Response Selection Processes Research Articles

On the dependence of P300 latency on stimulus evaluation processes.

ABSTRACTMcCarthy and Donchin (1981) found that the latency of a late positive component of the event‐related potential (ERP) was influenced by the presence of noise in a stimulus matrix but not by the compatibility between the stimulus presented and the response required. They concluded that this component is a P300 and that its latency was influenced by stimulus evaluation but not by response selection processes. The present experiments were designed to confirm that the component identified by McCarthy and Donchin was indeed a P300 and to determine if its latency varies systematically with increases in stimulus evaluation time produced by graded changes in noise level.In Experiment 1, subjects performed a standard oddball task in which they were required to count the rarer of two stimuli (the words RIGHT or LEFT) which were, or were not, embedded in a noise matrix (characters from the alphabet). The positive component of the ERP, whose amplitude was larger for rare target stimuli, was labeled a P300, and the latency of this component was longer when the stimuli were embedded in noise. In Experiment 2, subjects performed a choice reaction time task. Following the procedures used by McCarthy and Donchin, stimulus words RIGHT and LEFT required right or left hand responses depending on the presence of a cue word SAME or OPPOSITE which preceded the stimulus. Stimulus words were presented in four different degrees of noise, the levels of which were manipulated by varying the set size of the alphabetic characters which could surround the stimulus words. Reaction time increased both with noise (by 325 ms) and as a function of stimulus‐response incompatibility (by 127 ms). In contrast, P300 latency increased substantially with noise (by 200 ms) but, to a much lesser extent (by 14 ms), with response incompatibility. These results indicate that the P300 is sensitive to the ease with which a target stimulus can be discriminated from noise. They confirm that P300 latency can be used as a measure of the timing of stimulus evaluation processes that is relatively independent of response selection and execution.

A Response Model to Market Adversity

The process by which organisations respond to changes in their environment is a particularly complex one, involving considerations of resource availability, strategy formulation, organisational structure and culture, power and information availability. In considering the interdependencies between these variables, it is suggested that interactions between environment, strategy and structure affect the distribution of power within the organisation, and that power is used to affect the distribution of resources. The advent of a market intelligence report which forecasts market adversity provides an occasion when the organisation can select from among a number of possible responses. A model of the selection process by which responses to market adversity are chosen is developed, in which it is suggested that the distribution of resources within the organisation plays a critical role. The model is a dynamic one, since the response selected is likely to re‐distribute resources within the organisation. If executives are viewed as competing against each other for access to resources, the possibility arises that an executive may deliberately bias the market signal to promote a response more favourable to his/her own relative position. Other sources of bias may also exist, all of which complicate the process of response selection. It is however argued that in the longer term a learning process may be expected to take place which effectively de‐biases the market signal. It is therefore suggested that it is the distribution of resources within the organisation which dominates the choice of response to forecast market adversity.

The P3 complex as an index of information processing: The effects of response probability

The amplitude and latency of the late positive (P 3b) component of the cortical evoked potential were studied in a visual search task. The main independent variables were memory load, response type and relative response frequency. In the experiment we used the varied mapping procedure, a condition in which the target and distractor stimuli were thoroughly mixed across trials. The main goal of the study was to establish the locus of relative response frequency. In many models of choice reaction time the effect of this task variable is believed to occur in the response selection stage. If the latency of the P 3b only indexes stimulus evaluation, independent of response selection and organization processes, relative response frequency should only affect reaction time and not the latency of P 3b. The results indicated that the latency of P 3b was very sensitive to the number of comparisons, response type and relative response frequency. In addition, only a subset of subjects selectively prepared for the most probable response. Only these subjects showed the effects of relative response frequency in their reaction times too. Response preparation, however, did not affect the latency of P 3b. It was concluded that the latency of P 3b is a very sensitive index of the search and comparison process, the binary decision process, and the probability of the type of the decision, but insensitive to motor preparation.

Expectancy and frequency effects on perceptual and motor systems in choice reaction time.

Three experiments investigated the effects of expectancy and stimulus frequency in character classification and identification tasks. Both expectancy and frequency were found to have effects on overall response latency, but the two factors had different patterns of interaction with two other experimental variables. The effect of visual quality was larger for low-frequency stimuli than for high-frequency stimuli, whereas the effect of quality was independent of expectancy. The effect of S-R compatibility was more strongly influenced by whether a stimulus was expected than by the frequency of the stimulus. The results suggest that expectancy and frequency have somewhat different effects on human information processing mechanisms. Expectancy allows temporary preparation for a specific S-R pair in response selection processes, but it has no effect on perceptual processes. Stimulus frequency, on the other hand, influences the efficiency of both perceptual and response selection processes. The overall effect of stimulus probability may be interpreted as having as components both expectancy and frequency effects.

Input, decision, and response factors in picture–word interference.

