Interference and negative priming from ignored distractors: The role of selection difficulty

The relation between distractor interference and negative priming from identical distractors was examined in two experiments. Subjects responded to a target letter, which was indicated by an adjacent bar marker, and attempted to ignore a distracting letter. Onprime trials, distracting letters were either compatible or incompatible with the target, allowing for a measure of interference. On subsequentprobe trials, previously ignored distractors were sometimes presented as targets, allowing for a measure of negative priming. Reducing the spatial separation between targets and distractors on the prime trial increased the magnitude of interferenceand negative priming, but these effects appeared to be independent of each other (Experiment 1). In Experiment 2, the prime target location was precued on some trials, but not on others. Precuing attenuated the magnitude of interference, but not that of negative priming effects. This pattern indicates that measures of negative priming and measures of distractor interference on the immediately preceding trial are independent. The results are discussed in terms of a selective inhibition model of selective attention.     

Global/local processing and negative priming: the influence of selection difficulty and stimulus exposure

Negative priming is a decrement in performance observed when a previously ignored stimulus is re-presented as a target. The present study examined the relation between selection difficulty and negative priming in five experiments that used hierarchical stimuli (large letters made up by small letters). The results show that negative priming is greater when subjects direct attention to the local level (more difficult selection) than when they direct attention to the global level (less difficult selection). However, that occurs only when exposure of prime and probe is sufficiently long. With shorter presentations, negative priming is still observed but is no longer modulated by selection difficulty. These results suggest that both anticipatory and reactive mechanisms are responsible for the occurrence of negative priming and that instantiation of the reactive mechanism depends on the time available for prime and probe selection. Received: 17 January 2000 / Accepted: 3 July 2000     

The role of selection in generating auditory negative priming

The importance of selecting between a target and a distractor in producing auditory negative priming was examined in three experiments. In Experiment 1, participants were presented with a prime pair of sounds, followed by a probe pair of sounds. For each pair, listeners were to identify the sound presented to the left ear. Under these conditions, participants were especially slow to identify a sound in the probe pair if it had been ignored in the preceding prime pair. Evidence of auditory negative priming was also apparent when the prime sound was presented in isolation to only one ear (Experiment 2) and when the probe target was presented in isolation to one ear (Experiment 3). In addition, the magnitude of the negative priming effect was increased substantially when only a single prime sound was presented. These results suggest that the emergence of auditory negative priming does not depend on selection between simultaneous target and distractor sounds.     

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.     

Deeper processing at target selection increases the magnitude of negative priming

Do deeper levels of processing produce equivalent priming effects at all stages of task performance? In Experiment 1, we varied the level of processing factorially across two task stages—target selection and response selection. Each stage required perceptual (e.g., color) or conceptual (e.g., friendliness) processing of stimulus items (i.e., animal names). Negative priming was substantially greater when deeper processing was required at thetarget selection stage, but it was unaffected by the level of processing at the response selection stage. In contrast, positive priming was greater when deeper processing was required at theresponse selection stage, but it was unaffected by processing at the target selection stage. In Experiment 2, we generalized this finding using a task in which numeric targets were selected on the basis of their parity. As in Experiment 1, the deeper level of processing at the target selection stage produced a larger negative priming effect. These results illuminate the role of target selection demands in modulating the strength of negative priming.     

Influence of probe-trial selection on the location negative priming effect.

Using the location variant of the typical negative priming procedure, participants were cued (100% reliable) before (Experiment 1) or after (Experiment 2) the prime trial as to whether a distractor would or would not accompany the target on the probe trial. The crucial results were that on cued trials, the predictable absence, produced the removal of the negative priming effect (disengagement), and that this disengagement of the priming process, motivated by the predictable absence of a probe-trial distractor, could take place on-line. These findings demonstrated the "selection-state" dependency (probe trial) of the location negative priming process, supporting inhibition-based and episodic retrieval models in their contention that the ultimate function of this process is to enhance the efficiency of future distractor processing, and hence selection. The disengagement results revealed an adaptive feature of a process that can be detrimental or irrelevant to upcoming processing.     

