , and this pattern is the same whether or not responses near the sound source are differentially reinforcedmthis result may depend on a pre-experimental tendency in squirrel monkeys to orient head and eyes toward a sound , which would lead the animal to look at the response key in front of the loudspeaker producing the sound .
C0018670
head
C0015392
eyes