RT to tactile stimuli presented ipsi- and contralaterally to the responding hand

Subjects had to react with the hand which received a tactile stimulus (uncrossed condition) or with the hand opposite to the hand which received the stimulus (crossed condition). Four experiments were conducted. In the first three, subjects knew which hand would receive the stimulus and which hand would have to respond. In the first two experiments, subjects reacted to a simple tactile stimulus while in the third subjects had to perform a tactile discrimination before responding. No significant differences in RT under the crossed and uncrossed conditions were observed in the first three experiments. In the fourth experiment, subjects did not know which hand would receive the stimulus, and they also did not know which hand would have to respond. Under these conditions, large significant differences in RT between the crossed and uncrossed condition emerged.

The study includes a criticism of a simple structural interpretation of interhemispheric transmission time (IHTT) as proposed by Bashore (1981). Support is provided for the view that in paradigms of the kind used here, allocation of attention to a psychologically defined hemispace is a more important factor in observed RT than structural links between stimulus and response mechanisms.     

Attentional localization prior to simple and directed manual responses

The relationship between attention and the programming of motor responses was investigated, using a paradigm in which the onsets of targets for movements were preceded by peripheral attentional cues. Simple (button release) and reaching manual responses were compared under conditions in which the subjects either made saccades toward the target location or refrained from making eye movements. The timing of the movement onset was used as the dependent measure for both simple and reaching manual responses. Eye movement latencies were also measured. A follow-up experiment measured the effect of the same peripheral cuing procedure on purely visual processes, using signal detection measures of visual sensitivity and response bias. The results of the first experiment showed that reaction time (RT) increased with the distance between the cued and the target locations. Stronger distance effects were observed when goal-directed responses were required, which suggests enhanced attentional localization of target positions under these conditions. The requirement to generate an eye movement response was found to delay simple manual RTs. However, mean reaching RTs were unaffected by the eye movement condition. Distance gradients on eye movement latencies were relatively shallow, as compared with those on goal-directed manual responses. The second experiment showed that the peripheral cue had only a very small effect on visual detection sensitivity in the absence of directed motor responses. It is concluded that cue-target distance effects with peripheral cues are modulated by the motor-programming requirements of the task. The effect of the peripheral cue on eye movement latencies was qualitatively different from that observed on manual RTs, indicating the existence of separate neural representations underlying both response types. At the same time, the interactions between response modalities are consistent with a supramodal representation of attentional space, within which different motor programs may interact.     

Attentional localization prior to simpleand directed manual responses

The relationship between attention and the programming of motor responses was investigated, using a paradigm in which the onsets of targets for movements were preceded by peripheral attentional cues. Simple (button release) and reaching manual responses were compared under conditions in which the subjects either made saccades toward the target location or refrained from making eye movements. The timing of the movement onset was used as the dependent measure for both simple and reaching manual responses. Eye movement latencies were also measured. A follow-up experiment measured the effect of the same peripheral cuing procedure on purely visual processes, using signal detection mea-sures of visual sensitivity and response bias. The results of the first experiment showed that reaction time (RT) increased with the distance between the cued and the target locations. Stronger distance ef-fects were observed when goal-directed responses were required, which suggests enhanced attentional localization of target positions under these conditions. The requirement to generate an eye movement response was found to delay simple manual RTs. However, mean reaching RTs were unaffected by the eye movement condition. Distance gradients on eye movement latencies were relatively shallow, as compared with those on goal-directed manual responses. The second experiment showed that the peripheral cue had only a very small effect on visual detection sensitivity in the absence of directed motor responses. It is concluded that cue-target distance effects with peripheral cues are modulated by the motor-programming requirements of the task. The effect of the peripheral cue on eye movement latencies was qualitatively different from that observed on manual RTs, indicating the existence of separate neural representations underlying both response types. At the same time, the interactions be-tween response modalities are consistent with a supramodal representation of attentional space, within which different motor programs may interact.     

Response force is sensitive to the temporal uncertainty of response stimuli

Three experiments examined whether temporal uncertainty about the delivery of a response stimulus affects response force in a simple reaction time (RT) situation. All experiments manipulated the foreperiod; that is, the interval between a warning signal and the response stimulus. In the constant condition, foreperiod length was kept constant over a block of trials but changed from block to block. In the variable condition, foreperiod length varied randomly from trial to trial. A visual warning and response stimulus were used in Experiment 1; response force decreased with foreperiod length in the variable condition, but increased in the constant condition. This result is consistent with the hypothesis that responses are less forceful when the temporal occurrence of the response stimulus is predictable. In a second experiment with an auditory warning signal and a response stimulus, response force was less sensitive to foreperiod manipulations. The third experiment manipulated both the modality and the intensity of the response signal and employed a tactile warning signal. This experiment indicated that neither the modality nor the intensity of the response signal affects the relation between response force and foreperiod length. An extension of Näätänen’s (1971) motor-readiness model accounts for the main results.     

