Evidence of anticipatory eye movements in the spatial Hebb repetition effect: Insights for modeling sequence learning.

In the present study, the authors offer a window onto the mechanisms that drive the Hebb repetition effect through the analysis of eye movement and recall performance. In a spatial serial recall task in which sequences of dots are to be remembered in order, when one particular series is repeated every 4 trials, memory performance markedly improves over repetitions. This is known as the Hebb repetition effect. Eye movement recorded during the presentation of the to-be-remembered (TBR) information revealed that for the repeated sequence, participants fixated the location of the next TBR location before the actual presentation of the dot. The extent to which a TBR location was anticipated increased over repetition and occurred only for post-initial positions of the repeated sequence. Eye movement–based rehearsal activity was related to recall performance but not to sequence learning. The findings provide further evidence of anticipatory behavior in sequence learning and place key constraints on modeling the Hebb repetition effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A category adjustment approach to memory for spatial location in natural scenes.

Memories for spatial locations often show systematic errors toward the central value of the surrounding region. This bias has been explained using a Bayesian model in which fine-grained and categorical information are combined (Huttenlocher, Hedges, & Duncan, 1991). However, experiments testing this model have largely used locations contained in simple geometric shapes. Use of this paradigm raises 2 issues. First, do results generalize to the complex natural world? Second, what types of information might be used to segment complex spaces into constituent categories? Experiment 1 addressed the 1st question by showing a bias toward prototypical values in memory for spatial locations in complex natural scenes. Experiment 2 addressed the 2nd question by manipulating the availability of basic visual cues (using color negatives) or of semantic information about the scene (using inverted images). Error patterns suggest that both perceptual and conceptual information are involved in segmentation. The possible neurological foundations of location memory of this kind are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interference effects in the memory for serially presented locations in clark's nutcrackers, Nucifraga columbiana.

The authors tested the spatial memory of serially presented locations in Clark's nutcrackers (Nucifraga columbiana). Birds were serially presented with locations in an open room. The authors buried a seed in a sand-filled cup at each location and then tested nutcrackers for their memory for each location in the list by using the cluster method. For each item in the list, the authors opened a cluster of 6 holes. Accuracy was measured by how many tries were required for the bird to find the correct location within each cluster. In Experiments 1 and 2, the authors presented 2 lists of locations and found evidence for proactive and retroactive interference. Nutcrackers made errors by visiting the interfering list of locations during recovery of the target list. This finding demonstrates that nutcrackers are susceptible to proactive and retroactive interference during the recall of spatial information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Turning simple span into complex span: Time for decay or interference from distractors?

We investigated the effects of the duration and type of to-be-articulated distractors during encoding of a verbal list into short-term memory (STM). Distractors and to-be-remembered items alternated during list presentation, as in the complex-span task that underlies much of working-memory research. According to an interference model of STM, known as serial order in a box (SOB; Farrell & Lewandowsky, 2002), additional repeated articulations of the same word between list items should cause minimal further disruption of encoding into STM even though the retention interval for early list items is increased. SOB also predicts that the articulation of several different distractor items should lead to much enhanced disruption if the distractor interval is increased. Those predictions were qualitatively confirmed in 4 experiments that found that it is the type of distractors, not their total duration, that determines the success of encoding a list into STM. The results pose a challenge to temporal models of complex-span performance, such as the time-based resource sharing model (Barrouillet, Bernardin, & Camos, 2004). The results add to a growing body of evidence that memory for the short term is not exclusively governed by purely temporal processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transitional Information in Spatial Serial Memory: Path Characteristics Affect Recall Performance.

This study examined the role of stimulus characteristics in a visuospatial order reconstruction task in which participants were required to recall the order of sequences of spatial locations. The complexity of the to-be-remembered sequences, as measured by path crossing, path length, and angles, was found to affect serial memory, in terms of both recall accuracy and response times. The results demonstrate that not all sequences are remembered equally and that spatial characteristics of the sequences constitute an important variable in the understanding of visuospatial serial memory. More important, the data suggest that spatial path represents transitional information and that, as is the case in verbal serial memory, transitional information is of critical importance in serial memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preserved Spatial Memory Over Brief Intervals in Older Adults.