Levels of visuo-spatial selection: An ERP study of negative priming

Usually, a probe target appearing in a recently ignored distractor location is less efficiently processed. This robust phenomenon is called (visuo-) spatial negative priming (SNP). Among other explanations, concepts of persisting or retrieved spatial inhibition play a major role. Two relevant issues were investigated using event-related brain potentials (ERPs). The first pertains to context sensitivity of inhibition: Is a probe distractor necessary for SNP? The second concerns levels of processing at which spatial inhibition operates: Does SNP affect perception, selection, and/or stimulus classification? A localization task with and without probe distractors was employed while 64-channel EEG was recorded. Obviously, SNP does not require a probe distractor; the distractor-absent SNP effect was larger than the distractor-present SNP effect. Distractor-present SNP had two lateralized ERP effects, N1pc amplitude reduction and N2pc amplitude increase. Smaller N1pc may indeed reflect perceptual decrement, but was inversely related to size of behavioral SNP. By contrast, only strong-SNP participants showed N2pc increase, which points to selection disadvantage due to persisting inhibition of higher-level spatial representations. Distractor-absent SNP had no N1pc/N2pc correlates; instead, reduced amplitude of a broadly distributed P300 component suggests impaired stimulus classification due to episodic retrieval of inappropriate prime information. Overall, SNP seems to emerge from relatively late stages of processing, thus challenging the idea of context-free persisting inhibition of low-level spatial representations. Furthermore, distractor-present and distractor-absent SNP are qualitatively different from each other.     

Response-retrieval and negative priming

The existence of across-notation automatic numerical processing of two-digit (2D) numbers was explored using size comparisons tasks. Participants were Arabic speakers, who use two sets of numerical symbols—Arabic and Indian. They were presented with pairs of 2D numbers in the same or in mixed notations. Responses for a numerical comparison task were affected by decade difference and unit-decade compatibility and global distance in both conditions, extending previous findings with Arabic digits (Nuerk, Weger, & Willmes, 2001). Responses for a physical comparison task were affected by congruency with the numerical size, as indicated by the size congruency effect (SiCE). The SiCE was affected by unit-decade compatibility but not by global distance, thus suggesting that the units and decades digits of the 2D numbers, but not the whole number value were automatically translated into a common representation of magnitude. The presence of similar results for same- and mixed-notation pairs supports the idea of an abstract representation of magnitude.     

Sequence learning and selection difficulty

The authors studied the role of attention as a selection mechanism in implicit learning by examining the effect on primary sequence learning of performing a demanding target-selection task. Participants were trained on probabilistic sequences in a novel version of the serial reaction time (SRT) task, with dual- and triple-stimulus participants having to ignore irrelevant items in the SRT display. Despite large performance decrements under dual- and triple-stimulus configurations, testing under single-stimulus conditions revealed no impairment to sequence learning. These findings suggest that implicit sequence learning is resistant to disruption of the selection process. Results are discussed in terms of a componential model of attention and in relation to the implicit-explicit distinction.     

Fragment difficulty in priming on word-completion tests

Word-fragment completion is a frequently used test in implicit memory research. In this test priming is the relevant variable. Priming is obtained by subtracting the proportion of nonstudied word fragments correctly completed (called "completion difficulty baseline") from the studied word fragments correctly completed. Since completion difficulty can spuriously vary greatly between experimental conditions, its effect on magnitude of priming is studied. Normative frequency of occurrence of target words was considered because their influence over performance is known. In an experiment using a word-fragment completion test, participants' completion of fragments at three levels of completion difficulty and two levels of frequency was tested. Analysis showed that completion difficulty had a significant effect on global priming. The priming magnitude was higher for Difficult and Moderately Difficult fragments than for Easy ones. An interaction between fragment difficulty and normative word frequency was observed. When the fragments were easy to complete, the expected effect of higher priming for low-frequency words than for high-frequency words was not observed.     

