Biomedical subjects

A F Kramer

Publications and source records attributed to A F Kramer.

12 recordsLinked to original sources

PubMed1992

Aging, exercise, and attention.

The authors investigated the relationship among aging, attentional processes, and exercise in 2 experiments. First they examined age differences on 2 attentional tasks, a time-sharing task and an attentional flexibility task. Young adults alternated attention between 2 sequenced tasks more rapidly and time-shared the processing of 2 tasks more efficiently than older adults. They then investigated the effects of aerobic exercise on the same 2 attentional tasks in older adults. Following the 10-week exercise program, older exercisers showed substantially more improvement in alternation speed and time-sharing efficiency than older controls. Interestingly, this exercise effect was specific to dual-task processing. Both groups of subjects showed equivalent effects on single-task performance. These results indicate that aerobic exercise can exert a beneficial influence on the efficiency of at least 2 different attentional processes in older adults.

Adult↗

PubMed1992

Event related potentials and EEG components in a semantic memory search task.

This study examined the effects of memory search and related processes on both time and frequency domain components of electroencephalographic activity. More specifically, we were interested in the relationship between EEG and event-related potential (ERP) components as a function of memory load and response type. Subjects performed a semantic memory search task in which they matched word probes to category labels. Consistent with previous studies, reaction time increased and accuracy decreased with increasing memory loads. A negative component of the ERP (N400) was found to reflect semantic mismatch: N400s were larger for the nontargets than for the targets. Two ERP components were found to be reciprocally related to memory load. P300 decreased and Negative Slow Wave increased in amplitude with increases in the size of the memory set. These two ERP components were reflected by different components in a Principal Components Analysis. The power in the theta band (5-7 Hz) also increased as a function of memory load and appears to be functionally and topographically related to the Negative Slow Wave in the ERP. It is argued that both measures are jointly determined and reflect the difficulty of the conceptual operations during memory search.

Adult↗

PubMed1991

Integrated displays and the perception of graphical data.

Three experiments are presented that apply a principle of compatibility of proximity to the perception of graphical data. These experiments demonstrate that the merits and costs of integral displays relative to separable displays depend in part on the task being performed. Experiment 1 employs a data extrapolation task in which information must be integrated. Here an integral display is found to be superior to a separable display. Experiment 2 employed a data perception task that requires focused attention. This reveals superior performance with separable displays. Experiment 3 employed a multiple cue judgement task in which information integration could be manipulated. Data from Experiment 3 were analysed using the Brunswick lens procedures, and indicated that knowledge of the task structure was influenced by the display type. When selective attention was required, knowledge of the task was superior with separable displays. The results are discussed with reference to the principle of compatibility of proximity, and the implications of the results for the perception of scientific data are noted.

Adult↗

PubMed1991

Cognitive representations, control, and understanding of complex systems: a field study focusing on components of users' mental models and expert/novice differences.

Users' mental models of systems are frequently asserted to be important in their interactions with those systems. Although there are few explicit definitions of mental models in the literature, mental models are assumed to be important and researchers have seemed to accept and understand the concept intuitively. In our research, we have extracted three themes from the definitions of mental models including: (1) the relations among features or components of a system; (2) the capability of the mental model to aid in the control of the system; and (3) the capability of the mental model to enhance the user's understanding of the system. The relationships among the components of users' mental models, including procedural and declarative knowledge, perceptions of the use of system features, and the relations among the similarity of use of system features, were investigated in a field study. Trained and untrained novice users of a new business phone system rated the similarity of use of nine standard features on the phone. These ratings were used to derive cognitive representations of the relations among the system features. Users' ratings of features on univariate scales about the use of the features and scores obtained on a test of procedural knowledge were related to these representations. The two novice groups' mental models were similar except for the perception of one feature; it was more accurately depicted in the trained users' representation than those who did not attend a training programme. Two types of experts' similarity of use ratings were evaluated to determine an 'appropriate' representation of the use of the system features; this was then compared to the novices'. This comparison suggested that there were deficiencies in the mental models of novices. Designing training programmes and instructional aids for systems using the discrepancies between novices' and experts' mental models are discussed.

Adult↗

PubMed1991

Task versus component consistency in the development of automatic processing: a psychophysiological assessment.

