A switch in task affects priming of pop-out: evidence for the role of episodes

Maljkovic and Nakayama (Memory & Cognition, 22(6), 655-678, 1994) demonstrated that response times decrease in a pop-out search task when target-defining features repeat from one trial to the next. This priming of pop-out (PoP) effect has been explained by some researchers as reflecting low-level modulations in attentional control settings Lee, Mozer, and Vecera (Attention, Perception, & Psychophysics, 71(5), 1059-1071, 2009). The present experiments tested whether a shift in higher order task requirements from trial n - 1 to trial n alters PoP effects. The results of Experiments 1 and 2 demonstrated that a switch in task significantly modulated PoP effects when shape was the relevant pop-out dimension. Experiment 3 failed to show significant modulation of PoP as a function of task switch when the pop-out dimension was color, but the findings of Experiment 4 did show modulation of PoP for color when the relative salience of target and distractors was high. Together, the results strongly support the view that PoP effects can be sensitive to a switch in task, a result consistent with the view that PoP effects are modulated by trial-to-trial episodic integration processes.     

Revisiting the time course of inter-trial feature priming in singleton search

Current theories of the locus of inter-trial priming effects in efficient visual search posit an early perceptual component that reflects the short-term influence of a memory trace for low-level stimulus attributes. Despite the fact that this memory trace is hypothesized to be short term, and should therefore have a diminishing influence on performance over time, there has been relatively little study of the effect of time alone on singleton priming effects. The present series of experiments addresses this issue by systematically examining the effect of time on the priming of pop-out (PoP) effect. In Experiment 1, we show that the PoP effect does indeed diminish with increases in the RSI between trials, and does so in accord with a power-law function. In Experiment 2, we show that temporal discriminability of trial n ? 1 from the trial that precedes it does not contribute to PoP effects. The results of Experiment 3 revealed two key results: (1) the PoP effect survives an equivalent number of intervening trials across very different RSI conditions; and (2) the cumulative target repetition benefit does depend on the RSI between trials. Together, the results favor neither a simple passive decay nor a strong episodic retrieval account of the PoP effect.     

Learning what to expect: context-specific control over intertrial priming effects in singleton search

The present study explored the degree to which repetition effects in color pop-out search from trial n ? 1 to trial n are subject to the attentional control settings of the observer. Intertrial priming effects were compared between two contexts that differed in terms of the utility of immediate prior experience for current performance; in one context, the target was likely to repeat, and in the other context, the target was likely to alternate from one trial to the next. Across two experiments, priming of pop-out (PoP) effects (Malkjovic & Nakayama; Memory & Cognition 22:657-672, 1994) were modulated in accord with the probability of target color repetition in a given trial context. Importantly, this modulation persisted when trial history preceding trial n ? 1 was controlled for. Furthermore, this control over PoP seems not to derive from explicit strategies and is not an artifact of randomly occurring strings of same-target trials. We argue that priming effects in singleton search from trial n ? 1 to trial n are subject to a form of implicit top-down control.     

Visual search for singleton feature targets across dimensions: Stimulus- and expectancy-driven effects in dimensional weighting

Four pop-out search experiments investigated whether dimension-based visual attention is top-down modulable. Observers searched for singleton feature targets defined, variably across trials, by a color or an orientation difference to nontargets. Observers were precued to the most probable target-defining dimension (e.g., by the word color) or feature (red) on a given trial. Results revealed expedited reaction times (RTs) for valid-dimension targets relative to neutral-cue conditions, and slowed RTs for invalid-dimension targets. Cue information as to precise target feature yielded some extra effect only for color targets. The dimensional cuing significantly reduced, but did not abolish, the dimension-specific influence of the previous target on detection of the current target (same-dimension RT < different-dimension RT). These findings confirm that top-down dimensional set modulates stimulus-driven dimension processes in the detection of pop-out signals. ((c) 2003 APA, all rights reserved)     

Color singleton pop-out does not always poop out: An alternative to visual search

Folk psychology suggests that when an observer views a scene, a unique item will stand out and draw attention to itself. This belief stands in contrast to numerous studies in visual search that have found that a unique target item (e.g., a unique color) is not identified more quickly than a nonunique target. We hypothesized that this finding is the result of task demands of visual search, and that when the task does not involve visual search, uniqueness will pop out. We tested this hypothesis in a task in which observers were presented an array of letters and asked to respond aloud, as quickly as possible, with the identity of any one of the letters. The observers were significantly more likely to respond with a uniquely colored letter than would be expected by chance. In a task in which observers blurt out the first thing that they see, unique pop-out does not poop out.     

