Co-occurrence of sequential and practice effects in the Simon task: Evidence for two independent mechanisms affecting response selection

The Simon effect refers to the observation that responses to a relevant stimulus dimension are faster and more accurate when the stimulus and response spatially correspond than when they do not, even though stimulus position is irrelevant. Recent findings have suggested that the Simon effect can be strongly modulated by prior practice with a spatially incompatible mapping and by correspondence sequence. Although practice is thought to influence conditional stimulus —response (S-R) processing, leaving response priming through the unconditional route unaffected, sequential effects are thought to represent trial-by-trial adaptations that selectively involve unconditional S —R processing. In the present study, we tested this assumption by assessing the effects of correspondence sequence both when the Simon task alone was performed and when it was preceded by a spatial compatibility task with either incompatible (Experiments 1-2) or compatible (Experiment 2) instructions. The observation that practice and correspondence sequence co-occur and exert additive effects strongly demonstrates that the two factors affect different processing routes.     

Referential coding contributes to the horizontal SMARC effect

The present study tested whether coding of tone pitch relative to a referent contributes to the correspondence effect between the pitch height of an auditory stimulus and the location of a lateralized response. When left-right responses are mapped to high or low pitch tones, performance is better with the high-right/low-left mapping than with the opposite mapping, a phenomenon called the horizontal SMARC effect. However, when pitch height is task irrelevant, the horizontal SMARC effect occurs only for musicians. In Experiment 1, nonmusicians performed a pitch discrimination task, and the SMARC effect was evident regardless of whether a referent tone was presented. However, in Experiment 2, for a timbre-judgment task, nonmusicians showed a SMARC effect only when a referent tone was presented, whereas musicians showed a SMARC effect that did not interact with presence/absence of the referent. Dependence of the SMARC effect for nonmusicians on a reference tone was replicated in Experiment 3, in which judgments of the color of a visual stimulus were made in the presence of a concurrent high- or low-pitched pure tone. These results suggest that referential coding of pitch height is a key determinant for the horizontal SMARC effect when pitch height is irrelevant to the task.     

Auditory location negative priming: A case of feature mismatch

In an auditory four-alternative forced choice localization task, participants had to localize one of two simultaneously presented sounds while ignoring the location of the second sound. Negative priming—that is, sloweddown responses to a location that had to be ignored in the previous trial—was found only when the sound at the repeated location changed between prime and probe. There was also no increase in prime response errors to the probes of ignored repetition trials. These findings allow for the conclusion that auditory location priming is caused by feature mismatch only and that other mechanisms, such as inhibition of ignored locations or episodic retrieval of transfer-inappropriate prime information, do not play a role. The research reported in this article was supported by a grant from the Deutsche Forschungsgemeinschaft (Ma 2610/2-1).     

Visual and auditory accessory stimulus offset and the Simon effect

We investigated the effect on the right and left responses of the disappearance of a task-irrelevant stimulus located on the right or left side. Participants pressed a right or left response key on the basis of the color of a centrally located visual target. Visual (Experiment 1) or auditory (Experiment 2) task-irrelevant accessory stimuli appeared or disappeared at locations to the right or left of the central target. In Experiment 1, responses were faster when onset or offset of the visual accessory stimulus was spatially congruent with the response. In Experiment 2, responses were again faster when onset of the auditory accessory stimulus and the response were on the same side. However, responses were slightly slower when offset of the auditory accessory stimulus and the response were on the same side than when they were on opposite sides. These findings indicate that transient change information is crucial for a visual Simon effect, whereas sustained stimulation from an ongoing stimulus also contributes to an auditory Simon effect.     

