Accessory stimuli modulate effects of nonconscious priming

In a recent study, it was shown that subliminal priming (SP) effects are affected by the temporal predictability of a stimulus onset. If predictability is not given, SP effects are eliminated (Naccache, Blandin, & Dehaene, 2002). In two experiments, we investigated how different levels of preparation for target processing affect SP effects. For this purpose, an accessory tone stimulus was presented at different times prior to a subliminal priming task. The results demonstrate a clear modulation of the SP effects at different foreperiod intervals. Relative to conditions without an accessory stimulus, SP effects were smaller for short foreperiod intervals of the accessory stimulus, and larger for long foreperiod intervals. The results suggest that the presentation of an accessory stimulus facilitates response activation processes because of the participants' enhanced level of preparation for stimulus processing.     

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.     

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.     

Visual stimulus intensity and location probability: Interactive effects on choice reaction time

Three prevalent models predict different stimulus intensity effects on RT. These are: the serial-stage model (additivity), the variable criterion model (larger intensity effects with slower responding), and the temporal overlap model (smaller intensity effects with slower responding). The predictions were tested in a dual-response situation including oculomotor and manual responses (RT). Other variables were stimulus location probability (expectancy), foreperiod (alertness), and stimulus intensity (encoding. In Experiment I, an Intensity x Probability interaction was found such that the intensity-effect was smaller at low stimulus probability. Three further experiments were performed in order to specify some of the conditions relevant for this phenomenon. The results are consistent with the temporal-overlap interpretation. It was suggested that the obtained interaction results from a processing delay due to increased demands for cognitive and response processing (Stanovich & Pachella, 1977), or to the attention switch to an unexpected S-R event.     

Impact of contingency manipulations on accessory stimulus effects

Accessory tone stimuli facilitate response performance despite being irrelevant for the current task. In order to investigate which processes are affected by accessory stimuli, we presented accessory tones in a simple response time (RT) task while varying the contingencies between accessory stimulation and either responses(Experiment 1) or stimulus conditions (Experiment 2). Accessory tones speeded up responding to a larger degree when they were conjointly presented within go compared with no-go trials. In contrast, contingency variation with stimulus conditions did not alter the impact of accessory stimuli. Additionally, accessory tones increased response force. Thus, we conclude that in simple RT tasks accessory tones influence response-related stages such as response selection and response execution rather than perceptual processes.     

Reaction time indices of attention deficits in boys with disruptive behavior disorders

Boys with diagnoses in the disruptive behavior disorder (DBD) spectrum and normal controls were tested in two reaction time (RT) experiments. In Experiment I simple warned RT was measured and the length and regularity of the preparatory intervals were varied in order to study sustained attention in the sense of preparation. With age and IQ controlled, DBD boys had slower and more variable RT overall than controls and showed generally more pronounced effects of variations in the length and sequence of the preparatory intervals. The results suggest that DBD boys are subject to lapses of attention which are increased by a relatively long preparatory interval, and that they have a particular problem with temporal uncertainty. In Experiment II some aspects of selective attention were studied in a paradigm in which stimulus modality uncertainty and response selection were varied. DBD boys showed greater effects of modality uncertainty but not response selection than controls. No differences between subdiagnoses within the DBD spectrum could be demonstrated.     

Dissociative patterns of foreperiod effects in temporal discrimination and reaction time tasks

This study examined whether the process of temporal preparation for a target stimulus is the same regardless of the task required by the target stimulus. To this end, the same variable-foreperiod design was used in a temporal discrimination task (Experiment 1) and a reaction time task (Experiment 2). In Experiment 1, both temporal sensitivity and perceived duration increased as a function of foreperiod, whereas in Experiment 2, foreperiod did not influence reaction time. Furthermore, both temporal sensitivity and perceived duration revealed an asymmetric sequential effect of foreperiod, but the pattern of this effect was opposite to the pattern observed in the reaction time task. Together these dissociative patterns of foreperiod effects suggest that the mechanism of temporal preparation depends on the task required by the target stimulus.     