Two studies compared young and older adults' memory for location information after brief intervals. Experiment 1 found that accuracy of intentional spatial memory for individual locations was similar in young and older participants for set sizes of 3 and 6. Both groups also encoded individual locations in relation to the larger configuration of locations. Experiment 2 showed that like young adults, older adults' latency to respond to a test probe in a letter working memory task was negatively influenced by spatial information that was irrelevant to the task. This interference effect indicated preserved incidental memory for spatial information in older adults. Together, these data suggest that initial encoding of spatial information for relatively small numbers of items is largely preserved in healthy older adults and that representations of spatial information persist over short intervals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distractor interference during smooth pursuit eye movements.

When 2 targets for pursuit eye movements move in different directions, the eye velocity follows the vector average (S. G. Lisberger & V. P. Ferrera, 1997). The present study investigates the mechanisms of target selection when observers are instructed to follow a predefined horizontal target and to ignore a moving distractor stimulus. Results show that at 140 ms after distractor onset, horizontal eye velocity is decreased by about 25%. Vertical eye velocity increases or decreases by 1°/s in the direction opposite from the distractor. This deviation varies in size with distractor direction, velocity, and contrast. The effect was present during the initiation and steady-state tracking phase of pursuit but only when the observer had prior information about target motion. Neither vector averaging nor winner-take-all models could predict the response to a moving to-be-ignored distractor during steady-state tracking of a predefined target. The contributions of perceptual mislocalization and spatial attention to the vertical deviation in pursuit are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Disruption of short-term memory by changing and deviant sounds: Support for a duplex-mechanism account of auditory distraction.

The disruption of short-term memory by to-be-ignored auditory sequences (the changing-state effect) has often been characterized as attentional capture by deviant events (deviation effect). However, the present study demonstrates that changing-state and deviation effects are functionally distinct forms of auditory distraction: The disruption of visual-verbal serial recall by changing-state speech was independent of the effect of a single deviant voice embedded within the speech (Experiment 1); a voice-deviation effect, but not a changing-state effect, was found on a missing-item task (Experiment 2); and a deviant voice repetition within the context of an alternating-voice irrelevant speech sequence disrupted serial recall (Experiment 3). The authors conclude that the changing-state effect is the result of a conflict between 2 seriation processes being applied concurrently to relevant and irrelevant material, whereas the deviation effect reflects a more general attention-capture process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Enhanced Memory for Negatively Emotionally Charged Pictures Without Selective Rumination.

Emotionally charged materials have been found to elicit higher levels of recall in many studies. However, the use of slow presentations and/or uncontrolled retention intervals may have allowed subjects to rehearse emotional materials preferentially. The authors presented a series of 5 pictures (1 emotionally charged) at a rate of 4 pictures per second, precluding selective rehearsal. In Experiment 1, subjects recalled the pictures immediately or after performing an arithmetic task for 20 s. In Experiment 2, the pictures were described as to-be-ignored distractors, and the memory test was unexpected. Stimulus emotionality greatly enhanced recall in all conditions. The speed of the presentations and the fact that enhancement did not spread to temporally adjacent items argues against some widely discussed mechanisms for emotional enhancement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impairment of memory for spatial context in schizophrenia.

A group of 33 patients with schizophrenia were compared with control participants using a spatial memory task in which words were presented on locations of a grid. In the first part of the experiment, recognition of target information (words) was tested. In the second, 2 tasks of spatial location (contextual information) were given involving different sets of words placed in different locations: A location memory task (determining which word was in a particular spatial location) explored an associative form of spatial memory, and a relocation task (determining where a particular word was located) explored an associative and a nonassociative form of spatial memory. Patients were more impaired with regard to the location memory task than to the target recognition and relocation tasks. The impairment was negatively correlated with Stroop task performance. The results suggest that schizophrenia is associated with a spatial context memory deficit, which could be due to defective associations between target and spatial information. This deficit seemed to be related to frontal dysfunction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Feature-based memory-driven attentional capture: Visual working memory content affects visual attention.

