Intersensory facilitation and inhibition: immediate arousal and location effects of auditory noise on visual choice reaction time

Simon effects in action sequences

Most actions we perform in daily life consist of multiple movement elements. In two Simon task experiments, we investigated the impact of stimulus-response compatibility on planning and execution of action sequences. A total of 38 participants were instructed to perform action sequences consisting of multiple key presses (two to four key presses) as response to a left- or right-presented colored stimulus. Within one block, the requested action sequences were of the same length but differed in their spatial features. The results show Simon effects in reaction time for up to four-element long action sequences. The effects became especially apparent when participants were forced to finish action planning before action execution by the implementation of a no-go condition (Experiment 2). Simon effects in movement time emerged for two movement element actions, only. That is, dimensional overlap between spatial features embedded in an action sequence as well as in an imperative stimulus can affect action initiation.

Conflict tasks and the diffusion framework: Insight in model constraints based on psychological laws

Formal models of decision-making have traditionally focused on simple, two-choice perceptual decisions. To date, one of the most influential account of this process is Ratcliff's drift diffusion model (DDM). However, the extension of the model to more complex decisions is not straightforward. In particular, conflicting situations, such as the Eriksen, Stroop, or Simon tasks, require control mechanisms that shield the cognitive system against distracting information. We adopted a novel strategy to constrain response time (RT) models by concurrently investigating two well-known empirical laws in conflict tasks, both at experimental and modeling levels. The two laws, predicted by the DDM, describe the relationship between mean RT and (i) target intensity (Piéron's law), (ii) standard deviation of RT (Wagenmakers-Brown's law). Pioneering work has shown that Piéron's law holds in the Stroop task, and has highlighted an additive relationship between target intensity and compatibility. We found similar results in both Eriksen and Simon tasks. Compatibility also violated Wagenmakers-Brown's law in a very similar and particular fashion in the two tasks, suggesting a common model framework. To investigate the nature of this commonality, predictions of two recent extensions of the DDM that incorporate selective attention mechanisms were simulated and compared to the experimental results. Both models predict Piéron's law and the violation of Wagenmakers-Brown's law by compatibility. Fits of the models to the RT distributions and accuracy data allowed us to further reveal their relative strengths and deficiencies. Combining experimental and computational results, this study sets the groundwork for a unified model of decision-making in conflicting environments.

Auditory warning signals affect mechanisms of response selection: evidence from a Simon task

Irrelevant tone (accessory) stimuli facilitate performance in simple and choice reaction time tasks. In the present study, we combined accessory stimulation with a selective attention paradigm in order to investigate its influence on mechanisms of response selection. In the framework of a spatial stimulus-response compatibility task (Simon task), we tested whether accessory stimuli selectively affect bottom up triggered response activation processes (e.g., direct route processing), processing of task-relevant stimulus features (indirect route processing), or both/none. Results suggest a two-component effect of accessory stimuli within this selective attention task. First, accessory stimuli increased the Simon effect due to beneficial direct route processing. Second, accessory stimuli generally decreased reaction times indicating facilitation of indirect route processing.

Reducing and restoring stimulus-response compatibility effects by decreasing the discriminability of location words

In two experiments, we compared level of activation and temporal overlap accounts of compatibility effects in the Simon task by reducing the discriminability of spatial and non-spatial features of a target location word. Participants made keypress responses to the non-spatial or spatial feature of centrally presented location words. The discriminability of the spatial feature of the word (Experiment 1), or of both the spatial and non-spatial feature (Experiment 2), was manipulated. When the spatial feature of the word was task-irrelevant, lowering the discriminability of this feature reduced the compatibility effect. The compatibility effect was restored when the discriminability of both the task-relevant and task-irrelevant features were reduced together. Results provide further evidence for the temporal overlap account of compatibility effects. Furthermore, compatibility effects when the spatial information was task-relevant and those when the spatial information was task-irrelevant were moderately correlated with each other, suggesting a common underlying mechanism in both versions.

