The "short-long" reaction time effect in duration programming

The programming processes concerned with response duration were studied in a precueing and in a priming reaction time (RT) paradigm. Participants had to produce a motor response of a specified duration as soon as possible after a response signal (RS) preceded by a warning signal (WS), which could deliver information on 2 response parameters (duration and effector). In Experiment I (precueing; N = 12), 3 effectors (the right hand, the left hand, or the knees) and 3 durations (.7, 2.5, or 5.5 s) were contrasted. Two responses differing in their biomechanical features were required in 2 blocks of trials: Subjects had to accurately time the duration of either a sustained button press or an interval between 2 brief presses. The RT patterns revealed a short-long effect: Shorter RTs were produced before the short duration than before the longer, provided that the duration was not precued. This short-long effect occurred whatever type of response and effector were involved. Two conclusions were reached. First, response duration was included in the motor program elaborated before execution, whatever the biomechanical features of the response; and, second, the program for the short duration was activated on all trials and was used as a basis for programming longer durations when needed. These conclusions were tested in Experiment 2 (priming; N = 12), in which a small proportion of invalid trials concerning duration was provided. Thus, the duration required by the RS differed from that primed by the WS. Two durations (.7 or 2.5 s) and 2 effectors (the index or the middle finger) were involved. In the invalid trials, the responses of short and long durations did not yield any RT differences, thus confirming the particular status of the short duration. This suggests that deprogramming operations (which lengthen the RT) are needed after a RS to produce short response durations but not after a RS to produce long response durations in the invalid trials.     

An effect of spatial-temporal association of response codes: understanding the cognitive representations of time

The present study addresses the question of how such an abstract concept as time is represented by our cognitive system. Specifically, the aim was to assess whether temporal information is cognitively represented through left-to-right spatial coordinates, as already shown for other ordered sequences (e.g., numbers). In Experiment 1, the task-relevant information was the temporal duration of a cross. RTs were shorter when short and long durations had to be responded to with left and right hands, respectively, than with the opposite stimulus-response mapping. The possible explanation that the foreperiod effect (i.e., shorter RTs for longer durations) is greater with right than with left hand responses is discarded by results of Experiment 2, in which right and left hand responses alternated block-wise in a variable foreperiod paradigm. Other explanations concerning manual or hemispheric asymmetries may be excluded based on the results of control experiments, which show that the compatibility effect between response side and cross duration occurs for accuracy when responses are given with crossed hands (Experiment 3), and for RTs when responses are given within one hand (Experiment 4). This pattern suggests that elapsing time, similarly to other ordered information, is represented in some circumstances through an internal spatial reference frame, in a way that may influence motor performance. Finally, in Experiment 5, the temporal duration was parametrically varied using different values for each response category (i.e., 3 short and 3 long durations). The compatibility effect between hand and duration was replicated, but followed a rectangular function of the duration. The shape of this function is discussed in relation to the specific task demands.     

The specification of digit and duration during motor programming: a new method of precueing

This experiment manipulated digit uncertainty, duration uncertainty, and response duration (dit or dah) in a choice reaction time key press task. A new method of precueing was developed that effectively "precued" the digit and/or the duration of the key press task without confounding the number of stimulus response alternatives with the levels of uncertainty of digit and duration. When the duration of the response was certain, there were no RT differences between dit and dah responses, however, when duration was uncertain, RT to dah responses were longer than dit. In addition, level of duration uncertainty and digit uncertainty produced an overadditive interaction upon RT. These results are discussed in terms of generalized motor programs and a feature construction hypothesis. In addition, these results support the view that precueing of movement dimensions can be accomplished without confounding the number of stimulus response alternatives and the uncertainties of movement dimensions.     

