The effect of repetition on iconic memory

The present experiment examined the influence of repetition on iconic memory using the Sperling (1960) procedure. It was assumed that the whole-report procedure would estimate only information available from a somewhat more permanent memory system than the icon, while the partial report would estimate both that information and the information available in the icon. The difference between the whole and partial report was assumed to measure information available only in the icon. Across a series of 160 displays one particular display occurred half the time (80 repetitions). The results indicated that the repetition influenced recall from the more permanent memory system assessed by whole report, but had no influence on the information available from the icon (partial report minus whole report).     

The effects of memory load and the contrast of the rod signal on partial report superiority in a Sperling task

Subjects participated in a Sperling task. The independent variables included delay of report cue, dark background field vs. a light background field intense enough to nearly saturate the rod system (duration of rod icon), and whether or not subjects were required to retain a list of letters or words (memory load) while performing in the Sperling task. Partial report superiority is normally taken as an indication of iconic memory. However, the main result was that memory load, which presumably does not affect the duration of the icon, increased partial report superiority. The effect of luminance of the background field was to reduce the partial report superiority. The results show that the existence of a partial report superiority and/or a decaying partial report curve does not necessarily imply the existence of an icon or visual storage.     

Iconic memory and central processing capacity

Three experiments were conducted to assess whether or not iconic memory is influenced by demands placed upon central processing capacity. In Experiment 1 S was required to store material in short-term memory while performing an iconic memory task. In Experiments 2 and 3 S performed an auditory classification task concurrently with iconic storage. The three experiments did not reveal any significant impairment of iconic memory as a function of performing a subsidiary task. Similarly, performance on the subsidiary tasks did not suffer as a result of the concurrent iconic memory task.     

Iconic memory and visible persistence

There are three senses in which a visual stimulus may be said to persist psychologically for some time after its physical offset. First, neural activity in the visual system evoked by the stimulus may continue after stimulus offset (“neural persistence”). Second, the stimulus may continue to be visible for some time after its offset (“visible persistence”). Finally, information about visual properties of the stimulus may continue to be available to an observer for some time after stimulus offset (“informational persistence”). These three forms of visual persistence are widely assumed to reflect a single underlying process: a decaying visual trace that (1) consists of afteractivity in the visual system, (2) is visible, and (3) is the source of visual information in experiments on decaying visual memory. It is argued here that this assumption is incorrect. Studies of visible persistence are reviewed; seven different techniques that have been used for investigating visible persistence are identified, and it is pointed out that numerous studies using a variety of techniques have demonstrated two fundamental properties of visible persistence: theinverse duration effect (the longer a stimulus lasts, the shorter is its persistence after stimulus offset) and theinverse intensity effect (the more intense the stimulus, the briefer its persistence). Only when stimuli are so intense as to produce afterimages do these two effects fail to occur. Work on neural persistences is briefly reviewed; such persistences exist at the photoreceptor level and at various stages in the visual pathways. It is proposed that visible persistence depends upon both of these types of neural persistence; furthermore, there must be an additional neural locus, since a purely stereoscopic (and hence cortical) form of visible persistence exists. It is argued that informational persistence is defined by the use of the partial report methods introduced by Averbach and Coriell (1961) and Sperling (1960), and the term “iconic memory” is used to describe this form of persistence. Several studies of the effects of stimulus duration and stimulus intensity upon the duration of iconic memory have been carried out. Their results demonstrate that the duration of iconic memory is not inversely related to stimulus duration or stimulus intensity. It follows that informational persistence or iconic memory cannot be identified with visible persistence, since they have fundamentally different properties. One implication of this claim that one cannot investigate iconic memory by tasks that require the subject to make phenomenological judgments about the duration of a visual display. In other words, the so-called “direct methods” for studying iconic memory do not provide information about iconic memory. Another implication is that iconic memory is not intimately tied to processes going on in the visual system (as visible persistence is); provided a stimulus is adequately legible, its physical parameters have little influence upon its iconic memory. The paper concludes by pointing out that there exists an alternative to the usual view of iconic memory as a precategorical sensory buffer. According to this alternative, iconic memory is post-categorical, occurring subsequent to stimulus identification. Here, stimulus identification is considered to be a rapid automatic process which does not require buffer storage, but which provides no information about episodic properties of a visual stimulus. Information about these physical stimulus properties must, in some way, be temporarily attached to a representation of the stimulus in semantic memory; and it is this temporarily attached physical information which constitutes iconic memory.     

