Brown, P. L., & Jenkins, H. M. (1968).
Auto-shaping of the pigeon's key-peck.
Journal of the Experimental Analysis of Behavior,
11, 1-8.
Reliable acquisition of the pigeon's key-peck response resulted
from repeated unconditional (response-independent) presentations
of food after the response key was illuminated momentarily.
Comparison groups showed that acquisition was dependent upon
light-food pairings, in that order.