Effect of short and long exposure duration and dual-tasking on a global-local task

Past research has demonstrated a global advantage in responses to visually presented hierarchical stimuli such that, on incongruent trials, the global form interferes with responses to the local level [Kimchi, R. (1992). Primacy of wholistic processing and global/local paradigm: A critical review. Psychological Bulletin, 112, 24-38]. In Experiment 1, 32 adults performed alternating blocks of global or local identification of hierarchical letter stimuli in which the global and local letters were congruent, incongruent, or neutral, and were presented at either a short (17 ms) or long (100 ms) exposure duration. A global advantage was demonstrated at both durations. In the local-directed task, interference on incongruent, relative to neutral, trials was observed at both exposure durations, but facilitation on congruent trials, relative to neutral trials, was present only when stimuli were presented at the long exposure duration. In Experiment 2, global or local identification was performed by another group of 24 adults at either a long or short exposure duration, and also under conditions of full attention (FA) or dual-task (DT) conditions with a digit-monitoring task. Under FA, we again found significant interference at both exposure durations, but facilitation only at the long exposure duration. Under DT conditions, the pattern of facilitation and interference at the short duration remained unchanged. At the long duration, however, dual-tasking eliminated interference in the RT but not error data, while facilitation was present in both sets of data. Results are in line with a perceptual account of the global advantage, and suggest that facilitation requires consciously-mediated processes, whereas interference does not.     

The relationship between variability of intertap intervals and interval duration

Summary Subjects tracked intervals in a synchronization paradigm at interval durations of 180, 210, 240, 270, 300, 400, 500, 600, 700, 800, 900, and 1,000 ms. The variability of intertap intervals (ITIs) shows a sudden increase near 300 ms. This increase is interpreted as indicating the transition from automatic to controlled movement. It is suggested that the sudden change in the variability of ITIs does not reflect the operation of different timing mechanisms at short and long intervals, but differences in the way in which attentional processes come to bear on movement initiation for different interval durations. In contrast to previous findings reported in the literature, a U-shaped function between interval duration and variability in the 300-to-1,000-ms range was not observed.     

Effects of nonconscious perception on motor response

The present study reviews the literature on the empirical evidence for the dissociation between perception and action. We first review several key studies on brain-damaged patients, such as those suffering from blindsight and visual/tactile agnosia, and on experimental findings examining pointing movements in normal people in response to a nonconsciously perceived stimulus. We then describe three experiments we conducted using simple reaction time (RT) tasks with backward masking, in which the first (weak) and second (strong) electric stimuli were consecutively presented with a 40-ms interstimulus interval (ISI). First, we compared simple RTs for three stimulus conditions: weak alone, strong alone, and double, i.e., weak plus strong (Experiment 1); then, we manipulated the intensity of the first stimulus from the threshold (T) to 1.2T and 2T, with the second stimulus at 4T (Experiment 2); finally, we tested three different ISIs (20, 40, and 60 ms) with the stimulus intensities at 1.2T and 4T for the first and second stimuli (Experiment 3). These experiments showed that simple RTs were shorter for the double condition than for the strong-alone condition, indicating that motor processes under the double condition may be triggered by sensory inputs arising from the first stimulus. Our results also showed that the first stimulus was perceived without conscious awareness. These findings suggested that motor processes may be dissociated from conscious perceptual processes and that these two processes may not take place in a series but, rather, in parallel. We discussed the likely mechanisms underlying nonconscious perception and motor response to a nonconsciously perceived stimulus.     

The role of temporal unpredictability for process interference and code overlap in perception-action dual tasks

Two experiments explore interference in dual tasks. The first task required perceptual judgment of the movement direction (left vs right) of a briefly presented stimulus; the second task was a tone-discrimination reaction-time (RT) task. Participants reported their judgment at leisure. In 50% of the trials they were told to ignore the stimulus (no report). The directions of stimulus movement and response in the RT task could either be the same or different, establishing cross-task compatibility (CTC) relations. We varied the degree of temporal unpredictability by using two stimulus-onset asynchronies (SOA, 100 ms vs 1200 ms) for the task stimuli. In Experiment 1, SOA was varied randomly within blocks of trials in one group and between blocks in another group. In Experiment 2, only the short SOA was used in one group and only the long SOA in another group. In both experiments, we observed substantially longer RTs with the short compared with the long SOA, regardless of whether there was temporal certainty (blocked or constant SOA) or uncertainty (random SOA) about stimulus onset. We assume that the process of encoding into short-term memory in one task interferes with concurrent retrieval processes (i.e., response selection) in the other task. This process interference effect was strongly reduced in no-report trials. Furthermore, we found shorter RT in compatible than in incompatible trials. This CTC effect diminished with long SOA but occurred even in no-report trials, implying that it refers to an automatically activated and then decaying code that primes response selection in the RT task.     