Limited capacity for contour curvature in iconic memory

We measured the difference threshold for contour curvature in iconic memory by using the cued discrimination method. The study stimulus consisting of 2 to 6 curved contours was briefly presented in the fovea, followed by two lines as cues. Subjects discriminated the curvature of two cued curves. The cue delays were 0 msec. and 300 msec. in Exps. 1 and 2, respectively, and 50 msec. before the study offset in Exp. 3. Analysis of data from Exps. 1 and 2 showed that the Weber fraction rose monotonically with the increase in set size. Clear set-size effects indicate that iconic memory has a limited capacity. Moreover, clear set-size effect in Exp. 3 indicates that perception itself has a limited capacity. Larger set-size effects in Exp. 1 than in Exp. 3 suggest that iconic memory after perceptual process has limited capacity. These properties of iconic memory at threshold level are contradictory to the traditional view that iconic memory has a high capacity both at suprathreshold and categorical levels.     

Read-out of emotional information from iconic memory: the longevity of threatening stimuli

Previous research has shown that emotional stimuli are more likely than neutral stimuli to be selected by attention, indicating that the processing of emotional information is prioritized. In this study, we examined whether the emotional significance of stimuli influences visual processing already at the level of transient storage of incoming information in iconic memory, before attentional selection takes place. We used a typical iconic memory task in which the delay of a poststimulus cue, indicating which of several visual stimuli has to be reported, was varied. Performance decreased rapidly with increasing cue delay, reflecting the fast decay of information stored in iconic memory. However, although neutral stimulus information and emotional stimulus information were initially equally likely to enter iconic memory, the subsequent decay of the initially stored information was slowed for threatening stimuli, a result indicating that fear-relevant information has prolonged availability for read-out from iconic memory. This finding provides the first evidence that emotional significance already facilitates stimulus processing at the stage of iconic memory.     

Spatiotopic and retinotopic components of iconic memory

Summary Recently, there has been considerable interest in whether information in iconic memory is stored in retinotopic or spatiotopic coordinates. The present experiment examined the issue using a masking paradigm. In one set of conditions, subjects maintained fixation while a row of four letters appeared for 19 ms, centered about three degrees to the right of fixation. After a 153 ms ISI, the letters were followed by a blank field (no mask), a mask in the same position as the letters, or a mask displaced three degrees to the right of the letters. In a second set of conditions, the stimuli were the same but subjects were asked to shift fixation from the fixation point to the middle of the letter row during the interval between the letters and the mask. Subjects' eye movements were monitored in all conditions. Accuracy of report for the letters was lowered only with the mask over the letters with the no-eye-movement conditions and in both masking conditions with the eye movements. The results suggest that the icon includes two components, one that is retinotopic and one that is spatiotopic.     

Voluntary eyeblinks disrupt iconic memory

In the present research, we investigated whether eyeblinks interfere with cognitive processing. In Experiment 1, the participants performed a partial-report iconic memory task in which a letter array was presented for 106 msec, followed 50, 150, or 750 msec later by a tone that cued recall of onerow of the array. At a cue delay of 50 msec between array offset and cue onset, letter report accuracy was lower when the participants blinked following array presentation than under no-blink conditions; the participants made more mislocation errors under blink conditions. This result suggests that blinking interferes with the binding of object identity and object position in iconic memory. Experiment 2 demonstrated that interference due to blinks was not due merely to changes in light intensity. Experiments 3 and 4 demonstrated that other motor responses did not interfere with iconic memory. We propose a new phenomenon, cognitive blink suppression, in which blinking inhibits cognitive processing. This phenomenon may be due to neural interference. Blinks reduce activation in area V1, which may interfere with the representation of information in iconic memory.     

In defence of iconic memory

According to a model of visual information-processing which originated with Sperling (1960), and which currently enjoys wide acceptance, the contents of brief alphanumeric displays are initially held in a high-capacity fast-decay visual-information store (“iconic memory”). Some of these items are subsequently transferred to a more durable form of storage; the remaining non-transferred items are lost. Observers can select which items are to be transferred on the basis of physical characteristics of the items (such as colour, location, size, shape or brightness).