An investigation of spatial representation of pitch in individuals with congenital amusia

Spatial representation of pitch plays a central role in auditory processing. However, it is unknown whether impaired auditory processing is associated with impaired pitch–space mapping. Experiment 1 examined spatial representation of pitch in individuals with congenital amusia using a stimulus–response compatibility (SRC) task. For amusic and non-amusic participants, pitch classification was faster and more accurate when correct responses involved a physical action that was spatially congruent with the pitch height of the stimulus than when it was incongruent. However, this spatial representation of pitch was not as stable in amusic individuals, revealed by slower response times when compared with control individuals. One explanation is that the SRC effect in amusics reflects a linguistic association, requiring additional time to link pitch height and spatial location. To test this possibility, Experiment 2 employed a colour-classification task. Participants judged colour while ignoring a concurrent pitch by pressing one of two response keys positioned vertically to be congruent or incongruent with the pitch. The association between pitch and space was found in both groups, with comparable response times in the two groups, suggesting that amusic individuals are only slower to respond to tasks involving explicit judgments of pitch.     

Auditory,visual, and cross-modal negative priming

Auditory, visual, and cross-modal negative priming was investigated using a task in which participants judged whether stimuli were animals or musical instruments. Negative priming was observed, but only if the attended and the ignored primes evoked different responses. This pattern—negative priming after conflict, but not after nonconflict, primes—was demonstrated with visual stimuli and replicated with auditory stimuli, as well as across modalities, both auditory to visual and visual to auditory. Implications for theories of negative priming are discussed.     

Transfer of noncorresponding spatial associations to the auditory Simon task

Four experiments examined transfer of noncorresponding spatial stimulus-response associations to an auditory Simon task for which stimulus location was irrelevant. Experiment 1 established that, for a horizontal auditory Simon task, transfer of spatial associations occurs after 300 trials of practice with an incompatible mapping of auditory stimuli to keypress responses. Experiments 2-4 examined transfer effects within the auditory modality when the stimuli and responses were varied along vertical and horizontal dimensions. Transfer occurred when the stimuli and responses were arrayed along the same dimension in practice and transfer but not when they were arrayed along orthogonal dimensions. These findings indicate that prior task-defined associations have less influence on the auditory Simon effect than on the visual Simon effect, possibly because of the stronger tendency for an auditory stimulus to activate its corresponding response.     

A shift of attention may be necessary, but it is not sufficient, for the generation of the Simon effect

The Simon effect is the performance advantage for spatially corresponding, compared to non-corresponding, target-response ensembles when the location of the target is task irrelevant. In four experiments, we tested the predictions of the attention-shift account of the Simon effect. In all experiments, subjects made choice responses with respect to the identity of a central target that followed a spatially non-informative peripheral precue. The first experiment showed a Simon effect away from the precue when the precue was a go/no-go signal: responses to spatially non-corresponding precue-response pairs were faster than responses to spatially corresponding precue-response pairs. The results of the second experiment suggested that this “reverse” Simon effect was not due to inhibition. In the third experiment, a secondary working memory task required the encoding, and later recall, of “oddball” precues. Although the Simon effect was absent, larger Simon effects towards the precue (i.e., responses were faster to spatially corresponding, compared to non-corresponding, precue-response ensembles) were correlated with poorer performance on the memory task. In the last experiment, the identity of completely non-informative precues was congruent, incongruent, or unrelated to the identity of the target. With precues that were unrelated to the identity of the target, there was a Simon effect towards the precues. Conversely, the Simon effect occurred away from the precue when the identity of the precue was related to that of the target. The findings suggest that a shift of attention alone is not sufficient to produce the Simon effect. Rather, the shift of attention must originate from an intentionally defined object. The results are discussed within a framework that integrates the attention-shift and referential-coding hypotheses. Received: 2 December 1999 / Accepted: 23 March 2000     

Influence of auditory and audiovisual stimuli on the right–left prevalence effect