Dissociative patterns of foreperiod effects in temporal discrimination and reaction time tasks

This study examined whether the process of temporal preparation for a target stimulus is the same regardless of the task required by the target stimulus. To this end, the same variable-foreperiod design was used in a temporal discrimination task (Experiment 1) and a reaction time task (Experiment 2). In Experiment 1, both temporal sensitivity and perceived duration increased as a function of foreperiod, whereas in Experiment 2, foreperiod did not influence reaction time. Furthermore, both temporal sensitivity and perceived duration revealed an asymmetric sequential effect of foreperiod, but the pattern of this effect was opposite to the pattern observed in the reaction time task. Together these dissociative patterns of foreperiod effects suggest that the mechanism of temporal preparation depends on the task required by the target stimulus.     

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 foreperiod effect revisited

This paper explores four factors which could be important in accounting for the discrepant results which have previously been obtained with respect to the effect of foreperiod duration on reaction time (RT). In some studies a clear effect of foreperiod duration on auditory RT has been found, in contrast to a recent finding that foreperiod duration affected visual RT but not auditory RT. By means of two experiments, the effects of practice, time-on-task, reaction task (a-reaction versus selective reaction) and signal intensity were studied. The latter variable appears to be the principal determinant of the discrepant results in that there is an interaction between signal intensity, foreperiod duration and modality. The results fit the hypothesis that signals beyond a given intensity exert an immediate arousing effect which counteracts the foreperiod effect.     

Effects of auditory stimulus intensity on response force in simple, go/no-go, and choice RT tasks

In four experiments, increasing the intensities of both relevant and irrelevant auditory stimuli was found to increase response force (RF) in simple, go/no-go, and choice reaction time (RT) tasks. These results raise problems for models that localize the effects of auditory intensity on purely perceptual processes, indicating instead that intensity also affects motor output processes under many circumstances. In Experiment 1, simple RT, go/no-go, and choice RT tasks were compared, using the same stimuli for all tasks. Auditory stimulus intensity affected both RT and RF, and these effects were not modulated by task. In Experiments 2-4, an irrelevant auditory accessory stimulus accompanied a relevant visual stimulus, and the go/no-go and choice tasks were used. The intensity of the irrelevant auditory accessory stimulus was found to affect RT and RF, although the sizes of these effects depended somewhat on the temporal predictability of the accessory stimulus.     

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.     

On the locus of visual dominance

A series of six experiments explored the dominance of vision over audition reported by Colavita (1974). We first confirmed the existence of visual dominance in a paradigm somewhat different from Colavita’s: Mean reaction time (RT) to a light was found to be faster than to a simultaneously presented tone, even though the stimuli were equated in subjective intensity and even though RT to the tone presented alone was faster than to the light presented alone. Additional experiments showed that when subjects did not have to respond to light, tone RT was equal or faster (intersensory facilitation) when a light was present than when it was not. These findings suggest that sensory or perceptual processing of the tone is not affected by the light, i.e., that visual dominance is nonsensory in locus and depends on the relevance of the light stimulus. This interpretation was reinforced by other findings which showed that the degree of visual dominance was sensitive to the probability of light, tone, and light-plus-tone trials and to instructions to attend to a specific modality, but was not sensitive to the intensity of the light.     

Reaction time and temporal serial judgment: corroboration or dissociation?]

Dissociations between a motor response and the subject's verbal report have been reported from various experiments that investigated special experimental effects (e.g., metacontrast or induced motion). To examine whether similar dissociations can also be observed under standard experimental conditions, we compared reaction times (RT) and temporal order judgments (TOJ) to visual and auditory stimuli of three intensity levels. Data were collected from six subjects, each of which served for nine sessions. The results showed a strong, highly significant modality dissociation: While RTs to auditory stimuli were shorter than RTs to visual stimuli, the TOJ data indicated longer processing times for auditory than for visual stimuli. This pattern was found over the whole range of intensities investigated. Light intensity had similar effects on RT and TOJ, while there was a marginally significant tendency of tone intensity to affect RT more strongly than TOJ. It is concluded that modality dissociation is an example of "direct parameter specification", where the pathway from stimulus to response in the simple RT experiment is (at least partially) separate from the pathway that leads to a conscious, reportable representation. Two variants of this notion and alternatives to it are discussed.     

