1. the magnitude of a response to a drug regardless of dosage.

2. a measure of the efficacy of a drug-receptor complex in producing a pharmacological effect. Also called intrinsic efficacy.

3. the inborn readiness of babies to be inquisitive and to make contact with their environment. According to Jean Piaget, cognitive structures, by their very nature, seek to be active, predisposing the child to learn from experience with the environment.