A study was conducted to examine the role of consistency in the development of automatic processing. Subjects performed a memory search task in which consistent and inconsistent attending and responding were factorially combined. The task was performed with memory set sizes of two and four items. Results indicated that automaticity developed with consistent attending regardless of whether responding was consistent or inconsistent. However, measures of reaction time, P300 latency, and P300 amplitude revealed costs for inconsistent responding that were attributed to both stimulus evaluation and response related processes. The results suggest that total task consistency is not necessary for the development of automatic processing. Instead, it appears that automaticity can develop for consistent task components even when stimulus-response consistency is not maintained across the entire task.

Adolescent↗

PubMed1991

Perceptual organization and focused attention: the role of objects and proximity in visual processing.

The influence of the Gestalt grouping principles of similarity, closure, and proximity on the size of the response-compatibility effect was examined in a focused attention task. In three studies, subjects responded to a centrally located target and attempted to ignore adjacent distractors. The distractors, which served as targets on other trials, could be compatible, incompatible, or neutral with respect to the response of the target. In addition, the distractors and the target could be embedded in the same object, presented in the same color, presented on different objects, or presented in different colors. The typical response-compatibility effect (B. A. Eriksen & C. W. Eriksen, 1974) was found when the target and distractors were embedded in the same object or presented in the same color. Performance was poorer when the target was surrounded by response-incompatible distractors than when it was surrounded by response-compatible distractors. However, the response-compatibility effect was eliminated when the target and distractors were embedded in different objects, even when the distance between the items was less than .25 degrees of visual angle. Furthermore, the response-compatibility effect was of intermediate size when the distractors were not grouped strongly with the target or with neutral flankers. The results are discussed in terms of space- and object-based models of visual attention.

Adolescent↗

PubMed1991

Movement and focused attention: a failure to replicate.

Our original goal was to explore the nature of the grouping-by-movement phenomenon reported by Driver and Baylis (1989). In their studies, distractors that moved in common with a centrally located target had a larger influence on focused-attention performance than did more proximate but stationary distractors. These results seemed particularly important since they suggested, contrary to the predictions of space-based models of attention, that attention could be allocated to noncontiguous regions of the visual field. Their results also suggested mandatory processing of stimuli with common motion. Unfortunately, we were unable to replicate this grouping-by-movement effect. In the conditions of Experiment 1 in which we replicated Driver and Baylis's methodology, stationary distractors produced a larger response-compatibility effect than did the more distant distractors that moved in common with the target. In Experiment 2, we redundantly coded the centrally located target and the far distractors with common movement and color. However, the results were identical to those obtained in Experiment 1. The stationary near distractors that appeared in a different color from the target and the far distractors produced the largest response-compatibility effect. In a final experiment, we attempted to compensate for the reduced acuity of the moving distractors by adjusting their size by a cortical magnification factor. However, even with this manipulation, we found a larger response-compatibility effect for the stationary near distractors than for the moving distant distractors. Our results suggest that subjects are capable of selectively processing a target item that moves in common with distractors.

Adolescent↗

PubMed1990

Event-related brain potentials as indices of information extraction and response priming.

Measures of overt response and of the event-related brain potential (ERP) were used to investigate the processing of a priming stimulus varying in its information content. Subjects were shown sequences of 2 letters that served as a priming and an imperative stimulus. In 3 randomly interspersed conditions the imperative stimulus had a 0.80, 0.50, or 0.20 probability of physically matching the priming letter. The different probability conditions were signaled by the position of a dot flanking the priming letter. Reaction time and accuracy data indicated that the subjects primed their responses as a function of the information conveyed by the priming stimulus. The amplitude and latency of the P300 to the priming stimulus were sensitive to the amount of information conveyed by the priming stimulus and the duration of the processing required. The readiness potential in the foreperiod was lateralized as a function of the priming stimulus. Furthermore, the larger the amplitude of the P300 to the priming stimulus, the larger the lateralization of the readiness potential, indicating that information extraction, indexed by the P300, was related to response priming, indexed by the readiness potential. The results indicate that ERP measures make manifest covert aspects of the priming process occurring in the foreperiod.

Adolescent↗

PubMed1990

Development and transfer of automatic processing.