The effects of sound duration on newborns' head orientation

Two experiments assessed the importance of sound duration for eliciting head orientation responses from newborn infants. In Experiment 1, thirty infants turned with equal frequency toward 20-s continuous rattle sounds and 20-s trains of rattle segments. The duration of the rattle segments--14 and 100 ms (2/s), or 500 ms (1/s)--did not influence the likelihood of turning. Response latencies and durations proved quite similar for all stimuli. In Experiment 2, twenty-four infants heard continuous rattle sounds of four different durations: 1, 5, 10, and 20 s. They turned reliably to all stimulus durations; furthermore, the magnitude and temporal characteristics of head orientation responses did not differ for the four stimulus durations. These results suggest that the newborn's head orientation response may reflect a motor program that is initiated by auditory input and then executed in a similar fashion regardless of further stimulation.     

Time counts: Bidirectional interaction between time and numbers in human adults

Number is known for influencing time processing, but to what extent time influences number in human adults is unclear. We investigated possible bidirectional interactions (number on time and time on number) using a novel Stroop-like task; participants compared numbers or temporal durations in congruent (larger number presented for longer duration) or incongruent conditions (smaller number presented for longer duration). Time and number tasks were presented in different blocks (Experiment 1) or within the same block of trials with task instructions provided at the offset of the stimuli (Experiment 2). Analyses of response times (RTs) and their distribution revealed that number affected time from early RTs, and time affected number at late RTs – an asymmetry observed only when time and number tasks were presented in separate blocks. Thus, carefully chosen tasks and appropriate data analysis can reveal bidirectionality between time and number, consistent with shared magnitude or decision mechanisms.     

Programming of time-to-peak force for brief isometric force pulses: effects on reaction time

According to the parallel force unit model (PFUM) the programming of an isometric force pulse requires the specification of the number of force units and force unit duration. The programming of a force pulse with minimal time-to-peak force is an exception, however, as force unit duration is limited by the minimal possible value, which should be easier to adjust than larger force unit durations. Therefore, the duration of the programming process should be shorter for these force pulses and hence should result in shorter reaction time (RT). Four experiments assessed this prediction using a response precueing procedure. In each experiment the participants produced isometric flexions with their left or right index finger, and time-to-peak force was manipulated within a block. The results are consistent with the predictions of PFUM. The results, however, are at variance with alternative accounts which assume that RT depends primarily on response duration or rate of force production.     

Response preparation in Parkinson's disease: automatic vs. controlled processing

Using a finger cuing paradigm, we investigated response preparation in Parkinson's disease (PD). The central question was whether PD individuals are differentially affected by preparatory cues that specify a more automatic response set configuration (that induces within-hand preparation) as opposed to a more controlled one (that induces between-hands preparation). Reaction times (RTs) and error rates were measured in 20 non-demented individuals with PD and 20 healthy control participants with a long and short preparation interval (500 ms and 2000 ms). RT benefits and/or costs were measured for cues indicating a within- and between-hands motor preparatory set. Overall, RTs were significantly longer, and errors more frequent, for PD participants than for control participants. More importantly, in comparison with control subjects, PD individuals showed a significant deficit in between-hands preparation but not in within-hand preparation. Furthermore, longer preparation intervals slowed down cued RTs of the control participants, but not those of the PD individuals. Together, these findings suggest that whereas automatic response preparation processes are spared in PD, controlled response preparation processes operate at a slower rate and/or are delayed in time.     

Scalar timing without reference memory? Episodic temporal generalization and bisection in humans

Three experiments tested whether the scalar property of timing could occur when humans timed short durations under conditions in which it was unlikely that they developed reference memories of temporal "standards". Experiment 1 used an episodic version of a temporal generalization task where judgements were made of the potential equality of two durations presented on each trial. Unknown to the subject, one of these was always 200, 400, 600, or 800 ms, and the other was of variable duration. Temporal generalization gradients showed the scalar property of superimposition at standard values greater than 200 ms. Experiment 2 used a variant of the "roving bisection" method invented by Rodriguez-Girones and Kacelnik (1998) modified so that the scalar property of timing could be observed empirically. Data from bisection with short/long standard pairs of 100/400, 200/800, and 300/1,200 ms showed nearly perfect scalar-type superimposition. Experiment 3 again used episodic temporal generalization, but durations were never repeated and came from three distinct time ranges. Superimposition was found across these ranges except for the shortest visual stimuli timed. The data suggested that scalar timing could occur in humans in conditions where the formation of reference memories of temporal standards was highly improbable.     

