Response preparation and stimulus-response congruence to fractionating reaction time of upper and lower limbs

We measured the fractionating reaction time for upper and lower limbs of 18 young men, using an electromyogram to clarify the interaction of response preparation and stimulus-response congruence on premotor and motor time. The reaction time was divided into two periods with respect to the onset of the electromyogram, premotor and motor components. Manipulating the probability of the Go versus NoGo signals varied three different amounts of response preparation. Prior to the imperative stimulus, precue information about the position of a stimulus was presented. In the stimulus-response congruent task, subjects were required to release a key on the same side of the body using either an upper or lower limb in response to an imperative Go stimulus. In the stimulus-response incongruent task, subjects were required to act in a reverse manner. Subjects were not supposed to respond to the NoGo stimulus. The premotor time of the upper and lower limb responses was affected by the respective effects of response preparation and stimulus-response congruence. The motor time of the upper and lower limb responses increased as the probability of the Go signal decreased but not in relation to stimulus-response congruence. These results suggest that response preparation affects not only information processing time but also peripheral motor activity due to motor programming, and that the stimulus-response congruence effect on motor time disappears when information about the position of the imperative stimulus is precued.     

Conflicting visual and tactual-kinesthetic stimulation

The effects of stimulus and response probability on choice reaction time (RT) were independently investigated. In different conditions, two sets of three stimuli of probabilities of.1, .3, .6 and.3, .3, .4 were assigned to two responses-two of the stimuli assigned to one response. All combinations of S-R assignments were studied, yielding response probabilities of .1-.9, ,3-.7, and ,4-.6. With response probability held constant, variations in stimulus probability led to consistent and substantial effects on both RT and error rates. Response-probability effects were confined to error rates, and repetition effects were negligible. The results support the assumption of recent models of choice behavior that adjustments are made to the absolute (rather than just to the ordinal) values of stimulus probability.     

Stimulus-response compatibility and response preparation: effects on motor component of information processing for upper and lower limb responses

The effects of stimulus-response compatibility and response preparation on the motor component of the information processing system were investigated by analyzing the fractionated reaction time for the upper and lower limbs. The reaction time was divided into two periods with respect to the onset of electromyographic activity, premotor and motor times. The response preparation was manipulated by the probability that the locations of the precue and subsequent imperative stimulus corresponded. On a stimulus-response compatible task, subjects were required to release a key on the same side as an imperative stimulus, irrespective of the precued side. On an incompatible task, subjects were required to act in the reverse manner. The upper and lower limb responses were measured during both tasks. A repeated-measures design was used with 12 male university students. Analysis of the reaction and premotor times indicated that the stimulus-response compatibility effect became larger as response preparation decreased. The analysis of motor time yielded significant interactions between stimulus-response compatibility and limb and between response preparation and limb. These findings indicated that the motor component of information processing for the lower limb response is affected by both stimulus-response compatibility and response preparation.     

Probability effects on stimulus evaluation and response processes.

This study investigated the effects of probability information on response preparation and stimulus evaluation. Eight subjects responded with one hand to the target letter H and with the other to the target letter S. The target letter was surrounded by noise letters that were either the same as or different from the target letter. In 2 conditions, the targets were preceded by a warning stimulus unrelated to the target letter. In 2 other conditions, a warning letter predicted that the same letter or the opposite letter would appear as the imperative stimulus with .80 probability. Correct reaction times were faster and error rates were lower when imperative stimuli confirmed the predictions of the warning stimulus. Probability information affected (a) the preparation of motor responses during the foreperiod, (b) the development of expectancies for a particular target letter, and (c) a process sensitive to the identities of letter stimuli but not to their locations.     

Response probability and response latency to threshold electrocutaneous stimuli

A comparison was made between two measures of somatosensory sensitivity, response probability, and reaction time to electrocutaneous constant current pulses of 350-microsec duration. The psychometric functions are steeper than those obtained for other sensory modalities. Similarly, the reaction-time/intensity functions are also steeper than those obtained in other modalities, i.e., larger decreases in reaction time as a function of small increases in stimulus intensity. Ss exposed to a broad stimulus range, including high intensities, yield psychometric and reaction time functions displaced into a higher intensity region than when they are exposed to a narrow low-intensity range of stimuli. The data are discussed in terms of a decision-theory model of reaction time.     

