The role of attentional resources in automatic detection

The question of whether an automatic detection task requires the use of limited-capacity resources was investigated in a series of dual-task experiments. The automatic task required subjects to detect a consistently mapped target digit in a display of letters. This task was paired with a variety of concurrent visual discriminations that could either occur in close proximity to the automatic target or in a disparate display area. The main finding was that accuracy in each task was higher in conditions allowing attention to be shared than when it had to be divided between separate areas. These results indicate that detection of automatic targets depends on the allocation of spatial attention to the target's area.     

Stage analysis of the reaction process using brain-evoked potentials and reaction time

Summary Motor processes partly determine reaction time (RT) in both choice reaction time and in binary classification tasks. These latter tasks are popular in cognitive psychology because the experimenter believes that he has kept the motor component simple and constant and therefore can attribute changes in RT to perceptual or cognitive processes. In this paper we used the P3 component of the event-related potential (ERP) as a time marker indicating the duration of perceptual and cognitive processes. The latency of this component is believed to reflect stimulus evaluation time independent of response selection and organization time.Two types of tasks were used: a choice-reaction time task and a binary classification task. Signal similarity and S-R compatibility additively affected RT, but only signal similarity affected P3 latency. The number of items in the positive set and response type affected both P3 latency and RT. Relative response frequency changed the bias in the cognitive evaluation of the stimulus, reflected in the latency of the P3 component, and affected RT only if the subjects preset their motor system (indexed by the late CNV). A model was presented which proposes that motor processes may partially overlap with the perceptual and cognitive evaluation of the stimulus. Both ERPs and RT are necessary tools in the study of the relative timing of these processes.     

Selective effects of barbiturate and amphetamine on information processing and response execution

In a 3 × 2 × 2 factoral experiment, 12 subjects carried out a choice reaction task with reaction time (RT) and movement time (MT) as response measures.Independent variables were drug treatment (amphetamine, barbiturate, placebo), visual stimulus degradation and S-R compatibility. Visual stimulus degradation and S-R compatibility showed additive effect on the RT, but did not affect the MT. This confirms that stimulus encoding, response selection and response execution represent independent processing stages. The two drugs had selective effects on the RT and the MT. Barbiturate (as compared to placebo) had no effect on the MT, but it lengthened the RT, and this effect was additive with the effects of S-R compatibility but showed an interaction with the effects of stimulus degradation. Amphetamine (as compared to placebo) shortened the MT, but there was no significant main effect of amphetamine on the RT although the interaction with the effect of S— compatibility was significant. These results suggest that barbiturate affects stimulus encoding whereas amphetamine affects response-related processes..     

Task-set inertia and memory-consolidation bottleneck in dual tasks

Three dual-task experiments examined the influence of processing a briefly presented visual object for deferred verbal report on performance in an unrelated auditory-manual reaction time (RT) task. RT was increased at short stimulus-onset asynchronies (SOAs) relative to long SOAs, showing that memory consolidation processes can produce a functional processing bottleneck in dual-task performance. In addition, the experiments manipulated the spatial compatibility of the orientation of the visual object and the side of the speeded manual response. This cross-task compatibility produced relative RT benefits only when the instruction for the visual task emphasized overlap at the level of response codes across the task sets (Experiment 1). However, once the effective task set was in place, it continued to produce cross-task compatibility effects even in single-task situations (“ignore” trials in Experiment 2) and when instructions for the visual task did not explicitly require spatial coding of object orientation (Experiment 3). Taken together, the data suggest a considerable degree of task-set inertia in dual-task performance, which is also reinforced by finding costs of switching task sequences (e.g., AC → BC vs. BC → BC) in Experiment 3.     

Effects of stimulus-response uncertainty on watchkeeping performance and choice reactions

The present study was conducted to assess the effects of S-R uncertainty on performance in watchkeeping and typical type-b choice-reaction situations. The assessment was based in part on measurements of S-R compatibility effects in the two performance conditions. Four levels of S-R uncertainty (1, 2, 3 and 4 bits/S-R event) were combined factorially with two levels of S-R compatibility (high and low) and the two kinds of tasks (watchkeeping and choice-reaction); 12 Ss were assigned at random to each of the 16 conditions. A matrix of lights was used as stimuli in the choice-reaction condition; Ss monitored the matrix for a I-h duration in the watchkeeping condition. In both tasks, Ss responded by pressing a corresponding key after the presentation of a stimulus or “critical signal.” Reaction time (RT) was found to be an increas ing linear function of S-R uncertainty in both tasks. and the effects of S-R compatibility were essentially identical in the two. However, choice reactions were significantly faster than watchkeeping responses, and the rate of gain of information in watchkeeping was greater than in the comparable choice-reaction situations. The results are interpreted as supporting the hypothesis that watchkeeping differs from the simpler choice-reaction task principally in presenting an additional source of (temporal) uncertainty for information processing.     

