Visual marking across eye blinks

Visual search for a conjunction target can be made efficient by presenting one initial set of distractors as a preview, prior to the onset of the other items in the search display Watson & Humphreys (Psychological Review 104:90–122, 1997). However, this “preview advantage” is lost if the initial items are offset for a brief period before onsetting again with the search display Kunar, Humphreys, & Smith (Psychological Science 14:181–185, 2003). Researchers have long disputed whether the preview advantage reflects a process of internally coding and suppressing the old items or of the onset of the new items capturing attention Donk & Theeuwes (Perception & Psychophysics 63:891–900, 2001). In this study, we assessed whether an internally driven blink (in which participants close their eyes) acts in the same manner as an external blink produced by offsetting and then onsetting the preview. In the novel blink conditions, participants searched feature, conjunction, and preview displays after being cued to blink their eyes. The search displays were presented during the eye blink, and so were immediately available once participants opened their eyes. Having participants make an eye blink generally slowed search but had no effect on the search slopes. In contrast, imposing an externally driven blink disrupted preview search. The data indicated that visual attention can compensate for internally driven blinks, and this does not lead to the loss of the representations of distractors across time. Moreover, efficient preview search occurred when the search items had no abrupt onsets, demonstrating that onsets of new search items are not critical for the preview benefit.     

Task probability and report of feature information: What you know about what you ‘see’ depends on what you expect to need

We investigated the influence of dimensional set on report of object feature information using an immediate memory probe task. Participants viewed displays containing up to 36 coloured geometric shapes which were presented for several hundred milliseconds before one item was abruptly occluded by a probe. A cue presented simultaneously with the probe instructed participants to report either about the colour or shape of the probe item. A dimensional set towards the colour or shape of the presented items was induced by manipulating task probability — the relative probability with which the two feature dimensions required report. This was done across two participant groups: One group was given trials where there was a higher report probability of colour, the other a higher report probability of shape. Two experiments showed that features were reported most accurately when they were of high task probability, though in both cases the effect was largely driven by the colour dimension. Importantly the task probability effect did not interact with display set size. This is interpreted as tentative evidence that this manipulation influences feature processing in a global manner and at a stage prior to visual short term memory.     

Spontaneous eye blinks during creative task correlate with divergent processing

Creativity consists of divergent and convergent thinking, with both related to individual eye blinks at rest. To assess underlying mechanisms between eye blinks and traditional creativity tasks, we investigated the relationship between creativity performance and eye blinks at rest and during tasks. Participants performed an alternative uses and remote association task while eye blinks were recorded. Results showed that the relationship between eye blinks at rest and creativity performance was compatible with those of previous research. Interestingly, we found that the generation of ideas increased as a function of eye blink number during the alternative uses task. On the other hand, during the remote association task, accuracy was independent of eye blink number during the task, but response time increased with it. Moreover, eye blink changes in participants who responded quickly during the remote association task were different depending on their resting state eye blinks; that is, participants with many eye blinks during rest showed little increasing eye blinks and achieved solutions quickly. Positive correlations between eye blinks during creative tasks and yielding ideas on the alternative uses task and response time on the remote association task suggest that eye blinks during creativity tasks relate to divergent thinking processes such as conceptual reorganization.     

Items on the left are better remembered

Neurologically intact individuals show a spatial processing bias in perception tasks, specifically showing a bias towards the left in bisecting lines. We present evidence for a novel finding that a leftwards bias occurs in short-term memory for recently presented arbitrary bindings of visual features. Three experiments are reported, two of which involve a total of over 60,000 participants with a small number of trials for each. Experiment 3 involved a larger number of trials for each of 144 participants. Participants reproduced from immediate memory arrays of shape–colour–location bindings. In all three experiments, significantly more errors were observed in reproduction of items presented on the right of the array than on the left. Results could not be accounted for by perceptual errors, or by order of presentation or order of reproduction. Findings suggest that items presented on the left are better remembered, indicating a spatial asymmetry in forming or retrieving feature bindings in visual short-term memory.     

