Naming and categorization in young children: v. manual sign training.
Following pre-training with everyday objects, 8 children aged from 2 to 4 years learned to produce one manual sign (fists placed one above the other, in front of body) to one stimulus and an alternative manual sign (shoulders touched with ipsilateral hands) to the other stimulus, with each of three pairs of different arbitrary wooden shapes (Set 1). The six stimuli then were presented in category match-to-sample tests, which all subjects passed. Three of the children were next trained to produce the manual signs (denoted as fist/shoulder) for an additional six arbitrary stimuli, Set 2. All 3 children went on to pass category match-to-sample tests for Set 2, and for Set 1 and Set 2 combined. In the final experimental phase, 2 of the children were trained, for one of the six stimulus pairs, to produce the vocal tact "zag" to one stimulus and "vek" to the other. Both children showed category transfer of these vocalizations in test trials with each of the remaining five stimulus pairs, and all the stimuli combined in a 12-stimulus array. In line with Horne and Lowe's (1996) naming account, manual sign naming was found to be as effective as vocal naming in establishing arbitrary stimulus categorization, measured in terms of category sorting and transfer of function. The findings also have implications for the training of verbal repertoires in people with learning disabilities.