Conceptual activation of distractors during selection is not sufficient to produce negative priming

Negative priming (NP) occurs when responses are slower because the targets were distractors on the preceding trial. Word-naming NP occurs only with words that have been presented repeatedly as targets; novel words do not show NP. The activation-inhibition explanation is that representations of repeated-word distractors are activated already and must be inhibited; the inhibition carries over to the next trial. If this explanation is correct, novel-word NP should occur if the word is semantically primed (thus activating its representation) before it occurs as a distractor. In two experiments, there was NP for words from a repeated set, and the magnitude of NP increased when the same word could occur as a target on consecutive trials. There was positive, rather than negative, priming for novel-word targets that had been semantically primed as distractors. Either the activation from semantic priming was not sufficiently strong to require inhibition, or the activation-inhibition hypothesis does not refer to activation of conceptual representations.     

Increased perceptual and conceptual processing difficulty makes the immeasurable measurable: negative priming in the absence of probe distractors

Negative priming (NP) refers to the finding that people's responses to probe targets previously presented as prime distractors are usually slower and more error prone than to unrepeated stimuli. In a typical NP experiment, each probe target is accompanied by a distractor. It is an accepted, albeit puzzling, finding that the NP effect depends on the presence of these probe distractors; for, without probe distractors, NP diminishes. This phenomenon causes severe problems for the majority of theoretical accounts of NP. In the present study, we follow a simple argument, namely that without probe distractors, the difficulty of responding to the probe is so low that NP becomes irrelevant. Hence, by increasing perceptual processing difficulty, as well as by increasing conceptual processing difficulty, significant NP effects with constantly absent probe distractors can be reliably observed. In addition, our results also show that NP without probe distractors can be found by exclusively manipulating probe display processing. This finding furthers our understanding of the processes causing NP.     

Eliminating flanker effects and negative priming in the flankers task: evidence for early selection

Reports of negative priming in the absence of flanker effects (Fox, 1995) provide support for the notion that unattended stimuli are identified. I evaluated the hypothesis that such results are the outcome of attentional leakage to the flanker location. In Experiment 1, I assessed flanker effects and negative priming as a function of target-flanker proximity (.9 degrees and 2.7 degrees for near and far flankers, respectively) and of attention cuing to the target location (precued vs. uncued) on the prime trials. I report larger flanker effects in uncued than in precued conditions, and larger effects for near than for far flankers. More critically, when attention was precued, both flanker effects and negative priming vanished for far flankers. In Experiment 2, I show that the latter result was not linked to prime-probe contextual similarity (Neill, 1997). These results demonstrate that selective target processing is possible when attention is optimally focused to the target location.     

Varieties of positive and negative priming

Numerous recent investigations have focused on a particular relation between the roles a stimulus plays in successive displays: when a stimulus ignored by a subject on one occasion is to be attended on a succeeding occasion, reaction time to that stimulus is slowed relative to a control condition. But this is but one possible case ofnegative priming. There are other ways in which negative priming might occur, and there are several varieties of positive priming as well. All these possibilities were explored in the present experiment.     

Spatial stimulus-response compatibility and negative priming

According to Kornblum's (1992) dimensional overlap model, when an incongruent response to a stimulus is required, automatic activation of the congruent response must first be inhibited. Shiu and Kornblum (1996a) provided evidence for such inhibition in an incongruent symbolic negative priming task. Reaction time was longer when a trial's correct response was the name of the stimulus from the previous trial than when it was not. We report three experiments that test this inhibition hypothesis for spatial stimuli and responses. In Experiment 1, which used a spatial mapping analogous to the symbolic mapping used by Shiu and Kornblum (1996a), a similar negative priming effect was found. However, in Experiments 2 and 3, which used mappings that were conducive to simple transformational rules, a positive priming effect was obtained. The results suggest that inhibition in response selection may depend on the complexity of the relations between the stimuli and responses.     