Lateral stimulus-response compatibility effects in the oculomotor system.

Eye movement reaction time (RT) was measured in simple and choice RT situations in which monaural tones were presented to the left or right ear. In the choice RT conditions, tones of one frequency signaled a left looking response and tones of another frequency signaled a right looking response. In the simple RT condition, tones were presented in 2 blocks signaling right or left looking responses. RTs were measured by electro-oculogram (EOG), with electrodes placed over the outer canthus of each eye. In the choice RT condition, oculomotor RTs were faster when the tones signaling right or left looking were presented in the ears corresponding to the direction of looking than when they occured in the opposite ear. No such correspondence was present in the simple RT condition. Ss also performed a manual choice RT task. The lateral stimulus- response (S-R) compatibility effects obtained confirmed previous findings and were of the same magnitude as those obtained in the oculomotor response modality. Asymmetry in correlations between oculomotor and manual compatibility effects suggests differential hemispheric mediation.     

Dual-task slowing and the effects of cross-task compatibility

Recent studies have shown that visual encoding requires central processing, evidenced in the form of dual-task interference on response processes of a reaction time (RT) task. We report two experiments examining such dual-task interference: (1) at global level, to establish that visual encoding indeed requires central processing; and (2) at code level, to see whether two tasks may share the same representational codes. To this end, we manipulated the compatibility relation between the response codes for an auditory choice RTtask and the stimulus codes for a logically independent visual motion detection task. The results showed significant dual-task slowing of the response for the auditory task, demonstrating the interference at a global level. The effects of cross-task compatibility (CTC) were obtained at the short stimulus onset asynchrony (SOA), showing that the RTs were faster for compatible trials. Furthermore, the CTC effect remained even when the visual stimulus did not need to be “consolidated” (Jolicoeur & Dell'Acqua, 1998) for reporting, while the response postponement effect was greatly reduced. We interpret these results as indicating that the present two tasks share both “central” processes and common representational codes, but that these two levels of dual-task interference can be dissociated.     

Control of stimulus-response translation in dual-task performance

In contradiction to stimulus-response- (S-R-) translation bottleneck models of dual-task control, stimulus processing in a primary task is affected by its compatibility with the response in a secondary, later performed task (Hommel, 1998a)- an indication of parallel S-R translation. Here we show that this backward-compatibility effect is independent of working-memory load, whether this is induced by an extra memory task (Experiment 1) or by increasing the number of S-R alternatives in the primary task (Experiment 2). However, backward effects occur even when the secondary task is no longer carried out (Experiment 3) and they are strongly affected by the inconsistency of previously used S-R mappings (Experiment 4). These findings suggest that S-R translation is (or can be) capacity-independent and automatic even under multiple-task conditions, and that it is mediated by direct S-R associations that emerge after only little practice.     

Division of attention: The single-channel hypothesis revisited

Two experiments are reported in which subjects performed two forced-paced serial reaction time tasks separately and together at their maximum sustainable rates of information processing. Experiment 1 investigated the effects on the relationship between single- and dual-task performance of using tasks with the same or different input and output modality characteristics; an additional condition tested the effects on this relationship of using tasks with higher S-R compatibility. Experiment 2 investigated the effects on the relationship between single- and dual-task performance of varying information load (number of S-R alternatives). No significant differences were found in subjects' capacities to process information in single- and dual-task conditions. This finding was unaffected by: (a) the absolute information levels of the tasks, (b) whether inputs and/or outputs involved the same or different modalities, or (c) the level of S-R compatibility. The data from both experiments provide strong support for the single-channel hypothesis.     

Error-detection and correction latencies as a function of S-R compatibility

In choice-response tasks employing correction-procedure, error-correcting responses are typically found to be faster than equivalent correct responses. An experiment was made to compare error-correction RT under conditions of good and poor S-R compatibility in a two-choice task. After practice, variations in S-R compatibility producing significant variations in mean correct RT nevertheless have no effect on error-correction time. The contrast between this result, and one previously reported (Burns, 1965) leads to a re-discussion of the processes of error detection and correction.     

