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.     

序列依赖效应——一种全新的“历史效应”

自2014年来, 研究者在视觉加工中发现一种全新的历史效应——序列依赖效应(当前刺激加工向先前刺激方向偏移的吸引性加工偏差)。近期研究发现：该效应广泛存在于视觉加工的各个层面(既包括朝向、空间位置、数量等低级特征, 也包括身份、吸引力、美感等高级属性); 其来源极为复杂(包括感觉编码、高级皮层的反馈调节、工作记忆、决策模板、感知与决策的级联等), 反映出不同层次的过往加工痕迹向当前认知的投射。针对该效应的典型特征、影响因素、认知与神经机制, 已涌现大量研究, 同时也存在严重争论, 亟待研究者深入探讨和厘清。     

刺激放置朝向对返回抑制的影响:一项ERPs研究

返回抑制(inhibition of return, IOR)是指个体对出现在先前提示位置上的刺激反应更慢的现象。尽管大量ERPs研究发现呈现在线索化和非线索化位置上的靶刺激诱发的ERPs在250-300ms处存在一个稳定的差异(Nd250),但这一差异的方向却并不一致。本研究采用事件相关电位技术(Event-related Potentials, ERPs),结合经典的线索-靶子范式,考察刺激放置的朝向是否会影响到IOR中Nd250效应的极性。结果显示虽然刺激放置朝向并未有影响到Nd250的极性,却对早期P1成分的线索化效应的地形图分布有着显著的影响。这表明1）过往ERPs研究中的Nd250效应极性的不一致并非源于刺激放置朝向的作用;2）刺激的放置朝向会导致早期线索化效应(P1)在地形分布上出现差异。     

Object-based control of attention is sensitive to recent experience

How is attention guided by past experience? In visual search, numerous studies have shown that recent trials influence responses to the current trial. Repeating features such as color, shape, or location of a target facilitates performance. Here we examine whether recent experience also modulates a more abstract dimension of attentional control, object-based and location-based control. Participants performed a cued target discrimination task with stimuli presented on 2 rectangles. Response times to targets appearing in an uncued location on a cued rectangle were faster than to targets on the uncued rectangle, demonstrating an object-based attentional benefit. We investigated the object-based benefit on the current trial contingent on the cue-target relationship on the previous trial. The object-based benefit was significant only when the cued object contained the target on the previous trial, not when the uncued object contained the target. This effect of recent experience was not due to either the repetition of spatial cue-target location or the repetition of the response, but to adaptation to contingencies in the environment. Our results suggest a unifying view of attentional control that spans the concrete dimensions of control (e.g., determining the relative importance of red vs. blue) to the abstract (determining the relative importance of objects vs. locations in space). Attention closely tracks the short time scale structure of the environment and automatically adapts to optimize performance to this structure.     

Exogenous attention influences visual short-term memory in infants

Two experiments examined the hypothesis that developing visual attentional mechanisms influence infants' Visual Short-Term Memory (VSTM) in the context of multiple items. Five- and 10-month-old infants (N = 76) received a change detection task in which arrays of three differently colored squares appeared and disappeared. On each trial one square changed color and one square was cued; sometimes the cued item was the changing item, and sometimes the changing item was not the cued item. Ten-month-old infants exhibited enhanced memory for the cued item when the cue was a spatial pre-cue (Experiment 1) and 5-month-old infants exhibited enhanced memory for the cued item when the cue was relative motion (Experiment 2). These results demonstrate for the first time that infants younger than 6 months can encode information in VSTM about individual items in multiple-object arrays, and that attention-directing cues influence both perceptual and VSTM encoding of stimuli in infants as in adults.     

刺激放置朝向对返回抑制的影响:一项ERPs研究

返回抑制(inhibition of return, IOR)是指个体对出现在先前提示位置上的刺激反应更慢的现象。尽管大量ERPs研究发现呈现在线索化和非线索化位置上的靶刺激诱发的ERPs在250-300ms处存在一个稳定的差异(Nd250),但这一差异的方向却并不一致。本研究采用事件相关电位技术(Event-related Potentials, ERPs),结合经典的线索-靶子范式,考察刺激放置的朝向是否会影响到IOR中Nd250效应的极性。结果显示虽然刺激放置朝向并未有影响到Nd250的极性,却对早期P1成分的线索化效应的地形图分布有着显著的影响。这表明1）过往ERPs研究中的Nd250效应极性的不一致并非源于刺激放置朝向的作用;2）刺激的放置朝向会导致早期线索化效应(P1)在地形分布上出现差异。     

