Stimulus Control Issues in a Patient with Dementia

Stimulus control can be established by using differential reinforcement procedures such as in conditional discrimination. In an experiment by Steingrimsdottir and Arntzen (2011), the participant, a dementia patient, failed to respond in accordance to the experimenter-defined classes when the density of programmed consequences was reduced. This is different from what is seen in healthy elderly participants. In this experiment, a dementia patient was exposed to different conditional discrimination tasks, from matching different functional stimuli such as clothes and cutlery to identity MTS with only cutlery or colors. The participant failed to respond above chance level with the different functional stimuli during arbitrary MTS tasks and on identity MTS tasks with pictures of cutlery and colors. Specific instructions were introduced for the participant during identity MTS with colors and accuracy increased to up to 90%. However, the participant failed a test for generalized identity MTS (5 out of 8 correct) which might failure of establishing proper stimulus control. Thus, the number of training blocks to criterion was increased. The results showed that correct responding on a subsequent generalized identity matching test increased to 14 out of 16 correct. In a follow up test with cutlery stimuli the participant got 14 out of 16 correct. Establishing stimulus control is a topic for future experiments with dementia patients.