Visual selective attention after severe closed head injury

This study investigated the nature of selective attention deficits after severe closed head injury (CHI). Twenty participants with severe CHI (greater than 1 year postinjury) and 20 matched controls completed search and nonsearch visual selective attention tasks under conditions of low (Experiment 1) and high (Experiment 2) target-distractor similarity. In the search situations, participants searched visual displays that contained 1, 4, or 8 items for the targets. In the nonsearch situations, the location of the targets was visually cued with a peripheral arrow. The results revealed that in both the low and high target-distractor similarity search conditions. CHI participants required a longer time than controls to locate and identify the target. In contrast, in the nonsearch condition, CHI participants were able to successfully ignore irrelevant task information when target-distractor similarity was low. However, when target-distractor similarity was high, CHI participants had more difficulty than controls ignoring the irrelevant information. These results suggest that, in comparison to controls, CHI participants may be at a disadvantage in selective attention situations when visual search is required and when the discriminability between targets and distractors is difficult.     

The problem state: A cognitive bottleneck in multitasking.

The main challenge for theories of multitasking is to predict when and how tasks interfere. Here, we focus on interference related to the problem state, a directly accessible intermediate representation of the current state of a task. On the basis of Salvucci and Taatgen’s (2008) threaded cognition theory, we predict interference if 2 or more tasks require a problem state but not when only one task requires one. This prediction was tested in a series of 3 experiments. In Experiment 1, a subtraction task and a text entry task had to be carried out concurrently. Both tasks were presented in 2 versions: one that required maintaining a problem state and one that did not. A significant overadditive interaction effect was observed, showing that the interference between tasks was maximal when both tasks required a problem state. The other 2 experiments tested whether the interference was indeed due to a problem state bottleneck, instead of cognitive load (Experiment 2: an alternative subtraction and text entry experiment) or a phonological loop bottleneck (Experiment 3: a triple-task experiment that added phonological processing). Both experiments supported the problem state hypothesis. To account for the observed behavior, computational cognitive models were developed using threaded cognition within the context of the cognitive architecture ACT-R (Anderson, 2007). The models confirm that a problem state bottleneck can explain the observed interference. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Personal names and the attentional blink: a visual "cocktail party" effect

Four experiments were carried out to investigate an early- versus late-selection explanation for the attentional blink (AB). In both Experiments 1 and 2, 3 groups of participants were required to identify a noun (Experiment 1) or a name (Experiment 2) target (experimental conditions) and then to identify the presence or absence of a 2nd target (probe), which was their own name, another name, or a specified noun from among a noun distractor stream (Experiment 1) or a name distractor stream (Experiment 2). The conclusions drawn are that individuals do not experience an AB for their own names but do for either other names or nouns. In Experiments 3 and 4, either the participant's own name or another name was presented, as the target and as the item that immediately followed the target, respectively. An AB effect was revealed in both experimental conditions. The results of these experiments are interpreted as support for a late-selection interference account of the AB.     

Serial deployment of attention during visual search.

This study examined whether objects are attended in serial or in parallel during a demanding visual search task. A component of the event-related potential waveform, the N2pc wave, was used as a continuous measure of the allocation of attention to possible targets in the search arrays. Experiment 1 demonstrated that the relative allocation of attention shifts rapidly, favoring one item and then another. In Experiment 2, a paradigm was used that made it possible to track the absolute allocation of attention to individual items. This experiment showed that attention was allocated to one object for 100-150 ms before attention began to be allocated to the next object. These findings support models of attention that posit serial processing in demanding visual search tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Capacity limitations in visual word processing.

The ability of subjects to process English words in a spatially parallel manner was examined in several redundant-target detection tasks. When redundant targets were identical in a given display, processing limitations were evident in a task that required subjects to make semantic categorizations of words. However, parallel processing of identical redundant target words was exhibited in a lexical decision task that required a structural analysis of letter strings, but not an analysis of word meaning. The difference in performance in the two tasks suggests that the capacity for semantic processing is limited. Analyses designed to examine whether the redundancy gain in Experiment 2 could be attributed to limited capacity processing in conjunction with positional preferences provided evidence against this possibility. In addition, these analyses suggested that the processing times for the redundant targets in Experiment 2 might be positively correlated. In the third and fourth experiments, the redundant-target displays contained two different words. Processing interference, in the form of a redundancy loss, was evident in the lexical decision task, but not in the semantic categorization task, confirming a difference in the mode of processing between the two tasks. The results provide evidence against the unlimited-capacity, parallel processing hypothesis of late selection theories of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Response Selection Modulates Visual Search Within and Across Dimensions.