Understanding priming of color-singleton search: Roles of attention at encoding and “retrieval”

We investigated how the performance of a color-singleton search (the search for a single odd-colored item among homogeneously colored distractors) left a persistent memory trace (lasting up to six intervening trials or ～17 sec) that facilitated a subsequent color-singleton search (when the same targetdistractor color combination was repeated). Specifically, we investigated the roles of attention in the encoding and “retrieval” stages of this priming effect by intermixing trials in which the target location was precued by an onset cue. We found that the encoding of both target and distractor colors was automatic in that whether or not observers had to use color in locating the target in the preceding trial did not substantially affect priming. However, priming required that the color-singleton item be attended in the preceding trial. Once a color singleton display was encoded, our results indicated that priming facilitated the direction of attention to the color-singleton target on a subsequent trial. In short, when a color-singleton item happened to be a critical item to be attended in one situation, another color-singleton item defined by the same color combination tended to attract attention in subsequent encounters.     

Perceptual distinctiveness produces long-lasting priming of pop-out

Maljkovic and Nakayama (1994) demonstrated memory influences in singleton search from one trial to the next, an effect they termed priming of pop-out (PoP). This effect was described as resulting from the persistence of an implicit memory trace, the influence of which could be observed for around five to eight subsequent trials. The seemingly short-lived nature of this priming effect has been attributed to decay of the underlying memory representation that occurs when attention is directed to intervening search items, even when such items are perceptually dissimilar from the search trials upon which PoP is measured (Maljkovic & Nakayama, 2000). The present study reexamines the role of perceptual similarity as a mechanism of interference by examining the influence on PoP of rare search trials that were perceptually distinct with respect to the other, common trials. Long-lasting (n − 16) PoP was observed for rare trials that were composed of distinct target/distractor colors, suggesting that PoP can be observed across at least twice as many trials as has previously been reported. Thus, the time span across which PoP can be measured depends heavily on the nature of the intervening search displays, a result that must be accommodated by current theoretical accounts of PoP.     

Understanding priming of color-singleton search: roles of attention at encoding and "retrieval"

We investigated how the performance of a color-singleton search (the search for a single odd-colored item among homogeneously colored distractors) left a persistent memory trace (lasting up to six intervening trials or approximately 17 sec) that facilitated a subsequent color-singleton search (when the same target-distractor color combination was repeated). Specifically, we investigated the roles of attention in the encoding and "retrieval" stages of this priming effect by intermixing trials in which the target location was precued by an onset cue. We found that the encoding of both target and distractor colors was automatic in that whether or not observers had to use color in locating the target in the preceding trial did not substantially affect priming. However, priming required that the color-singleton item be attended in the preceding trial. Once a color singleton display was encoded, our results indicated that priming facilitated the direction of attention to the color-singleton target on a subsequent trial. In short, when a color-singleton item happened to be a critical item to be attended in one situation, another color-singleton item defined by the same color combination tended to attract attention in subsequent encounters.     

A crossed random effects diffusion model for speeded semantic categorization decisions

Choice reaction times (RTs) are often used as a proxy measure of typicality in semantic categorization studies. However, other item properties have been linked to choice RTs as well. We apply a tailored process model of choice RT to a speeded semantic categorization task in order to deconfound different sources of variability in RT. Our model is based on a diffusion model of choice RT, extended to include crossed random effects (of items and participants). This model retains the interesting process interpretation of the diffusion model’s parameters, but it can be applied to choice RTs even in the case where there are few or no repeated measurements of each participant-item combination. Different aspects of the response process are then linked to different types of item properties. A typicality measure turns out to predict the rate of information uptake, while a lexicographic measure predicts the stimulus encoding time. Accessibility measures cannot reliably predict any component of the decision process.     

