Acquisition and transfer of language function

Literatures relating to speech and sign acquisition for people with a severe mental handicap, and the efficacy of such language studies and programmes, are critically reviewed. Skinner's view of language as a verbal behaviour consisting of separately acquired functions is focused upon. Following Skinner, the importance of training language behaviours which are functional for the child is emphasised. In a series of four studies conducted with severely mentally handicapped children, single subject design experiments were used to assess mand and tact acquisition, and subsequent transfer between these two language functions. In the first experiment, expressive signing using the mand and tact methods of training were compared. It was found that less able children acquired signs faster under the mand method; there were no differences between methods for the more able children. In contrast with the literature, posttests suggested that transfer between mand and tact language functions occurred routinely. Difficulties with the mand task and the posttests used were identified. The aim of the series of studies conducted in Experiment Two was to overcome the problems identified by implementing a different technique to establish manding, and to examine the issue of transfer specifically. More precisely, the aim was to discover whether (1) signs trained as tacts can be used as mands, (2) if so whether this transfer is symmetrical and (3) in the absence of transfer, whether training on a different set of mands facilitates transfer. It was found that tact to mand transfer occurred, and was symmetrical, for two of the three children. The child who did not initially show transfer subsequently benefitted from the new mand training intervention. However, a possible artefact was identified with the mand condition, thereby throwing doubt over the claims of transfer. The aim of Experiment Three was to replicate Experiment Two but removing the artefact. More importantly, the relevance of an equivalence framework to transfer was assessed. Such a model has not been applied to the transfer issue before. Finally, in the fourth experiment, the relationships considered important in mand to tact transfer, using the equivalence framework, were examined and manipulated. It was concluded that the use of this model provides a valuable theoretical and practical tool for explaining and establishing transfer. The implications for language training programmes are discussed.