Sequential effects in rudimentary auditory and visual tasks

Three experiments examined sequential effects in choice reaction time tasks. On each trial, a right/left positional judgment was made to a either a pure tone or a luminance increment in a visual array of box elements. In the first two experiments, a preparatory signal was presented prior to each imperative signal to indicate the relevant stimulus modality. At a short stimulus onset asynchrony (SOA) between the preparatory and the imperative signal (i.e., 60 msec), subjects were quicker to repeat the same response than to change their response when presented with successive tones, although no such repetition effect occurred on the visual target trials. Subjects were impaired if the stimulus modality changed across successive trials regardless of the modality of the target. At a longer SOA (i.e., 500 msec), these sequential effects were abolished; subjects were assumed to be able to prepare for the relevant modality because of the presentation of the preparatory signal. When the preparatory signals were omitted, in a final experiment, the modality-switching costs were still evident, but now inhibition of return occurred on both the auditory and the visual target trials-subjects were now impaired in responding when the target reappeared at its immediately previous location. It seems, therefore, that the repetition effect and modality-switching effects do dissociate. The data revealed clear differences between orienting attention to a particular spatial locale and focusing attention to a particular sensory modality.     

On measuring selective attention to an expected sensory modality

Perceptual judgments can be affected by expectancies regarding the likely target modality. This has been taken as evidence for selective attention to particular modalities, but alternative accounts remain possible in terms of response priming, criterion shifts, stimulus repetition, and spatial confounds. We examined whether attention to a sensory modality would still be apparent when these alternatives were ruled out. Subjects made a speeded detection response (Experiment 1), an intensity or color discrimination (Experiment 2), or a spatial discrimination response (Experiments 3 and 4) for auditory and visual targets presented in a random sequence. On each trial, a symbolic visual cue predicted the likely target modality. Responses were always more rapid and accurate for targets presented in the expected versus unexpected modality, implying that people can indeed selectively attend to the auditory or visual modalities. When subjects were cued to both the probable modality of a target and its likely spatial location (Experiment 4), separable modality-cuing and spatial-cuing effects were observed. These studies introduce appropriate methods for distinguishing attention to a modality from the confounding factors that have plagued previous normal and clinical research.     

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.     

Reaction time and movement time measured in a key-press and a key-release condition.

Reaction time (RT) and movement time (MT) are measured in two conditions, a key-press and a key-release condition. The latter makes a greater demand on perceptual feedback than the former. RT increases in the key-release condition and a fraction of MT denoted key-press time (KT) decreases in the key-press condition. It is argued that KT of a response button in the simple reaction-time experiment may serve as a proper measure of the motor component. The foreperiod prior to onset of the reacting stimulus affects RT, KT, and MT, suggesting that preparatory set or expectancy influences both the perceptual and motor components of simple human performance. The results indicate that the relation of RT and MT depends upon methodological conditions.     

The role of preparation and cue-modality in crossmodal task switching

The present study examined the effects of cue-based preparation and cue-target modality mapping in crossmodal task switching. In two experiments, we randomly presented lateralized visual and auditory stimuli simultaneously. Subjects were asked to make a left/right judgment for a stimulus in only one of the modalities. Prior to each trial, the relevant stimulus modality was indicated by a visual or auditory cue. The cueing interval was manipulated to examine preparation. In Experiment 1, we used a corresponding mapping of cue-modality and stimulus modality, whereas in Experiment 2 the mapping of cue and stimulus modalities was reversed. We found reduced modality-switch costs with a long cueing interval, showing that attention shifts to stimulus modalities can be prepared, irrespective of cue-target modality mapping. We conclude that perceptual processing in crossmodal switching can be biased in a preparatory way towards task-relevant stimulus modalities.     

An additive factor analysis of the effect of depression on the reaction time of old patients

Depressed participants display longer reaction times (RTs) than control participants. The present study was aimed at deciphering which stages of processing are affected by depression in old adults. Sixteen old depressed patients and 16 old healthy volunteers performed a two-choice visual RT task. Signal intensity, stimulus-response mapping and foreperiod duration were manipulated so as to affect the stages of stimulus preprocessing, response selection and motor adjustment, respectively. Reaction time data suggest that depression spares the stage of stimulus preprocessing but affects the stage of motor adjustment. An analysis of the error rate leaves open the possibility that depression alters the stage of response selection.