Judging Cumulative Risk1

The accuracy of young adults' perceptions of how cumulative risks to life, health, and property change over time was tested by asking subjects to judge the long-term probabilities associated with different periods of exposure to risks that are very small in the short term. Process analyses revealed evidence that strategy choice and associated accuracy depended on context and framing variables. Subjects asked to judge conjunctive probabilities adopted a variety of strategies, all of which failed to yield consistently accurate long-term probability judgments. However, subjects asked to judge disjunctive probabilities often reframed the probability questions into questions about the expected number of times the hazard would strike, which they could answer more accurately. Implications of the research for promoting public understanding of the long-term implications of cumulative risks are discussed.     

A cognitive‐emotional account of the shape of the probability weighting function

Research has shown a tendency of decision makers to overweight small probabilities and to underweight moderate and large probabilities. In standard treatments this is graphically modeled by an inverse S‐shaped probability weighting function. We suggest that emotions play a significant role in the shaping of the probability weighting function. In particular, the weighting function is proposed to be some function of objective probability, expected elation, and expected disappointment. The overweighting of small probabilities results from the anticipated elation after having won, given that winning was very unlikely. The underweighting of large probabilities results from anticipated disappointment after having failed to win, given that winning was very likely. Hence, probability is assumed to influence utility. Three experiments investigate these hypotheses. Experiments 1 and 2 show that a convex function relates probability to surprise. Experiment 3 elicits choice data and further supports the proposed hypotheses. The model adds to the understanding of the cognitive and emotional processes underlying the shape of the probability weighting function. Copyright © 2002 John Wiley & Sons, Ltd.     

Timing of expectancy peak in simple reaction time situation

The present study attempted to determine the moment of the peak expectancy of the imperative stimulus in a simple reaction-time situation with constant foreperiods of 0.25, 0.5, 1, 2 and 4 sec. Four Ss were instructed to indicate the expected moment of the presentation of the imperative stimulus by a key press, i.e., to try to synchronize the key press with the onset of the imperative stimulus. Also a parallel simple reaction-time task was given using these foreperiods. It was found that when the foreperiod was prolonged from 0.5 sec on, the accuracy of prediction of the moment of the imperative stimulus as well as the reaction speed were continuously decreased.     

Non-aging fore-periods and simple reaction time

This study deals with the relationship between the momentary objective probability of the delivery of a stimulus and the reaction time in a simple reaction-time task. The hypothesis was that the reaction time is closely related to the objective probability via expectancy i.e., the momentary probability of the delivery of the stimulus as experienced by the subject. This problem was experimentally approached from two directions: (1) by varying the objective probability, in which case the reaction times should change inversely with the objective probability, and (2) by keeping the objective probability constant (by using the Bernoulli process), in which case the reaction times should not change. Eight male subjects were used. The first assumption proved to be correct, whereas the second held only when certain mean inter-stimulus intervals were used.     

Selective effects of barbiturate and amphetamine on information processing and response execution

In a 3 × 2 × 2 factoral experiment, 12 subjects carried out a choice reaction task with reaction time (RT) and movement time (MT) as response measures.Independent variables were drug treatment (amphetamine, barbiturate, placebo), visual stimulus degradation and S-R compatibility. Visual stimulus degradation and S-R compatibility showed additive effect on the RT, but did not affect the MT. This confirms that stimulus encoding, response selection and response execution represent independent processing stages. The two drugs had selective effects on the RT and the MT. Barbiturate (as compared to placebo) had no effect on the MT, but it lengthened the RT, and this effect was additive with the effects of S-R compatibility but showed an interaction with the effects of stimulus degradation. Amphetamine (as compared to placebo) shortened the MT, but there was no significant main effect of amphetamine on the RT although the interaction with the effect of S— compatibility was significant. These results suggest that barbiturate affects stimulus encoding whereas amphetamine affects response-related processes..     

