Notes on fixed-ratio and fixed-interval escape responding in the pigeon.

Researchers placed pigeons in a small chamber with a lighted key. If the bird pecked the key, the lights briefly turned off. This tiny "timeout" acted as negative reinforcement.

The team arranged two schedules. Fixed-ratio (FR) required a set number of pecks for each timeout. Fixed-interval (FI) made the first peck after a set time produce the timeout. They wanted to see if escape responding would hold up under these intermittent schedules.

Once the pigeons learned the response, they pecked steadily under both FR and FI. The pattern looked like escape data from rats and monkeys.

No extra shaping steps were needed. The birds kept pecking even though the payoff only came now and then.

Retzlaff et al. (2017) later showed pigeons also escape when rich food schedules turn lean. Both studies show the same species handles different kinds of aversive control.

Mulvaney et al. (1974) found squirrel monkeys stopped key-pressing when food no longer followed the light. The monkeys gave up, but the pigeons in Hineline et al. (1969) kept going under intermittent negative reinforcement. The difference looks like a contradiction, but the monkey study removed all reinforcement while the pigeon study still gave timeouts. The lesson: check what is still reinforcing before you call a response fragile.

Hart et al. (1968) showed monkeys can auto-shape a key press. Together with the pigeon data, we see key pressing can be started and maintained across species, as long as the contingency is clear.

If you are shaping escape behavior with a client, this old pigeon paper says: once the response is built, thinning the schedule should go smoothly. Expect steady responding on FR or FI escape, just like you would with humans or other animals. No special tricks are required after the first few reinforced responses.