ELICITATION OF AGGRESSION BY A PHYSICAL BLOW.

Scientists pinched the tails of six squirrel monkeys. They used three pinch strengths: light, medium, and hard.

Each monkey got 20 pinches at each strength in one session. After every pinch the monkey could bite a rubber tube. The team counted how many bites and how hard.

Harder pinches made more bites. Light pinch = almost no bites. Hard pinch = lots of bites.

The bite force also went up with pinch strength. One clear line: stronger aversive stimulus → stronger aggression.

HOFFMAN et al. (1963) showed shocks can suppress behavior for years. CHARNEY et al. (1965) shows the same kind of stimulus can also make aggression. Same lab, same era, opposite results. The difference: suppression studies gave shocks after a lever press; aggression study gave pinch before any response. Timing changes the outcome.

Hoffman et al. (1966) next year asked, "What if two warning tones were trained?" They got twin peaks of suppression. Together the three papers map how aversive stimuli can suppress, release, or shape behavior depending on what response is available.

Terrace (1969) later moved to pigeons and steady generalization gradients. The monkey work reminds us that before pretty curves, we need to know how strong the stimulus is—intensity drives the whole gradient.

When you probe or treat aggressive behavior, start soft. A mild aversive might do nothing, but a stronger one can spark the very aggression you want to reduce. Use graduated intensity in assessment and in desensitization programs. Track the client’s responses at each level so you stay below the aggression threshold.