强迫倾向个体的信息加工灵活性

摘 要 以高低强迫倾向个体为研究对象,考察其在不同概率情景设置的Flanker任务中的信息加工灵活性,研究结果表明：高强迫倾向个体的信息加工方式相对较缓慢、单一,以集中加工方式为主;高强迫倾向个体对情境的变化较少做出反应,在信息加工的灵活性上存在缺陷,而低倾向个体的信息加工方式相对较灵活;高强迫倾向个体不易受线索提示的影响,对信息加工方式的策略性调控能力不足。     

Deficits in the endogenous control of covert visuospatial attention in children with developmental coordination disorder

Deficits in the covert orienting of visuospatial attention have been reported in children with Developmental Coordination Disorder (DCD). Using two new versions of the covert orienting of visuospatial attention task (COVAT), the study presented here sought to investigate how generalised deficits are in this domain by using longer time intervals between cue and imperative stimulus. Twenty children with DCD and 20 controls were tested on two different COVATs with the interval between cue and peripheral imperative stimulus (or stimulus onset asynchrony, SOA) of 150 and 850 ms presented in a random sequence: the first used peripheral cues and no probability information (exogenous mode) and the second used central cues and an 80% probability that imperative stimuli would appear at the cued location (endogenous mode). Results showed that the time course of covert orienting to peripheral cues was normal in both groups. For central cues, however, children with DCD were more disadvantaged by invalid cues compared with controls, regardless of SOA; this finding was consistent with a deficit in the disengage operation of directing covert attention. These results confirm and extend our earlier finding that impairments in the endogenous control of covert visuospatial attention exist in children with DCD.PsycINFO classification: 2820; 2330; 2346; 3250     

Multidimensional Fechnerian Scaling: Basics

Fechnerian scaling is a theory of how a certain (Fechnerian) metric can be computed in a continuous stimulus space of arbitrary dimensionality from the shapes of psychometric (discrimination probability) functions taken in small vicinities of stimuli at which these functions reach their minima. This theory is rigorously derived in this paper from three assumptions about psychometric functions: (1) that they are continuous and have single minima around which they increase in all directions; (2) that any two stimulus differences from these minimum points that correspond to equal rises in discrimination probabilities are comeasurable in the small (i.e., asymptotically proportional), with a continuous coefficient of proportionality; and (3) that oppositely directed stimulus differences from a minimum point that correspond to equal rises in discrimination probabilities are equal in the small. A Fechnerian metric derived from these assumptions is an internal (or generalized Finsler) metric whose indicatrices are asymptotically similar to the horizontal cross-sections of the psychometric functions made just above their minima. Copyright 2001 Academic Press.     

Multidimensional Fechnerian Scaling: Perceptual Separability

A new definition of the perceptual separability of stimulus dimensions is given in terms of discrimination probabilities. Omitting technical details, stimulus dimensions are considered separable if the following two conditions are met: (a) the probability of discriminating two sufficiently close stimuli is computable from the probabilities with which one discriminates the projections of these stimuli on the coordinate axes; (b) the psychometric differential for discriminating two sufficiently close stimuli that differ in one coordinate only does not depend on the value of their matched coordinates (the psychometric differential is the difference between the probability of discriminating a comparison stimulus from a reference stimulus and the probability with which the reference is discriminated from itself). Thus defined perceptual separability is analyzed within the framework of the regular variation version of multidimensional Fechnerian scaling. The result of this analysis is that the Fechnerian metric of a stimulus space with perceptually separable dimensions has the structure of a Minkowski power metric with respect to these dimensions. The exponent of this metric equals the psychometric order of the stimulus space, or 1, whichever is greater.     

Response force in RT tasks: Isolating effects of stimulus probability and response probability

Mattes, UIrich, and Miller (1997) found that as response probability decreases in a simple reaction time (RT) task, participants produce more forceful responses as well as longer RTs, suggesting a direct influence of preparatory processes on the motor system. In this previous study, however, response probability was confounded with stimulus probability, leaving open the possibility that response force was sensitive to stimulus- rather than response-related preparation. The present study was conducted to unravel the effects of stimulus and response probability. Experiment 1 manipulated stimulus probability and revealed that responses to a more probable stimulus are less forceful than responses to a less probable stimulus even when both stimuli require the same response. Experiment 2 demonstrated that this stimulus probability effect does not depend on the overall level of response probability. Experiment 3 showed an analogous effect for response probability when stimulus probability is kept constant. The complete pattern of results suggests that both stimulus probability and response probability affect the forcefulness of a response. It is argued that response probability exerts adirect influence on the motor system, whereas stimulus probability influences the motor system indirectly via premotoric adjustments.     

