The relation between physical stimulus properties and the effect of foreperiod duration on reaction time

Seven subjects were used in an experiment on the relation between signal modality and the effect of foreperiod duration (EP) on RT. With visual signals the usually reported systematic increase of RT as a function of FP duration (1, 5 and 15 s) was confirmed; with auditory signals no difference was found between FP's of 1 and 5 s while the effect at 15 s was equivalent to that found at 5 s with the visual signal. The results suggest that besides factors such as time uncertainty the FP effect is also largely dependent on the arousing quality of the signal.     

Conditional probability and components of rt in the variable foreperiod experiment

If the passage of time during the foreperiod in a variable foreperiod experiment is marked by a series of tones, RT decreases with the conditional probability of stimulus occurrence. RTs at short foreperiods, however, are rather slower than would be expected on the basis of a simple conditional probability effect. It is suggested that this is attributable to an independent “initial slow reaction” effect, and it is shown that the degree of this effect is influenced by the duration of the prior foreperiod. The results are related to those of variable foreperiod a-reactions in which no conditional probability effect has been found, and it is argued that in a marked reaction of the kind described above, the initial slow reaction effect behaves like an a-reaction component of RT. It is suggested that the absence of a conditional probability effect in the a-reaction and its presence in the marked reaction are related to the fact that a different type of sensory process is used to identify the signal in each case.     

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.     

A suppressing effect of response selection on immediate arousal in a choice reaction task

A clear conflict exists between experiments showing either additive or interactive effects of foreperiod duration and S-R compatibility on choice reaction time. It is hypothesized that in principle S-R compatibility and foreperiod duration have additive effects but that the effect of foreperiod duration is reduced in conditions where a signal is immediately arousing and where the S-R relations are highly compatible. In the case of low S-R compatibility the effect of immediate arousal is supposed to be ineffective.This hypothesis is tested and confirmed in an experiment in which the combined effects of foreperiod duration and S-R compatibility were studied with either loud (85 dBA) or weak (45 dBA) auditory signals. As predicted, additive effects were found in the latter case, while an interaction was observed with 85 dBA signals.     

Stimulus intensity and foreperiod effects in intersensory facilitation

Intersensory facilitation refers to the more rapid reaction time (RT) to a target in one modality and an accessory stimulus in a different modality compared to a RT to the target alone. Prior studies suggest two processes contribute to the phenomenon, termed the preparatory state and energy integration which refer to the action of accessory stimulation in providing forewarning and intensifying the reaction signal, respectively. Experiment I factorially varied foreperiod duration, light (target) intensity and tone (accessory) intensity in a discriminative RT task. The results were that foreperiod (preparatory state) and intensity (energy integration) effects were additive, implying that they affected separate processing stages. Accessory stimulus intensity affected false alarm rate on catch trials. This suggests that energy integration involves a form of response bias (increased likelihood of responding) and not facilitation (more rapid information processing). Experiment II indicated that comparable energy integration effects obtain with tone as target and light as accessory, as well as vice versa. The findings further indicated that RT to a bisensory pairing is more rapid when attention is directed to the more potent member of the pair.     

Stimulus intensity effects on auditory and visual reaction processes.

Literature on the effect of stimulus intensity on reaction processes was reviewed. It was shown that there is no agreement as to whether intensity effects are limited to encoding or whether they are extended to later processing stages. The situation can be characterized as an asymmetry between modalities: vision is consistent with the first alternative and audition with the second.Chronometric analysis was used to bear on the question. It was shown that the effects of visual intensity and foreperiod (FP) are additive in a simple RT situation both for constant and mixed blocks FP. Auditory intensity and FP interact in both simple and two-choice situations. In a control experiment visual intensity and S-R compatibility were found to be additive. The asymmetry was accounted for by auditory alerting, previously discussed by several authors.The framework of stimulus intensity research utilizing RT measures was briefly evaluated.     

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.     

The relationship between estimates of foreperiod duration and simple time reaction

The relationship between estimates of foreperiod length and simple reaction time (RT) was examined using constant foreperiods. It was learned that neither the average accuracy nor the variability of the foreperiod estimates necessarily manifested themselves in appropriate simple RT change. Of secondary interest was the discovery that the average accuracy of foreperiod duration estimations differed greatly from that obtained for similar time lengths in a time-estimation task. Finally, an attempt was made to determine whether subjects actually utilized the directional knowledge of results inherent in the imperative stimulus to influence their foreperiod duration judgments. Unfortunately, the evidence obtained did not permit a definite answer regarding this possibility.     