Application of a variable criterion model to auditory reaction time as a function of the type of catch trial

A variable criterion model has been applied to data from an RT experiment by LaBerge in which catch trial stimuli varied in similarity to a single auditory RT signal. Estimates of a sensory recruitment function and the parameters of hypothetical criterion distributions were obtained by a scaling solution. Auditory recruitment was an exponential growth function, and the criterion distributions were normal. In combination, these estimates successfully predicted the empirical RT distributions.     

The influence of catch trial frequency on simple reaction time

The major purpose of the present investigation was to examine the combined influence of variations in foreperiod length (1.0, 5.0 sec) and catch trial frequency (0.0, 0.1, 0.2) on simple reaction time (RT) magnitude when verbal mediation was permitted and when it was not. A significant foreperiod length, catch trial frequency, mediation type interaction was obtained supporting the notion that all three factors influence a common process (i.e. Sternberg 1969), here called ‘preparation’. More specifically, for the non-mediation group, foreperiod length and catch trial frequency had both additive (0.0 vs 0.1) and interactive (0.1 vs 0.2) effects on mean simple RT while only catch trial frequency significantly altered simple RT for the mediating group. In all instances, mean simple RT increased significantly when some catch trials were employed as opposed to when none were used, a finding which was interpreted as reflecting an induced preparation decrement upon the introduction of catch trials.     

Effects of variations in force and stimulus uncertainty on fractionated reaction time.

Previous research has shown that reaction time (RT) and premotor time varied as a function of force even in simple-RT paradigm. The present purpose was to examine whether stimulus uncertainty induced by catch trials would cause programming delay until after the signal to respond. Subjects were required to react and produce a designated peak force as soon as possible after a visual stimulus, with and without catch trials. Five different levels of force were 10, 30, 50, 70, and 90% of the maximum grip strength of subjects. Analysis showed that simple RT and premotor time changed as a function of force, regardless of whether catch trials were removed. These findings suggest that stimulus uncertainty is not a necessary condition for programming delay.     

What are human express saccades?

When a fixation point is removed 200 msec prior to target onset (the gap condition), human subjects are said to produce eye movements that have a short latency (80–120 msec), that form the early peak of a bimodal latency distribution, and that have been labeled “human express saccades” (see, e.g., Fischer, 1987; Fischer & Breitmeyer, 1987; Fischer & Ramsperger, 1984, 1986). In three experiments, we sought to obtain this express saccade diagnostic pattern in the gap condition, We orthogonally combined target location predictability with the presence versus absence of catch trials (Experiment 1). When target location was fixed and catch trials were not used, we found mostly anticipations. In the remaining conditions, where responses were under stimulus control, bimodality was not frequently observed, and, whether it was or not, latencies were not in the express saccade range. Using random target locations, we then varied stimulus luminance and the mode of stimulus presentation (LEDs vs. oscilloscope) in the gap and overlap (fixation is not removed) conditions (Experiment2). Bimodality was rarely observed, the gap effect (overlap minus gap reaction time) was additive with luminance, and only the brightest targets elicited saccades in the express range. When fixed locations and no catch trials were combined with latency feedback (Experiment 3), we observed many responses in the express saccade range and some evidence for bimodality, but the sudden introduction of catch trials revealed that many early responses were not under stimulus control. Humanscan make stimulus-controlled saccades that are initiated very rapidly (80–120 msec), but unless catch trials or choice reaction time is used, it is not possible to distinguish such saccades from anticipatory responses that are prepared in advance and timed to occur shortly after target onset. Because the express saccade diagnostic pattern is not a characteristic feature of human saccadic performance, we urge investigators to focus their attention on the robustgap effect     

Application of variable criterion theory to choice reaction time

A theory of choice reaction time ICRT is presented which is based on a variable criterion model assuming the decision criterion to be normally distributed. The theory provides functions of time describing the growth of component processes following stimulus onset. For correct responses, these processes are sensory and associative strength. For errors, the processes are sensory strength, generalized associative strength, and associative inhibition. A model for separating the effects of these processes from that of response competition is presented. The theory describes, with great accuracy, the CRT distributions of correct responses and errors, not only for the experiment for which it was derived, but also for a second experiment in which the criterion was experimentally manipulated. It accounts for the basic facts of the speed-accuracy tradeoff, not only with respect to the two experiments with different speed requirements, but also with respect to the variation of speed over trials within each experiment. While derived from group data, the theory also describes the performance of individual subjects. The mean and variability of the criterion distribution and the ability to utilize associative inhibition are identified as the major sources of individual differences. Methodological problems involved in the scaling analysis of group data are also discussed.     