This model has recently been attacked by Holding (1970, 1971, 1972, 1973), sometimes by claiming that iconic memory does not exist, and at other times by claiming that transfer from iconic memory cannot be selectively controlled by the observer. We argue in this paper that Holding's criticisms are incorrect, and that, even if they were correct, the experiment we report would not be open to objections he has raised concerning previous studies of iconic memory. Despite this, evidence fully supporting the orthodox model was obtained, and we therefore conclude that this model remains tenable.     

Visual attribute modulates the time course of iconic memory decay

Studies on iconic memory demonstrate that rich information from a visual scene quickly becomes unavailable with the passage of time. The decay rate of iconic memory refers to the dynamics of memory availability. The present study investigated the iconic memory decay of different stimulus attributes that comprised an object. Specifically, in Experiment 1, participants were presented with eight coloured numbers (e.g., red 4) and required to remember only one attribute, either colour or number, over different blocks of trials. The participants then reported the cued attribute in which the cue Stimulus Onset Asynchrony (SOA) from the memory array onset was varied (0, 100, 200, 300, 500, and 1000?ms). We found that numerical information became unavailable more quickly than colour information, despite the fact that the memory accuracies at 0 and 1000?ms SOAs were comparable between the two attributes. In Experiment 2, we replicated the finding that a numerical representation was lost more quickly than a colour representation when visual masks followed the target stimulus. These results suggest that the various visual attributes comprising an object are lost over time at different rates in iconic memory. We discuss this finding in relation to how perceptual representation is transferred to the capacity-limited visual working memory.     

Always look on the broad side of life: happiness increases the breadth of sensory memory

Research has shown that positive affect increases the breadth of information processing at several higher stages of information processing, such as attentional selection or knowledge activation. In the present study, we examined whether these affective influences are already present at the level of transiently storing incoming information in sensory memory, before attentional selection takes place. After inducing neutral, happy, or sad affect, participants performed an iconic memory task which measures visual sensory memory. In all conditions, iconic memory performance rapidly decreased with increasing delay between stimulus presentation and test, indicating that affect did not influence the decay of iconic memory. However, positive affect increased the amount of incoming information stored in iconic memory. In particular, our results showed that this occurs due to an elimination of the spatial bias typically observed in iconic memory. Whereas performance did not differ at positions where observers in the neutral and negative conditions showed the highest performance, positive affect enhanced performance at all positions where observers in the neutral and negative conditions were relatively "blind." These findings demonstrate that affect influences the breadth of information processing already at earliest processing stages, suggesting that affect may produce an even more fundamental shift in information processing than previously believed.     

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.     

Iconic memory for natural scenes: Evidence using a modified change-detection procedure

ABSTRACT

Change blindness for the contents of natural scenes suggests that only items that are attended while the scene is still visible are stored, leading some to characterize our visual experiences as sparse. Experiments on iconic memory for arrays of discrete symbols or objects, however, indicate observers have access to more visual information for at least several hundred milliseconds at offset of a display. In the experiment presented here, we demonstrate an iconic memory for complex natural or real-world scenes. Using a modified change detection task in which to-be changed objects are cued at offset of the scene, we show that more information from a natural scene is briefly stored than change blindness predicts and more than is contained in visual short-term memory. In our experiment, a cue appearing 0, 300, or 1000?msec after offset of the pre-change scene or at onset of the second scene presentation (a Post Cue) directed attention to the location of a possible change. Compared to a no-cue condition, subjects were significantly better at detecting changes and identifying what changed in the cue condition, with the cue having a diminishing effect as a function of time and no effect when its onset coincided with that of the second scene presentation. The results suggest that an iconic memory of a natural scene exists for at least 1000?msec after scene offset, from which subjects can access the identity of items in the pre-change scene. This implies that change blindness underestimates the amount of information available to the visual system from a brief glance of a natural scene.     