The relationship between reaction time and intensity in discrete auditory tasks

The effect of signal intensity upon reaction time (RT) was studied in three auditory RT tasks in which the signal was a tone of high or low frequency. Experiment I showed the well-known negative gradient with intensity of simple RT when the subject was instructed to ignore the frequency and give the same response to both tones. But when the subject had to discriminate the frequency in a choice RT task, the RT/intensity relationship appeared to be U-shaped. Experiment II showed that when the subject was required to make a response to one signal but withhold it for the other, a task which requires discrimination of the frequency of the tone but removes the necessity to choose between overt responses, no increase in RT at high intensities was obtained. The results indicate that it is the response choice stage rather than the stimulus encoding stage which is retarded at higher energy levels. Experiment I also demonstrated that visual and auditory leading signals have similar facilitating effects without affecting the RT/intensity relationships.     

The modality shift effect and the effectiveness of warning signals in different modalities

Which is better, a visual or an auditory warning signal? Initial findings suggested that an auditory signal was more effective, speeding reaction to a target more than a visual warning signal, particularly at brief foreperiods [Bertelson, P., & Tisseyre, F. (1969). The time-course of preparation: confirmatory results with visual and auditory warning signals. Acta Psychologica, 30. In W.G. Koster (Ed.), Attention and Performance II (pp. 145-154); Davis, R., & Green, F. A. (1969). Intersensory differences in the effect of warning signals on reaction time. Acta Psychologica, 30. In W.G. Koster (Ed.), Attention and Performance II (pp. 155-167)]. This led to the hypothesis that an auditory signal is more alerting than a visual warning signal [Sanders, A. F. (1975). The foreperiod effect revisited. Quarterly Journal of Experimental Psychology, 27, 591-598; Posner, M. I., Nissen, M. J., & Klein, R. M. (1976). Visual dominance: an information-processing account of its origins and significance. Psychological Review, 83, 157-171]. Recently [Turatto, M., Benso, F., Galfano, G., & Umilta, C. (2002). Nonspatial attentional shifts between audition and vision. Journal of Experimental Psychology: Human Perception and Performance, 28, 628-639] found no evidence for an auditory warning signal advantage and showed that at brief foreperiods a signal in the same modality as the target facilitated responding more than a signal in a different modality. They accounted for this result in terms of the modality shift effect, with the signal exogenously recruiting attention to its modality, and thereby facilitating responding to targets arriving in the modality to which attention had been recruited. The present study conducted six experiments to understand the cause of these conflicting findings. The results suggest that an auditory warning signal is not more effective than a visual warning signal. Previous reports of an auditory superiority appear to have been caused by using different locations for the visual warning signal and visual target, resulting in the target arriving at an unattended location when the foreperiod was brief. Turatto et al.'s results were replicated with a modality shift effect at brief foreperiods. However, it is also suggested that previous measures of the modality shift effect may still have been confounded by a location cuing effect.     

Lengthening fixed preparatory foreperiod durations within a digit magnitude classification task serves mainly to shift distributions of response times upwards

In this study, the effect of lengthening foreperiod duration (i.e. the time between the presentation of a warning signal and a subsequent target stimulus) on choice RTs is examined. The foreperiod durations used were either 2 or 8 s and were fixed within pure blocks of trials. The task was to determine whether a single-digit target stimulus was either smaller or larger than 5 and responses were provided manually. An additive relation between foreperiod duration length and numerical distance from 5 was present in the mean RTs. Subsequent ex-Gaussian analyses of the shapes of the RT distributions indicated that they become shifted upwards as the foreperiod increased with relatively smaller increases in the sizes of their tails. It is argued mainly that the latter finding is incompatible with the strategic time estimation view of the fixed foreperiod duration effect.     

The effect of motor preparation on changes in h reflex amplitude during the response latency of a warned reaction time task

Monosynaptic Hoffman reflexes (H reflexes) were recorded from the soleus muscle during the response latency of a warned reaction time (RT) task that required plantarflexion of the foot. The task was done under four conditions of predictability of the response signal (RS), created by the factorial combination of foreperiod duration (1 and 4 s) and variability (fixed and variable). RT varied systematically with RS predictability and was facilitated in conditions that favored prediction of the RS. The response latency was divided into two successive phases by the onset of reflex augmentation: a premotor phase of constant reflex amplitude and a succeeding motor phase marked by progressively increasing reflex amplitude. Reflex augmentation during the motor phase was coupled more closely to the imminent movement than to the preceding signal to respond. The duration of the premotor phase was unaffected by RS predictability, but the duration of the motor phase (like RT) was shorter when the RS was more predictable. The maximum H reflex amplitude reached during the motor phase was greater when the RS was more predictable. The tonic level of H reflex amplitude during the premotor phase was greater in conditions that made prediction of the RS difficult. A second experiment showed that this difference was present throughout the foreperiod. These results suggest that conditions that favor prediction of the RS enhance motor preparation. changes in motor preparation (which affect RT) affect the processes underlying reflex amplitudes in the premotor phase and throughout the preceding foreperiod, in conditions that make prediction of the RS difficult, appear to reflect heightened general arousal.     