When auditory stimuli are used in two-dimensional spatial compatibility tasks, where the stimulus and response configurations vary along the horizontal and vertical dimensions simultaneously, a right–left prevalence effect occurs in which horizontal compatibility dominates over vertical compatibility. The right–left prevalence effects obtained with auditory stimuli are typically larger than that obtained with visual stimuli even though less attention should be demanded from the horizontal dimension in auditory processing. In the present study, we examined whether auditory or visual dominance occurs when the two-dimensional stimuli are audiovisual, as well as whether there will be cross-modal facilitation of response selection for the horizontal and vertical dimensions. We also examined whether there is an additional benefit of adding a pitch dimension to the auditory stimulus to facilitate vertical coding through use of the spatial-musical association of response codes (SMARC) effect, where pitch is coded in terms of height in space. In Experiment 1, we found a larger right–left prevalence effect for unimodal auditory than visual stimuli. Neutral, non-pitch coded, audiovisual stimuli did not result in cross-modal facilitation, but did show evidence of visual dominance. The right–left prevalence effect was eliminated in the presence of SMARC audiovisual stimuli, but the effect influenced horizontal rather than vertical coding. Experiment 2 showed that the influence of the pitch dimension was not in terms of influencing response selection on a trial-to-trial basis, but in terms of altering the salience of the task environment. Taken together, these findings indicate that in the absence of salient vertical cues, auditory and audiovisual stimuli tend to be coded along the horizontal dimension and vision tends to dominate audition in this two-dimensional spatial stimulus–response task.     

Attention capture is modulated in dual-task situations

Because some features affect the efficiency of visual search even when they are irrelevant to the task, they are thought tocapture attention in a stimulus-driven manner. If such attention shifts are stimulus driven, they should be unaffected by reduced resources. We added a concurrent auditory task to a traditional attention capture paradigm and found that capture by an irrelevant, abruptly appearing stimulus (i.e., an onset) was eliminated. In contrast, prioritization of an irrelevant color singleton—a stimulus that at most receives only mild prioritization in this paradigm—was increased under dual-task conditions. These results challenge the hypothesis that attention capture by irrelevant features is stimulus driven. Instead, prioritization depends on and is modulated by the availability of resources.     

The Simon task with multi-component responses: two loci of response–effect compatibility

The stimulus–response compatibility (SRC) effect refers to the phenomenon that responses are faster and more accurate when stimulus and response correspond than when they do not. The phenomenon is robust in that it is observed even when SRC is irrelevant to performing the task, a variant known as the Simon effect. Recent studies also demonstrated that responses are faster when they are spatially compatible with their effects in the environment (action effects) than when they are incompatible. This response–effect (R–E) compatibility effect is thought to stem from the fact that stimuli first activate anticipated effect codes, which then activate corresponding action codes. In the present study, the Simon task was used to examine influences of multiple response components on performance. Three response components were orthogonally manipulated. The results of three experiments indicated that there are two separate processes that are influenced by R–E compatibility; one that is responsible for the SRC effect (S–R translation) and the other that is independent of SRC (action programming). The influence of R–E compatibility on the former process depended on manipulations that varied attentional demands of the task.     

Priming the mental time line

Growing experimental evidence suggests that temporal events are represented on a mental time line, spatially oriented from left to right. Support for the spatial representation of time comes mostly from studies that have used spatially organized responses. Moreover, many of these studies did not avoid possible confounds attributable to target stimuli that simultaneously convey both spatial and temporal dimensions. Here we show that task-irrelevant, lateralized visuospatial primes affect auditory duration judgments. Responses to short durations were faster when the auditory target was paired with left- than with right-sided primes, whereas responses to long durations were faster when paired with right- than with left-sided primes. Thus, when the representations of physical space and time are concurrently activated, physical space may influence time even when a lateralized, spatially encoded response is not required by the task. The time-space interaction reported here cannot be ascribed to any Spatial-Temporal Association of Response Codes effect. It supports the hypothesis that the representation of time is spatially organized, with short durations represented on the left space and longer ones on the right.     