In 7 experiments, the authors explored whether visual attention (the ability to select relevant visual information) and visual working memory (the ability to retain relevant visual information) share the same content representations. The presence of singleton distractors interfered more strongly with a visual search task when it was accompanied by an additional memory task. Singleton distractors interfered even more when they were identical or related to the object held in memory, but only when it was difficult to verbalize the memory content. Furthermore, this content-specific interaction occurred for features that were relevant to the memory task but not for irrelevant features of the same object or for once-remembered objects that could be forgotten. Finally, memory-related distractors attracted more eye movements but did not result in longer fixations. The results demonstrate memory-driven attentional capture on the basis of content-specific representations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of spatial location in remembering and forgetting peripheral words.

This study examined whether spatial location mediates intentional forgetting of peripherally presented words. Using an item-method directed forgetting paradigm, words were presented in peripheral locations at study. A recognition test presented all words at either the same or a different location relative to study. Results showed that while recognition of Remember words was unaffected by test location, when Forget words were presented in the same location at test as at study, recognition accuracy was significantly greater than when presented in a different location. Experiment 2 showed that the speed to localize a previously studied word was faster when it was presented in the same rather than a different study-test location but that the magnitude of this spatial priming was unaffected by memory instruction. We suggest that the location of peripherally presented words is represented in memory and can aid the retrieval of poorly encoded words. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The time course of attentional and oculomotor capture reveals a common cause.

Eye movements are often misdirected toward a distractor when it appears abruptly, an effect known as oculomotor capture. Fundamental differences between eye movements and attention have led to questions about the relationship of oculomotor capture to the more general effect of sudden onsets on performance, known as attentional capture. This study explores that issue by examining the time course of eye movements and manual localization responses to targets in the presence of sudden-onset distractors. The results demonstrate that for both response types, the proportion of trials on which responses are erroneously directed to sudden onsets reflects the quality of information about the visual display at a given point in time. Oculomotor capture appears to be a specific instance of a more general attentional capture effect. Differences and similarities between the two types of capture can be explained by the critical idea that the quality of information about a visual display changes over time and that different response systems tend to access this information at different moments in time. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Concurrent working memory load can facilitate selective attention: Evidence for specialized load.

Load theory predicts that concurrent working memory load impairs selective attention and increases distractor interference (N. Lavie, A. Hirst, J. W. de Fockert, & E. Viding, see record 2004-17825-003). Here, the authors present new evidence that the type of concurrent working memory load determines whether load impairs selective attention or not. Working memory load was paired with a same/different matching task that required focusing on targets while ignoring distractors. When working memory items shared the same limited-capacity processing mechanisms with targets in the matching task, distractor interference increased. However, when working memory items shared processing with distractors in the matching task, distractor interference decreased, facilitating target selection. A specialized load account is proposed to describe the dissociable effects of working memory load on selective processing depending on whether the load overlaps with targets or with distractors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial and object working memory deficits in Parkinson's disease are due to impairment in different underlying processes.

Working memory maintenance processes for visual-spatial and visual-object information were evaluated in patients with Parkinson's disease (PD). PD patients and controls performed a working memory task with two conditions that differed only in the aspect of the stimuli that the participant was instructed to remember: their locations or shapes. Maintenance processes were investigated by measuring accuracy over 1-s, 5-s, and 10-s delays. Results indicated that patients were impaired in maintaining object information over the delay. In contrast, the patients showed impairment on the spatial condition only when the to-be-remembered stimulus was highly similar in location to the probe, but this impairment was equivalent across the delays, suggesting that this deficit was not due to maintenance impairment. These results suggest that deficits in working memory for spatial and object information are mediated by distinct cognitive processes in nondemented patients with PD and may differ in their pathophysiological basis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the locus of visual selection: Evidence from focused attention tasks.

