Aggression during the fixed-ratio and extinction components of a multiple schedule of reinforcement.
Hard ratios or extinction can spark aggression even in animals, so thin schedules need safety checks.
01Research in Context
What this study did
Researchers worked with three pigeons in a small chamber.
The birds pecked a key for food.
Some periods gave food every peep (continuous).
Other periods made them peck 15, 60, or 120 times for one bite (FR 15, FR 60, FR 120).
Extinction periods gave no food at all.
A second bird sat behind a clear wall so the first bird could attack it.
What they found
No attacks happened during continuous food or FR 15.
Aggression showed up when the ratio climbed to FR 60 and FR 120.
The birds also attacked during extinction, when food stopped.
High work or no pay turned calm birds into fighters.
How this fits with other research
Waite et al. (1972) saw the same anger, but under fixed-interval pay.
Both studies prove any tough schedule can spark aggression, not just FR.
Duker et al. (1996) added that bigger food portions make interval-based attack even worse.
So thicker reinforcement can still provoke if the schedule is hard.
MIGLELong (1963) first noticed pigeons trying to escape when FR got large.
Dardano (1970) shows escape wasn’t enough; the birds turned on a cage-mate instead.
Together they map a line from mild strain to full fight as ratios grow.
Why it matters
Your client may not peck keys, but tough demands and sudden extinction happen daily.
Watch for aggression when you stretch ratios past easy levels or place skills on extinction.
Drop ratio size or add prompts before the first sign of frustration.
Your safety, and the client’s, can depend on spotting schedule-induced anger early.
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02At a glance
03Original abstract
Pigeons were trained to key peck for food on multiple reinforcement schedules including components of continuous and fixed-ratio reinforcement and extinction. At the end of the chamber opposite the response key was a restrained target pigeon. The target restraining equipment was designed to record automatically blows struck against the target. When the experimental pigeons were paired with restrained target pigeons they attacked the target. Attack occurred during extinction after both continuous and fixed-ratio reinforcement. Attack also occurred occasionally during fixed-ratio 25 and fixed-ratio 40 and frequently during fixed-ratio 60 and fixed-ratio 120. No attack occurred during fixed-ratio 15 and continuous reinforcement. After a history of stable responding without a target bird present, the introduction of a target bird resulted in severely strained key-peck responding characterized by long periods of neither key pecking nor aggressing.
Journal of the experimental analysis of behavior, 1970 · doi:10.1901/jeab.1970.13-221