Partial Report Procedure Research Articles

Out with the old? The role of selective attention in retaining targets in partial report.

In the partial-report task, subjects are asked to report only a portion of the items presented. Selective attention chooses which objects to represent in short-term memory (STM) on the basis of their relevance. Because STM is limited in capacity, one must sometimes choose which objects are removed from memory in light of new relevant information. We tested the hypothesis that the choices among newly presented information and old information in STM involve the same process-that both are acts of selective attention. We tested this hypothesis using a two-display partial-report procedure. In this procedure, subjects had to select and retain relevant letters (targets) from two sequentially presented displays. If selection in perception and retention in STM are the same process, then irrelevant letters (distractors) in the second display, which demanded attention because of their similarity to the targets, should have decreased target report from the first display. This effect was not obtained in any of four experiments. Thus, choosing objects to keep in STM is not the same process as choosing new objects to bring into STM.

QPR: An adaptive partial-report procedure based on Bayesian inference.

Iconic memory is best assessed with the partial report procedure in which an array of letters appears briefly on the screen and a poststimulus cue directs the observer to report the identity of the cued letter(s). Typically, 6–8 cue delays or 600–800 trials are tested to measure the iconic memory decay function. Here we develop a quick partial report, or qPR, procedure based on a Bayesian adaptive framework to estimate the iconic memory decay function with much reduced testing time. The iconic memory decay function is characterized by an exponential function and a joint probability distribution of its three parameters. Starting with a prior of the parameters, the method selects the stimulus to maximize the expected information gain in the next test trial. It then updates the posterior probability distribution of the parameters based on the observer's response using Bayesian inference. The procedure is reiterated until either the total number of trials or the precision of the parameter estimates reaches a certain criterion. Simulation studies showed that only 100 trials were necessary to reach an average absolute bias of 0.026 and a precision of 0.070 (both in terms of probability correct). A psychophysical validation experiment showed that estimates of the iconic memory decay function obtained with 100 qPR trials exhibited good precision (the half width of the 68.2% credible interval = 0.055) and excellent agreement with those obtained with 1,600 trials of the conventional method of constant stimuli procedure (RMSE = 0.063). Quick partial-report relieves the data collection burden in characterizing iconic memory and makes it possible to assess iconic memory in clinical populations.

Effects of the number of objects and locations on attentional allocation and processing in a visual short-term memory task.

Using a partial report procedure, we tried to dissociate the effect of increasing the number of attended locations from that of increasing the number of objects (digits) appearing in these locations. Participants had to allocate their attention to different locations among a set of distractors (letters). After a delay of 500 ms they had to process either one, two, three or four digits appearing at one, two, three or four previewed locations. We found that the capacity of attentional allocation over locations decreased at three attended locations and also after the increase in the number of objects while attending to four locations. The same procedure was used in Experiment 2, except that digits were used as distractors to eliminate the possible attentional re-allocation bias towards targets during the processing phase. We introduced in Experiment 3 a color contrast between targets and distractors in order to facilitate their discrimination and to reduce the spatial configuration effect of locations. The results are in line with Experiment 1 findings and showed that the processing of multiple objects is constrained by two interacting difficulties. The first relies on resources distribution over the attended locations whereas the second relies on parallel encoding of objects.

Spatial eccentricity and temporal transition of split attentional foci

Various investigations have demonstrated that attentional focus is unitary, not splitable, over contiguous regions of space. However, others find that observers can split attentional foci concurrently over noncontiguous regions concurrently (e.g., Awh & Pashler, 2000). Key differences among studies remain unclear. We manipulated the spatial eccentricity of targets and explored temporal transition of attentional foci using Awh and Pashler’s (2000) partial report procedure. We also tested whether individual differences in working memory capacity affect the style of deploying attentional foci. Literature shows that individuals with high working memory capacity were able to simultaneously allocate their attention to noncontiguous regions. This leads to the prediction that working memory capacity contributes to differences in the style of deployment of attentional focus/foci. In the present study, prior to the onset of a search display consisted of nontargets (letters) and two targets (digits), two cues appeared at noncontiguous locations either horizontally or vertically. These cues indicated target locations in 80% of the trials. Cues and targets were separated by an SOA (50ms or 750ms) to probe the development of an attentional split, if any, over time. Results demonstrated a split of attention: target identification accuracy was higher at noncontiguous locations relative to those at the intervening uncued locations. This is consistent with results of Awh and Pasher (2000), with the exception that no cueing effect was obtained with vertical cues for short SOAs (50ms). No effect of working memory capacity was found on the split of attention. These results suggest that attentional split develops over time and space regardless of individual differences in working memory capacity. Meeting abstract presented at VSS 2012