Simon effect with and without awareness of the accessory stimulus

The authors investigated whether a Simon effect could be observed in an accessory-stimulus Simon task when participants were unaware of the task-irrelevant accessory cue. In Experiment 1A a central visual target was accompanied by a suprathreshold visual lateral cue. A regular Simon effect (i.e., faster cue-response corresponding reaction times [RTs]) was found. Experiment 1B demonstrated that this effect cannot be attributed to perceptual grouping of the target and cue. Experiments 2A, 2B, and 2C showed a reverse Simon effect (i.e., faster noncorresponding RTs) when participants were not aware of the cue. In this condition, the Simon effect would occur relative to the reorientation of attention from the cue, which would initially capture attention, toward the target. This conclusion is supported by the results of Experiments 3A and 3B, in which the reorientation of attention was induced by having the target flash after its onset. With suprathreshold cues either a reverse or regular Simon effect was observed by using a 100-ms or > or = 200-ms onset flashing interval, respectively, whereas with subthreshold cues a reverse Simon effect was found irrespective of the interval length.

Two stages in crossmodal saccadic integration: evidence from a visual-auditory focused attention task

Saccadic reaction time (SRT) toward a visual target stimulus was measured under simultaneous presentation of an auditory non-target (accessory stimulus). Horizontal position of the target was varied (25 degrees left and right of fixation) as well as position and intensity of the auditory accessory. SRT was reduced under the presence of the accessory, and it decreased both with increasing intensity of the auditory accessory and with decreasing distance between target and accessory. The absence of a significant interaction between distance and auditory intensity suggests (1) that the intensity of the accessory stimulus has no direct influence on the process of crossmodal integration, and (2) that spatial position and intensity of the accessory are processed in separate stages. This was supported by a probability inequality test showing that the amount of neural coactivation depends on spatial distance but not on auditory intensity. The results are discussed in the framework of a two-stage model assuming separate processing of unimodal and bimodal characteristics of the stimuli. These results are related to several recent neurophysiological findings.

Display-control arrangement correspondence and logical recoding in the Hedge and Marsh reversal of the Simon effect

When left and right keypresses are made to stimuli in left and right locations, and stimulus location is irrelevant to the task, responses are typically faster when stimulus location corresponds with response location than when it does not (the Simon effect). This effect reverses when the relevant stimulus-response mapping is incompatible, with responses being slower when stimulus and response locations correspond (the Hedge and Marsh reversal). Simon et al. (Acta Psychol. 47 (1981) 63) reported an exception to the Hedge and Marsh reversal for a situation in which the relevant stimulus dimension was the color of a centered visual stimulus and the irrelevant location information was left or right tone location. In contrast, similar experiments have found a reversal of the Simon effect for tone location when relevant visual locations were mapped incompatibly to responses. We conducted four experiments to investigate this discrepancy. Both results were replicated. With an incompatible mapping, irrelevant tone location showed a small reverse Simon effect when the relevant visual dimension was physical location but not when the color of a centered stimulus or the direction in which an arrow pointed conveyed the visual location information. The reversal occurred in a more standard Hedge and Marsh task in which the irrelevant dimension was location of the colored stimulus, but only when the response keys were visibly labeled. Several of the results suggest that display-control arrangement correspondence is the primary cause of the Hedge and Marsh reversal, with logical recoding playing only a secondary role.

The ability to activate and inhibit speeded responses: separate developmental trends

When children grow older they respond faster and are less susceptible to interference caused by task-irrelevant information. These observations suggested the hypothesis that a global mechanism may account for developmental change in the speed of responding and that inhibitory function may underlie the ability to activate speeded responses. The current study examined these issues by comparing the performance of 4 age groups (5-, 8-, and 11-year-olds and young adults) on a battery of 6 speeded performance tasks, 4 of which required the inhibition of response activation. An analysis of reaction and inhibition times supported a hypothesis of generalized developmental changes in response activation, but revealed a less pronounced development of inhibition. A nonselective mechanism of response inhibition seems to be fully developed during early childhood.

Auditory stress effects on preparation and execution of graphical aiming: a test of the neuromotor noise concept

Effects of physical and mental stress, on the preparation and execution of a psychomotor task were studied to test the applicability of the neuromotor noise concept (Van Gemmert and Van Galen, 1997) as an explanation of stress effects. Central to this notion is that both physical stress and mental load raise neuromotor noise levels in the human information processing system. It is proposed that increased levels of neuromotor noise lead to decreased processing times during task preparation (activation effect), decreased or increased reaction times during task initiation, depending on task difficulty (impoverished signal-to-noise effect) and increased limb stiffness during task execution (biomechanical filtering effect). To test these predictions, an experiment was conducted in which two types of auditory stressors, physical stress and mental load, were manipulated across the stages of preparation, initiation, and execution of a graphical aiming task. The results confirmed the notion that the neuromotor noise concept is a tenable approach to explain the effects of stress on human performance.