Active versus passive maintenance of visual nonverbal memory

Forgetting over the short term has challenged researchers for more than a century, largely because of the difficulty of controlling what goes on within the memory retention interval. But the “recent-negative-probe” procedure offers a valuable paradigm, by examining the influences of (presumably) unattended memoranda from prior trials. Here we used a recent-probe task to investigate forgetting for visual nonverbal short-term memory. The target stimuli (two visually presented abstract shapes) on a trial were followed after a retention interval by a probe, and participants indicated whether the probe matched one of the target items. Proactive interference, and hence memory for old trial probes, was observed, whereby participants were slowed in rejecting a nonmatching probe on the current trial that nevertheless matched a target item on the previous trial (a recent-negative probe). The attraction of the paradigm is that, by uncovering proactive influences of past-trial probe stimuli, it can be argued that active maintenance in memory of those probes is unlikely. In two experiments, we recorded such proactive interference of prior-trial items over a range of interstimulus (ISI) and intertrial (ITI) intervals (between 1 and 6 s, respectively). Consistent with a proposed two-process memory conception (the active–passive memory model, or APM), actively maintained memories on current trials decayed, but passively “maintained,” or unattended, visual memories of stimuli on past trials did not.     

Eye movements during change detection: implications for search constraints, memory limitations, and scanning strategies

Search, memory, and strategy constraints on change detection were analyzed in terms of oculomotor variables. Observers viewed a repeating sequence of three displays (Scene 1-->Mask-->Scene 2-->Mask...) and indicated the presence-absence of a changing object between Scenes 1 and 2. Scenes depicted real-world objects arranged on a surface. Manipulations included set size (one, three, or nine items) and the orientation of the changing objects (similar or different). Eye movements increased with the number of potentially changing objects in the scene, with this set size effect suggesting a relationship between change detection and search. A preferential fixation analysis determined that memory constraints are better described by the operation comparing the pre- and postchange objects than as a capacity limitation, and a scanpath analysis revealed a change detection strategy relying on the peripheral encoding and comparison of display items. These findings support a signal-in-noise interpretation of change detection in which the signal varies with the similarity of the changing objects and the noise is determined by the distractor objects and scene background.     

Auditory List Memory in Rhesus Monkeys

Auditory memory of 2 rhesus monkeys was tested in a serial probe recognition task. Lists of four environmental or natural sounds were followed by a retention interval and a test. The test matched one of the list items on half of the trials. The retention interval was varied across sessions. Six experiments showed similar results and changes in the serial position function. At short retention intervals, there was good memory for first list items (primacy effect) and poor memory for last list items. At intermediate retention intervals, memory improved for last list items (recency effect). At long retention intervals (20 s and 30 s), the recency effect was strong, and the primacy effect had dissipated. These auditory primacy and recency effects and their changes with retention interval were opposite to those for visual memory. Implications for processes and mechanisms of memory are discussed.     

视觉工作记忆中特征绑定关系的记忆机制

弱客体理论认为, 视觉工作记忆系统是由众多特征存储的子系统组成, 不同纬度的特征独立存储在相应的有限容量的子系统中, 相互之间不会竞争记忆资源。而对于特征之间绑定关系的记忆存在不同的观点。一种观点认为绑定关系的记忆需要注意维持, 因此绑定关系的记忆会占用到特征记忆的资源; 另一种观点认为绑定关系的记忆是自动发生的, 不需要注意的维持。本实验的目的是探究特征绑定关系的记忆是否是自动发生的。在实验中, 我们设计了两种任务, 一种任务是只记忆颜色, 另一种任务是记忆颜色跟位置及其之间的绑定关系, 并测试分析视觉工作记忆相关的ERP成分CDA。结果发现两种任务条件下的CDA波幅之间没有显著差异, 说明视觉工作记忆中的特征绑定是自动发生的。     

Overwriting of phonemic features in serial recall

We tested two explanations of the phonological similarity effect in verbal short-term memory: The confusion hypothesis assumes that serial positions of similar items are confused. The overwriting hypothesis states that similar items share feature representations, which are overwritten. Participants memorised a phonologically dissimilar list of CVC-trigrams (Experiment 1) or words (Experiment 2 and 3) for serial recall. In the retention interval they read aloud other items. The material of the distractor task jointly overlapped one item of the memory list. The recall of this item was impaired, and the effect was not based on intrusions from the distractor task alone. The results provide evidence for feature overwriting as one potential mechanism contributing to the phonological similarity effect.     

An attentional blink for nontargets?

In a typical attentional blink experiment, viewers try to detect two target items among distractors in a Rapid Serial Visual Presentation (RSVP): processing of the first target impairs participants' ability to recall a subsequent target at short stimulus onset asynchronies (SOAs). However, little is known about whether target detection interferes with memory for nontarget items. To answer this question, in two experiments, we employed a novel dual-task procedure: participants searched for a word target (e.g., "a four-footed animal") and then were tested for recognition of nontarget words. Detection of the target word, which was present on half the trials, produced a standard attentional blink effect on memory for nontarget words, with lag 1 sparing followed by an attentional blink at longer lags. This result shows that target processing has a generalized effect on processing of later events, not only other targets.     

