Enhanced distress vocalization through selective reinforcement

Eighteen Peking ducklings were imprinted and tested for their tendency to emit distress calls during the presentation and withdrawal of the imprinted stimulus. A subsequent arrangement in which each distress vocalization led to a 5-second presentation of the imprinted stimulus resulted in an enhanced tendency to emit distress calls.

AN UNUSUAL CASE OF METAPHYSIAL DYSPLASIA

1. A case of metaphysial dysplasia observed for eleven years is reported.

2. Only one case with similar features has previously been reported.

3. The literature on the subject is reviewed.