Threefold effect of peripheral precues: alertness, orienting, and response tendencies

Three experiments were run revealing that peripheral cues exert an alerting and orienting effect. Novel is the finding that peripheral cues induce a (hidden) tendency to respond to the cued side, which interacts with the response tendency elicited by the subsequent following target. Compatible S-R mappings revealed either a reversed or no response tendency in cue conditions as compared to uncued conditions. Incompatible mappings mostly showed a decrease in response tendencies under influence of the peripheral cue. An increase of the interval between the cue and the target up to 500 ms resulted in a return to the baseline condition (without cue). The findings for the compatible mappings may be interpreted in terms of an extra recoding operation that was induced by peripheral cues. Inconsistencies found for incompatible S-R mappings might be attributed to the dual presence of recoding operations on account of the cue and the target.

Alerting effects on choice reaction time and the photic eyeblink reflex

To test the possibility that a common mechanism might be responsible for alerting effects on voluntary and reflexive reactions, choice reaction times (RT) to intense flashes of light were compared with eyeblink reflexes simultaneously evoked by those stimuli. An acoustic accessory stimulus, irrelevant to the RT task, facilitated both voluntary and reflexive reactions. A time uncertainty manipulation also generated facilitation of both responses under conditions in which phasic arousal was presumably greatest. However, there were several dissociations between alerting effects on voluntary and reflexive reactions and between effects on the early and late subcomponents of the photic orbicularis oculi reflex. In conjunction with other research in humans and animals, these data support the assumption that alerting involves the activation of multiple neuromodulatory (e.g. monoamine) systems, each of which is characterized by a distinct behavioral, neuropharmacological, and electrophysiological profile.

The role of attention for the Simon effect

It has been claimed that spatial attention plays a decisive role in the effect of irrelevant spatial stimulus-response correspondence (i.e., the Simon effect), especially the way the attentional focus is moved onto the stimulus (lateral shifting rather than zooming). This attentional-movement hypothesis is contrasted with a referential-coding hypothesis, according to which spatial stimulus coding depends on the availability of frames or objects of reference rather than on certain attentional movements. In six experiments, reference objects were made available to aid spatial coding, which either appeared simultaneously with the stimulus (Experiments 1-3), or were continuously visible (Experiments 4-6). In contrast to previous experiments and to the attentional predictions, the Simon effect occurred even though the stimuli were precued by large frames surrounding both possible stimulus positions (Experiment 1), even when the reference object's salience was markedly reduced (Experiment 2), or when the precueing frames were made more informative (Experiment 3). Furthermore, it was found that the Simon effect is not reduced by spatial correspondence between an uninformative spatial precue and the stimulus (Experiment 4), and it does not depend on the location of spatial precues appearing to the left or right of both possible stimulus locations (Experiment 5). This was true even when the precue was made task-relevant in order to ensure attentional focusing (Experiment 6). In sum, it is shown that the Simon effect does not depend on the kind of attentional operation presumably performed to focus onto the stimulus. It is argued that the available data are consistent with a coding approach to the Simon effect which, however, needs to be developed to be more precise as to the conditions for spatial stimulus coding.

Response inhibition initiates cardiac deceleration: evidence from a sensory-motor compatibility paradigm

Two experiments tested the hypothesis that response selection processes alter the timing of the shift between anticipatory cardiac deceleration and acceleratory recovery. Experiment 1 compared changes in cardiac interbeat interval induced by the manipulation of sensory-motor compatibility in a four choice reaction time task. A direct spatial mapping between a linear array of light-emitting diodes (LEDs) was compared to randomly assigned, indirect (non-compatible) mappings. Experiment 2 repeated these two tasks and added a two choice condition with direct spatial mapping, a task frequently employed to examine heart rate deceleration. Fifteen college aged males participated in Experiment 1; 18 college aged males participated in Experiment 2. In both experiments anticipatory cardiac deceleration either reached a plateau or shifted to acceleration by the interbeat interval in which the stimulus occurred. In contrast to previous reports, a secondary deceleration, rather than cardiac acceleration, often followed the stimulus. The secondary deceleration was greater with non-compatible mapping, slow response speeds, and short intertrial intervals. The findings suggested that the motoric inhibition required during response selection induces a phasic cardiac deceleration.