形象度对图标内隐记忆和外显记忆的影响

记忆心理学领域大量研究证实了内隐记忆和外显记忆的ERP分离,且内隐记忆相比外显记忆在记忆容量、保持时间及稳定性上均有优势。实验记录了15名被试在内隐记忆任务与外显记忆任务中形象图标和抽象图标的行为及ERP数据。结果表明:内隐记忆中,形象图标的行为和300～500ms顶区差异波的启动量均显著高于抽象图标。外显记忆中,形象图标的外显记忆正确率显著高于抽象图标,而反应时无显著差异; 300～500ms额区的差异波,形象图标显著负向于抽象图标,而500～800ms顶区的晚成分差异波两者无显著差异。研究结果表明,形象图标在浅加工下进行无意识记忆具有明显的优势。形象图标与抽象图标在图形化界面语言的使用中一直存在争论,通过实验在行为指标与脑电生理指标上提供了量化证据。     

Capacity, duration, and position effects in visual memory following a successive field procedure

This study considered the efficacy of a Successive Field procedure in revealing properties of iconic memory. 8 subjects were required to identify differences between sequentially presented stimulus and target arrays of letters. While results were broadly in line with previous estimates of the capacity and duration of iconic storage, there was also evidence that identification of target letters depended on their position in the array.     

Fragile visual short-term memory is an object-based and location-specific store

Fragile visual short-term memory (FM) is a recently discovered form of visual short-term memory. Evidence suggests that it provides rich and high-capacity storage, like iconic memory, yet it exists, without interference, almost as long as visual working memory. In the present study, we sought to unveil the functional underpinnings of this memory storage. We found that FM is only completely erased when the new visual scene appears at the same location and consists of the same objects as the to-be-recalled information. This result has two important implications: First, it shows that FM is an object- and location-specific store, and second, it suggests that FM might be used in everyday life when the presentation of visual information is appropriately designed.     

Do masks terminate the icon?

Iconic memory is operationally defined by part-report experiments (Sperling, 1960). If a mask is presented after the target, the mask is thought to be superposed on the target in the iconic representation, or to displace it from the representation. But could a cue presented after a pattern mask still allow selection within the target array? A target array of letters was followed by a checkerboard mask. We compared two target-mask interstimulus intervals (ISIs; 0 and 100 ms), and six cue delays. At ISI = 0 ms, performance was at chance, for part report and whole report. At ISI = 100 ms, with the shortest cue delay, observers demonstrated a part-report advantage of 25-30%. As cue delay increased the part-report advantage decreased. These results are inconsistent with an iconic memory that is automatically displaced or overwritten by new information. We consider two alternatives: a second-stage store, which represents letters in terms of their high-level features and which the mask cannot penetrate, or a four-dimensional store that preserves separately the representations of the target and its aftercoming mask. We discuss the implications of our results for studies that use backward masking to "terminate the icon".     

A model of visual spatio-temporal memory: The icon revisited

With a minimal set of assumptions resulting from considerations about the perception of temporal structure, we argue for the existence of a spatio-temporal memory established by the mapping of time into simultaneous physical properties. The important point of this model is the distinction between external, physical time and the internal representation of time. An immediate consequence of such a structure is the emergence of properties usually associated with the concept of iconic memory or informational persistence. Some of these properties may hence be regarded as epiphenomena produced by the testing of a spatio-temporal system with tachistoscopic spatial stimuli. The model can explain properties of the immediate memory span, the lack of effect of exposure duration on tachistoscopic report, the partial-report superiority, the decay of iconic memory, and effects of a backward mask. It does not only avoid the incompatibility problems of the frozen-image concept in dynamic vision, but also provides an adequate basis for the processing of time-varying scenes.     

Some neglected contributions of Wilhelm Wundt to the psychology of memory

Wilhelm Wundt, whose name is rarely associated with the scientific study of memory, conducted a number of memory experiments that appear to have escaped the awareness of modern cognitive psychologists. Aspects of Wundt's system are reviewed, particularly with respect to his experimental work on memory. Wundt investigated phenomena that would fall under the modern headings of iconic memory, short-term memory, and the enactment and generation effects, but this research has been neglected. Revisiting the Wundtian perspective may provide insight into some of the reasons behind the historical course of memory research and in general into the progress of science in psychology.     

The effect of a subsidiary task on iconic memory

Memory & Cognition - Using a subsidiary task technique, Doest and Turvey (1971) concluded that iconic memory was independent of the central processing system. However, they did not control the...