Stimulus and response contributions to the children's reaction-time repetition effect

Influence of Sex, Age, and Trial Blocks on Simple Reaction Times of Elementary School Children

The present study was conducted to examine the influence of sex, age, and trial blocks on the simple reaction times of elementary school children. Each of 78 right-handed 6-, 8-, and 10-yr.-old boys and girls depressed a key in response to the onset of a blue light imperative stimulus for 4 familiarization- and 20 test-trials. Changes across the test-trials were assessed by grouping simple RTs into five blocks of four reactions each. A three-way factorial analysis of variance (sex × age × trial blocks) with repeated measures on the last factor indicated that all three main effects were significant and that none of the interactions was significant. Boys reacted faster than girls, simple RT decreased with each successive age and was faster during trial Blocks 1 and 2 than at Block 5.

Development of task switching and post-error-slowing in children

BACKGROUND

Executive control processes such as task switching and error processing have been shown to change with age. The present study explored from a developmental perspective whether shared or different mechanisms underlie these processes.

METHODS

The sample included 180 children (30 in each of the six age groups from 6-11 years) who were required to perform two different tasks: identification of a digit, or counting the number of digits. We computed switch costs as a function of response-repetition, stimulus-response (S-R) compatibility, and post-error-slowing. We also analyzed reaction time distributions.

RESULTS AND DISCUSSION

The results showed a switch cost in the response-repetition condition, with a reduction in switch cost between 7 to 8 and 9 to 10 years of age, and an S-R compatibility effect in 6 to 9 years old children. Reaction time (RT) distributions showed that the decrement in the switch cost is due to the overall decrease in RTs in fast (5th percentile) trials in 9 to 11 year olds, and slow (95th percentile) trials in 7 to 8 and 9 to 11 years old children, in both the task switch and non-switch trials. A major reduction in RT was found between 9 to 11 years in both the response type and S-R compatibility type conditions. RT distributions for post-error trials revealed that the large decrement seen in 7 to 8 and 9 to 10 years old children is primarily due to the sudden decrease in RTs in the fast and slow trials respectively. The developmental pattern of error processing was similar to one component of task switching (switch cost of the response-repetition condition), indicating that inhibition could be a common mechanism underlying both the processes. However, the failure to maintain task set was found only with task switching.

CONCLUSION

The development of task switching and error processing is not gradual. The developmental pattern of error processing is similar to that of the switch cost of the response-repetition condition in task switching, indicating that inhibition could be a common mechanism underlying both processes. The present results have implications for theories of executive control.

Switching between tasks and responses: a developmental study

Task switching requires the ability to flexibly switch between task rules and responses, and is sensitive to developmental change. We tested the hypothesis that developmental changes in task switch performance are associated with changes in the facilitating or interfering effect of the previously retrieved stimulus-response (S-R) association. Three age groups (7-8-year-olds, 10-12-year-olds and 20-25-year-olds) performed a two-choice reaction time (RT) task in which spatially compatible or incompatible responses were required. The RT costs associated with switching between tasks were larger when responses were repeated than when responses were alternated. Younger children showed a greater cost than adults when switching between tasks but repeating responses. This age difference decreased when the interval between the previous response and the upcoming stimulus increased. Switch costs were larger when switching to the compatible task than to the incompatible task, but this effect did not differ between age groups. These findings suggest that young children build up stronger transient associations between task sets and response sets, which interfere with their ability to switch to currently intended actions. A similar pattern has previously been observed for older adults (Mayr, 2001), suggesting a common contributor to task switching deficits across the life span.

Sequential effects on speeded information processing: A developmental study

Two experiments were performed to assess age-related changes in sequential effects on choice reaction time (RT). Sequential effects portray the influence of previous trials on the RT to the current stimulus. In Experiment 1, three age groups (7-9, 10-12, and 18-25 years) performed a spatially compatible choice task, with response-to-stimulus intervals (RSIs) of 50 and 500 ms varied between trial blocks. In Experiment 2, three age groups (7-9, 15-16, and 18-25 years) performed the task with spatial stimulus-response (S-R) mappings (compatible versus incompatible) varied between participants. For adults, the experiments yielded a pattern of sequential effects suggestive of "automatic facilitation" (i.e., a first-order repetition effect and a higher order benefit-only pattern for short RSIs) and "subjective expectancy" (i.e., a first-order alternation effect and a higher order cost-benefit pattern for long RSIs). Automatic facilitation was more pronounced for incompatible responses than for compatible responses. Both experiments showed the anticipated decrease in automatic facilitation with advancing age. Finally, the first-order alternation effect showed the predicted age-related increase, but the cost-benefit pattern revealed an opposite trend, suggesting that the first-order and higher order indexes of subjective expectancy may relate to dissociable mechanisms.

On the discrimination between global and local trend hypotheses of life-span changes in processing speed

Meta-analyses of age effects on processing speed suggest a single, global mechanism underlying developmental speeding and slowing in the elderly. Myerson, Hale, Wagstaff, Poon and Smith (1990) proposed an information loss model assuming that a constant amount of information is lost at each processing step in all age groups whereas the rate of information loss differs between age groups. In this study, a series of simulations has been conducted comparing global versus local information loss. This has been outcomes of these deterministic and stochastic varieties of the information loss model. The outcomes of these comparisons were consistently negative; the information loss model fails to discriminate between global and local age effects on the reaction process. The simulations were followed by a discussion of Hohle's (1967) scheme for investigating selective age effects on processing speed. It was concluded that the combined approach of stage and distribution analysis of the reaction process augmented with psychophysiological time markers provides a powerful tool for the study of life-span changes in processing speed.

The rise and fall in information-processing rates over the life span

We surveyed studies that measured information-processing durations in groups of experimental subjects (children or elderly adults) and a group of college-aged control subjects. Some studies varied the type of processing while keeping the age of a subject group fixed. Process-durations in experimental subjects could be described by a multiplicative function of the control durations, regardless of the type of processing. Other studies varied the age of the subject groups while keeping the type of processing fixed. Process-durations declined during childhood, in a manner that could be described by a negative exponential function of age. Process-durations increased throughout middle- and old-age, in a manner that could be described by a positive exponential function of age. The sum of the two exponentials defined a U-shaped function that described process-durations over the life span. The most important studies varied both the type of processing and the age of the subject groups. An array of measurements of this kind could be described by a two-dimensional function that combined the multiplicative effect of process-duration and the exponential effects of age. The multiplicative effect of process-duration suggested that the execution of a processing sequence was conditioned by a single developmental parameter in both the experimental subject and the control subject. The exponential components determined the magnitude of the developmental parameter as the age of the subject changed. Given the global character of these effects, it seemed to us that the developmental mechanism may operate at a more elementary level than the information-processing stages conceived by cognitive theories. In a developmental framework, information processing may be reducible to a large number of small steps of a homogeneous duration or reliability, such as might be realized on a neural network. The exponential rate constants may be related to constant-probability hazards that act on one or another population of neural elements to create minute defects or incremental improvements. Their cumulative effects alter the functioning of the network over its lifetime, in a way that parallels the observed changes in process-durations.