A random-walk model of accuracy and reaction time applied to three experiments on pigeon visual discrimination

A random-walk model of visual discrimination is described and applied to reaction time (RT) distributions from three discrete-trial experiments with pigeons. Experiment 1 was a two-choice hue discrimination task with multiple hues. Choice percentages changed with hue discriminability; RTs were shortest for the least and most discriminable stimuli. Experiments 2 and 3 used go/no-go hue discriminations. Blocks of sessions differed in reward probability associated with a variable red stimulus in Experiment 2 and with a constant green stimulus in Experiment 3. Changes in hue had a large effect on response percentage and a small effect on RT; changes in reward shifted RT distributions on the time axis. The "random-walk, pigeon" model applied to these data is closely related to Ratcliff's diffusion model (Ratcliff, 1978; Ratcliff & Rouder, 1998). Simulations showed that stimulus discriminability affected the speed with which evidence accumulated toward a response threshold, in line with comparable effects in human subjects. Reward probability affected bias, modeled as the amount of evidence needed to reach one threshold rather than the other. The effects of reward probability are novel, and their isolation from stimulus effects within the decision process can guide development of a broader model of discrimination.     

Loci of signal probability effects and of the attentional blink bottleneck

To investigate the locus of signal probability effects and the influence of stimulus quality on this locus, the authors manipulated probability in Task 2 of a psychological refractory period (PRP) paradigm. The effect was additive with stimulus onset asynchrony (SOA) when the target was not masked but underadditive with decreasing SOA when the target was masked. Even with masking, however, a range of probabilities had effects additive with SOA. The results suggest loci of stimulus probability before the PRP bottleneck as well as at or after the bottleneck. A second issue addressed was the locus of interference in the attentional blink (AB). The AB was larger when the probability of the first of 2 targets was lower. The results lead to the conclusion that one cause of the AB effect is a locus at least as late as the PRP bottleneck.     

Compounds of conditioned fear stimuli

A differential conditioning procedure was used with rats to establish different levels of suppression to two different stimuli. One stimulus was paired with shock every time it was presented, while the other stimulus cued shock on only 25% of its presentations. When these two component stimuli were subsequently tested as a simultaneous compound, two different types of component-compound relationships were observed. Some subjects showed greater suppression to the compound than they did to either component stimulus, while other subjects showed an intermediate level of suppression to the compound. The difference in type of component-compound relationship appeared to be related to the degree of stability (over trials) of each subject's reaction to the probabilistic (25%) cue.When a similar discrimination was established based on the intensity of the shock, rather than its probability of occurrence, all subjects showed more suppression to the compound than to its individual component stimuli. These results are discussed in terms of their implications for choice of model for characterizing the interaction of conditioned states.     

Rule learning in children: Multiple-set training and intermediate-size transposition

Two experiments were conducted in which the subjects were trained to choose the middle-size stimulus in either a single stimulus set or in each of two nonoverlapping stimulus sets. Following criterion, each subject was presented with a series of 12 test trials involving a new stimulus set. In Experiment 1, kindergarten children tended to choose the middle-size test stimulus if the test set consisted of stimuli intermediate in size to the stimuli in the smaller and larger training sets. When the test stimuli were all larger than any of the training stimuli, the probability of choosing the middle-size stimulus increased as the distance between the two training sets increased. Three groups of children participated in Experiment 2: a kindergarten group, a first-grade group, and a first-grade group that experienced middle-size training a year earlier. The distance between training sets and two training procedures affected the three groups in a similar manner during acquisition, but several interactions were obtained during the test. The findings were discussed in terms of the Lane and Rabinowitz (D. M. Lane & F. M. Rabinowitz, Child Development, 1977, 48, 412–426) rule based theory of intermediate-size transposition and suggestions were made as to how children acquire the concept of middle.     

Subjective probabilities and moral judgments

The two experiments reported here examined the relationship between subjective probability estimates and moral judgments (credit and blame assignment, trait attributions, and behavior evaluations). Subjects read about situations that varied in outcome valence (moral or immoral); in addition, the nature of situational demands (Experiment 1) or behavior frequency (Experiment 2) was varied. In the first experiment, subjective probabilities were related to judgments of immoral behaviors (but not moral behaviors), whereas the situational demands only had an impact on judgments of moral behaviors. Experiment 2 included a wider range of behavioral situations, and the probability estimates and moral judgments were assessed independently. In contrast to the first experiment, subjective probabilities were related to trait and behavior ratings of both moral and immoral acts. Consistent with the first experiment, however, subjective probabilities predicted blame but not credit. Across both studies, the prior expectancies were more strongly related to evaluations of immoral acts than moral acts. Implications for understanding the determinants of judgments of moral and immoral acts are discussed.