Studies of nonhuman primate grooming and human touch reveal that a key function of tactile contact includes all but which one of the following

Control subordinates.

Explanation:

Animal behavior may be defined as the field of biology that studies the experimental study on the animals. Different types of behavior of animals can be analyzed by the experiments of animal behavior.

The control and uncontrol group both can be involved in the experiments. During the study on the non human primate and the effect of the human touch shows the control subordinates in the experiment.

Thus, the answer is control subordinates.