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Thesis (PhD)-- Stellenbosch University, 1924. / ENGLISH ABSTRACT: No abstract available / AFRIKAANSE OPSOMMING: Sien artikel vir opsomming

In the present study, footshock, which produces a powerful aversive emotional response was used in a Pavlovian conditioning experiment as an unconditioned stimulis (UCS), and was paired with the presentation of a light used as a conditioned stimulis (CS). There is an accumulation of evidence that supports the assertion that dopaminergic (DA) neurons within the ventral tegmental area (VTA) are active in processes that contribute to the amygdala-based circuitry involved in regulating emotionally salient responses. To build upon findings implicating VTA DA, excitatory glutamate (Glu), NMDA and AMPA receptors, were examined with respect to their role in Pavlovian conditioned fear responding. Fear potentiated startle (FPS) was used to assess the effects of intra-VTA infused AP5, and intra-VTA infused CNQX on conditioned fear responding in laboratory rats. The administration of the NMDA receptor antagonist AP5 (at 1.0, 2.5, and 5.0ug doses), blocked the ability of a conditioned stimulus (CS) previously paired with footshock to become conditioned to the UCS. Similarly, administration of the AMPA receptor antagonist CNQX (at 1.0, 2.5, 5.0ug doses), inhibited the ability of the CS to become conditioned to the UCS. The results of this study indicate the VTA is an important site for synaptic modifications associated with fear learning, and that activation of excitatory Glutamatergic receptors in the VTA play a necessary part of the processing underlying fear conditioning. Measures of shock reactivity demonstrated that the infusion of AP5 and CNQX into the VTA did not inhibit baseline startle amplitudes. The administration of AP5 and CNQX did not suppress the perception of footshock as an aversive stimulus. This study provides further definition to established knowledge surrounding the neural processes whereby neutral environmental cues gain negative emotional salience as occurs in fear conditioning. It was hypothesised that the action of excitatory glutamatergic transmission within the VTA acts on NMDA and AMPA receptors is to assist in the acquisition of Pavlovian conditioned fear, possibly through the same synaptic mechanisms that govern LTP.

Several studies have demonstrated that fixed-time (FT) schedules of stimulus delivery can function to reduce a variety of behaviors. The purpose of this study was to evaluate the immediate and subsequent effects of FT food deliveries on mouthing. In Phase 1, a preference assessment showed that caramel popcorn, chocolate cookies and pretzels were highly preferred food items. Thus, providing the basis for use of food items during treatment. In Phase 2, a functional analysis showed that mouthing was a nonsocially maintained problem behavior. Phase 3 demonstrated the use of FT schedules of food deliveries as treatment for nonsocially maintained mouthing. Results indicated that FT schedules of food significantly reduced mouthing. In addition, levels of mouthing observed during post-FT observations were reliably lower than pre-FT observations. Treatment effects, operative mechanisms responsible for the treatment effects and the experimental arrangement used to investigate varying FT schedules are discussed.

A functional analysis, conducted to assess the variables maintaining the chronic eye poking of a female diagnosed with profound mental retardation, indicated that the behavior persisted in the absence of social contingencies. A procedure was initiated in a training environment in which a punisher (mild reprimand) was delivered contingent on eye poking in the presence, but not in the absence, of a neutral stimulus (wristbands). Using a combination of multiple baseline and multielement experimental designs, it was determined that that eye poking was suppressed in the presence of the previously neutral stimulus, even in environments in which the reprimand contingency was inoperative.

No description available.

This study partially replicated the research of Cook, Kwak, Hoffman, & Loftus where they examined post-event activities that induces subjects to pick a wrong person in a forced choice identification procedure. The goal was to investigate if providing a neither option to a match to sample task increases the accuracy of responding. Subjects were asked to study three faces for 10 seconds, after which they were asked to pick out the faces in a forced choice setting where two other faces were presented. Later the subjects were asked to pick out faces in a setting in which they could use a neither option. Results indicated that a generalization effect occurs when identifying faces and the effect is seen as subjects choosing the wrong face. This suggests that when using faces with some similar features in a lineup setting the procedure may cause the subject to pick the wrong person.

One language intervention approach for individuals with autism involves teaching one response topography under multiple sources of control and then establishing that response under individual controlling variable. Another approach involves establishing one response topography under singular control and then using that response to establish the response topography under different controlling variables. The study sought to extend previous research by investigating the impact of each approach on the acquisition of verbal responses. Three of the eight participants acquired all target responses for at least one response topography. The results of previous research were not replicated directly and the findings were discussed in terms of preexperimental verbal repertoires and restricted interests.

An experiment was conducted to examine the functionality of using auditory stimuli in isolation as fading stimuli. A review of the literature revealed very few reports regarding the usage of the auditory modality for fading purposes. The study employed auditory prompts as fading stimuli in the transfer of stimulus control across stimulus modalities, specifically, the transfer of stimulus control from auditory to visual stimulus properties. A single subject was employed for the experiment. The results were that the intensity of the auditory stimulus was an ineffective dimension to use for fading operations in the transfer of stimulus control across stimulus modalities, Further investigation is needed regarding the conditions that limit the transfer of stimulus control when auditory prompts are employed as fading stimuli.

Matrix training techniques arrange instruction for stimulus relations that facilitate emergent responding to novel stimulus arrangements, which is a phenomenon known as recombinative generalization. The current study compared two common matrix training approaches, an overlapping (OV) design and a non-overlapping (NOV) design, with respect to arranging relations targeted for training. Two, typically-developing toddlers were taught compound action-object labels in either an OV or NOV matrix training design. Results suggest that an OV matrix design facilitates recombinative generalization more effectively than a NOV design.