Magnitude of negative priming varies with conceptual task difficulty: Attentional resources are involved in episodic retrieval processes

In a variant of the negative priming (NP) procedure, the larger of two presented animals is to be named in each trial. Eight animals of different sizes are used, which allows a manipulation of conceptual task difficulty in terms of pair distance (difficult: one step, versus easy: three steps) on the series. Distances are varied for prime pairs and probe pairs orthogonally. NP effects were found for easy (wide) probe distances (Experiments 1 and 2) and, additionally, for easy (wide) prime distances (Experiment 2). This pattern is interpreted in terms of different theories of NP, which emphasize either forward-acting (prime to probe) or backward-acting (probe to prime) processes. The present results are most compatible with a backward-acting mechanism defined by the episodic retrieval perspective; they are less compatible with a forward-acting inhibition perspective. The results have implications for resource requirements of retrieval-based accounts of NP.     

Spatial negative priming in bilingualism

Balanced bilinguals have been shown to have an enhanced ability to inhibit distracting information. In this study, we investigated the hypothesis that the bilinguals’ efficiency in inhibitory control can be advantageous in some conditions, but disadvantageous in others—for example, negative priming conditions, in which previously irrelevant information becomes relevant. Data collected in a target-stimulus locating task from 29 early bilingual adults and 29 age-matched monolinguals showed that the bilinguals’ greater inhibition of irrelevant spatial information (i.e., the position of a distractor stimulus) resulted in a smaller effect of the distractor presence (i.e., a smaller difference in error rates in trials with and without distractors) and a larger negative priming effect (i.e., a larger difference between the error rates shown in trials wherein the target position corresponded to the position of the previous-trial distractor and trials wherein the target was presented in a previously vacant position). These findings support the hypothesis of specific nonlinguistic cognitive effects of bilingualism on inhibitory control functions, which are not necessarily reflected in cognitive advantages.     

Dissociations between identity and location negative priming

Negative priming refers to the phenomenon of a slowed response time to a previously ignored distractor. Identity negative priming can be observed when the identity of a previous distractor is repeated as the target identity, and location negative priming can be observed when the spatial location of a previous distractor is repeated as the target location. This article reviewed and integrated previous findings and provided empirical evidence to show the dissociations between location and identity negative priming: (a) the removal of probe distractor impeded identity negative priming but not location negative priming; (b) identity negative priming was modulated by the distance between the target and distractor, while location negative priming was not; and (c) perceptual grouping of the target and distractor affected identity negative priming but not location negative priming.     

Mask-induced priming and the negative compatibility effect

Under certain conditions, masked primes have produced counter-intuitive negative compatibility effects (NCE), such that RT is increased, not decreased, when the target is similar to the prime. This NCE has been interpreted as an index of automatic motor inhibition, triggered to suppress the partial motor activation caused by the prime. An alternative explanation is that perceptual interactions between prime and mask produce positive priming in the opposite direction to the prime, explaining the NCE without postulating inhibition. Here the potential role of this "mask-induced priming" was investigated in two experiments, using masks composed of random lines. Experiment 1 compared masks that included features of the primes and targets with masks that did not. The former should create more mask-induced priming, but the NCE did not differ between masks. Experiment 2 employed masks that contained features of either one target or the other, but not both. These asymmetric masks produced significant mask-induced priming, but it was insufficient in size to account for the prime-related NCE. Thus mask composition can contribute to NCEs, but when random line masks are employed, the major source of the NCE seems to be motor-inhibition.     

Divided attention, aging, and priming in exemplar generation and category verification

Transfer-appropriate processing theories differentiate between conceptual- and perceptual-priming tasks. The former are said to be influenced by the nature of processing engaged in at study, but not by changes in modality between study and test; the latter are sensitive to changes in format between study and test, but not to variations in the extent of semantic processing at study. In the present experiments, we examined the effects of divided attention and aging on priming in exemplar generation and category verification, two tasks that require access to semantic information at test. Manipulations of attention during encoding affected the extent of priming in exemplar generation, but not in category verification. Priming effects were similar in young and older adults in exemplar generation following study in both full and divided attention. Although older adults did not demonstrate priming in category verification in one experiment, no effects of age or divided attention were observed in a second experiment. In addition, priming in category verification was unaffected by varying the level of processing at encoding. However, the absence of levels-of-processing and attention effects in category verification does not signal that priming in this task has a perceptual basis; priming in category verification was insensitive to modality shifts between study and test. The implications of these findings for theories of priming and cognitive aging are considered.