The time course of effort mobilization and strategic adjustments of response criteria

 In two-choice reaction time experiments, participants were instructed within a variable precueing interval to speed up responding in 20% of trials and to maintain their basic level of performance in the remaining trials. The achievement of this goal was rewarded by a monetary bonus. The requirement to speed up was signaled at varying intervals before the onset of the imperative stimulus. The main questions to be answered were whether participants would be able to dynamically adjust their response speed, and if so, whether a speed up would be due to enhanced effort with a genuine improvement of performance or due to an adjusted response criterion, accompanied by a speed-accuracy trade-off. The data of both experiments suggest that participants were able to invest some extra effort, the amount of which varied as a function of the length of the precueing interval. This speed-up was evident already in the fastest bins of the reaction time distribution, indicating a continuous modulation of processing efficiency. Only in the first experiment was there clear evidence for a speed-accuracy trade-off in addition to effort mobilization. Received: 14 March 2000 / Accepted: 2 March 2001     

Manual reaction times and error rates in stutterers.

In this study 18 stutterers and 18 nonstutterers were presented trials on which they should press a button as fast as possible, intermixed with trials which required no responding. Stutterers had slightly faster reaction times but also made slightly more errors, that is, they tended to press the button when they should not have done so. As neither difference was significant, it was concluded that stutterers did not differ from normal speakers in manual reaction speed, nor did they choose a different speed-accuracy trade-off criterion for the given task.     

Stimulus intensity,catch trial effects,and the speed-accuracy tradeoff in reaction time: A variable criterion theory interptation

Ss responded to a 1,000-Hz tone of 50, 80, or 100 dB. Catch trial conditions were none, blank trials, a red light, a noise, and an 1,800-Hz tone. Auditory catch signals were of the same intensities. RT distributions in the first three conditions were well described by a family of exponential growth functions dependent upon stimulus intensity and by the parameters of normal criterion distributions dependent upon catch trial conditions and between-session variability. Performance in the auditory catch trial conditions was not dependent upon the same set of sensory growth functions. Performance in these conditions was described by a two-dimensional analysis of information transmitted as a function of time and interpreted in terms of variable criterion theory. The speed-accuracy tradeoff in this situation appears to depend upon differential rates of growth of intensity and associative information and the criterion used in responding to this information.     

The “Poffenberger” and “Dimond” Paradigms: Interrelated Approaches to the Study of Interhemispheric Dynamics?

Brown and Jeeves (1993) found that an evoked potential estimate of interhemispheric transfer time, from the left to the right hemisphere, correlated negatively with a bilateral field advantage (BFA) in a response-choice letter matching task. We implemented a go no-go dot size matching task to determine whether the crossed-uncrossed difference (CUD) in reaction time, commission errors and omission errors (estimates of the “cost” of interhemispheric transfer) would correlate with BFAs in data from the same experiment and whether the type of decision (“same” versus “different”) would modulate the CUDs and/or BFAs. Sixteen normal right-handed subjects were tested. The CUDs were negatively correlated with the BFAs. Canonical correlation analysis of this set of relations was highly significant (r= .95). Estimates of left-to-right relay were far more strongly related to BFA (p= .0001) than were estimates of right-to-left relay (p= .03). “Same” decisions yielded a unilateral field advantage and “different” decisions a bilateral field advantage in omission error data, this crossed interaction reaching significance. More efficient interhemispheric relay favored BFAs, i.e., strongly suggesting in such cases an advantage of interhemispheric over intrahemispheric integration. This effect appeared to be markedly asymmetric. Furthermore, resource sharing within and between the hemispheres was a function of the “same” versus “different” dimensions of the decision to be made, especially in omission errors. The opposite dissociation occurred less markedly in the reaction times, this double dissociation reaching significance, revealing presence of a subtle speed–accuracy trade-off in interhemispheric dynamics.     

Forgetting is effortful: Evidence from reaction time probes in an item-method directed forgetting task

Reaction time (RT) was measured in response to visual detection probes embedded within an item-method directed forgetting paradigm. In Experiment 1, study words were presented individually followed by an instruction to remember (R) or forget (F). Probes were presented at stimulus onset asynchronies (SOAs) of 1,400, 1,800, or 2,600 msec in relation to the study word or memory instruction. After the study trials, a yes-no recognition task measured retention of R and F words. Experiment 2 added a no-word control condition and no-probe catch trials. In both experiments, post-F probe RTs were longer than post-R probe RTs at early SOAs. Confirming that participants attended to the memory instructions, there was a significant directed forgetting effect, with greater recognition of R than of F words. These findings contradict the view that directed forgetting in the item-method paradigm is due to the passive decay of nonrehearsed F items; instead, they are consistent with the view that intentional forgetting in an item-method paradigm occurs via the operation of an active, potentially inhibitory, cognitive process.     