试次历史对跨通道非空间返回抑制的影响

个体对刺激的反应不仅受刺激本身的影响, 还会受到先前刺激的影响, 表现为对当前试次中刺激的反应会受到前一试次的影响, 即试次历史。本研究采用“线索-中性线索-靶子”范式探讨前一试次有效性对跨通道的非空间返回抑制的影响。实验1通过连续两个试次间的线索有效性考察在跨通道非空间返回抑制中试次历史的影响。为了在跨通道非空间返回抑制中减小试次历史的影响, 实验2通过延长试次间时间间隔考察跨通道非空间返回抑制中试次历史的作用是否减小。结果发现, 前一试次线索无效时, 当前试次中的返回抑制效应量显著小于前一试次有效时, 这种影响会根据试次中线索和靶子通道的不同而不同。并且当延长试次间的时间间隔可以有效地减少前一试次对当前试次的影响。因此本研究表明, 试次历史能够对跨通道非空间返回抑制产生影响, 并且这种影响可以通过增大试次间时间间隔来减小。     

Sequence effects in a spatial cueing task: Endogenous orienting is sensitive to orienting in the preceding trial

In a spatial cueing paradigm it was investigated whether endogenous orienting is sensitive to orienting processes in the previous trial. Specifically, the effect of the previous cue direction, the previous trial type (valid, invalid, neutral, catch) and target alternation effects were studied. Strategic effects were shown as attentional costs and benefits were larger after a valid than after an invalid trial. Following catch trials, an overall response slowing was observed, but costs and benefits were unaffected. This was interpreted as a reduction in alertness and as support for the dissociation between spatial and temporal attentional mechanisms. Repetition of target position per se had no effect, but in neutral trials responses were slower to targets appearing at the location that was cued in the previous trial, independent of validity of the preceding trial. This suggests that long-term inhibition-of-return can occur between trials when attention is controlled endogenously.     

Eye movements in search in visual neglect

We report data on eye movements in a patient (MP) with unilateral visual neglect, in a task of searching a real-world scene. We demonstrate that MP missed some contralesional targets after fixating on them. On such “miss”; trials, MP's eye movements were similar to those on objects in target-absent trials trials, where MP was cued to search for a target that was not actually present. In addition, MP showed little evidence of memory for the locations of objects that remained across a trial, though poor memory fails to explain performance on trials where targets were fixated. We suggest that, in this case, neglect reflected the poor uptake of information from the contralesional side of space, so that even fixated targets sometimes failed to match a “template” held in his memory.     

Temporal reproductions are influenced by an internal reference: Explaining the Vierordt effect

Several findings from duration perception literature suggest that when making decisions about time, participants rely on an internal reference memory for time rather than merely on the current physical stimuli. According to a recent account, such an internal reference is formed by a continuous dynamic updating process that integrates duration information from previous trials and the current trial. In the present work, we show how such a dynamic mechanism can account for the classical yet unresolved Vierordt effect, which refers to the overestimation of relatively short and the underestimation of relatively long temporal intervals. We conducted an experiment to examine this and related predictions by means of a temporal reproduction task. Specifically, participants were presented with two successive time intervals — a standard s with constant duration and a comparison c with variable duration. Instead of performing a comparison judgment, however, the participants were subsequently cued to reproduce one of the two presented stimuli. Reproductions were affected not only by the temporal position of the to-be-reproduced stimulus, but also by the stimuli presented on earlier trials. These results support the notion of a dynamically updated internal reference underlying our judgments about the time elapsed, which might also be the basis of the Vierordt effect.     

Sequential effects in pigeon delayed matching-to-sample performance

Pigeons were tested in a three-alternative delayed matching-to-sample task in which second-choices were permitted following first-choice errors. Sequences of responses both within and between trials were examined in three experiments. The first experiment demonstrates that the sample information contained in first-choice errors is not sufficient to account for the observed pattern of second choices. This result implies that second-choices following first-choice errors are based on a second examination of the contents of working memory. Proactive interference was found in the second experiment in the form of a dependency, beyond that expected on the basis of trial independent response bias, of first-choices from one trial on the first-choice emitted on the previous trial. Samples from the previous trial were not found to exert a significant influence on later trials. The magnitude of the intertrial association (Experiment 3) did not depend on the duration of the intertrial interval. In contrast, longer intertrial intervals and longer sample durations did facilitate choice accuracy, by strengthening the association between current samples and choices. These results are incompatible with a trace-decay and competition model; they suggest strongly that multiple influences act simultaneously and independently to control delayed matching-to-sample responding. These multiple influences include memory for the choice occurring on the previous trial, memory for the sample, and general effects of trial spacing.     