Stimulus-Response Compatibility and Motor-Programming Effects: A Test of Theoretical Accounts of Compatibility

Traditional mental coding accounts of stimulus-response (S-R) compatibility suggest that the S-R translation stage is the locus for the effect (Umilta & Nicoletti, 1990; Wallace, 1971). However, recent response-priming accounts have suggested that the S-R translation and response-programming stages may interact to produce S-R compatibility effects (Kornblum, Hasbroucq, & Osman, 1990; Wickens. 1984; Zelaznik & Franz, 1990). Our study investigated the nature of the relation between these two stages relative to the S-R compat- ibility effect. Subjects performed a choice reaction-time task in response to visual stimuli. The critical manipulations in the study were of compatibility and response programming. The analysis revealed a significant compatibility effect but no interaction between the factors affecting compatibility and those affect- ing response programming. The results were consistent with the notion that the S-R translation stage of information processing is the locus of S-R compatibility effects. Thus S-R compatibility is an effect of the mental operations that occur within the S-R translation stage of human information processing.     

A role for set in the control of automatic spatial response activation

Spatial stimulus-response (S-R) compatibility effects are widely assumed to reflect the automatic activation of a spatial response by the spatial attributes of a stimulus. The experiments reported here investigate the role of the participant's set in enabling or interacting with this putatively automatic spatial response activation. Participants performed a color discrimination task (Experiment 1) or a localization task (Experiment 2). In each experiment, two different S-R mappings were used and a task-cue indicated the appropriate mapping on each trial. S-R compatibility and the time between the task-cue and target were manipulated, and compatibility effects were assessed as a function of (a) the time between the task-cue and the stimulus, and (b) whether the S-R mapping repeated or switched on consecutive trials. Critically, whether response mappings repeated or switched on consecutive trials determined the relation between compatibility effects and the time between task-cue and stimulus. These results are discussed in terms of an interaction between automatic spatial response activation and the participant's set.     

Working memory involvement in dual-task performance: Evidence from the backward compatibility effect

In three experiments, the authors supported the hypothesis that parallel response activation seen in dual-task performance results from holding Task 2 rules in working memory (WM) while performing Task 1. To this end, the authors used the backward compatibility effect (BCE; quicker primary responses when the Task 2 response is compatible with codes of Task 1) as a marker for parallel response activation and manipulated WM load. Increasing the number of primary task rules from two to four did not modulate BCE, replicating Hommel and Eglau (2002), but a higher load condition, involving six primary task rules, reduced the BCE to nonsignificant levels. Experiment 3 further showed that WM is loaded by rules associating abstract stimulus categories to responses, and not by rules tt associate individual stimuli to responses (S-R rules).     

Concurrent deployment of visual attention and response selection bottleneck in a dual-task: Electrophysiological and behavioural evidence

Visual attention and response selection are limited in capacity. Here, we investigated whether visual attention requires the same bottleneck mechanism as response selection in a dual-task of the psychological refractory period (PRP) paradigm. The dual-task consisted of an auditory two-choice discrimination Task 1 and a conjunction search Task 2, which were presented at variable temporal intervals (stimulus onset asynchrony, SOA). In conjunction search, visual attention is required to select items and to bind their features resulting in a serial search process around the items in the search display (i.e., set size). We measured the reaction time of the visual search task (RT2) and the N2pc, an event-related potential (ERP), which reflects lateralized visual attention processes. If the response selection processes in Task 1 influence the visual attention processes in Task 2, N2pc latency and amplitude would be delayed and attenuated at short SOA compared to long SOA. The results, however, showed that latency and amplitude were independent of SOA, indicating that visual attention was concurrently deployed to response selection. Moreover, the RT2 analysis revealed an underadditive interaction of SOA and set size. We concluded that visual attention does not require the same bottleneck mechanism as response selection in dual-tasks.     

Attributed influence: The importance of observing change

The presence of a target's unexpected change in behavior following an influence attempt was hypothesized to be a critical variable for attributing influence to a particular agent. Observers read a brief story in which an agent's intervention was followed by the target's compliance, noncompliance, or countercompliance to the request. The results indicated that influence was attributed to the agent in the conditions demonstrating change, i.e., compliance and countercompliance, regardless of the direction of that change. Additional findings indicated that influence attributed to an agent decreased if the target delayed final compliance with the intervention.     