Visual short-term memory operates more efficiently on boundary features than on surface features

A change detection task was used to estimate the visual short-term memory storage capacity for either the orientation or the size of objects. On each trial, several,objects were briefly presented, followed by a blank interval and then by a second display of objects that either was identical to the first display or had a single object that was different (the object changed either orientation or size, in separate experiments). The task was to indicate whether the two displays were the same or different, and the number of objects remembered was estimated from the percent correct on this task. Storage capacity for a feature was nearly twice as large when that feature was defined by the object boundary, rather than by the surface texture of the object. This dramatic difference in storage capacity suggests that a particular feature (e.g., right tilted or small) is not stored in memory with an invariant abstract code. Instead, there appear to be different codes for the boundary and surface features of objects, and memory operates on boundary features more efficiently than it operates on surface features.     

Overt is no better than covert when rehearsing visuo-spatial information in working memory

In the present study, we examined whether eye movements facilitate retention of visuo-spatial information in working memory. In two experiments, participants memorised the sequence of the spatial locations of six digits across a retention interval. In some conditions, participants were free to move their eyes during the retention interval, but in others they either were required to remain fixated or were instructed to move their eyes exclusively to a selection of the memorised locations. Memory performance was no better when participants were free to move their eyes during the memory interval than when they fixated a single location. Furthermore, the results demonstrated a primacy effect in the eye movement behaviour that corresponded with the memory performance. We conclude that overt eye movements do not provide a benefit over covert attention for rehearsing visuo-spatial information in working memory.     

Remembering left-right orientation of pictures

In a study of recognition memory for pictures, we observed an asymmetry in classifying test items as "same" versus "different" in left-right orientation: Identical copies of previously viewed items were classified more accurately than left-right reversals of those items. Response bias could not explain this asymmetry, and, moreover, correct "same" and "different" classifications were independently manipulable: Whereas repetition of input pictures (one vs. two presentations) affected primarily correct "same" classifications, retention interval (3 hr vs. 1 week) affected primarily correct "different" classifications. In addition, repetition but not retention interval affected judgments that previously seen pictures (both identical and reversed) were "old". These and additional findings supported a dual-process hypothesis that links "same" classifications to high familiarity, and "different" classifications to conscious sampling of images of previously viewed pictures.     

Time-dependent forgetting in visual short-term memory

ABSTRACT

Whether visual short-term memory can be lost over an unfilled delay, in line with time-dependent forgetting, is controversial and prior work has yielded mixed results. The present study explored time-dependent forgetting in visual short-term memory in relation to other factors. In three experiments, participants compared single target and probe objects over a 2 s or 10 s retention interval. The objects across trials were either similar or dissimilar (Experiment 1) and had to be remembered in the presence of an additional distractor (Experiment 2) or under conditions where the amount of time separating trials varied (Experiment 3). In all experiments, the retention interval manipulation made the biggest contribution to performance, with accuracy decreasing as the retention interval was lengthened from 2 s to 10 s. These results pose problems for interference and temporal distinctiveness models of memory but are compatible with temporal forgetting mechanisms such as decay.     

Selective weighting of action-related feature dimensions in visual working memory

Planning an action primes feature dimensions that are relevant for that particular action, increasing the impact of these dimensions on perceptual processing. Here, we investigated whether action planning also affects the short-term maintenance of visual information. In a combined memory and movement task, participants were to memorize items defined by size or color while preparing either a grasping or a pointing movement. Whereas size is a relevant feature dimension for grasping, color can be used to localize the goal object and guide a pointing movement. The results showed that memory for items defined by size was better during the preparation of a grasping movement than during the preparation of a pointing movement. Conversely, memory for color tended to be better when a pointing movement rather than a grasping movement was being planned. This pattern was not only observed when the memory task was embedded within the preparation period of the movement, but also when the movement to be performed was only indicated during the retention interval of the memory task. These findings reveal that a weighting of information in visual working memory according to action relevance can even be implemented at the representational level during maintenance, demonstrating that our actions continue to influence visual processing beyond the perceptual stage.     