Acquisition of information from rapidly presented verbal and nonverbal stimuli

Two experiments tested recognition memory for rapidly presented stimuli. In Experiment I 16 words were presented at exposure times ranging from 25 to 500 msec followed by a yes-no recognition test. The results showed a strong dependence of memory performance on both exposure time and serial position. In Experiment II 16 random forms were presented at exposure times ranging from 125 to 2000 msec followed by a yes-no recognition test. Results for random forms showed that memory performance was strongly dependent on exposure time but not on serial position. Taken together, the results of Experiments I and II suggest qualitative encoding differences between verbal vs nonverbal stimuli.     

Attentional effects on orientation judgements are dependent on memory consolidation processes

Are the effects of memory and attention on perception synergistic, antagonistic, or independent? Tested separately, memory and attention have been shown to affect the accuracy of orientation judgements. When multiple stimuli are presented sequentially versus simultaneously, error variance is reduced. When a target is validly cued, precision is increased. What if they are manipulated together? We combined memory and attention manipulations in an orientation judgement task to answer this question. Two circular gratings were presented sequentially or simultaneously. On some trials a brief luminance cue preceded the stimuli. Participants were cued to report the orientation of one of the two gratings by rotating a response grating. We replicated the finding that error variance is reduced on sequential trials. Critically, we found interacting effects of memory and attention. Valid cueing reduced the median, absolute error only when two stimuli appeared together and improved it to the level of performance on uncued sequential trials, whereas invalid cueing always increased error. This effect was not mediated by cue predictiveness; however, predictive cues reduced the standard deviation of the error distribution, whereas nonpredictive cues reduced “guessing”. Our results suggest that, when the demand on memory is greater than a single stimulus, attention is a bottom-up process that prioritizes stimuli for consolidation. Thus attention and memory are synergistic.     

Motion and position shifts induced by the double-drift stimulus are unaffected by attentional load

The double-drift stimulus produces a strong shift in apparent motion direction that generates large errors of perceived position. In this study, we tested the effect of attentional load on the perceptual estimates of motion direction and position for double-drift stimuli. In each trial, four objects appeared, one in each quadrant of a large screen, and they moved upward or downward on an angled trajectory. The target object whose direction or position was to be judged was either cued with a small arrow prior to object motion (low attentional load condition) or cued after the objects stopped moving and disappeared (high attentional load condition). In Experiment 1, these objects appeared 10° from the central fixation, and participants reported the perceived direction of the target’s trajectory after the stimulus disappeared by adjusting the direction of an arrow at the center of the response screen. In Experiment 2, the four double-drift objects could appear between 6 ° and 14° from the central fixation, and participants reported the location of the target object after its disappearance by moving the position of a small circle on the response screen. The errors in direction and position judgments showed little effect of the attentional manipulation—similar errors were seen in both experiments whether or not the participant knew which double-drift object would be tested. This suggests that orienting endogenous attention (i.e., by only attending to one object in the precued trials) does not interact with the strength of the motion or position shifts for the double-drift stimulus.     

Readout from iconic memory and selective spatial attention involve similar neural processes

Iconic memory and spatial attention are often considered separately, but they may have functional similarities. Here we provide functional magnetic resonance imaging evidence for some common underlying neural effects. Subjects judged three visual stimuli in one hemifield of a bilateral array comprising six stimuli. The relevant hemifield for partial report was indicated by an auditory cue, administered either before the visual array (precue, spatial attention) or shortly after the array (postcue, iconic memory). Pre- and postcues led to similar activity modulations in lateral occipital cortex contralateral to the cued side. This finding indicates that readout from iconic memory can have some neural effects similar to those of spatial attention. We also found common bilateral activation of a fronto-parietal network for postcue and precue trials. These neuroimaging data suggest that some common neural mechanisms underlie selective spatial attention and readout from iconic memory. Some differences were also found; compared with precues, postcues led to higher activity in the right middle frontal gyrus.     

Sequence effects of the involuntary and the voluntary components of symbolic cueing

The orienting of attention has been found to be influenced by the previous cueing status in a spatial-cueing paradigm. The explanation for this sequence effect remains uncertain. This study separated the involuntary and the voluntary components of arrow cueing by manipulating the predicted target locations. For example, a left arrow cue may have indicated that the target was more likely to appear at the up location. Therefore, three trial types were repeated or switched between trials: cued (targets appeared along the direction of the arrows), predicted (targets appeared at the locations predicted by the arrows), and unrelated (targets appeared at the other two locations, neither cued nor predicted). RTs of cued trials were found to be significantly facilitated after a previous cued trial; however, the same effect was not observed for predicted trials. The results suggest that significant sequence effects are induced only in the involuntary component of arrow cueing. The findings support the feature-integration hypothesis for the sequence effect of symbolic cueing.

