APA Dictionary of Psychology

in Piagetian theory, an infant’s action that creatively alters former schemes to fit the requirements of new situations. Tertiary circular reactions emerge toward the end of the sensorimotor stage, at about the beginning of the 2nd year; they differ from earlier behaviors in that the child can, for the first time, develop new schemes to achieve a desired goal. Also called discovery of new means through active experimentation. See also primary circular reaction; secondary circular reaction.