Sustained attention in language production: An individual differences investigation

Whereas it has long been assumed that most linguistic processes underlying language production happen automatically, accumulating evidence suggests that these processes do require some form of attention. Here we investigated the contribution of sustained attention: the ability to maintain alertness over time. In Experiment 1, participants’ sustained attention ability was measured using auditory and visual continuous performance tasks. Subsequently, employing a dual-task procedure, participants described pictures using simple noun phrases and performed an arrow-discrimination task while their vocal and manual response times (RTs) and the durations of their gazes to the pictures were measured. Earlier research has demonstrated that gaze duration reflects language planning processes up to and including phonological encoding. The speakers’ sustained attention ability correlated with the magnitude of the tail of the vocal RT distribution, reflecting the proportion of very slow responses, but not with individual differences in gaze duration. This suggests that sustained attention was most important after phonological encoding. Experiment 2 showed that the involvement of sustained attention was significantly stronger in a dual-task situation (picture naming and arrow discrimination) than in simple naming. Thus, individual differences in maintaining attention on the production processes become especially apparent when a simultaneous second task also requires attentional resources.     

Programming of time-to-peak force for brief isometric force pulses: Effects on reaction time

According to the parallel force unit model (PFUM) the programming of an isometric force pulse requires the specification of the number of force units and force unit duration. The programming of a force pulse with minimal time-to-peak force is an exception, however, as force unit duration is limited by the minimal possible value, which should be easier to adjust than larger force unit durations. Therefore, the duration of the programming process should be shorter for these force pulses and hence should result in shorter reaction time (RT). Four experiments assessed this prediction using a response precueing procedure. In each experiment the participants produced isometric flexions with their left or right index finger, and time-to-peak force was manipulated within a block. The results are consistent with the predictions of PFUM. The results, however, are at variance with alternative accounts which assume that RT depends primarily on response duration or rate of force production.     

时距的短时保持: 缩短还是变长

采用Wearden和Ferrara(1993)的经典方法, 分别考察了1s以下(350 ms~650 ms)和1s以上(1000 ms ~ 2000 ms)不同类型(空、实时距)和通道(视、听)时距的短时保持效应。实验1发现, 不同刺激通道条件下, 1s以下时距的短时保持都呈现出主观缩短, 其中视觉条件比听觉条件明显; 实验2表明, 1s以上时距在不同刺激通道条件下都呈现出主观变长, 其中听觉条件比视觉条件明显。分析表明, 主观缩短趋势可能是由主观缩短效应和正的顺序误差效应共同作用所致, 而主观变长趋势是由主观变长效应和负的顺序误差效应造成的。     

Evoked potentials in reaction time with a variable foreperiod

The reaction times (RTs) of 12 subjects were recorded in a design where a visual or auditory warning signal preceded an auditory RT signal by one of four short foreperiods 500, 750, 1000 or 1250 ms long, which occured in a random sequence. For the 16 trials at each foreperiod, with each modality of warning signal, the average of the 2-s long EEG samples following the warning signal was computed so that the record showed the scalp recorded (vertex--left mastoid) evoked potentials (EPs) to both warning and RT signals, and also the contingent negative variation or expectancy wave occurring during the foreperiod.

Differences between RTs with different foreperiods were not reflected in negatively correlated differences in the amplitude of the RT signal EPs, taking the major positive going deflection between peaks N1 and P2 at mean latencies of 126 and 231 msec after the RT signal. Furthermore RT signal EPs preceded by a warning signal were highly attenuated in amplitude relative to control EPs which were not preceded by a warning signal, whether or not an RT response was required. This was despite the fact that alerted RTs were slightly faster than non-alerted RTs, so that these findings contradict previous findings associating augmented EPs with responding versus not responding and with speeded RTs.

