Absence of a cross-modal “suffix effect” in short-term memory

Three experiments are reported involving the presentation of lists of either letters or digits for immediate serial recall. The main variable was the presence or absence of a suffix-prefix, an item (tick or cross) occurring at the end of the list which had to be copied before recall of the stimulus list. With auditory stimuli and an auditory suffix-prefix there was a large and selective increase in the number of errors on the last few serial positions—the typical “suffix effect”. The suffix effect was not found with auditory stimuli and a visual suffix-prefix nor with a visual stimulus and an auditory suffix-prefix. These results are interpreted as supporting a model for short-term memory proposed by Crowder and Morton (1969) in which it is suggested that with serial recall information concerning the final items following auditory presentation has a different, precategorical, origin from that concerning other items.     

Spatial modulation of repetition blindness and repetition deafness

When two identical visual items are presented in rapid succession, people often fail to report the second instance when trying to recall both (e.g., Kanwisher, 1987). We investigated whether this temporal processing deficit is modulated by the spatial separation between the repeated stimuli within both audition and vision. In Experiment 1, lists of one to three digits were rapidly presented from loudspeaker cones arranged in a semicircle around the participant. Recall accuracy was lower when repeated digits were presented from different positions rather than from the same position, as compared to unrepeated control pairs, demonstrating that auditory repetition deafness (RD) is modulated by the spatial displacement between repeated items. A similar spatial modulation of visual repetition blindness (RB) was reported when pairs of masked letters were presented visually from either the same or different positions arranged on a semicircle around fixation (Experiment 2). These results cannot easily be accounted for by the token individuation hypothesis of RB (Kanwisher, 1987; Park & Kanwisher, 1994) and instead support a recognition failure account (Hochhaus & Johnston, 1996; Luo & Caramazza, 1995, 1996).     

Stimulus factors and listening strategies in auditory memory: An experimental demonstration

Three experiments are reported in which digits spoken at different rates were recalled and monitored. In Experiment I, digits to be recalled were embedded in varying levels of noise. In Experiment II noise was presented only during the inter-digit intervals, either to the same or to the opposite ear as the digits. In Experiment III Ss monitored these sequences for a specified digit and reported its successor. Stimulus rate and signal-to-noise ratio affected perceptual processing time, as evidenced by the frequency and relative proportion of item and order errors. These stimulus factors induce listening strategies that influence the shape of the serial position curve and that persist after stimulus conditions are changed. The data are consistent with a two-stage processing model for the temporal course of speech perception and the nature of listening strategies.     

Two scenes or not two scenes: The effects of stimulus repetition and view-similarity on scene categorization from brief displays

Previous research suggests that understanding the gist of a scene relies on global structural cues that enable rapid scene categorization. This study used a repetition blindness (RB) paradigm to interrogate the nature of the scene representations used in such rapid categorization. When stimuli are repeated in a rapid serial visual presentation (RSVP) sequence (~10 items/sec), the second occurrence of the repeated item frequently goes unnoticed, a phenomenon that is attributed to a failure to consolidate two conscious episodes (tokens) for a repeatedly activated type. We tested whether RB occurs for different exemplars of the same scene category, which share conceptual and broad structural properties, as well as for identical and mirror-reflected repetitions of the same scene, which additionally share the same local visual details. Across 2 experiments, identical and mirror-image scenes consistently produced a repetition facilitation, rather than RB. There was no convincing evidence of either RB or repetition facilitation for different members of a scene category. These findings indicate that in the first 100–150 ms of processing scenes are represented in terms of local visual features, rather than more abstract category-general features, and that, unlike other kinds of stimuli (words or objects), scenes are not susceptible to token individuation failure.     

Repetition blindness under minimum memory load: Effects of spatial and temporal proximity and the encoding effectiveness of the first item

Repetition blindness (RB) refers to the reduced performance in reporting a repeated as opposed to a nonrepeated item in rapid serial visual presentation. In Experiment 1, we found RB for two-item stimuli in uncertain locations. The magnitude of RB decreased significantly with increases in interstimulus interval, but not with increases in spatial separation, indicating that RB is determined primarily by temporal factors. In Experiment 2, we found RB when subjects were required to report only the second of two successively presented items. The magnitude of RB increased with the duration of the first item, indicating that RB is determined by the encoding effectiveness of the first item. The results of this study collectively indicate that RB is not a memory or a sensory phenomenon, but rather a perceptual phenomenon occurring at the stage of identity encoding. The findings also undermine the arguments (Kanwisher, 1987) that have been offered in favor of the type-token binding failure hypothesis and indicate instead that type-node refractoriness may be the cause of RB.     

The role of transparency in perceptual grouping and pattern recognition.

The shortest stimulus exposure time for which transparency can be seen was examined. In the first experiment, overlapping digits were presented for 120 ms and the luminance in the overlapping regions was varied. Subjects reported, in separate blocks of trials, either the apparent transparency of the digits or the identity of the digits. When the luminance was set so that one set of digits appeared to be seen through the other, recognition of the digits was high. When the luminance in the overlapping regions did not produce impressions of transparency, digit recognition was low. In the second experiment, digit identification at several stimulus durations was compared between stimuli that had luminance that was valid for transparency and stimuli that had invalid luminance. Performance was found to be higher in the valid luminance condition than in the invalid condition after as little as 60 ms exposure duration. This result suggests that the impression of transparency requires only relatively short exposure durations.     

