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G D Logan

Publications and source records attributed to G D Logan.

13 recordsLinked to original sources
PubMed1992

Shapes of reaction-time distributions and shapes of learning curves: a test of the instance theory of automaticity.

The instance theory assumes that automatic performance is based on single-step direct-access retrieval from memory of prior solutions to present problems. The theory predicts that the shape of the learning curve depends on the shape of the distribution of retrieval times. One can deduce from the fundamental assumptions of the theory that (1) the entire distribution of reaction times, not just the mean, will decrease as a power function of practice; (2) asymptotically, the retrieval-time distribution must be a Weibull distribution; and (3) the exponent of the Weibull, which is the parameter that determines its shape, must be the reciprocal of the exponent of the power function. These predictions were tested and mostly confirmed in 12 data sets from 2 experiments. The ability of the instance theory to predict the power law is contrasted with the ability of other theories to account for it.

Attention↗
PubMed1992

Attention and preattention in theories of automaticity.

The theoretical relation between preattentive processes and automatic processes is different in different approaches to attention and automaticity. In the modal view, automatic and preattentive processes are one and the same; automatic processing is preattentive. In recent views that treat automaticity as a memory phenomenon, automatic processing is postattentive. These views are described and evidence for them is discussed. Two experiments are reported that test whether the training that makes processing automatic also makes it preattentive. The data suggest a dissociation between automatic and preattentive processes that is more consistent with the memory view of automaticity than with the modal view.

Adult↗
PubMed1991

The transition from algorithm to retrieval in memory-based theories of automaticity.

Two memory-based theories of automaticity were compared. The mixture model and the race model both describe automatization as a transition from algorithmic processing to memory retrieval. The mixture model predicts that, with training, the variability of reaction time will initially increase, and later decrease in a concave downward manner, whereas the race model predicts the variability will decrease only in a concave upward manner. The mixture model predicts that using both algorithm and retrieval on a single trial will be slower than using the algorithm alone, whereas the race model predicts the reverse. The experiments used an alphabet arithmetic task, in which subjects verified equations of the form H + 3 = K and made subjective reports of their strategies on individual trials. Both the variability of reaction times and the pattern of reaction times associated with the strategy reports supported the race model.

Algorithms↗
PubMed1989

Effects of methylphenidate on inhibitory control in hyperactive children.

This study investigated the effects of methylphenidate (MPH) on inhibitory control in hyperactive children. A double-blind, placebo-control, within-subject (crossover) design was used in which 12 children, between 6 and 11 years of age, were each tested four times in each drug condition: 0.3 mg/kg and 1.0 mg/kg of methylphenidate, and placebo. Dependent measures included (a) the probability of inhibiting responses to a primary choice reaction time task given a stop signal, on the Stopping Task, and (b) response latency and errors on the Matching Familiar Figures Test (MFFT). MPH improved the efficiency of the central inhibitory mechanism by speeding the inhibitory process, thereby affording the children greater control over their actions and enabling them to increase the probability with which they inhibited responses given a stop signal. MPH increased response latency but did not reduce errors on the MFFT, and observation of the children's task performance highlighted the interpretive problems associated with this task. Performance on both tasks was better at a dosage of 1.0 mg/kg than at 0.3 mg/kg.

Arousal↗
PubMed1989

Is there a search in fixed-set memory search?

We discuss the hypothesis that structural factors in the fixed-set memory-search task may contribute to the standard linear set-size effect typically observed in this task. We constructed a lexical decision task that contained the same structural factors as the memory-search task. Two structural factors are discussed: (1) the priming of the probe by the memory set, and (2) the confounding of repetitions per item with set size. Our experiment demonstrated that these structural factors play a role in the set-size effect. The implications of these effects for the memory-search task and for models proposed to account for memory-search data are discussed.

Adult↗
PubMed1989

Dose-response effects of methylphenidate on academic performance and overt behavior in hyperactive children.

In the present study, the effects of 0.3 mg/kg and 1.0 mg/kg of methylphenidate on the overt behavior and academic functioning of 12 children with an established diagnosis of attention deficit disorder with hyperactivity were evaluated. A double-blind, placebo-control, within-subject (crossover) design was used, in which each child was tested four times in each drug condition. Drug conditions were alternated on a bidaily basis and each child received two different drug conditions each day. The academic tasks were designed for evaluation of the relationship between task complexity and dose. Whereas overt behavior improved with increasing dose, academic functioning was improved with methylphenidate, but did not vary with either dose or task complexity. Also, investigated were potential carryover effects of a morning dose of methylphenidate on performance in the afternoon. Behavioral and academic improvements produced by a dose of 0.3 mg/kg in the morning were no longer evident in the afternoon, but a morning dose of 1.0 mg/kg produced behavioral improvements that were clinically and statistically discernible in the afternoon, although the academic improvements had dissipated.

Attention Deficit Disorder with Hyperactivity↗
PubMed1986

On the autonomy of mental processes: a case study of arithmetic.

We define a process as autonomous if it can begin without intention, and if it can run on to completion without intention. We develop empirical criteria for determining whether a process can begin without intention, for determining whether it begins in the same way without intention as it does with intention, and for determining whether it can run on to completion without intention once it begins. We apply these criteria to assess the autonomy of the processes underlying simple mental arithmetic--the addition and multiplication of single digits--and find evidence that simple arithmetic may be only partially autonomous: It can begin without intention, but does not begin in the same way without intention as with intention and does not run on to completion without intention. This conclusion suggests there may be a continuum of autonomy, ranging from completely autonomous to completely nonautonomous.

Association Learning↗