     

Facilitating and inhibiting effects of priming and selection criteria in a sequence of dichotic listening trials

Competing models of attention make different predictions of how priming from recent stimulus processing could interact with intended selection. The present experiment examined the interaction between exogenous attention and endogenous priming across trial sequences. A sound cue directed attention to left, right or both sides before a dichotic syllable pair was presented. Participants were asked to report one syllable from each trial. Results showed that responses were slower on trials where one of the presented syllables had also been presented on the previous trial. Within these trials, the repeated syllable was selected less frequently, and the responses doing so were slower. Examined according to response choice on the preceding trial, syllables that had been ignored on the preceding trial tended to be ignored on the current trial (negative priming), while syllables that had been selected on the preceding trial tended to be selected on the current trial (positive priming). Responses that followed these selection biases were faster than responses that did not. Response selection was also influenced by the attention direction cue for the current trial, but not by the cue presented on the preceding trial. The results support an attentional model where traces from the preceding processing are retained, and current selection is biased to minimize cognitive conflict between recent and current processing. Negative priming appears to be due to after-effects of preceding processing, independently of the intentions behind that processing. The study accounts for positive and negative priming of dichotic listening sequences within an established, computationally viable biased competition framework.     

Tactile order memory: evidence for sequence learning phenomena found with other stimulus types

We examine serial order memory for sequences of tactile stimuli and investigate whether established characteristics of order memory, namely serial position effects, error distributions, and Hebb repetition learning, are observed with tactile memory. Visually obscured participants received six tactile stimulations: one to each of six fingers. At test, participants lifted the six fingers in the order of stimulation. For every third trial participants received the same order of stimulation (i.e. the Hebb sequence). Serial recall accuracy produced the canonical bowed serial position function found for immediate serial recall. In addition, recall for the Hebb sequence improved relative to the filler sequences, providing the first demonstration of the Hebb repetition effect with tactile stimuli. Analysis of errors revealed close similarities to that reported with verbal and visual stimuli. This experiment further generalises established features of order memory to tactile memory, supporting the utilisation of an analogous order memory mechanism across stimuli.     

The relation between memory and expectancy as revealed by percentage and sequence of reward investigations

There is growing agreement that to explain instrumental learning properly, one should emphasize memory as well as expectancy. I call this approachmemory-expectancy theory. Amsel’s (1992) frustration theory is one variety of memory-expectancy theory. Capaldi’s (1994) sequential theory is another. In this report, I examine in considerable detail the effects of percentage and sequence of reward on extinction following different levels of acquisition training. These extinction findings, taken together with certain serial learning acquisition findings, seem to support a novel version of memory-expectancy theory, one that in some respects is similar to and in some respects is different from that suggested by Amsel. First, on the basis of this analysis, we may reject two ideas: that animals remember only the prior reward event and that animals anticipate only the reward event contingent upon the current response. Second, the analysis supports three salient propositions of the present memory-expectancy approach. Memories of reward events may serve as conditioned stimuli for expectancies of reward events. On any current trial, the animal may remember each of the reward events associated with one or more prior trials. On any current trial, the animal may anticipate not only the current reward event, but also reward events contingent upon subsequent trials. Essentially, according to this model, the stimuli that elicit expectancies, as well as the expectancies themselves, may change progressively over a series of learning trials.     

A revised spatial serial learning and memory procedure using Corsi's Block-tapping apparatus

The purpose of this study was to use Corsi's Block Tapping Test as a spatial analog of Benton's Serial Digit Learning Test, using the cognitive neuroscience approach utilized in the California Verbal Learning Test. 60 normal participants, ages 19-52 years, were included and administered an 8-block sequence for 9 trials or until they recalled the entire sequence for 3 consecutive errorless trials. The score was the number of blocks tapped in the correct serial order. An interference trial was administered. Following a 10-min. delay, free recall of the original sequence, cued recall, and recognition measures were obtained. Retroactive interference was significant, but no proactive interference emerged. Scores showed a strong primacy effect. Most participants who learned the sequence to the criterion of three successive errorless trials recalled the sequence after the 10-min. delay. Scores on the cued recall and recognition trials tended to support their validity as less demanding retrieval tasks. The use of this spatial learning and memory procedure allows finer discriminations among nonverbal memory deficits and may facilitate direct comparisons with scores on verbal memory tasks such as Serial Digit Learning and the California Verbal Learning Test.