A response-discrimination account of the Simon effect

Simon effects might partly reflect stimulus-triggered response activation. According to the response-discrimination hypothesis, however, stimulus-triggered response activation shows up in Simon effects only when stimulus locations match the top-down selected spatial codes used to discriminate between alternative responses. Five experiments support this hypothesis. In Experiment 1, spatial codes of each response differed by horizontal and vertical axis position, yet one axis discriminated between alternative responses, whereas the other did not. Simon effects resulted for targets on discriminating axes only. In Experiment 2, both spatial axes discriminated between responses, and targets on both axes produced Simon effects. In Experiment 3, Simon effects resulted for a spatial choice-reaction task but not for a go/no-go task. Even in the go/no-go task, a Simon effect was restored when a two-choice reaction task preceded the go/no-go task (Experiment 4) or when participants initiated trials with responses spatially discriminated from the go response (Experiment 5).     

Masked nonword repetition effects in yes/no and go/no-go lexical decision: A test of the evidence accumulation and deadline accounts

The pattern of masked repetition priming effects for word and nonword targets differs across tasks: Maskedpriming effects in lexical decision occur for positive responses (i.e., words), but not for negative responses (nonwords), whereas masked-priming effects in the cross-case same-different task occur for positive responses (same), but not for negative responses (different)—regardless of lexical status. Here, we examined whether masked nonword priming effects are greater when the task involves an active go response to nonwords than when it involves the standard yes/no procedure in lexical decision. The obtained masked repetition priming effect for nonwords was of similar size in yes/no and go/no-go tasks. This finding is compatible with accounts of nonword priming that posit that nonword responses are produced by actively accumulating evidence for the nonword alternative in yes/no and go/no-go procedures, whereas it is inconsistent with the assumption of a deadline for no responses in the yes/no task.     

Sequence learning in Parkinson's disease: the effect of spatial stimulus-response compatibility

Patients with Parkinson's disease (PD) have repeatedly demonstrated reduced sequence-specific learning effects in serial reaction time tasks (SRTs). Previous research with PD patients has mainly employed the 'classical' SRT task, involving a spatially compatible assignment of stimuli and responses. From cognitive research, it is known that spatial compatibility triggers rapid, automatic responses in the direction of the stimulus. Automatic responding has shown to be disinhibited in PD patients and may therefore interfere with stimulus anticipation during the learning process. The aim of the present study was to test this hypothesis by investigating if reduced sequence-specific learning depends on spatial stimulus-response compatibility. PD patients and age-matched controls were examined either with an SRT variant involving central stimulus presentation, thereby preventing automatic linking of stimulus and response locations, or with a spatially compatible SRT task. Patients showed reduced sequence-specific learning effects only when the stimulus-response assignment was spatially compatible. This pattern of results confirms the hypothesis that sequence learning deficits in PD may result from a predominance of automatic response activation over learning-based stimulus anticipations during the learning phase.     

Role of serial order in the impact of talker variability on short-term memory: testing a perceptual organization-based account

In two experiments, we examined the impact of the degree of match between sequential auditory perceptual organization processes and the demands of a short-term memory task (memory for order vs. item information). When a spoken sequence of digits was presented so as to promote its perceptual partitioning into two distinct streams by conveying it in alternating female (F) and male (M) voices (FMFMFMFM)—thereby disturbing the perception of true temporal order—recall of item order was greatly impaired (as compared to recall of item identity). Moreover, an order error type consistent with the formation of voice-based streams was committed more quickly in the alternating-voice condition (Exp. 1). In contrast, when the perceptual organization of the sequence mapped well onto an optimal two-group serial rehearsal strategy—by presenting the two voices in discrete clusters (FFFFMMMM)—order, but not item, recall was enhanced (Exp. 2). The results are consistent with the view that the degree of compatibility between perceptual and deliberate sequencing processes is a key determinant of serial short-term memory performance. Alternative accounts of talker variability effects in short-term memory, based on the concept of a dedicated phonological short-term store and a capacity-limited focus of attention, are also reviewed.     