Capturing and evaluating blinks from video-based eyetrackers

Blinks are related to several emotional states, and the present report describes a simple, reliable way to measure blinks from the video stream of an eye obtained during eyetracking, where the source of the eye video is a video camera attached to a head-mounted eyetracker. Computer vision techniques are employed to determine the moments that a blink starts and ends, for the purpose of calculating blink frequency and duration. The video is first processed to show blocks of eyelid and pupil movements, and is then analyzed for blink starts and ends. The moment of a blink start is reported when the eyelid starts to move quickly, exceeding a predetermined threshold. The end of a blink arises when the pupil size increases by less than a separate threshold. We observed several different blink patterns from different subjects, and our algorithm was designed to work for all of these patterns. We evaluated our algorithm by manually measuring the true blinks of five different subjects while they were eyetracked. To test the sensitivity and specificity of the algorithm, we employed a series of threshold values to plot the receiver operating characteristic curves. Using the best thresholds, we achieved excellent sensitivity (>90 %) and specificity (>99 %) over the five subjects. Potential applications of this research include real-time, nonintrusive, continuous and automated measurements of mental workload and other emotional states related to blink rates and durations.     

Change detection and occlusion modes in road-traffic scenarios

Change blindness phenomena are widely known in cognitive science, but their relation to driving is not quite clear. We report a study where subjects viewed colour video stills of natural traffic while eye movements were recorded. A change could occur randomly in three different occlusion modes—blinks, blanks and saccades—or during a fixation (as control condition). These changes could be either relevant or irrelevant with respect to the traffic safety. We used deletions as well as insertions of objects. All occlusion modes were equivalent concerning detection rate and reaction time, deviating from the control condition only. The detection of relevant changes was both more likely and faster than that of irrelevant ones, particularly for relevant insertions, which approached the base line level. Even in this case, it took about 180 ms longer to react to changes when they occurred during a saccade, blink or blank. In a second study, relevant insertions and the blank occlusion were used in a driving simulator environment. We found a surprising effect in the dynamic setting: an advantage in change detection rate and time with blanks compared to the control condition. Change detection was also good during blinks, but not in saccades. Possible explanation of these effects and their practical implications are discussed.     

The attentional blink reflects retrieval competition among multiple rapid serial visual presentation items: tests of an interference model

When people respond to a target (T1) in a rapid serial visual presentation stream, their perception of a subsequent target (T2) is impaired if the intertarget stimulus onset asynchrony is between about 100 and 500 ms. Three experiments supported the interference model's (K. L. Shapiro, J. E. Raymond, & K. M. Arnell, 1994) claim that this attentional blink reflects competition for retrieval among multiple items in visual short-term memory. Experiments 1 and 2 revealed that items appearing during the blink are named as T2 on an above-chance proportion of trials when T2 must be identified. Experiment 3 demonstrated that both the size of the blink and sensitivity to T2 reflected the number of items competing for retrieval as T2; such competition, moreover, occurred at a conceptual or categorical level rather than at a purely visual one. The relationship between the interference and alternative models of the attentional blink is discussed.     

Attention is required for maintenance of feature binding in visual working memory

Working memory and attention are intimately connected. However, understanding the relationship between the two is challenging. Currently, there is an important controversy about whether objects in working memory are maintained automatically or require resources that are also deployed for visual or auditory attention. Here we investigated the effects of loading attention resources on precision of visual working memory, specifically on correct maintenance of feature-bound objects, using a dual-task paradigm. Participants were presented with a memory array and were asked to remember either direction of motion of random dot kinematograms of different colour, or orientation of coloured bars. During the maintenance period, they performed a secondary visual or auditory task, with varying levels of load. Following a retention period, they adjusted a coloured probe to match either the motion direction or orientation of stimuli with the same colour in the memory array. This allowed us to examine the effects of an attention-demanding task performed during maintenance on precision of recall on the concurrent working memory task. Systematic increase in attention load during maintenance resulted in a significant decrease in overall working memory performance. Changes in overall performance were specifically accompanied by an increase in feature misbinding errors: erroneous reporting of nontarget motion or orientation. Thus in trials where attention resources were taxed, participants were more likely to respond with nontarget values rather than simply making random responses. Our findings suggest that resources used during attention-demanding visual or auditory tasks also contribute to maintaining feature-bound representations in visual working memory—but not necessarily other aspects of working memory.     

The eye movement measure of memory and its relationship with explicit measures

This study examined whether the eye movement can be used to measure memory of past events and its relationship with the explicit measures. In Experiment 1, after studying a list of Chinese characters, the participants received a recognition memory test. For each trial the participants had to indicate, among one studied character and two nonstudied homonyms, which character they had studied. Participants’ eye movements were monitored while they viewed the three-character test display. Both the time-course and response-locked measures showed that participants viewed the studied character longer than the nonstudied character regardless of their explicit response. Experiment 2 used a wagering task to assess participants’ conscious awareness and found that wagering points predicted viewing time for the target better than the recognition accuracy did. These findings suggest that the effect of memory on viewing time occurs automatically and is weakly associated with subsequent conscious awareness of the studied event.