These results are also compatible with the suggestions by Keller and Schoenfeld (1950) that the stimulus to be conditioned through operant discrimination must be established as a discriminative stimulus if it is to function as a conditioned reinforcer.
These interactions can and must be avoided because the handling of the researchers may be functioning as a discriminative stimulus. Also, the intensity of the electric shocks (6.3 mA) administered to the animals can be significantly decreased.
They found positive transfer between a discriminative stimulus trained with one instrumental response and a different instrumental response that shared the outcome, uncovering the role of the SD-O association in controlling instrumental performance.
Perhaps the most important of these is that if females never encounter a negative discriminative stimulus during sexual imprinting (a mother in our example), then we would expect no elaboration of their sexual preferences.