Implicit sequence learning is represented by stimulus—response rules

For nearly two decades, researchers have investigated spatial sequence learning in an attempt to identify what specifically is learned during sequential tasks (e.g., stimulus order, response order, etc.). Despite extensive research, controversy remains concerning the information-processing locus of this learning effect. There are three main theories concerning the nature of spatial sequence learning, corresponding to the perceptual, motor, or response selection (i.e., central mechanisms underlying the association between stimulus and response pairs) processes required for successful task performance. The present data investigate this controversy and support the theory that stimulus—response (S—R) rules are critical for sequence learning. The results from two experiments demonstrate that sequence learning is disrupted only when the S—R rules for the task are altered. When the S—R rules remain constant or involve only a minor transformation, significant sequence learning occurs. These data implicate spatial response selection as a likely mechanism mediating spatial sequential learning.     

Keys and seats: Spatial response coding underlying the joint spatial compatibility effect

Spatial compatibility effects (SCEs) are typically observed when participants have to execute spatially defined responses to nonspatial stimulus features (e.g., the color red or green) that randomly appear to the left and the right. Whereas a spatial correspondence of stimulus and response features facilitates response execution, a noncorrespondence impairs task performance. Interestingly, the SCE is drastically reduced when a single participant responds to one stimulus feature (e.g., green) by operating only one response key (individual go/no-go task), whereas a full-blown SCE is observed when the task is distributed between two participants (joint go/no-go task). This joint SCE (a.k.a. the social Simon effect) has previously been explained by action/task co-representation, whereas alternative accounts ascribe joint SCEs to spatial components inherent in joint go/no-go tasks that allow participants to code their responses spatially. Although increasing evidence supports the idea that spatial rather than social aspects are responsible for joint SCEs emerging, it is still unclear to which component(s) the spatial coding refers to: the spatial orientation of response keys, the spatial orientation of responding agents, or both. By varying the spatial orientation of the responding agents (Exp. 1) and of the response keys (Exp. 2), independent of the spatial orientation of the stimuli, in the present study we found joint SCEs only when both the seating and the response key alignment matched the stimulus alignment. These results provide evidence that spatial response coding refers not only to the response key arrangement, but also to the—often neglected—spatial orientation of the responding agents.     

Measurement of auditory cues in drivers' distraction

A driving simulator was used to examine the effects on driving performance of auditory cues in an in-vehicle information search task. Drivers' distraction by the search tasks was measured on a peripheral detection task. The difficulty of the search task was systematically varied to test the distraction caused by a quantified visual load. 58 participants completed the task. Performance on both search tasks and peripheral detection tasks was measured by mean response time and percent error. Analyses indicated that in-vehicle information search performance can be severely degraded when a target is located within a group of diverse distractors. Inclusion of an auditory cue in the visual search increased the mean response time as a result of a change in modality from auditory to visual. Inclusion of such an auditory cue seemed to influence distraction as measured by performance on the peripheral detection task; accuracy was lower when auditory cues were provided, and responses were slower when no auditory cues were provided. Distraction by the auditory cue varied according to the difficulty of the search task.     

Integrating the irrelevant sound

A distractor can be integrated with a target response and the subsequent repetition of the distractor can facilitate or hamper responding depending on whether the same or a different response is required, a phenomenon labeled distractor-response binding. In two experiments we used a priming paradigm with an identification task to investigate influences of stimulus grouping on the binding of irrelevant stimuli (distractors) and responses in audition. In a grouped condition participants heard relevant and irrelevant sounds in one central location, whereas in a non-grouped condition the relevant sound was presented to one ear and the irrelevant sound was presented to the other ear. Distractor-based retrieval of the prime response was stronger for the grouped compared to the non-grouped presentation of stimuli indicating that binding of irrelevant auditory stimuli with responses is modulated by perceptual grouping.