Biomedical subjects

K Geoffrey White

Publications and source records attributed to K Geoffrey White.

4 recordsLinked to original sources

PubMed2003

Social influence in pigeons (Columba livia): the role of differential reinforcement.

Socially-influenced learning was studied in observer pigeons that observed a demonstrator in an adjacent chamber performing a target response comprising standing on a box and pecking a key 10 times. In Experiment 1 there was no evidence for social learning in the absence of reinforcement of the observer's behavior. When the target response was already established in the observer's repertoire, but was not differentially reinforced in relation to the demonstrator's behavior, rates of extinction were not influenced by the demonstrator's behavior (Experiment 2). Reinforcement of the observer's target response in the presence of the modeled target response, and not in its absence, resulted in control of the observer's responding by the behavior of the demonstrator (Experiments 3 and 4). This control was extended in Experiment 5 to deferred responses that occurred following a delay since the demonstrator's target responses. The acquisition of social influence depended on differential reinforcement of the observer's target response, with the demonstrator's target behavior serving as the explicit discriminative stimulus.

Animals↗

PubMed2002

Temporal generalization and diffusion in forgetting.

Two processes may contribute to the decrement in discriminability with increasing temporal distance between the occasioning event and later choice. One is the length of the interval and the other is generalization decrement. In the model described by White and Wixted [J. Exp. Anal. Behav. 71 (1999) 91-113], choice was predicted by the relative payoff for correct delayed matching responses, conditional on the current value of the stimulus sampled from Thurstone-like probability distributions of the effect of the sample stimuli. In the model, discriminability decreased with increasing temporal distance because the variance of the distributions increased with time. However, White and Wixted did not specify the function relating variance to temporal distance. If a diffusion process is assumed, and if diffusion increases exponentially with time, the resulting forgetting function is a negative exponential. An additional process involves exponential generalization of remembering from one time to other times. Alternative diffusion functions result in hyperbolic or power forgetting functions. The combination of two exponential processes yields forgetting functions that are double exponential in form and which appear consistent with a wide range of data.

Journal Article↗

PubMed2002

Demystifying wine expertise: olfactory threshold, perceptual skill and semantic memory in expert and novice wine judges.

We investigated recognition and identification of wine-relevant odours as a function of domain-specific expertise. Eleven wine experts and 11 wine novices participated in tasks measuring olfactory threshold, odour recognition, odour identification, and consistency of odour naming. Twenty-four wine-relevant odorants were sampled orthonasally by each participant in the semantic (identification; consistency of naming) and episodic (recognition) memory tasks. Results showed superior olfactory recognition by expert wine judges, despite their olfactory sensitivity and bias measures being similar to those of novices. Contrary to predictions based on reports of an association between odour memory and semantic processing, wine experts did not perform better than novices on the verbal memory tasks. Further, ability to recognize odours and ability to name odours were not positively correlated, although the novices' data showed a trend in this direction. The results imply that the source of superior odour recognition in wine experts was not enhanced semantic memory and linguistic capabilities for wine-relevant odours. One interpretation of the data is that wine experts were less susceptible than wine novices to verbal overshadowing. When forced to identify the odorants, experts' superior perceptual skills protected them from verbal interference, whereas novices' generated verbal representations of the odours were emphasized at the expense of the odorant itself. This has implications for training in wine-evaluation skills.

1-Butanol↗

PubMed2002

Memory deficits in Alzheimer's disease: the encoding hypothesis and cholinergic function.

Forgetting functions generated by delayed matching-to-sample procedures allow delay-dependent effects to be distinguished from delay-independent effects on working memory. Parameters of negative exponential functions estimate initial discriminability (intercept) and rate of forgetting (slope). Forgetting functions for patients with Alzheimer's disease indicate that they differ from normal controls in terms of reduced initial discriminability--that is, in the encoding component of memory performance--but not convincingly in rate of forgetting. Reanalyses of previous studies with different species suggest that pro- and anticholinergic drugs influence initial discriminability in delayed matching-to-sample performance, but not rate of forgetting. The results of our reanalyses are consistent with the conclusion that the cholinergic system plays a role in the encoding component of working memory and that this is the main characteristic of the memory deficit shown by patients with Alzheimer's disease.

Aged↗