Tactile short-term memory for stimuli presented on the fingertips and across the rest of the body surface

The aim of this study was to investigate the extent to which tactile information that is unavailable for full conscious report can be accessed using partial-report procedures. In Experiment 1, participants reported the total number of tactile stimuli (up to six) presented simultaneously to their fingertips (numerosity judgment task). In another condition, after being presented with the tactile display, they had to detect whether or not the position indicated by a (visual or tactile) probe had previously contained a tactile stimulus (partial-report task). Participants correctly reported up to three stimuli in the numerosity judgment task, but their performance was far better in the partial-report task: Up to six stimuli were perceived at the shortest target-probe intervals. A similar pattern of results was observed when the participants performed a concurrent articulatory suppression task (Exp. 2). The results of a final experiment revealed that performance in the partial-report task was overall better for stimuli presented on the fingertips than for stimuli presented across the rest of the body surface. These results demonstrate that tactile information that is unavailable for report in a numerosity task can nevertheless sometimes still be accessed when a partial-report procedure is used instead.

Effects of Viewing Time, Fixations, and Viewing Strategies on Visual Memory for Briefly Presented Natural Objects

We investigated the impact of viewing time and fixations on visual memory for briefly presented natural objects. Participants saw a display of eight natural objects arranged in a circle and used a partial report procedure to assign one object to the position it previously occupied during stimulus presentation. At the longest viewing time of 7,000 ms or 10 fixations, memory performance was significantly higher than at the shorter times. This increase was accompanied by a primacy effect, suggesting a contribution of another memory component-for example, visual long-term memory (VLTM). We found a very limited beneficial effect of fixations on objects; fixated objects were only remembered better at the shortest viewing times. Our results revealed an intriguing difference between the use of a blocked versus an interleaved experimental design. When trial length was predictable, in the blocked design, target fixation durations increased with longer viewing times. When trial length was unpredictable, fixation durations stayed the same for all viewing lengths. Memory performance was not affected by this design manipulation, thus also supporting the idea that the number and duration of fixations are not closely coupled to memory performance.

Iconic Decay in Schizophrenia

Working memory impairment is considered a core deficit in schizophrenia, but the precise nature of this deficit has not been determined. Multiple lines of evidence implicate deficits at the encoding stage. During encoding, information is held in a precategorical sensory store termed iconic memory, a literal image of the stimulus with high capacity but rapid decay. Pathologically increased iconic decay could reduce the number of items that can be transferred into working memory before the information is lost and could thus contribute to the working memory deficit seen in the illness. The current study used a partial report procedure to test the hypothesis that patients with schizophrenia (n = 37) display faster iconic memory decay than matched healthy control participants (n = 28). Six letters, arranged in a circle, were presented for 50 ms. Following a variable delay of 0-1000 ms, a central arrow cue indicated the item to be reported. In both patients and control subjects, recall accuracy decreased with increasing cue delay, reflecting decay of the iconic representation of the stimulus array. Patients displayed impaired memory performance across all cue delays, consistent with an impairment in working memory, but the rate of iconic memory decay did not differ between patients and controls. This provides clear evidence against faster loss of iconic memory representations in schizophrenia, ruling out iconic decay as an underlying source of the working memory impairment in this population. Thus, iconic decay rate can be added to a growing list of unimpaired cognitive building blocks in schizophrenia.

Short term memory for tactile stimuli

Research has shown that unreported information stored in rapidly decaying visual representations may be accessed more accurately using partial report than using full report procedures (e.g., [Sperling, G., 1960. The information available in brief visual presentations. Psychological Monographs, 74, 1–29.]). In the 3 experiments reported here, we investigated whether unreported information regarding the actual number of tactile stimuli presented in parallel across the body surface can be accessed using a partial report procedure. In Experiment 1, participants had to report the total number of stimuli in a tactile display composed of up to 6 stimuli presented across their body (numerosity task), or else to detect whether or not a tactile stimulus had previously been presented in a position indicated by a visual probe given at a variable delay after offset of a tactile display (i.e., partial report). The results showed that participants correctly reported up to 3 stimuli in the numerosity judgment task, but their performance was significantly better than chance when up to 5 stimuli were presented in the partial report task. This result shows that short-lasting tactile representations can be accessed using partial report procedures similar to those used previously in visual studies. Experiment 2 showed that the duration of these representations (or the time available to consciously access them) depends on the number of stimuli presented in the display (the greater the number of stimuli that are presented, the faster their representation decays). Finally, the results of a third experiment showed that the differences in performance between the numerosity judgment and partial report tasks could not be explained solely in terms of any difference in task difficulty.

Eye movements and scene perception: memory for things observed.

