Biomedical subjects

G D Logan

Publications and source records attributed to G D Logan.

At least 37 records · Page 2Linked to original sources

PubMed1997

Fluency and response speed in recognition judgments.

Previous research has suggested that perceptual fluency can contribute to recognition judgments. In this study, we examined whether fluency in recognition is based upon the speed of preceding operations, as suggested by studies of perceptual fluency. Subjects studied items in both lexical decision and naming tasks, and were then tested on two blocks of lexical decision trials with probe recognition trials. Jacoby's process dissociation procedure was used, and results from this procedure suggested that recognition judgments in the task were based largely upon familiarity. However, the estimated discriminability available from response time distributions was significantly less than the observed recognition discriminability. Simulated memory operating characteristics confirmed this under determination of recognition by response times. The results demonstrate, contrary to previous suggestions, that fluency in recognition is not based upon speed.

Adult↗

PubMed1997

The role of attention in automatization: does attention operate at encoding, or retrieval, or both?

In this research, we investigated whether attention operates in the encoding of automatized information, the retrieval of automatized information, or in both cases. Subjects searched two-word displays for members of a target category in focused-attention or divided-attention conditions that were crossed with block (training vs. transfer). To see whether subjects encoded all available items or only attended items, we compared performance for subjects in different training conditions but in the same transfer condition. Subjects encoded attended items. To see whether subjects retrieved all the items they had in memory, or only items associated with that to which they were attending at retrieval, we compared performance for subjects in the same training conditions but in different transfer conditions. Subjects retrieved attended items. Attention was found to operate at both encoding and retrieval. These findings support the instance theory of automaticity, which predicts the role of attention at encoding and retrieval.

Adult↗

PubMed1996

Magnitude versus parity in numerical judgements: event-related brain potentials implicate response conflict as the source of interference.

When subjects make 'odd/even' and 'low/high' decisions about digits, information about the digit's magnitude can interfere with the decision about the digit's parity. The present experiment used a psychophysiological approach to examine whether this interference arises at the level of response processing. Subjects performed a choice-reaction time task involving low/high and odd/even judgements about the digits 2 through 9. The data point to a response locus for the interference effect with the size of the effect being dependent on the ease with which magnitude information can be used to prime the appropriate response. This, in turn, is influenced by the 'naturalness' of the mapping between magnitude and response hand as well as by the distance of a digit to the low/high cut-point.

Adult↗

PubMed1996

Distance and distraction effects in the apprehension of spatial relations.

Theories of the apprehension of spatial relations differ in the predictions they make about the effects of distance between the arguments of spatial relations and the effects of distracting stimuli presented along with the arguments. One theory predicts no effect of distance, another predicts a monotonic increase in reaction time (RT) with distance, and a third predicts a monotonic decrease. Most theories predict slower RTs but reasonable accuracy when distractors are present, but 1 theory predicts chance-level accuracy. These predictions were tested in 3 sentence-picture comparison experiments, in which subjects searched for targets exemplifying the relations above and below. Distance had no effect when no distractors were present. Distractors slowed RT but did not reduce accuracy to chance levels. These results suggest modifications to many of the theories of apprehension.

Humans↗

PubMed1996

The CODE theory of visual attention: an integration of space-based and object-based attention.

This article presents a theory that integrates space-based and object-based approaches to visual attention. The theory puts together M.P. van Oeffelen and P.G. Vos's (1982, 1983) COntour DEtector (CODE) theory of perceptual grouping by proximity with C. Bundesen's (1990) theory of visual attention (TVA). CODE provides input to TVA, accounting for spatially based between-object selection, and TVA converts the input to output, accounting for feature- and category-based within-object selection. CODE clusters nearby items into perceptual groups that are both perceptual objects and regions of space, thereby integrating object-based and space-based approaches to attention. The combined theory provides a quantitative account of the effects of grouping by proximity and distance between items on reaction time and accuracy data in 7 empirical situations that shaped the current literature on visual spatial attention.

Attention↗

PubMed1995

Linguistic and conceptual control of visual spatial attention.

A theory of voluntary, top-down control of visual spatial attention is presented that explains how linguistic cues like "above," "below," "left," and "right" are used to direct attention from one object to another. The theory distinguishes between perceptual and conceptual representations of space and views attention as a set of mechanisms that establish correspondences between the representations. Spatial reference frames play an important part in this analysis. The theory interprets reference frames as mechanisms of attention, similar to spatial indices but with more computational power. The theory was tested in 11 experiments that assessed the importance of linguistic distinctions between classes of spatial relations (basic, deictic, and intrinsic) and examined the flexibility with which subjects manipulated spatial reference frames.