Early and late selection models of attention disagree about whether visual objects are identified before or after selection, with recent evidence of interference from to-be-ignored stimuli favoring late selection over early selection accounts. However, these tests may not have permitted optimal attentional focusing. In 4 experiments subjects identified an attentionally cued target letter embedded among distractors. Only minimal effects of information appearing in to-be-ignored locations were observed. This striking efficiency of selection provides support for early selection theories and calls into question some late selection theories holding that stimuli throughout the display are immediately and fully identified prior to attentional selection. In order to explain the larger pattern of results across a variety of focused- and divided-attention paradigms, a hybrid model is advanced with a flexible locus for visual selection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Emotion-attention interactions in recognition memory for distractor faces.

Effective filtering of distractor information has been shown to be dependent on perceptual load. Given the salience of emotional information and the presence of emotion-attention interactions, we wanted to explore the recognition memory for emotional distractors especially as a function of focused attention and distributed attention by manipulating load and the spatial spread of attention. We performed two experiments to study emotion-attention interactions by measuring recognition memory performance for distractor neutral and emotional faces. Participants performed a color discrimination task (low-load) or letter identification task (high-load) with a letter string display in Experiment 1 and a high-load letter identification task with letters presented in a circular array in Experiment 2. The stimuli were presented against a distractor face background. The recognition memory results show that happy faces were recognized better than sad faces under conditions of less focused or distributed attention. When attention is more spatially focused, sad faces were recognized better than happy faces. The study provides evidence for emotion-attention interactions in which specific emotional information like sad or happy is associated with focused or distributed attention respectively. Distractor processing with emotional information also has implications for theories of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of visual working memory in attentive tracking of unique objects.

When tracking moving objects in space humans usually attend to the objects’ spatial locations and update this information over time. To what extent do surface features assist attentive tracking? In this study we asked participants to track identical or uniquely colored objects. Tracking was enhanced when objects were unique in color. The benefit was greater when the distance between distractors and targets was smaller, but was eliminated when the objects changed colors 1 to 4 times per second, even though at any instant they were always uniquely colored. In addition, tracking uniquely colored objects impaired a secondary color-memory task more than tracking identical objects, and holding several colors in working memory eliminated the advantage of tracking uniquely colored objects. Contrary to previous studies showing that feature information is poorly retained during tracking, these findings indicate that surface properties are stored in visual working memory to facilitate tracking performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An fMRI Study of Episodic Memory: Retrieval of Object, Spatial, and Temporal Information.

Sixteen participants viewed a videotaped tour of 4 houses that highlighted a series of objects and their spatial locations. Participants were tested for memory of object, spatial, and temporal-order information while undergoing functional magnetic resonance imaging. Preferential activation was observed in the right parahippocampal gyrus during the retrieval of spatial-location information. Retrieval of contextual information (spatial location and temporal order) was associated with activation in the right dorsolateral prefrontal cortex. In bilateral posterior parietal regions, greater activation was associated with processing of visual scenes regardless of the memory judgment. These findings support current theories positing roles for frontal and medial temporal regions during episodic retrieval and suggest a specific role for the hippocampal complex in the retrieval of spatial-location information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

When do additional distractors reduce the attentional blink?

When 2 targets are embedded in a rapid serial visual presentation stream of distractors, perception of the second target is impaired when the intertarget lag is relatively short (less than 500 ms). Stimuli concurrently presented with the stream can affect this phenomenon, which is called attentional blink (AB). Previous studies have yielded conflicting results concerning the direction of the effect of added distractors on the AB: Some studies report an increased AB, whereas others report a decreased AB. The present study explored the boundary conditions of the exaggeration–reduction effects of distractors on the AB and investigated underlying mechanisms by manipulating the spatial configuration, timing, and type of distractors. The results indicate that the magnitude of the AB deficit increased, regardless of the type of distractors, when spatial uncertainty of the target locations was involved. The reduction of the AB occurred at optimal presentation of distractors and disappeared when the second target was presented at a suprathreshold level. These results suggest that stochastic resonance or the center-surround attentional mechanism may contribute to the reduction effect of distractors on the AB deficit. (PsycINFO Database Record (c) 2010 APA, all rights reserved)