Reinforcement of inhibitory positional priming by spatial working memory contents

This study examined whether positional priming of pop-out is modulated by spatial working memory (WM). In Experiments 1A and 1B, observers were presented with a to-be-memorized item (Experiment 1A: triangle; Experiment 1B: circle) prior to performing a block of search trials, with triangular stimulus configurations (one target, two distractors) on an underlying elliptical frame. Each search block was followed by a memory test (i.e., memory conditions). In Experiment 1C, the presentation of the memory item (triangle) was immediately followed by the memory test, and the search block was performed after this test (i.e., no-memory condition). It was found that targets presented at a previous target were detected faster and targets presented at a previous distractor location slower, relative to a previous empty (‘neutral’) stimulus location, respectively. While facilitatory position priming was uninfluenced by the memory manipulation, inhibitory positional priming was larger in the memory than no-memory condition, but only when the memory stimulus (triangle) matched the (triangle) configuration formed by the three search items. This finding of larger inhibitory priming under memory conditions provides further evidence that positional priming, rather than being purely bottom-up determined, is open to top-down influences.     

Distinct,but top-down modulable color and positional priming mechanisms in visual pop-out search

Three experiments examined reaction time (RT) performance in visual pop-out search. Search displays comprised of one color target and two distractors which were presented at 24 possible locations on a circular ellipse. Experiment 1 showed that re-presentation of the target at a previous target location led to expedited RTs, whereas presentation of the target at a distractor location led to slowed RTs (relative to target presentation at a previous empty location). RTs were also faster when the color of the target was the same across consecutive trials, relative to a change of the target’s color. This color priming was independent of the positional priming. Experiment 2 revealed larger positional facilitation, relative to Experiment 1, when position repetitions occurred more likely than chance level; analogously, Experiment 3 revealed stronger color priming effects when target color repetitions were more likely. These position and color manipulations did not change the pattern of color (Experiment 2) and positional priming effects (Experiment 3). While these results support the independency of color and positional priming effects (e.g., Maljkovic and Nakayama in Percept Psychophys 58:977–991, 1996), they also show that these (largely ‘automatic’) effects are top-down modulable when target position and color are predictable (e.g., Müller et al. in Vis Cogn 11:577–602, 2004).     

Alphanumeric category effects: Evidence against the sufficiency of a localization explanation

The Hatfield Polytechnic, Hatfield, Herts ALIO 9AB, England The experiment utilized a serial choice reaction time (RT) paradigm in which only one alphanumeric stimulus was presented per trial, and the target set consisted of a single identified item. The categorical relationship between the target and nontarget items was varied as a property of blocks of trials. Target and nontarget RTs were smaller when the specified target item (e.g., the number 6) was categorically distinct from the nontargets (e.g., letters) than when it was from the same category (e.g., digits). The processing of catch-trial stimuli (items from the alternate category to the nontargets) and homographie category-ambiguous items was inhibited only in the former, between-category, condition. The results are contrasted with those obtained in visual search tasks. They suggest that a “locational-cue” explanation of alphanumeric category effects is inadequate.     

Exploring the contributions of spatial and non-spatial working memory to priming of pop-out

Priming of pop-out (PoP) refers to the facilitation of performance that occurs when a target-defining feature is repeated across consecutive trials in a pop-out oddball search task. The underlying mechanism of PoP has been poorly understood and raises important questions about how our visual system is guided by past experiences, even during bottom-up processing. Lee, Mozer, and Vecera (Attention, Perception, & Psychophysics, 71, 1059–1071, 2009) demonstrated that PoP remained unaffected by a concurrent non-spatial visual working memory (VWM) load, and they concluded that PoP occurs through feature gain modulation, essentially eliminating the contribution of memory representations in VWM to PoP. In the present study, we followed up on those results by (a) replicating the null effect of non-spatial VWM load on PoP and (b) examining the effect of spatial VWM load on PoP. The results showed that spatial VWM load does interfere with PoP, supporting the notion that spatial VWM is involved in PoP. In Experiment 2, we extended this finding by manipulating VWM load and observing its consequence on the magnitude of PoP. Increasing spatial VWM load decreased the amount of PoP observed, in a dose-dependent manner, whereas changes in non-spatial VWM load did not. Contrary to Lee et al.’s conclusions, these results suggest that VWM resources appear to contribute to the occurrence of PoP, supporting the theory that PoP is, in fact, a multilevel process in which the deployment of spatial attention, relying on VWM representations, plays an important role.     