The Effect of Motor Preparation on Changes in H Reflex Amplitude During the Response Latency of a Warned Reaction Time Task

Monosynaptic Hoffman reflexes (H reflexes) were recorded from the soleus muscle during the response latency of a warned reaction time (RT) task that required plantarflexion of the foot. The task was done under four conditions of predictability of the response signal (RS), created by the factorial combination of foreperiod duration (1 and 4 s) and variability (fixed and variable). RT varied systematically with RS predictability and was facilitated in conditions that favored prediction of the RS. The response latency was divided into two successive phases by the onset of reflex augmentation: a premotor phase of constant reflex amplitude and a succeeding motor phase marked by progressively increasing reflex amplitude. Reflex augmentation during the motor phase was coupled more closely to the imminent movement than to the preceding signal to respond. The duration of the premotor phase was unaffected by RS predictability, but the duration of the motor phase (like RT) was shorter when the RS was more predictable. The maximum H reflex amplitude reached during the motor phase was greater when the RS was more predictable. The tonic level of H reflex amplitude during the premotor phase was greater in conditions that made prediction of the RS difficult. A second experiment showed that this difference was present throughout the foreperiod.

These results suggest that conditions that favor prediction of the RS enhance motor preparation. Changes in motor preparation (which affect RT) affect the processes underlying reflex augmentation in the motor phase. Enhanced preparation may allow more efficient organization of the descending commands to move, causing higher levels of spinal excitability to be reached in a briefer time. The higher tonic reflex amplitudes in the premotor phase and throughout the preceding foreperiod, in conditions that make prediction of the RS difficult, appear to reflect heightened general arousal.     

Does increasing the warning signal intensity decrease or increase simple reaction time?

The purpose of the study was to reconcile the contradictory evidence reporting either a shortening or lengthening of the simple reaction time (RT) as a function of the intensity of a warning signal. The lengthening of auditory RT is obtained when short visual or auditory warning signals are of constant intensity within a session and succeeded by a fore-period. Visual RT did not vary under similar circumstances. There was no effect when a warning signal of constant intensity overlapped in time with the response stimulus. The shortening of RT occurred with auditory warning signals of variable intensity and overlapping in time with the response stimulus. The shortening of RT was interpreted as facilitation-by-arousal. The lengthening of RT is a contextual effect but the data do not support accounts based on sensory-neural adaptation or criterion changes.     

Foreperiod and visual stimulus intensity: A reappraisal

The joint effects of stimulus modality, stimulus intensity, and foreperiod on simple RT were investigated. In experiment 1 an interaction was found between stimulus intensity, both visual and auditory, and a variable FP such that the intensity-effect on RT was largest at the shortest FP. Experiment 2 provided a successful replication with smaller and weaker visual stimuli. No interaction was observed with a constant FP, although the visual stimuli were identical and the auditory ones psychophysically equivalent to the visual stimuli of experiment 1.It is proposed that an additive or interactive relationship between stimulus intensity and FP can be inferred only when the mental processes called for by the various uses of FP are simultaneously considered. Another precondition is an adequate sampling of the intensity-continuum with special reference to the retinal size of visual stimuli.     

VEP latency and some properties of simple motor reaction-time distribution

Summary The median of simple motor reaction (RT) to a flash parallels the latencies of visually evoked potential (VEP) deflections if flash intensity is varied. However, mean and median reaction times are not equal because of the skewness of RT distribution. It therefore seemed plausible that the mean reaction time — intensity relationship would be steeper than that for VEP latency. Such divergence would account for the intensity-dependent motor component of RT revealed by other psychophysical studies. The latencies of VEP deflections were measured as a function of intensity and the results were compared with mean and median RTs. The difference between mean and median RT is constant and independent of flash intensity. Moreover, both values are parallel to VEP latency. The general pattern of results remains the same after a change in the distribution from which the foreperiod is sampled.     

