Cardiac and respiratory conditioning, differenatiation, and extinction in the pigeon.

Researchers paired a light with a mild foot-shock to pigeons. They watched heartbeats and breathing across many trials. The birds never had to peck a key; the body simply learned to react.

After a few pairings the light alone sped up heart rate and breathing. New lights that were never followed by shock did not trigger the change. Even after 100 shock-free trials the fear reaction stayed strong.

Dove et al. (1974) later used the same heart-rate method to show pigeons can hear tiny pitch differences. This extends the 1966 finding: if the heart can learn fear, it can also learn fine sound rules.

Zimmerman (1969) swapped heart rate for a freezing measure and used smells instead of lights. Both studies got fast, clear discrimination, showing the pigeon brain easily links new cues to danger.

Poling et al. (1977) kept pecking alive after food stopped, just as H et al. kept heart changes alive after shock stopped. Together they show extinction does not erase the first learned link; it only adds new rules.

Your clients may keep strong bodily fear long after the real threat is gone. Use this as a reminder to test for hidden triggers and to plan longer extinction or counter-conditioning phases. When you need a sensitive measure of stimulus control, think beyond button presses: heart rate, breathing, or skin temperature can tell you a rule has been learned before the child can say it.