An apparent-motion confound causes the negative exogenous cuing effect at SOAs with larger numbers of target locations

Salient but irrelevant stimuli seem to cause an automatic orienting of covert attention, facilitating the detection of targets at the cued location for a brief period of time. However, this finding is highly dependent on the number of possible target locations, at least when the simple detection of targets is all that the task requires. Whereas small numbers of possible target locations (e.g., 2 or 3) produce the well-known advantage in response time for valid cue trials (i.e., a positive cuing effect), larger numbers of possible target locations (e.g., 6 or 8) produce a negative cuing effect. If not explained in terms of a nonattentional mechanism, this latter finding raises serious questions about the standard interpretation of positive cuing effects. The present experiment tested a particular nonattentional mechanism: that a confound between target presence and apparent motion, which occurs only on invalid cue trials, is responsible for negative cuing effect. We reduced or eliminated this confound by the use of a new type of catch trial and eliminated the negative cuing effect with large numbers of target locations.     

Effects of task-irrelevant grouping on visual selection in partial report

Perceptual grouping modulates performance in attention tasks such as partial report and change detection. Specifically, grouping of search items according to a task-relevant feature improves the efficiency of visual selection. However, the role of task-irrelevant feature grouping is not clearly understood. In the present study, we investigated whether grouping of targets by a task-irrelevant feature influences performance in a partial-report task. In this task, participants must report as many target letters as possible from a briefly presented circular display. The crucial manipulation concerned the color of the elements in these trials. In the sorted-color condition, the color of the display elements was arranged according to the selection criterion, and in the unsorted-color condition, colors were randomly assigned. The distractor cost was inferred by subtracting performance in partial-report trials from performance in a control condition that had no distractors in the display. Across five experiments, we manipulated trial order, selection criterion, and exposure duration, and found that attentional selectivity was improved in sorted-color trials when the exposure duration was 200 ms and the selection criterion was luminance. This effect was accompanied by impaired selectivity in unsorted-color trials. Overall, the results suggest that the benefit of task-irrelevant color grouping of targets is contingent on the processing locus of the selection criterion.     

S-R Compatibility Effects Without Response Uncertainty

Five experiments investigated whether cognitively based spatial S-R correspondence effects or "compatibility" effects can occur in simple reaction time (SRT) tasks and if so, which factors might be responsible for their occurrence and size. In Experiment 1, responses were cued before each trial, but made only after presentation of a Go signal. There were considerably faster responses with spatial correspondence of Go signal and response, demonstrating that response certainty does not prevent a compatibility effect. Experiment 2, a SRT task with "extra" trials requiring responses with the same or the opposite hand, indicated a major determinant of this effect to be the keeping of two task-relevant responses in a state of readiness. Experiment 3 provided preliminary evidence for 'inertia' effects-that is, for stronger correspondence effects with frequent than with infrequent alternations between left-hand and right-hand blocks. Experiment 4 showed that correspondence effects can be obtained by using a within-hand response repertoire. Experiment 5, a replication of Experiment 3 with within-hand responses, found further evidence for inertia effects. For all experiments, reaction time distribution analyses were carried out to gain insight into the temporal dynamics of correspondence effects. Altogether the results strongly suggest that most if not all correspondence effects had a cognitive rather than an anatomical origin. This raises some doubts about conclusions from prior attempts to measure interhemispheric transmission costs by means of SRT tasks.     

Endogenous temporal orienting of attention in detection and discrimination tasks

Endogenous temporal-orienting effects were studied using a cuing paradigm in which the cue indicated the time interval during which the target was most likely to appear. Temporal-orienting effects were defined by lower reaction times (RTs) when there was a match between the temporal expectancy for a target (early or late) and the time interval during which the target actually appeared than when they mismatched. Temporal-orienting effects were found for both early and late expectancies with a detection task in Experiment 1. However, catch trials were decisive in whether temporal-orienting effects were observed in the early-expectancy condition. No temporal-orienting effects were found in the discrimination task. In Experiments 2A and 2B, temporal-orienting effects were observed in the discrimination task; however, they were larger when temporal expectancy was manipulated between blocks, rather than within blocks.     

事件性前瞻记忆的加工机制：来自ERP的证据

采用事件相关电位技术,对前瞻记忆的加工机制——主要是执行前的加工机制进行研究。控制条件为单纯的背景任务,实验条件为背景任务含前瞻记忆任务,对两种条件下非靶线索的行为数据进行比较,结果表明实验条件下被试的反应时显著长于控制条件,可能说明两种条件的认知过程存在差异,这种差异在ERPs上主要体现为刺激呈现200ms以后,两种条件的波形和脑地形图存在显著差异。结果支持预备注意加工和记忆加工理论,也部分支持多重加工理论