Overshadowing of a stimulus-reinforcer association by an instrumental response

In two experiments, rats were first exposed to pairings of a clicker and food; they were subsequently, in order to measure the effectiveness of the clicker as a conditioned reinforcer, given the opportunity to press a lever which turned the clicker on. For one group of animals the food originally delivered in the presence of the clicker had been contingent on their performance of an instrumental response (running in a running wheel); for a second the contingency between clicker and food had been purely classical. Although the actual correlation between clicker and food was identical for the two groups, the clicker was a less effective conditioned reinforcer for the first group than for the second. In a third experiment, all animals were initially required to run to obtain food in the presence of the clicker, but one group received additional trials on which food was delivered contingent on running in the absence of the clicker. This group showed less tendency to lever press for the clicker than a second group that had received free food on trials when the clicker was not presented. The results of all three experiments suggest that conditioning to the clicker could be overshadowed if the occurrence of food was more reliably predicted by the execution of an instrumental running response; they thus support the view that instrumental conditioning depends on the establishment of an association between response and reinforcer similar to the association between stimulus and reinforcer underlying classical conditioning.     

Interference in Visual Working Memory

This paper uses the theoretical distinction that has recently developed between the passive visual store and the active spatial rehearsal mechanism of the visuo-spatial component of working memory (VSSP). It examines the circumstances under which visual fields gain functional access to the passive visual store and seeks to cast light on the circumstances under which irrelevant visual fields interfere with concurrent visual processing. Experiment 1 contrasts a dynamic visual noise field with a static noise field and shows that the static field, in contrast to the dynamic noise field, causes no interference when presented concurrently with a visual task. Experiment 2 investigates the reason for this contrast and concludes that the static field is susceptible to decay and so fails to cause interference. Experiment 3 investigates further the circumstances under which dynamic visual noise causes interference and shows that manipulation of the number of changes within the noise field is also of importance in causing interference. The results allow further consideration of the characteristics of the VSSP.     

The control of appetitive instrumental responding does not depend on classical conditioning to the discriminative stimulus

In Experiment I, rats were exposed to a classical relationship between a clicker-light compound and response-independent food. Conditioning to the light was blocked if the clicker had previously served as a classical signal for food, but not if it had been established as a discriminative stimulus for food-reinforced lever pressing. In Experiment II, a tone-light compound served as a discriminative stimulus for lever pressing. Control by the light was blocked if the tone was independently trained as a discriminative stimulus, but not if it was trained as a classical signal for response-independent food. These results suggest that discriminative stimuli do not come to control appetitive instrumental responding by virtue of their implicit classical relationship to the instrumental reinforcer.     

EFFECTIVENESS OF FUNCTIONAL COMMUNICATION TRAINING WITH AND WITHOUT EXTINCTION AND PUNISHMENT: A SUMMARY OF 21 INPATIENT CASES

Functional communication training (FCT) is a frequently used treatment for reducing problem behavior exhibited by individuals with developmental disabilities. Once the operant function of problem behavior is identified by a functional analysis, the client is taught to emit an appropriate communicative response to obtain the reinforcer that is responsible for behavioral maintenance. Studies on FCT have typically used small numbers of participants, have reported primarily on clients for whom FCT was successful, and have varied with respect to their use of other treatment components. The main purposes of the present study were to evaluate the efficacy of FCT for treating severe problem behavior in a relatively large sample of individuals with mental retardation (N = 21) and to determine the contribution of extinction and punishment components to FCT treatment packages. FCT with extinction was effective in reducing problem behavior for the majority of clients and resulted in at least a 90% reduction in problem behavior in nearly half the applications. However, when demand or delay-to-reinforcement fading was added to FCT with extinction, treatment efficacy was reduced in about one half of the applications. FCT with punishment (both with and without fading) resulted in at least a 90% reduction in problem behavior for every case in which it was applied.     

Perseverative Writing Errors in a Patient with Alzheimer's Disease

This study reports the writing performance of a dysgraphic patient with Alzheimer's disease and moderate dementia who frequently perseverated on strokes and letters. Letter formation errors were also frequently produced. Oral spelling was superior to written spelling. The habitual style of writing (cursive writing) was significantly more prone to perseverations than writing in uppercase letters, a form of writing less frequently used by the patient. Central (linguistic) spelling processes were relatively preserved. The pattern of preserved and impaired functions is consistent with impairment of the peripheral mechanism that generates the graphic motor patterns code. We suggest that damage to the peripheral orthographic mechanism may cause deficits in some patients with Alzheimer's disease.