In this study, we examined the characteristics of on-line scene representations, using a partial-report procedure. Subjects inspected a simple scene containing seven objects for 1, 3, 5, 9, or 15 fixations; shortly after scene offset, a marker cued one scene location for report. Consistent with previous research, the results indicated that scene representations are relatively sparse; even after 15 fixations on a scene, the subjects remembered the position/identity pairings for only about 78% of the objects in the scene, or the equivalent of about five objects-worth of information. Report of the last three objects that were foveated and of the object about to be foveated was very accurate, however, suggesting that recently attended information in a scene is represented quite well. Information about the scene appeared to accumulate over multiple fixations, but the capacity of the on-line scene representation appeared to be limited to about five items. Implications for recent theories of scene representation are discussed.

Evidence for split attentional foci.

A partial report procedure was used to test the ability of observers to split attention over noncontiguous locations. Observers reported the identity of 2 targets that appeared within a 5 x 5 stimulus array, and cues (validity = 80%) informed them of the 2 most likely target locations. On invalid trials, 1 of the targets appeared directly in between the cued locations. Experiments 1, 1a, and 2 showed a strong accuracy advantage at cued locations compared with intervening ones. This effect was larger when the cues were arranged horizontally rather than vertically. Experiment 3 suggests that this effect of cue orientation reflects an advantage for processing targets that appear in different hemifields. Experiments 4 and 4a suggest that the primary mechanism supporting the flexible deployment of spatial attention is the suppression of interference from stimuli at unattended locations.

Eye Movements, Attention and Trans-saccadic Memory

The eyes make rapid, saccadic movements from point to point in space several times each second. It is generally assumed that some mental representation of the visual environment is maintained across eye movements in a trans-saccadic memory. We examined the role of attention in the encoding of information into trans-saccadic memory using a partial report procedure. A letter array was presented in one fixation, then a bar marker probed report of one array position after a saccade was made to a new location. Accuracy was high for positions that subjects had been told to attend to, but it was also high for positions near the saccade target, even if subjects had been instructed to attend elsewhere. These results indicate that attention determines what information is encoded into trans-saccadic memory and hence remembered across eye movements. Because attention automatically precedes the eyes to the saccade target location, information near the saccade target is likely to be encoded. The results are discussed in terms of VAM, the neurocognitive model of visual attention proposed by Schneider (1995).

Memory for position and identity across eye movements.

A «transsaccadic» partial report procedure was used to measure memory for position and identity information across saccades. Delaying the partial-report cue after the eye movement had little effect on report accuracy. Mask presentation hindered recall only at the shortest delay. Accuracy was much higher when the letter array contained 6 letters than when it contained 10 letters. Intra-array errors were much more frequent than extra-array errors. These results suggest that memory across eye movements decays slowly, has a limited capacity, is maskable for a brief time, and retains identity information better than position information

A Microgenetic Study of the Müller-Lyer Illusion

In two experiments a decomposed Müller-Lyer pattern was used to measure the time course of the illusion. A partial report procedure was used to prevent the subjects from focusing only on parts of the pattern and to maximize visual processing. The Müller-Lyer figure was decomposed into two parts, its angles and its line. A configuration of three pairs of angles, each corresponding to a row in the usual partial report arrangement, was used. A line that did or did not fit the gap was shown with a variable delay (interstimulus interval, ISI). By this procedure the relevant row (line gap) was cued. The subject had to decide whether the line fitted or was too short/long. Two exposure times for the angles were used, 50 or 200 ms in one experiment and 50 or 500 ms in the other. The result of the first experiment, with outward-pointing fins, was a stable illusion for all values of ISI (25-400 ms) and all exposure times, with one significant exception: exposure for 50 ms with an ISI of 50 ms yielded an illusion peak. It was shown that this was not caused by a reduction in length-discrimination performance. In the second experiment, with inward-pointing fins, no such peak occurred. There was only a tendency for the illusion to vanish with zero ISI. The results are discussed with respect to 'global to local' theories of visual processing.

Effects of repetition on short-term retention of order information.

Two experiments examined the effects of repetition on the short-term retention of order information. A partial report procedure was coupled with the distractor paradigm to vary which one of two 4-letter sequences was tested after a digit-filled retention interval. Repeatedly presenting the stimulus but not its testing did not increase recall, but recall did increase when both presentation and testing were repeated. Recall was also improved by precues that informed subjects in advance which sequence was to be recalled. The perturbation model of Estes (1972; Lee & Estes, 1981) was able to account for the qualitative and quantitative aspects of the results by making an explicit distinction between two types of rehearsal: the reactivation process, which corresponds to a passive, automatic rehearsal process; and an active, conscious rehearsal process that crystallizes the memory structure and makes perturbations less likely. Language: en

Effects of repetition on short-term retention of order information.