Locus of the intensity effect in simple reaction time tasks

Evidence is still inconclusive regarding the locus of the stimulus intensity effect on information processing in reaction tasks. Miller, Ulrich, and Rinkenauer (1999) addressed this question by assessing the intensity effect on stimulus- and response-locked lateralized readiness potentials (LRPs) as indices of the sensory and motor parts of reaction time (RT). In the case of visual stimuli, they observed that application of brighter stimuli resulted in a shortening of RT and stimulus-locked LRP (S-LRP), but not of response-locked LRP (R-LRP). The results for auditory stimuli, however, were unclear. In spite of a clear RT reduction due to increased loudness, neither S-LRP nor R-LRP onset was affected. A reason for this failure might have been a relatively small range of intensity variation and the type of task. To check for this possibility, we performed three experiments in which broader ranges of stimulus intensities and simple, rather than choice, response tasks were used. Although the intensity effect on the R-LRP was negligible, S-LRP followed RT changes, irrespective of stimulus modality. These findings support the conclusion that stimulus intensity exerts its effect before the start of motoric processes. Finally, S-LRP and R-LRP findings are discussed within a broader information-processing perspective to check the validity of the claim that S-LRP and R-LRP can, indeed, be considered as pure estimates of the duration of sensory and motor processes.     

Finger Pairings in Two-Choice Reaction Time Taskscolon: Does the Between-Hands Advantage Reflect Response Preparation?

Two fractionated RT experiments tested whether the response-preparation or response-implementation hypothesis better accounts for the observation that two-choice reaction time (RT) usually takes longer when the responses are performed by the fingers of the same hand (within-hand repertoire) than by the fingers of the two hands (between-hands repertoire). In Experiment I (n equals 8), the effect of repertoire on the premotor time and the motor time were studied. RT was divided into the two periods with respect to the onset of change in electromyographic (EMG) activity of the flexor digitorum profundus. Type of repertoire affected both time periods. In Experiment 2 (n = 16), the effects of repertoire and foreperiod duration on the premotor and motor times of the flexor digitorum profundus and flexor digitorum sublimis were studied. The results of Experiment I were confirmed, and the effects of repertoire and foreperiod duration were found to be additive on premotor time but interactive on motor time. These findings led to rejection of the response-preparation hypothesis and instead supported the view that the central command for the flexion of the right middle finger differs according to the type of repertoire. The command appears to specify a lower rate of recruitment of the prime movers in the within-hand repertoire than in the between-hands repertoire. The execution of the central commands may depend on the state of excitability of the spinal neurons. Analysis of the EMG signals revealed that speed of contraction of the prime movers depends on repertoire when the foreperiod is long but not when it is short. The additivity of the effects of repertoire and of foreperiod duration on premotor time support the view that regardless of the state of preparation of the subject the pattern of EMG activity required for flexion of the right middle finger in each repertoire is specified during the premotor time.     

Sequential effects of foreperiod duration and conditional probability of the signal in a choice reaction time task

The aim of the present study was to determine whether the negative relationship usually found between reaction time and foreperiod duration in the variable foreperiod paradigm is entirely due to sequential foreperiod effects. It has been shown that when a particular foreperiod has been preceded by a longer one on the previous trial, reaction time is longer than when the preceding foreperiod was equal or shorter. This may be sufficient to explain the increase in reaction time observed for short foreperiods in variable foreperiod conditions.The present results show that, when sequential effects were controlled by the elimination of all trials where the foreperiod was shorter than the preceding one, the negative slope of the reaction time-foreperiod function diminished but did not disappear. The results suggest an interpretation of the role of conditional probability of stimulus arrival in terms of variation in the tendency to reprepare when the moment initially chosen for preparation appears to fall short of the moment at which the stimulus is actually presented.     

Effects of foreperiod interval upon reaction time, alpha blocking, and heart rate under variable conditions with reduced learning factors

The present experiment was to investigate the effects of foreperiod interval upon reaction time (RT), alpha blocking, and heart rate (HR) under conditions in which learning factors and conditional probability were minimized. Twenty college students were given a series of 44 randomized foreperiod intervals (0–30 sec). The fastest RT was obtained at 0.6 sec foreperiod. Alpha blocking provided the same trend as that of RT, showing that the 0.6 sec foreperiod yielded the largest alpha blocking. Positive correlation was observed between the speed of RT and alpha blocking (r = 0.56, p<0.001). HR curve was different from those of RT and alpha blocking. No significant correlation was obtained between RT and HR. The results were discussed, particularly, in terms of the theory of classical conditioning.