Attention↗

PubMed1995

Strategies and mechanisms in nonselective and selective inhibitory motor control.

Motor inhibition was studied in 3 versions of the stop-signal paradigm, with the stop signal requiring inhibition of any response (stop-all), a fixed alternative response (stop-change), or selective inhibition of only 1 of the responses (selective-stop). The lateralized readiness potential was used in Experiment 1 to distinguish between a selective, central, and a global peripheral inhibition mechanism. Inhibition was found to be effected by the central mechanism in the stop-change condition and by the peripheral mechanism in the other conditions. Manipulation of stimulus discriminability in Experiment 2 strongly affected the speed of selective motor inhibition, confirming that such inhibition was achieved by conditionally engaging the peripheral mechanism. These results support the idea that functionally distinct mechanisms and strategies are involved in inhibitory motor control in different situations.

Adolescent↗

PubMed1994

Spatial attention and the apprehension of spatial relations.

Seven experiments examined the role of spatial attention in apprehending spatial relations above, below, left, and right. In Experiment 1, visual search was difficult when targets differed from distractors only in the spatial relation between their elements. Reaction time increased linearly with display size with a slope greater than 60 ms/item. In Experiment 2, search was easy (the slope was flat) when targets differed from distractors in the identity of their elements. In Experiments 3 and 4, target position was cued with a discrepant color, and performance was better when attention was pulled toward spatial-relation targets than away from them. Experiments 5-7 generalized the results over different displays and extended practice. The results suggest that apprehending spatial relations requires spatial attention.

Analysis of Variance↗

PubMed1994

Aging and inhibition: beyond a unitary view of inhibitory processing in attention.

The authors examined the question of whether a decrease in the efficiency of inhibitory processing with aging is a general phenomenon. Thirty elderly and 32 young adults performed a series of tasks from which the authors could extract measures of inhibitory function. The tasks and task components included response compatibility, negative priming, stopping, spatial precuing, Wisconsin Card Sorting Test (WCST), and the Cognitive Failures Questionnaire (CFQ). Only limited evidence for age-related differences in inhibitory function was obtained. Old adults had more difficulty than young adults in stopping an overt response and adopting new rules in a categorization task. However, elderly and young adults produced equivalent negative priming effects, response compatibility effects, spatial precuing effects, and self-reported cognitive failures. The findings are discussed in terms of the relationship between aging, inhibitory processes, and neuroanatomical and physiological function.

Adolescent↗

PubMed1993

Memory-based automaticity in the discrimination of visual numerosity.

In the development of memory-based models of automaticity, it is crucial to specify the nature of the memory representation. Seven experiments with 94 students use a counting task to determine whether a feature (i.e., identity, color, or orientation) is explicitly represented in memory. It is assumed that the degree of transfer to a pattern differing on one feature is determined by that feature's importance in supporting skilled performance. Experiment 1 determined the practice necessary to obtain automaticity. In Experiments 2a, 3a, and 4a, which investigated the nature of the representation after extended practice, changing neither the identity nor color of elements had strong effects on transfer, but changing pattern orientation did impair memory retrieval, thus suggesting that for the counting task, pattern orientation is more important than element identity or color. Experiments 2b, 3b, and 4b replicated these results after limited practice.

Attention↗

PubMed1993

The loss of repetition priming and automaticity over time as a function of degree of initial learning.

Two experiments were performed to investigate the buildup of repetition priming in a lexical decision task with repeated presentations and its decline over the course of 2 months. Priming was found to accumulate as a power function of presentations and to decline as a power function of time. Accuracy measures indicated that the loss rate of priming was unaffected by the amount of initial priming. Response time measures indicated the same result when the experiments were analyzed separately; however, when the data were combined, increased initial priming was associated with greater losses in priming over time. The data were interpreted in terms of automaticity, and the power function decline in priming was taken as support for memory-based models of automaticity. Possible ways to incorporate forgetting into memory-based theories of automaticity are discussed.

Adult↗

PubMed1993

Evaluating a computational model of perceptual grouping by proximity.

A formal approach to the phenomenon of perceptual grouping by proximity was investigated. Grouping judgments of random dot patterns were made by the CODE algorithm (van Oeffelen & Vos, 1982) and several related algorithms, and these judgments were compared with subjects' grouping judgments for the same stimuli. Each algorithm predicted significantly more subject judgments than would be expected by chance. The more subjects agreed on how a given dot pattern should be grouped, the more successful was the algorithms' ability to match the judgments for that pattern. CODE predicted significantly fewer subject judgments than did some of the other algorithms, largely because of its overemphasis on the extent of interactivity among dots as they are being grouped.

Adult↗

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↗