Two experiments examined the effects of repetition on the short-term retention of order information. A partial report procedure was coupled with the distractor paradigm to vary which one of two 4-letter sequences was tested after a digit-filled retention interval. Repeatedly presenting the stimulus but not its testing did not increase recall, but recall did increase when both presentation and testing were repeated. Recall was also improved by precues that informed subjects in advance which sequence was to be recalled. The perturbation model of Estes (1972; Lee & Estes, 1981) was able to account for the qualitative and quantitative aspects of the results by making an explicit distinction between two types of rehearsal: the reactivation process, which corresponds to a passive, automatic rehearsal process; and an active, conscious rehearsal process that crystallizes the memory structure and makes perturbations less likely.

Iconic memory ? an artifact of perceptual reconstruction processes?

Two experiments, using a partial vs. whole report procedure to isolate ‘iconic’ from short-term memory loss, are reported. In the first experiment 10 Ss had to judge the difference between two line lengths in a display of three pairs of lines (in rows). Results showed no significant variation in d' with cue delay in spite of a medium overall performance, and in contrast to preliminary partial/whole report experiments. To counter the possibility that the short-term memory load was too small in this experiment, a second experiment was performed with displays containing nine instead of three pairs, i.e., three pairs per row. Equivalence of performance for all conditions was about the same as before. This was true for both hit- and false-alarm rates. The results are interpreted as evidence against the view of ‘iconic’ memory as a high capacity store containing a lot of information. An alternative ‘reconstructive’ theory is put forward to explain both conventional ‘iconic’ loss and our results. According to this account, partial report measures processed material rather than reflecting an ‘iconic’ store of uninterpreted ‘sensory’ events. Some consequences of this model are discussed in the context of some weak effects in our data; and suggestions are put forward for further investigation of visual processing.

Partial Report and Other Sampling Procedures Overestimate the Duration of Iconic Memory

In three experiments, subjects estimated the duration of a brief visual image (iconic memory) either directly by adjusting onset of a click to offset of the visual image, or indirectly with a Sperling partial report (sampling) procedure. The results indicated that partial report and other sampling procedures may reflect other brief phenomena along with iconic memory. First, the partial report procedure yields a greater estimate of the duration of iconic memory than the more direct click method. Second, the partial report estimate of the duration of iconic memory is affected if the subject is required to simultaneously retain a list of distractor items (memory load), while the click method estimate of the duration of iconic memory is not affected by a memory load. Finally, another sampling procedure based on visual cuing yields different estimates of the duration of iconic memory depending on how many items are cued. It was concluded that partial report and other sampling procedures overestimate the duration of iconic memory.

The tachistoscopic recognition of letters under whole and partial report procedures as related to intelligence.

Investigations of the short-term memory task performance of retarded individuals have indicated that these individuals demonstrate a deficit in the mechanisms necessary for the acquisition, storage and/or retrieval of information. The present study examined the tachistoscopic letter recognition task performance of retarded and non-retarded individuals under a partial report and a whole report procedure. The results revealed that the retarded subjects did significantly more poorly relative to the non-retarded subjects under both procedures. The data were interpreted as indicating that the retarded subjects were inefficient in their strategy to make the simultaneous imput task manageable. Further, the data provided no support for the suggestion that a visual-to-auditory encoding process exists between iconic and short-term memory.

Motion information in iconic memory

Motion perception was investigated in two experiments using Sperling's partial report procedure. In Experiment 1, subjects were presented with 8 moving squares; at array offset an arrow cued subjects to locate all squares moving in the direction of the arrow. The partial report was found to be superior to the whole report and this was taken as evidence for the existence, in iconic memory, of information about the direction of motion. The second experiment revealed only a minor decay in this superiority with the indicator delayed up to 1 sec. The importance of optical transformations in vision was stressed and it was argued that information processing models need pay greater attention to them.

Components of the laterality effect in letter recognition: asymmetries in iconic storage.

A partial report procedure and a backward masking paradigm were employed to explore lateral asymmetries in components of letter recognition. Stimulus displays were displaced off-centre into the left visual field (LVF) or the right visual field (RVF). Visual field differences in the effect of a delayed backward mask indicated an RVF superiority in the rate of read-out or encoding. Comparison of masked and unmasked full report also yielded estimates of iconic persistence. The persistence of these peripheral displays was surprisingly brief, although it was significantly longer in the LVF (57 ms) than in the RVF (34 ms). Precueing by colour and by location produced a larger partial report advantage in the RVF, reflecting a superiority in selective sampling. With postcueing no partial report effect was obtained at any delay, and this failure was attributed to the briefness of the iconic persistence.