In feature search tasks, uncertainty about the dimension on which targets differ from the nontargets hampers search performance relative to a situation in which this dimension is known in advance. Typically, these cross-dimensional costs are associated with less efficient guidance of attention to the target. In the present study, participants either had to perform a feature search task or had to perform a nonsearch task, that is, respond to a target presented without nontargets. The target varied either in one dimension or across dimensions. The results showed similar effects both in search and nonsearch conditions: Preknowledge of the target dimension gave shorter response times than when the dimension was unknown. Similar results were found using a trial-by-trial cueing. It is concluded that effects that typically have been attributed to early top-down modulation of attentional guidance may represent effects that occur later in processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual search in a multi-element asynchronous dynamic (MAD) world.

In visual search tasks participants search for a target among distractors in strictly controlled displays. We show that visual search principles observed in these tasks do not necessarily apply in more ecologically valid search conditions, using dynamic and complex displays. A multi-element asynchronous dynamic (MAD) visual search was developed in which the stimuli could either be moving, stationary, and/or changing in luminance. The set sizes were high and participants did not know the specific target template. Experiments 1 through 4 showed that, contrary to previous studies, search for moving items was less efficient than search for static items and targets were missed a high percentage of the time. However, error rates were reduced when participants knew the exact target template (Experiment 5) and the difference in search efficiency for moving and stationary targets disappeared when lower set sizes were used (Experiment 6). In all experiments there was no benefit to finding targets defined by a luminance change. The data show that visual search principles previously shown in the literature do not apply to these more complex and “realistically” driven displays. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Modulating the interference effect in timing with varying stimulus onset asynchrony.

The interference effect on time judgments, when subjects are also required to perform a concurrent nontemporal task, is one of the most reliable findings in the time perception literature. In the present study, the interference between a time discrimination task (short or long tone) and a digit classification task (even or odd digit) was analysed using the overlapping tasks paradigm. Reaction times in the digit task were shorter at longer values of stimulus onset asynchrony (SOA) in Experiment 1, showing a clear modulation of interference with varying the relative position of the tasks. Using longer tone durations in Experiment 2, reaction times in the digit task were affected not only by the overlap between the tasks but also by the temporal proximity of responses in the timing and digit tasks. In Experiment 3, the effect of varying the SOA on performance on the digit task was abolished when the auditory tone was irrelevant, thus eliminating an interpretation in terms of distraction from the tone offset. We conclude that the interference effect in concurrent time discrimination and digit classification may be modulated by the degree of overlap between the tasks as well as by the overlap between late processing stages related to decision and response components in the 2 tasks. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Attentional resources in timing: interference effects in concurrent temporal and nontemporal working memory tasks

Three experiments examined interference effects in concurrent temporal and nontemporal tasks. The timing task in each experiment required subjects to generate a series of 2- or 5-sec temporal productions. The nontemporal tasks were pursuit rotor tracking (Experiment 1), visual search (Experiment 2), and mental arithmetic (Experiment 3). Each nontemporal task had two levels of difficulty. All tasks were performed under both single- and dual-task conditions. A simple attentional allocation model predicts bidirectional interference between concurrent tasks. The main results showed the classic interference effect in timing. That is, the concurrent nontemporal tasks caused temporal productions to become longer (longer productions represent a shortening of perceived time) and/or more variable than did timing-only conditions. In general, the difficult version of each nontemporal task disrupted timing more than the easier version. The timing data also exhibited a serial lengthening effect, in which temporal productions became longer across trials. Nontemporal task performance showed a mixed pattern. Tracking and visual search were essentially unaffected by the addition of a timing task, whereas mental arithmetic was disrupted by concurrent timing. These results call for a modification of the attentional allocation model to incorporate the idea of specialized processing resources. Two major theoretical frameworks--multiple resource theory and the working memory model--are critically evaluated with respect to the resource demands of timing and temporal/nontemporal dual-task performance.     

A fair test of the spreading activation hypothesis: a study of affective congruency effects in the Stroop test

It is argued that the Stroop color-naming task is especially suited to investigate affective priming effects in the sense of an automatic spreading of activation to other concepts of the same valence, because (a) the Stroop task is not prone to an explanation of affective congruency effects on the basis of reaction priming or reaction interference, and (b) it is possible to detect specific (fast and efficient stimulus processing due to heightened accessibility) as well as nonspecific (cognitive interference, triggering of global action tendencies) effects of an activation of valenced concepts in the Stroop task. Two experiments were conducted to investigate associative and affective priming effects with the Stroop task. In a first experiment (N = 36, SOA = 300 ms) a standard priming procedure was chosen; the primes were presented without any processing instructions. In a second experiment (N = 48, SOA = 500ms) the primes had to be reproduced after naming the color of the target. In both experiments significant association effects were found for the associative material. For the valenced material no affective congruency effects were found in either experiment. The present results are not compatible with the hypothesis of an automatic affective spreading of activation that was given as an explanation of affective congruency effects in previous studies using different tasks.     