Mechanisms of priming of pop-out: Stored representations or feature-gain modulations?

Previous research has shown that repetition of a task-relevant attention-capturing feature facilitates popout search. This priming of pop-out effect is due to some residual memory from recent trials. We explore two possible mechanisms of priming of pop-out: a top-down attentional benefit from a memory of the previous target representation that is stored in visual short-term memory (VSTM) and a bottom-up change of attentional gains from perceptual features of the previously attended target. We manipulated participants’ ability to form a memory trace in VSTM by occupying it with a distractor task and found that occupying VSTM did not interfere with priming of pop-out. We next manipulated attentional gains associated with feature values by inserting an irrelevant task between pop-out searches. We found that the color of the target from the intervening perceptual task influenced pop-out search: The current pop-out search was facilitated when the intervening task’s target matched the target color of the pop-out search. These results suggest that priming of pop-out might not be due to a memory trace of the previous targets in VSTM but, rather, might be due to changes in attentional control based on priming from relatively low-level feature representations of previously attended objects.     

Fortune and reversals of fortune in visual search: Reward contingencies for pop-out targets affect search efficiency and target repetition effects

Rewards have long been known to modulate overt behavior. But their possible impact on attentional and perceptual processes is less well documented. Here, we study whether the (changeable) reward level associated with two different pop-out targets might affect visual search and trial-to-trial target repetition effects (see Maljkovic & Nakayama, 1994). Observers searched for a target diamond shape with a singleton color among distractor diamond shapes of another color (e.g., green among red or vice versa) and then judged whether the target had a notch at its top or bottom. Correct judgments led to reward, with symbolic feedback indicating this immediately; actual rewards accumulated for receipt at study end. One particular target color led to a higher (10:1) reward for 75% of its correct judgments, whereas the other singleton target color (counterbalanced over participants) yielded the higher reward on only 25% of the trials. We measured search performance in terms of inverse efficiency (response time/proportion correct). The reward schedules not only led to better performance overall for the more rewarding target color, but also increased trial-to-trial priming for successively repeated targets in that color. The actual level of reward received on the preceding trial affected this, as did (orthogonally) the likely level. When reward schedules were reversed within blocks, without explicit instruction, corresponding reversal of the impact on search performance emerged within around 6 trials, asymptoting at around 15 trials, apparently without the observers’ explicit knowledge of the contingency. These results establish that pop-out search and target repetition effects can be influenced by target reward levels, with search performance and repetition effects dynamically tracking changes in reward contingency.     

网络成瘾倾向者在视觉工作记忆引导下的注意捕获

采用工作记忆任务和视觉搜索任务相结合的双任务范式, 探讨网络成瘾倾向者在视觉工作记忆引导下的注意捕获。实验1考察了单一分心刺激视场中分心刺激的性质对网络成瘾倾向者选择性注意的影响, 实验2通过控制匹配试验出现的概率来诱发不同的抑制动机, 探讨多分心刺激视场中两种抑制动机下网络成瘾倾向者的注意表现。结果发现：(1)无论在单一分心刺激还是多分心刺激视场中, 网络成瘾倾向被试的目标搜索反应时均显著短于正常组被试, 且两组的搜索正确率没有差异。(2)在单一分心刺激视场中, 无论是与工作记忆项目匹配还是不匹配的分心刺激都会捕获正常组被试的注意, 但不会捕获网络成瘾倾向被试的注意。(3)在多分心刺激视场中, 当抑制动机水平较低时, 两组被试均对匹配分心物产生注意捕获效应, 且网络成瘾倾向被试受工作记忆引导的注意捕获效应小于正常组被试; 当抑制动机较高时, 两组被试均对匹配分心物产生注意抑制效应, 且没有差异。研究结果表明, 面对非网络相关视觉刺激时, 网络成瘾倾向者受工作记忆引导的注意捕获效应小于正常组, 并表现出了知觉加工上的优势。     

