Signals for food: reinforcers or informants?
Ring doves pecked one of two keys for food. Pecks at the chosen key then stopped being reinforced, and the signals that normally preceded food were either present or absent. In the presence of signals for food, the dove switched to the second key more quickly. When only one key was used, the same signals acted, as expected, to keep the bird pecking the extinguished key.
Cherfas
J J
JJ