Two studies were performed to examine the role of consistency in the development and transfer of automatic processing. Ss performed a rule-based memory search task in which they compared multidimensional probes to 1, 2, or 3 memory set rules. Results indicated that learning occurred in the absence of consistency at lower levels of task description (e.g., mapping of individual task components to responses) as long as higher level consistencies existed in the task (e.g., consistent) mapping of task components to a conceptual framework). However, the asymptotic level of this learning was modulated by the consistency with which conjunctions of task components were mapped to decisions. High positive transfer was obtained despite replacement of the exemplars of the memory set rules, suggesting that learning was not specific to the items encountered during training. On the other hand, the magnitude of positive transfer was reduced when the rules were replaced, suggesting that most of the learning took place at the level of specific rules. Some evidence was also obtained for more general process-based learning. Results are discussed in terms of their implications for models of learning and transfer.

Adolescent↗

PubMed1990

An analysis of memory-based theories of automaticity.

Memory-based theories of automaticity predict that performance in a memory search task which is automatic will not require a representation of the memory set in working memory. The information contained in working memory was manipulated by inserting an interference task between the presentation of a memory set and a probe stimulus in a memory search task. The interference task prevented rehearsal, necessitating the retrieval of the memory set from long-term memory in variably mapped (VM) conditions. Performance in consistently mapped (CM) conditions provided strong support for memory-based theories of automaticity. With CM practice, both the effects of memory load and the effect of the interference task were eliminated. Furthermore, there was a temporal coupling in the reduction of these two effects with consistent practice. Monte Carlo simulations of memory-based automaticity predict such a temporal coupling. Automaticity is viewed as a continuum reflecting the relative contribution of the direct memory access of past solutions from long-term memory on performance.

Adolescent↗

PubMed1989

Resource reciprocity: an event-related brain potentials analysis.

The amplitude of the P300 component of the Event-Related Potential (ERP) has proven useful in identifying the resource requirements of complex perceptual-motor tasks. In dual-task conditions, increases in primary task difficulty result in decreases in the amplitude of P300s elicited by secondary tasks. Furthermore, P300s elicited by discrete primary task events increase in amplitude with increases in the difficulty of the primary task. The reciprocity in P300 amplitudes has been used to infer the processing tradeoffs that occur during dual-task performance. The present study was designed to investigate further the P300 amplitude reciprocity effect under conditions in which primary and secondary task ERPs could be concurrently recorded within the same experimental situation. Forty subjects participated in the study. Measures of P300 amplitude and performance were obtained within the context of a pursuit step tracking task (the primary task) performed alone and with a concurrent auditory discrimination task (the secondary task). Primary task difficulty was manipulated by varying both the number of dimensions to be tracked (from one to two), and the control dynamics of the system (velocity or acceleration). ERPs were obtained from both secondary task tones and primary task step changes. Average root-mean-square (RMS) error estimates were also obtained for each tracking condition. Increased primary task difficulty, reflected in increased RMS error scores, was associated with decreased secondary task P300 amplitudes and increased primary task P300 amplitudes. The increases in primary task P300 amplitudes were complementary to the decrements obtained for the secondary task, supporting the hypothesis of reciprocity between primary and secondary task P300 amplitudes across different manipulations of primary task difficulty.

Adolescent↗

PubMed1989

Simulation studies of latency measures of components of the event-related brain potential.

We compared the accuracy of P300 latency estimates obtained with different procedures under several simulated signal and noise conditions. Both preparatory and signal detection techniques were used. Preparatory techniques included frequency filters and spatial filters (single electrode selection and Vector filter). Signal detection techniques included peak-picking, cross-correlation, and Woody filter. Accuracy in the latency estimation increased exponentially as a function of the signal-to-noise ratio. Both Woody filter and cross-correlation provided better estimates than peak-picking, although this advantage was reduced by frequency filtering. For all signal detection techniques, Vector filter provided better estimates than single electrode selection. Large component overlap impaired the accuracy of the estimates obtained with both single electrode selection and Vector filter, but with Vector filter impairment occurred only when the overlapping component had a scalp distribution that was similar to the scalp distribution of the signal component. The effects of varying noise characteristics, P300 duration and latency, and the parameters of Vector filter were also investigated.

Arousal↗