Priming of popout: III. A short-term implicit memory system beneficial for rapid target selection

The priming of popout (PoP) (Maljkovic & Nakayama, 1994, 1996) increases the speed of attentional deployment to subsequent targets having the same feature characteristic and relative position, it lasts for approximately 5-8 trials, and is cumulative. Here we establish PoP as an example of short-term implicit memory by showing that it is qualitatively different from explicit memory. Using a post-cued recall procedure embedded in the stream of search task trials, we show that explicit memory is not selective as is PoP and is of much shorter duration. As such we argue that explicit memory is unlikely to account for the properties of PoP. In examining the decay of PoP, we find that: PoP is not evident after a 90sec delay, it does not show passive decay over much shorter intervals (1-3sec), and it gets decremented by attentional deployments to visually dissimilar stimuli, the size of the decrement being related to task difficulty. The results, taken together, suggest that PoP reflects a functionally beneficial memory system, specialized for the rapid and automatic selection of items for focal attention and saccadic eye movements.     

Visual search for arbitrary objects in real scenes

How efficient is visual search in real scenes? In searches for targets among arrays of randomly placed distractors, efficiency is often indexed by the slope of the reaction time (RT) × Set Size function. However, it may be impossible to define set size for real scenes. As an approximation, we hand-labeled 100 indoor scenes and used the number of labeled regions as a surrogate for set size. In Experiment 1, observers searched for named objects (a chair, bowl, etc.). With set size defined as the number of labeled regions, search was very efficient (~5 ms/item). When we controlled for a possible guessing strategy in Experiment 2, slopes increased somewhat (~15 ms/item), but they were much shallower than search for a random object among other distinctive objects outside of a scene setting (Exp. 3: ~40 ms/item). In Experiments 4–6, observers searched repeatedly through the same scene for different objects. Increased familiarity with scenes had modest effects on RTs, while repetition of target items had large effects (>500 ms). We propose that visual search in scenes is efficient because scene-specific forms of attentional guidance can eliminate most regions from the “functional set size” of items that could possibly be the target.     

Lengthening fixed preparatory foreperiod durations within a digit magnitude classification task serves mainly to shift distributions of response times upwards

In this study, the effect of lengthening foreperiod duration (i.e. the time between the presentation of a warning signal and a subsequent target stimulus) on choice RTs is examined. The foreperiod durations used were either 2 or 8 s and were fixed within pure blocks of trials. The task was to determine whether a single-digit target stimulus was either smaller or larger than 5 and responses were provided manually. An additive relation between foreperiod duration length and numerical distance from 5 was present in the mean RTs. Subsequent ex-Gaussian analyses of the shapes of the RT distributions indicated that they become shifted upwards as the foreperiod increased with relatively smaller increases in the sizes of their tails. It is argued mainly that the latter finding is incompatible with the strategic time estimation view of the fixed foreperiod duration effect.     

Haptic pop-out in a hand sweep

Visually, a red item is easily detected among green items, whereas a mirrored S among normal Ss is not. In visual search, the former is known as the pop-out effect. In daily life, people often also conduct haptic (tactual) searches, for instance, when trying to find keys in their pocket. The aim of the present research was to determine whether there is a haptic version of the pop-out effect. Blindfolded subjects had to search for a target item which differed in roughness from the surrounding distractor items. We report reaction time slopes as low as 20 ms/item. When target and distractor identities were interchanged the slopes increased indicating a search asymmetry. Furthermore, we show that differences in search slope were accompanied by search strategy differences. In some conditions a single-hand sweep over the display was sufficient, while in others a more detailed search strategy was used. By relating haptic search slopes to parallel and serial search strategies we show, for the first time, that pop-out effects occur under free manual exploration.