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In Stroop matching tasks, participants indicate whether the color of an object matches the meaning of a color word printed in color. Previously in this journal, Luo (1999) concluded that interference between two incongruent representations of the same attribute (ink color) occurs prior to the response stage. However, this conclusion was based on questionable data analysis. We suggest analyzing the data by separating 'same' and 'different' responses and then analyzing three congruency conditions within the 'different' responses: (a) congruence between word color and word meaning, (b) congruence between word color and object color, and (c) incongruence between word color, word meaning, and object color. In an experiment similar to Luo's, such an analysis revealed that responding was slowest in the first condition. This pattern of results does not fit with previous conclusions regarding this task, but rather indicates that task conflict and response competition contribute to interference. This analysis has implications for matching tasks other than the Stroop matching task.

The rapid serial visual presentation (RSVP) experiment reported here investigated the role of conceptual interference in the attentional blink (AB). Subjects were presented with RSVP streams that contained five stimuli: Target 1, a distractor, Target 2, a second distractor, and a symbol mask. Target 1 was a green letter, Target 2 was a red letter, and the distractors were either white letters or white digits. The stimuli were presented in a font typically seen on the face of a digital watch. Thus, 'S' and 'O' were identical to '5' and '0,' respectively. This allowed us to present streams that were conceptually different even though featurally identical: The two letter targets were followed by distractors that were recognized either as '5' and '0' or as 'S' and 'O.' The AB was substantially attenuated when subjects were told the distractors were digits rather than letters. This result indicates that conceptual interference plays a role in the AB.

Previous studies of contextual interference have shown that practicing several motor skills randomly (high contextual interference) facilitates retention and transfer in comparison to practicing the same tasks in a blocked order (low contextual interference). However, many studies have not supported this phenomenon in motor learning, and some researchers have questioned whether the effect can be tested by using only a few trials on the transfer test. The present study used a different methodological approach in which the number of test trials was increased to assess whether the contextual interference effect is sustained over an extended number of trials in the transfer phase. Undergraduate students (N = 32) were randomly allocated to either a blocked or random group. The participants practiced 80 acquisition trials in the dart-throwing task from distances of 300 cm and 420 cm, using two different grips. The transfer test after a 10-min. interval consisted of 40 trials with a new grip at a distance of 360 cm. The results did not support the contextual interference effect since there were no significant differences between groups on transfer. These findings suggest that the contextual interference effect may not be a global learning phenomenon which can be generalized to all learning situations.

Three experiments were conducted to determine whether spatial stimulus--response compatibility effects are caused by automatic response activation by stimulus properties or by interference between codes during translation of stimulus into response coordinates. The main evidence against activation has been that in a Simon task with hands crossed, responses are faster at the response location ipsilateral to the stimulus though manipulated by the hand contralateral to the stimulus. The experiments were conducted with hands in standard and in crossed positions and electroencephalogram measures showed coactivation of the motor cortex induced by stimulus position primarily during standard hand positions with visual stimuli. Only in this condition did the Simon effect decay with longer response times. The visual Simon effect appeared to be due to specific mechanisms of visuomotor information transmission that are not responsible for the effects obtained with crossed hands or auditory stimuli.

Both spatial and temporal selection require focused attention. The authors examine how temporal attention affects spatial selection. In a dual-task rapid serial visual presentation paradigm, temporal selection of a target (T1) impairs processing of a second target (T2) that follows TI within 500 ms. This process is the attentional blink (AB). To test the effects of withdrawing temporal attention, the authors measured concurrent distractor interference on T2 when the distractors were presented during and outside of the AB. Perceptual interference was manipulated by the similarity in color between T2 and concurrent distractors, and response interference was manipulated by the flanker congruency task. Results showed that perceptual interference was larger during the AB. Response interference also increased during the AB, but only when perceptual interference was high. The authors conclude that temporal selection and spatial selection rely on a common attentional process.

In comparison with the situation in which target and distractor are presented until response, Stroop interference substantially decreases when the target color is removed from the display 150-160 ms after stimulus onset (W. La Heij, N. A. Kaptein, A. C. Kalff, & L. de Lange, 1995; O. Neumann, 1986). Six experiments showed that this paradoxical exposure-duration effect is robust, that it is not due to the target's exposure duration per se, and that it is not due to an increased spatial selectivity of input selection. The present findings support and extend earlier observations that changes in the display during stimulus exposure affect attentional selection. The findings are tentatively interpreted in terms of (a) reduced duration of input selection or (b) facilitation of attribute selection.