Search and retrieval patterns for performance information: Effects on evaluations of multiple targets.

Examined search, organization, and use of performance information about multiple targets. In Exp I, 41 undergraduates searched among 64 performance vignettes, stored in a 4?×?4?×?4 (Target?×?Task?×?Occasion) computer array. The predominant search pattern involved examining a set of performances by one target before proceeding to another. Exp II tested whether various acquisition patterns affect organization and use of performance information. 125 Ss were shown 16 vignettes from Exp I, organized in target-by-target (target blocked), task-by-task (task blocked), or mixed sequences. Results indicate greater recall under blocked than under mixed conditions. Blocking also influenced organization in recall. Target blocking produced clustering by target; task blocking produced clustering by task; mixed presentation produced no discernible clustering. Accuracy of ratings for overall target performance was unaffected by blocking, but task blocking produced better differentiation among instances of good and poor performance exhibited by specific targets. (22 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Interference in spatial memory.

Four experiments examined interference in human spatial memory. The first two tested for retroactive interference by varying the similarity between the interpolated task and the task that was learned originally. Retroactive interference was observed during relearning of a radial stylus maze and during relearning of the locations of pairs of playing cards in a concentration game. In the third and fourth experiments, proactive interference was tested during the relearning of the locations of pairs in a concentration game. Some proactive interference was observed when the number of proactive games was varied (Experiment 3), and substantial proactive interference was found when the similarity between the proactive and target tasks was the independent variable (Experiment 4). Although extensive evidence indicates that spatial memory differs from other types of memory, spatial memory is subject to interference effects, as are verbal memory, motor memory, visual discriminative memory in animals, and animal spatial memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dimension-specific intertrial priming effects are task-specific: Evidence for multiple weighting systems.

Feature singleton search is faster when the target-defining dimension repeats across consecutive trials than when it changes (Found & Müller, 1996). However, this dimension repetition benefit (DRB) has also been demonstrated for the tasks with no search component (Mortier, Theeuwes, & Starreveld, 2005). If DRBs in the search and non-search tasks have the same origin, significant DRBs across trials of different tasks should rise. Two different tasks varied either in a predictable manner (Experiment 1) or randomly (Experiment 2) across trials. In detection task, search displays containing either color or orientation singletons were used. Discrimination task required identification of either color or orientation of a single presented item (non-search display). In Experiment 3, participants performed only the discrimination task, while the search and non-search displays varied randomly. There were significant DRBs for both tasks when the task repeated but not when the task changed (Experiments 1 and 2). DRBs were significant both when the display type repeated and when it changed (Experiment 3). Overall, the findings can be well explained by assuming multiple, independent dimension-weighting systems generating DRBs in different tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reaching while calculating: Scheduling of cognitive and perceptual-motor processes.

To address the neglected question of how cognitive and perceptual-motor processes are coordinated, the authors asked participants to move a cursor from one target to another to reveal operators and operands for a running arithmetic task. In Experiment 1 performance on this task was compared with performance on tasks requiring only aiming or only arithmetic. Aiming was faster in the aiming-only task than in the combined task. More importantly, times for steps requiring calculation were equivalent in the combined and arithmetic-only tasks. The results from this and a second experiment suggest that participants slowed their aiming to allow calculations to be completed before subsequent targets were entered. As a whole, the results suggest that cognitive and perceptual-motor processes are coordinated through scheduling. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The influence of selection for response on repetition priming of word identification.

Repetition priming of word identification was examined using study tasks that required participants either to search for targets appearing in rapid serial visual presentation of word lists or to read aloud a list of target words. Nontarget words embedded in search lists produced a small amount of repetition priming on a masked word identification test, independent of presentation duration in the search list (200–1,000 ms), but no priming when they appeared as targets in a second search task used at test. For both test tasks, words that were originally encoded in a read-aloud task or served as detected targets during a search task generated more priming than nontarget words from search lists. These results suggest that priming effects are strongest when study tasks require an item to be selected as the basis for an overt response, even though the information on which study and test responses are based may be different. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Semantic interference effects on naming using a postcue procedure: Tapping the links between semantics and phonology with pictures and words.