Two variations of the picture-word analogue of the Stroop task were examined in an effort to gain a better understanding of the processes involved in responding to picture-word stimuli. Four stages in this process were outlined and then evaluated as potential sources of the interference in these types of tasks. In Experiment 1 subjects were required to respond yes or no (vocally or manually) to whether the picture was that of a dog. In Experiment 2 subjects were asked to respond by naming the picture's semantic category. Taken together, the results of these experiments indicate that (a) input factors contribute very little to the interference observed, (b) in certain situations some of the interference is due to an interaction of the semantic information from the word and the picture during a decision process, and (c) the response selection and output processes account for most of the interference but only in situations in which the word's name is potentially a response. Implications of these results for the study of automatic semantic processing of words are discussed. As Quillian (1968) pointed out over 12 years ago, an individual's storehouse of information about any well-known concept is virtually limitless; yet of this information

Response selection in choice reaction time: test of a buffer model.

Two experiments were conducted to test a buffer model of response selection. Subjects reacted to the onset of one of six possible visual stimuli by pressing either a left- or a right-hand key. Two stimuli were assigned to one key Itwo-item set) and four stimuli were assigned to the other key flour-item set). An irrelevant monaural tone accompanied the visual stimulus in Experiment 1 but not in Experiment 2. Results of Experiment 1 showed that reactions were faster when the location of the tone corresponded with the response than when it did not, and the difference between these corresponding and noncorresponding conditions was greater for the two-item set than for the four-item set. Results supported the notion that the response selection process involved a serial self-terminating search of response buffers and that the tone determined the buffer searched first. In both experiments, reactions were faster to stimuli from the twoitem set than to stimuli from the four-item set

The Relation of P300 Latency to Reaction Time as a Function of Expectancy

This chapter discusses the relation of P300 latency to reaction time as a function of expectancy. The amplitude of the P300 component of the event-related potential (ERP) is inversely related to the subjective probability, or “expectancy,” for a task-relevant event. The assertion that P300 reflects the timing of stimulus evaluation has sometimes been interpreted as implying that P300 latency is positively correlated with reaction time (RT). The finding that, under certain conditions, P300 and RT is dissociated need not, however, cast doubt on the validity of P300 latency as a measure of processing time. Data showing dissociation may be reconciled by noting that the subject's response is only one of many possible consequences of stimulus presentation, rather than the end point of information processing activities invoked by a stimulus. It is thus plausible to expect P300 latency to be determined by one subset of the processes invoked by a stimulus and RT to be determined by another. Since stimuli may initiate multiple, parallel processes, the relative timing of P300 and RT would then depend on the degree of overlap between the processes of stimulus evaluation and response selection.

On the rate of gain of information in children

Previous studies of the development of information processing in children have frequently been methodologically suspect and inconclusive in outcome. A study was designed to overcome some of the difficulties encountered in earlier studies. Six boys and six girls at each year of age from 5 to 11 inclusive were tested for one week on a serial, numerals-keys choice reaction time task with 2, 4, and 8 alternatives. Results were consistent with Hick's (1952) law. Both reaction time (RT) and the rate of gain of information improved with age, but the intercept constant, a more labile index, did not. These findings suggest that development is largely restricted to the process of response selection within a 4-stage decomposition of RT. Girls consistently exhibited both faster RTs and higher rates of gain of information than boys. These sex differences are interpreted in relation to recent notions of cerebral maturation in males and females.

An EEG method to monitor drug effects on the stimulus, response and motor components of reaction time [proceedings

British Journal of Clinical PharmacologyVolume 4, Issue 5 p. 659P-659P Free Access An EEG method to monitor drug effects on the stimulus, response and motor components of reaction time [proceedings] JE Millman, JE MillmanSearch for more papers by this author JE Millman, JE MillmanSearch for more papers by this author First published: October 1977 https://doi.org/10.1111/j.1365-2125.1977.tb00831.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. References ASHTON, H., MILLMAN, J.E., TELFORD, R. & THOMPSON, J.W. (1974). The effect of caffeine, nitrazepam and cigarette smoking on the contingent negative variation in man. Electroenceph. clin. Neurophysiol., 37, 59– 71. ASHTON, H., MILLMAN, J.E., TELFORD, R. & THOMPSON, J.W. (1976). A comparison of some physiological and psychological effects of propranolol and diazepam in normal subjects. Br. J. clin. Pharmac., 3, 551– 559. MARSHALL, W.L. (1973). Cognitive functioning in schizophrenia: stimulus analyzing and response selection processes. Br. J. Psychiatr., 123, 413– 433. REBERT, C.S. (1972). Cortical and subcortical slow potentials in the monkey's brain during a preparatory interval. Electroenceph. clin. Neurophysiol., 33, 389– 402. Volume4, Issue5October 1977Pages 659P-659P ReferencesRelatedInformation