Attention to auditory and peripheral visual stimuli: effects of arousal and predictability

Changes in the distribution of attention among auditory and peripheral visual stimuli were examined in a choice reaction time paradigm. Two variables were manipulated: predictability of stimulus locations and arousal state of subjects. The arousal level of some subjects was raised by occasionally exposing them to brief, mild electric shocks. On most trials either a tone or a light was presented alone (single-stimulus trials). However, on 20% of the trials both a tone and light were presented simultaneously (dual trials). Two dependent variables were used to assess dominance of attention: reaction time (on all trials) and percentage of time each modality was chosen on dual trials. Neither modality was dominant when subjects were in a nonaroused state and stimulus locations were unpredictable. However, peripheral vision dominated when stimulus locations were predictable or when the subjects' level of arousal was raised. The results are discussed with reference to previous research on sensory dominance and on the facilitating or inhibiting effects of auditory stimuli on reaction time.

An additive factors analysis of the effect(s) of location cues associated with auditory stimuli on stages of information processing

The additive factors method (AFM) was used as a tool for assessing the locus (or loci) of the detrimental effect of auditory location cues in the chain of (visual) information processing. In the first experiment the location variable was factorially combined with response specificity, which is assumed to affect the response adjustment stage. A second experiment was performed in which movement amplitude, assumed to affect the response programming stage, was manipulated in addition to the location variable and a different variety of response specificity. Finally, the location variable was combined with relative S-R frequency, which is also assumed to affect the response programming stage, in a third experiment. The results of these experiments showed additive effects of the location variable with motor variables. The remaining two experiments were designed to assess the effects of location cues on response selection. In these experiments the location variable was combined with the number of response alternatives. Response speed decreased with an increase in the number of response alternatives. However, the effects of the location variable and number of response alternatives were additive. According to the additive factor logic, then, the results of experiments 1, 2 and 3 seem to indicate that the locus of interference of the location cues is not in the later response stages of the reaction process. The results of the last two experiments were interpreted to suggest that the effects of location cues and the number of response alternatives affect either different processes within the response selection stage or affect different process stages. It was concluded that the latter alternative explains most of the data currently available and that the stimulus identification stage is the most likely candidate for the locus of the location effect.

Could parkinsonian akinesia be attributable to a disturbance in the motor preparatory process?

To test the hypothesis that parkinsonian akinesia could be due to a disturbance in motor preparatory process, we measured the extent to which the normal pattern of H-reflex excitability prior to a ballistic movement, in a simple reaction time (RT) paradigm, is modifiable by akinesia. Nine age-matched normals and 11 parkinsonians were examined. They were instructed to plantarflex their ankle rapidly in response to a visual signal (RS) following a bleep (WS), while EMGs were recorded from soleus and tibialis anterior (TA) simultaneously with ankle position. Under this 'control' condition: mean soleus EMG and movement RTs were significantly longer in parkinsonians than normals. Given no evidence of fatigue or other effects, this finding indicated that our patients were akinetic. Furthermore, the normal pattern of agonist-antagonist bursts was often delayed, reduced or prolonged in these patients. Next, we measured changes in soleus motoneuronal pool excitability at 4 predetermined intervals relative to the RS but prior to EMG onset, by means of H-reflex testing. Three findings emerged: mean soleus EMG and movement RTs were again significantly delayed in parkinsonians. However, no intersensory facilitation/inhibition of the RTs occurred between H-reflex and visual stimuli, in that these values remained unchanged within the group, despite the addition of H-test stimulation. More importantly, facilitation of H-reflex was similarly time-locked to EMG onset for the two groups, with increases in H-reflex amplitude commencing some 60 ms prior to agonist discharge. Bearing in mind the prolonged RTs in parkinsonians, these findings pointed to a delay in the facilitation of the H-reflex relative to the RS as a cause of akinesia. Our proposition that parkinsonian akinesia could be attributable to an impairment in the motor preparatory process therefore remains a tantalizing possibility.