Interference between related items in the identification of objects was examined using a postcue procedure. Pairs of objects were presented as differently colored line drawings followed by a color cue to indicate which object to name. Naming latencies were longer when both objects were from the same superordinate category than when they were unrelated. This interference effect was replicated when subjects were cued to report the color of a drawing rather than its name. Interference was greatly reduced when more distinctive attributes were used to distinguish members of a pair, both when the task required naming an object and when it required report of an object's attribute. These results challenge accounts of interference in the postcue paradigm that are based on competitive interactions in the activation of phonological representations by semantics and instead implicate object-attribute integration in memory as the source of interference.

Proactive interference was assessed with a variant of the process-dissociation procedure, which separates effects of habit (accessibility bias) and recollection (discriminability). In three cued-recall experiments, proactive interference was shown to be an effect of bias rather than an effect on actual remembering. Divided attention, age, and study duration selectively influenced the recollection parameter, whereas training probability selectively influenced the habit parameter. Furthermore, in Experiments 2 and 3, subjective reports of remembering were highly correlated with, and nearly identical to, objective estimates of recollection gained from the process-dissociation procedure. The authors discuss the relevance of the results to theories of proactive interference and argue that older adults' greater susceptibility to interference effects is sometimes caused by an inability to recollect rather than by an inability to inhibit a preponderant response.

The speed of naming the color of a colored square was examined with acoustic distraction to study the effects of the formation of a mental representation (neural model) of distractors. In Experiment 1, practice with the distractors (color words, noncolor words, and tones) was examined, and in Experiments 2 and 3 each color-naming trial was preceded by preexposures to sounds that could be dissimilar, similar, or identical to the upcoming auditory distractor. Consistency in the identity of ignored sounds, whether during color-naming practice or between preexposures and test, reduced interference with color naming. Consistency in voice played no role, and attended preexposures were ineffective in reducing interference. Given these results, the authors propose that mental representations of distractors include information about their task relevance, which modulates disruption of the primary task.

To study the operation of selective attention in a conflict situation with automatic processes, we trained 4 Japanese macaques (Macaca fuscata) extensively on a manual go/no-go task. The monkey had to discriminate either the color, shape, motion direction, or location of a visual stimulus. In each trial, the behavioral meaning of the relevant feature (go or no-go) could either be congruent or incongruent with irrelevant features of the same stimulus. Reaction times were slowed, and error rates increased when irrelevant stimulus features were incongruent with the required response. The effects were obtained when the monkey attended to the color, shape, or motion direction, but not when it attended to the location of the stimulus. The effects were cumulative so that the interference from 1 incongruent feature was smaller than that from 2 incongruent features. We propose that the present paradigm provides a behavioral analogue of the human Stroop effect.

Previous studies have shown that bizarre and common images produce equivalent levels of recall in unmixed-list designs. Using unmixed lists, we tested the view that bizarre images would be less susceptible than common images to common sources of interference. In all experiments, subjects imaged a list of either bizarre or common sentences and then performed some kind of interfering task before recalling the initial list of sentences. Experiment 1 showed that bizarre images were better accessed than common images after imaging an intervening list of common sentences. Also, components of common images tended to be better recalled than those of bizarre images after imaging an intervening list of bizarre sentences. Experiments 2a and 2b showed that interfering tasks consisting of study lists of common concrete nouns did not differentially affect memory for bizarre and common images. In Experiment 3, labeling and imaging an interfering list of common pictures produced higher recall of bizarre images. Generally, bizarre images appeared to be less susceptible than common images to interference from certain types of common encodings. Importantly, the superior recall of bizarre images was always due to greater image (sentence) access, whereas higher recall of common images was associated with greater recovery of the image (sentence) constituents. Explanation of the precise pattern of results requires consideration of the distinctive properties of bizarre images.

This study investigated the mechanisms that mediate changes in dual-task interference. Sixteen Ss in each of 4 transfer-of-training conditions completed 4 hrs of practice on a speeded keypressing task, with a block of concurrent digit-span trials administered early in practice to 3 groups and late in practice to all 4 groups. Changes in the amount of interference were examined in relation to the transfer conditions, the length of the keypressing sequences performed, the frequency of practice for specific sequences, and the amount of experience with dual-task trials. Results indicated that reductions of dual-task interference are consistent with formulations of intratask automaticity in which chunking and progressive information encapsulation underlie the formation of an intergrated motor program. They are not consistent with formulations of strategic deployment of resources between tasks based on attention switching or task integration.