Five experiments are reported in which a new technique for assessing the processes involved in mapping semantic representations onto name information in simple naming tasks was used. This technique, the postcue naming procedure, requires participants to name 1 of 2 potential target stimuli after they receive a relevant selection cue. Naming performance is slowed when the 2 potential targets are semantically related, relative to when they are unrelated. Effects on picture and word targets are of equal magnitude, providing these 2 types of stimulus are intermingled in the experiment. When words are presented alone, semantic interference is abolished (although evidence for lexical processing of words can be demonstrated). The effect on picture naming is also eliminated when the interfering stimulus has to be categorized rather than named. These results suggest that the locus of the interference is in the processes mapping semantic information onto names. These processes seem to be shared by pictures and words when the semantic processing of words is induced. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Face–name interference.

Investigated interference effects between the processing of simultaneously presented photographs of faces of familiar people and printed names of familiar people in 5 experiments each with 12 adult Ss. Results show that printed names interfered with identifying faces, whereas faces did not interfere with saying printed names. In contrast, faces interfered more with name categorization than names interfered with face categorization. It is suggested that despite a priori reasons as to why faces might be thought to possess functional properties different from those of other visual objects, the observed effects are comparable to those found in object–word interference studies, with photographs of faces behaving like pictures of objects and printed people's names behaving like printed names of objects. In face naming tasks, the presence of related names produced more interference than did the presence of unrelated names. This effect was examined in greater detail in Exp III, where it was found that the effect arose when the face and the name belonged to people of similar appearance. An effect of common category membership was not found in Exp III. Exp V, however, showed that names of people highly associated with the person whose face was presented also produced more interference than did names of unrelated people. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Phonology can help or hurt the perception of print.

Phonological manipulations affect performance in a letter search task that requires only a shallow level of processing. In Experiment 1, phonology reduced accuracy in the letter search task when a pseudohomophone (GAIM) contained a target letter ("i") that was missing in the spelling of its (nonpresented) sound-alike base word (GAME). In Experiment 2, phonology increased accuracy in the letter search task when the target letter was present in both the spelling of the pseudohomophone and the spelling of its sound-alike base word ("m" in GAIM and GAME). In Experiment 3, we showed that the phonology-hurts effect of Experiment 1 is not peculiar to nonword letter strings but generalizes to familiar words. In Experiment 4, we obtained a phonology-hurts effect on correct response times when stimuli were visible until participants responded (stimuli were not masked). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Transient structures": the effects of practice and distractor grouping on within-dimension conjunction searches

It has been stated that whereas between-dimension (color x orientation) conjunctions can be searched in a "parallel" fashion, within-dimension (color x color) conjunctions are necessarily searched in a "serial self-terminating" fashion (Wolfe et al., 1990). We explored the effects of practice (within 1-h experimental session) and distractor grouping on within-dimension conjunction search tasks. In Experiments 1 and 3, the stimuli were rectangles formed by two adjacent squares; in Experiment 2, the stimuli were plus signs formed by two segments and an intersection. In Experiments 1 and 2, observers were assigned to one of two experimental conditions: In one, all the distractors shared a simple feature (the color blue); in the other, distractors did not share that simple feature. In the first condition, search became more efficient with practice and observers' performance was characterized by a shallow reaction time (RT) x set size slope; in the second condition, observers' performance did not improve as much with practice. We propose that the differential effects of practice between these two experimental conditions can be explained in terms of distractor grouping induced by the shared color of the distractors. Experiment 3 showed that, with practice, a shallow RT x set size slope characterized observers' search for a color x color target among four different distractors that shared a common color. The present results contradict a main tenet of some current visual search models--namely, that within-dimension conjunctions cannot be searched in parallel, and question the validity of using RT x set size slope functions to distinguish between preattentive versus attentive search.     

Visual search with biological threat stimuli: Accuracy, reaction times, and heart rate changes.

Twenty-four participants were given a visual search task of deciding whether all the pictures in 3×3 search arrays contained a target picture from a deviant category, and heart rate was measured. The categories were snakes, spiders, flowers, and mushrooms. Shorter reaction times (RTs) were observed for fear-relevant (snake and spider) targets rather than for fear-irrelevant/neutral (flower and mushroom) targets. This difference was most pronounced for the participants presented with a gray-scale version of the search arrays. The 1st interbeat interval (IBI), after the search array onset, showed an effect of the target, whereas the 2nd IBI also showed an effect of the distractors. The results suggest that controlled processing of the task operates together with automatic processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)