However, it was also found that RT signal EP amplitudes were greater with the more effective modality of warning signal than the less effective, which was consistent with previous findings. The divergence from previous findings when comparing EPs preceded by a warning with those having no prior warning is tentatively accounted for in terms of persisting physiological refractoriness following the warning signal EP.     

Actively Controlling Anticipation of Irregular Events

There have been no investigations as to how people respond to sequences of events which occur at brief, unpredictable intervals as in everyday life. Eleven young adults were practised at a two-choice, continuous, serial choice-response task in which intervals between each response and the onset of the next signal (RSIs) varied randomly from trial to trial. On half the trials in each of four conditions the RSI was 20 ms, and on the other trials 200, 400, 800 and 1600 ms respectively. Reaction times fell as RSIs increased from 20-200 ms but thereafter appeared to be unaffected by RSI duration. In the 20/200 and 20/400 ms RSI conditions RT was not affected by transitions between different RSIs but in the 20/800 and 20/1600 ms conditions RTs were faster when the longer RSI recurred on immediately successive trials than if the long RSI followed the short (20 ms) RSI. These results are discussed in terms of a control system model for the way in which subjects actively trade off between their internal performance limitations to optimally meet task demands.     

Intermanual cross-talk effects in unimanual choice reactions

Intermanual interactions originate at different levels of motor control. Interactions during specification of movement characteristics should affect reaction time for choice between left-hand and right-hand movements. In two experiments combinations of short and long target amplitudes for reversal movements of the left and right hand were cued with variable precueing intervals. Upon presentation of the response signal a unimanual left-hand or right-hand movement had to be produced. Reaction time was faster when same target amplitudes were precued than when different target amplitudes were. At short precueing intervals the longer reaction time with different target amplitudes (early effect) was accompanied by an amplitude assimilation: Short amplitudes were too long, and long amplitudes were too short. At longer precueing intervals the longer reaction time with different target amplitudes (late effect) was accompanied by a higher choice accuracy. These findings are taken to indicate a transient parametric coupling of amplitude specifications, which produces the early and the late effects by way of different mechanisms-namely different degrees of advance specification and generalized de-coupling, which affects the process of choice between hands.     

Target-size influences on reaction time with movement time controlled

The variable that affect motor programming time may be studied by changing the nature of the response and measuring the subsequent changes in reaction time (RT). One notion of motor programming suggests that aiming responses with reduced target size and/or increased target amplitude require more "complex" motor programs that require longer RTs. In a series of five experiments which movement time (MT) was experimentally varied target size neither influences RT when the movement amplitude was 2 or 30 cm nor when the target sizes differed by as much as a factor of 16:1. Increasing the movement amplitude from 15 to 30 cm also had no influence on RT. Movement time, however, did affect RT, with 200-msec movements having longer RTs than 120-msec movements. Target size and movement amplitude did not appear to be factors that influence programming time or program complexity.     

Effects of time-order, interstimulus interval, and feedback in duration discrimination of noise bursts in the 50- and 1000-ms ranges

Participants compared durations of paired white-noise bursts, with interstimulus interval (ISI) 100, 300, 900, or 2700 ms, presented in the order standard (St)-comparison (Co) or Co-St. St was 50 or 1000 ms, and 75% difference thresholds for "longer" and "shorter" judgments were estimated. In Experiment 1 feedback was given; in Experiment 2, with ISIs 900 and 2700 ms, there was no feedback. For St=1000 ms, the just noticeable difference (JND) in noise duration was generally smaller with the order St-Co than with Co-St; for St=50 ms, the JND relation was the opposite. JNDs increased with shorter ISIs. Time-order errors were positive for St=50 ms and negative for St=1000 ms, and approached zero for longer ISIs. Using Hellstr?m's sensation-weighting (SW) model, the ratio of the stimulus weights for the first and second burst was estimated; this ratio was generally >1 for St=50 ms and <1 for St=1000 ms. JNDs were smaller with feedback than without; the greatest reduction was found for St=1000 ms and an ISI of 2700 ms with the order Co-St, possibly because feedback increased participants' attention to the first stimulus. These results demonstrate the sensitivity of discrimination measures for long as well as brief durations to the factors of ISI, presentation order, and feedback. They also suggest different modes of stimulus processing for short and long durations.