The interfering effects of distractor letters are known to diminish with increasing distance from the target letter (Eriksen & Eriksen, 1974). This result is held to support spotlight models in which visual attention can only be assigned to contiguous regions of the visual field. However, the result is also consistent with the rival claim that attention is assigned to perceptual groups. Four experiments show that grouping of target and distractors by common motion can have more influence than their proximity. Distant distractor letters that move with a target letter produce more interference than static distractors that are nearer the target. Near distractors are equally ineffective if the target is static while they move. These results imply that attention is directed to perceptual groups whose components may be spatially dispersed. The spotlight metaphor seems inappropriate for visual attention in a dynamic environment.

To study the mechanisms underlying covert orienting of attention in visual space, subjects were given advance cues indicating the probable locations of targets that they had to discriminate and localize. Direct peripheral cues (brightening of one of hour boxes in peripheral vision) and symbolic central cues (an arrow at the fixation point indicating a probable peripheral box) were compared. Peripheral and central cues are believed to activate different reflexive and voluntary modes of orienting (Jonides, 1981; Posner, 1980). Experiment 1 showed that the time courses of facilitation and inhibition from peripheral and central cues were characteristic and different. Experiment 2 showed that voluntary orienting in response to symbolic central cues is interrupted by reflexive orienting to random peripheral flashes. Experiment 3 showed that irrelevant peripheral flashes also compete with relevant peripheral cues. The amount of interference varied systematically with the interval between the onset of the relevant cue and of the distracting flash (cue-flash onset asynchrony) and with the cuing condition. Taken together, these effects support a model for spatial attention with distinct but interacting reflexive and voluntary orienting mechanisms.

Increasing the physical distinction between targets and distractors can eliminate Stroop interference, which has prompted claims that noninterfering distractors are not identified (e.g., Francolini & Egeth, 1980). However, such claims assumed that identification always produces interference. By using Francolini and Egeth's task of counting red items in arrays of red and black items, we found that noninterfering black digits produced identity-specific negative priming comparable to that produced by interfering red digits. This suggests that interfering and noninterfering distractors are both identified and then inhibited. A similar pattern of results is observed in a task of word naming for picture-word stimuli. The contrast between interference and priming measures of the distractor processing urges reconsideration of many data previously held as evidence that distractors can be completely filtered out.

Why do people often find that performing two tasks at once is harder than performing one task at a time? Three mechanisms of task interference that might answer that question were investigated: resource competition, confusions, and incompatible task proximity between processing stages. The subjects performed dual-axis compensatory tracking with error displays that were either integrated or separated, with axis controls that either were integrated into one stick or remained separate, and with control dynamics on the two axes that were either the same or different. Tracking error increased and control activity decreased as a function of the combined difficulty of the two control dynamics. Integrated displays and integrated controls both led to increased confusions between tracking axes although error was not reliably affected. Significantly, performance was also affected by whether the integrality of displays matched that of controls. These results suggest that resource competition, confusions, and compatibility of proximity play distinct roles in dual-axis tracking performance.

Four experiments investigating the effects of transfer specific (A-B, A-C) paired associate learning on long-term retention performance were conducted. It was shown that the critical list (C) responses were retained better under conditions of A-B, A-C learning than under conditions of D-B, A-C learning when the critical list (A) stimuli were not presented at test (e.g., free recall). This reversal of the typical interference effect was observed in each of the four experiments. It was suggested that extent theories of interference and forgetting cannot easily explain these results. However, when proactive interference is viewed in terms of differential processing of individual-item and relational information during study of the critical list response items, the results are easily interpreted.

In the present study, interactions of contextual interference and the cognitive style reflection-impulsivity were examined for training and retention performance. 64 subjects were randomly assigned to either a random or blocked practice schedule in learning a cursor-movement task. Reflectivity indices were determined by means of our computerized version of the Matching Familiar Figures Test. Analysis showed that the generally positive effect of practicing under a random practice schedule decreased for more reflective subjects. Further, training under a random practice schedule forced impulsive subjects to behave more like reflective ones, which improved their performance at retention. It was concluded that reflection-impulsivity is an important factor to be incorporated into the design of effective training programs.

Proactive interference in motor skill acquisition occurs when a desired response in adversely affected by a previously learned skill. The purpose of this study was to assess the effects of learning a forehand tennis grounedstroke on the subsequent learning of a backhand. 96 subjects equally representing seventh and eighth grade boys and girls who had never played tennis were randomly assigned to two methods of instruction. This resulted in four groups of 24. The experimental groups received instruction and practice in a forehand skill. The experimental and control groups received backhand instruction and practice and both groups were tested on backhand. Results of a 2 X 2 multivariate analysis of variance indicated significant between-subjects main effects for sex and groups. There were significant within-subjects effects for days and group x days. These results suggest that learning the forehand independent of the backhand may interfere with learning the backhand.