Anticipatory response control in motor sequence learning: evidence from stimulus-response compatibility

Three experiments using a serial four-choice reaction-time (RT) task explored the interaction of sequence learning and stimulus-based response conflict. In Experiment 1, the spatial stimulus-response (S-R) mapping was manipulated between participants. Incompatible S-R mappings produced much higher RTs than the compatible mapping, but sequence learning decreased this S-R compatibility effect. In Experiment 2, the spatial stimulus feature was made task-irrelevant by assigning responses to symbols that were presented at unpredictable locations. The data indicated a Simon effect (i.e., increased RT when irrelevant stimulus location is spatially incompatible with response location) that was reduced by sequence learning. However, this effect was observed only in participants who developed an explicit sequence representation. Experiment 3 replicated this learning-based modulation of the Simon effect using explicit sequence-learning instructions. Taken together, the data support the notion that explicit sequence learning can lead to motor 'chunking', so that pre-planned response sequences are shielded from conflicting stimulus information.     

Ultrastable stimulus-response latencies: Acquisition and stimulus control

Modifications were made to Kristofferson’s (1976) response-stimulus synchronization procedure which resulted in a further reduction in the estimate of minimum S-R latency variance. Minimum variances near 50 msec² were obtained whether mean latency was 310 or 550 msec. Within this range, latency distributions were the same, symmetrical and sharp-peaked, and unlike typical RT. All responses fell within a 50-msec time window. This independence of mean latency and latency variance was present throughout acquisition. A special technique allowed isolation of the controlling stimulus for synchronization timing, and showed that subjects were able to transfer control to another modality with no loss of performance. Results are discussed in terms of support for the notion of nonvariable, internally timed delays which can be inserted in the S-R chain. These delays are easily adjustable, but, once set, are deterministic. The role of feedback in acquisition and maintenance of synchronization performance is also examined.     

The effect of memory load on reaction time in character classification

In order to investigate the effect of memory load on reaction time (RT), choice RT trials were embedded in a binary character classification task using the varied set procedure. Twelve Ss performed in experimental blocks, as well as in control blocks consisting of character classification trials only. In experimental blocks, every trial began as a classification trial with the presentation of a new positive set. On a random half of these trials, however, a choice RT stimulus was presented instead of a probe letter and S simply made the indicated response. Results indicated that memory load had no effect on the choice RT trials. Embedding choice RT trials in the classification task affected the intercept (but not the slope) of the function relating classification RT to memory load. This result implies that the increase in latency usually obtained in classification experiments is entirely due to an increase in the duration of the memory searching stage of processing.     

The cognitive representation of persons and groups and its effect on recall and recognition memory

A conceptualization of the manner in which trait and behavioral information is organized in memory is proposed and applied in predicting both the recall and recognition of information about persons and groups. Three information presentation conditions were considered: (1) Subjects are told to form an impression of a target (person or group) on the basis of the target's behaviors, and are given a trait-based concept of what the target is like before learning about these behaviors. (2) Subjects are told to form an impression of the target, but a general traitbased concept of the target is not induced until after they learn about the target's behaviors. (3) Subjects receive information about the target's behaviors with instructions to remember the information, and only subsequently are told to form an impression and are given more general information about the target's traits. The proposed model accounted for between-condition differences in both the recall and recognition of behaviors that were consistent and inconsistent with a general trait-based concept of the target, and for contingencies of these differences on whether the target was a single person or a group.     

The identification and transfer of timesharing skills

Performance on two different task combinations was examined for evidence that timesharing skills are learned with practice and can transfer between task combinations. One combination consisted of two discrete informaion processing tasks, a short-term memory task and a classification task; the other consisted of two identical one-dimensional compensatory tracking tasks. Three groups of 16 subjects were employed in the experiment. The first received dual-task training on both combinations; the second received single-task training on the discrete-task combination and dual-task training on the tracking combination; the third received dual-task training on the tracking combination only. Evidence for distinct timesharing skills was found in both combinations using a new technique designed to separate improvements in timesharing skills from improvements in single-task performance. Transfer of timesharing skills also was found. Several fine-grained analyses performed on the data from the discrete task combination and a Control Theory Analysis of the tracking data indicated that skills in parallel processing were learned in each combination and transferred between them.