Effects of secondary tasks on serial short-term memory were investigated to test conflicting predictions derived from the working-memory model (A. D. Baddeley, 1986, 1997) and the changing-state hypothesis (D. M. Jones, P. Farrand, G. Smart, & N. Morris, 1995). In Experiments 1 and 2, disruptions due to the changing-state characteristic of secondary tasks occurred in the encoding phase of spatial and verbal serial memory tasks but not in a retention interval. Experiments 3 and 4 revealed changing-state effects on tasks relying on central-executive resources. In Experiments 5 and 6, interference between central-executive demanding secondary tasks and serial short-term memory was larger during the encoding phase than the retention interval. Crossover dissociations emerged between spatial and verbal serial short-term memory. The results extend the findings of D. M. Jones et al. (1995) and support the working-memory account for interference in short-term memory.

For three consecutive days, two groups of adult female cockroaches (Periplaneta americana) (ns = 10) received inescapable shock. 24 hr. later one group was exposed to 10 min. of forced exercise on a treadmill while the other group received no exercise. Both groups were then run in a shuttlebox escape task. The cockroaches exposed to forced exercise did not become helpless in the shuttlebox escape task.

40 subjects given equal and random amounts of practice on a variable speed pursuit rotor exhibited no contextual interference effect on the performance of two transfer tasks (35 and 60 rpm) 48 hours later.

Two experiments examined metamemory ratings following differing amounts of retroactive interference for paired associates. Participants made both feeling of knowing (FOK) ratings and judgments of learning (JOLs) for first-list responses after learning different types of second lists. Both types of ratings were higher when stimuli were repeated and responses were associates across two lists than when stimuli were repeated and responses were different. Repetition of either the stimuli or the responses across lists produced lower ratings than nonrepetition, especially for recalled responses. The results provided support for competition as an important factor in JOLs and FOKs following interference.

This paper investigates visual search in displays in which distractors are spatially grouped. Detection of targets at the border of two regions where distractors are coherent is easier than can be predicted by models that do not take spatial organization into account. Thus, models of visual search need to incorporate effects of spatial organization in addition to bottom-up difference calculations.

In bar-probe partial report experiments, subjects are presented with a brief array of letters, followed by a cue that singles out a target letter. Using this procedure, V. M. Townsend (1973) reported a counterintuitive effect: As the duration of a cue was increased, target performance decreased dramatically. The aim of the present study was to isolate the locus of the cue-duration effect. To this end, several characteristics of the bar-probe display were manipulated in a single experiment: the interstimulus interval between the array and the cue, array density, the number of letters, and the number of symbols adjacent to the target. These factors were manipulated on a priori grounds so as to affect the different sources of information used in the bar-probe task - namely, durable storage, abstract identity information, and feature level information. The data were accurately fit by a simple quantitative, multinomial model that assumes that the different sources of information used in the bar-probe task make independent contributions to performance. The critical assumption of the model is that cue duration interferes with only one source of information - namely, feature level information.

In a series of experiments, we examined the effect of requiring subjects to attend to distractors in a test of negative priming. This was accomplished by using a referent size-selection task in which subjects were instructed to name the larger animal and to ignore the smaller animal in a word pair. The result was a quadrupling of the standard negative priming effect, suggesting that negative priming not only occurs for attended distractors, it is actually enhanced. We demonstrated that this enhancement of the effect was not due solely to increased latencies in the referent size-selection task, because neither decreasing base response times in other referent size-selection tasks nor increasing base response times in typical color-selection tasks substantially affected the respective negative priming effects. Although these findings can be accommodated within current theories of negative priming, they challenge the basic assumption that the negative priming effect arises because the critical item was ignored or not attended to on the prime trial.

Interfering with the perceptual processing of a stimulus can improve memory. The perceptual-interference effect was investigated from the perspective of the item-specific/relational encoding distinction. This perspective suggests that perceptual interference enhances item-specific encoding but disrupts the encoding of relational and order information. The results of 6 experiments were largely consistent with this view. In Experiments 1 and 2, perceptual interference (a hypothesized item-specific manipulation) and list organization (a relational manipulation) both enhanced free recall but had opposite effects on a measure of relational processing (category clustering). Increasing list organization increased clustering, whereas perceptual interference decreased clustering. In addition, perceptual interference typically decreased memory for order. Finally, when order information was an important determinant of free recall, the perceptual-interference effect was eliminated or reversed. When reliance on order information was lessened, the perceptual-interference effect reemerged.