Recognition memory for tactile sequences.

In three experiments participants were required to compare the similarity in item order for two temporally separated sequences of tactile stimuli presented to the fingers of the hand. Between-sequence articulatory suppression but not tactile interference impaired recognition accuracy (Experiment 1), and the null effect of tactile interference was not due to the second tactile sequence overwriting the sensory record of the first sequence (Experiment 2). Experiment 3 showed that compared to a condition where the second sequence was presented in the tactile modality only, recognition was enhanced when the second sequence was seen presented either to the hand or on a diagrammatic representation of a hand. A final experiment showed that the effects of Experiment 1 were replicated when the underside of the forearm was used for stimulus presentation, suggesting that the data are not idiosyncratic to the first method of presentation. The pattern of results suggests memory for a sequence of tactile stimuli involves the deployment of strategies utilising a combination of verbal rehearsal and visuo-spatial recoding rather than relying solely on the retention of sensory traces. This is taken to reflect limitations in both the capacity and duration of tactile sensory memory.     

Perception of sequentially presented tactile point stimuli

Either two or three brief (10 msec) airjet stimuli were sequentially presented to any of the 24 interjoint regions of the fingers (thumbs excluded). The stimulus onset interval (SOI) ranged from zero (simultaneous presentation) through 200 msec. The S’s task in one part of the experiment was to report the positions stimulated in the order that the stimuli were presented; in a second part it was to rate the apparent motion produced by the stimulus sequence. While the ability of Ss to spatially localize the stimuli was a constant independent of SOI, their ability to temporally order the stimuli depended strongly on SOI. With two stimuli, these sequential errors decayed exponentially with SOI with a time constant of 26 msec. With three stimuli, however, both the sequential errors and equivalent temporal Urnen were more than twice as large as with two stimuli, indicating that the three-stimulus task is considerably more difficult than the two, and that the same simple temporal resolution model does not explain both cases. A model with a constant rate of information uptake, however, can explain both of these cases.     

重复刺激的末位优势效应

探讨在RSVP任务中重复刺激的呈现位置和报告方式对重复知盲效应的影响, 检验该研究提出的注意资源最优化假设和末位优势效应。实验1操作了刺激性质和重复刺激位置, 得出了刺激性质和重复刺激位置的交互效应; 实验2操作了刺激性质和情景信息, 结果是交互效应不显著; 实验3操作了刺激性质和报告方式, 出现了刺激性质和报告方式的交互效应。该结果表明: (1)由于注意资源分配的优化, 重复刺激有末位优势效应。(2)重复知盲的产生不是发生在知觉阶段, 而是发生在报告阶段。(3)注意资源分配最优化理论比建构/归因理论能更合理地解释重复知盲的发生。     

Does an instruction to forget enhance memory for other presented items?

In an item-method directed forgetting paradigm, participants were required to attend to one of two colored words presented on opposite sides of a central fixation stimulus; they were instructed to Remember or Forget the attended item. On a subsequent recognition test, the Attended words showed a typical directed forgetting effect with better recognition of Remember words than Forget words. Our interest was in the fate of the Unattended words. When the study display disappeared before the memory instruction, there was no effect of that instruction on unattended words; when the study display remained visible during presentation of the memory instruction, there was a reverse directed forgetting effect with better recognition of unattended words from Forget trials than from Remember trials. Incidental encoding of task-irrelevant stimuli occurs following presentation of a Forget instruction - but only when those task-irrelevant stimuli are still visible in the external environment.     

Two bs or not two Bs? A signal detection theory analysis of repetition blindness in a counting task

Stimulus repetition usually benefits performance. A notable exception is repetition blindness (RB), in which subjects fail to report a repeated stimulus in a rapid serial visual presentation. Theories differ in attributing RB to either perceptual encoding or memory retrieval and to impaired discrimination versus response bias. In the present study, subjects judged whether one or two letters were imbedded in sequences of digits. Unlike previous studies, false guesses of two unrepeated letters were distinguished from false guesses of two repeated letters. When repeated- and unrepeated-letter trials were randomly intermixed (Experiment 1), RB was entirely attributable to response bias. However, when they were separately blocked (Experiments 2 and 3), RB was manifested in discriminability (d'). The results support perceptual-encoding accounts of RB but indicate that effects on discriminability depend on subjects' processing strategies.     

Age-related associative deficits are absent with nonwords

Words and nonwords were used as stimuli to assess item and associative recognition memory performance in young and older adults. Participants were presented with pairs of items and then tested on both item memory (old/new items) and associative memory (intact/recombined pairs). For words, older participants performed worse than young participants on item and associative tests but to a greater extent on the latter. In contrast, for nonwords, older participants performed equally worse than young participants on item and associative tests. This is the first study to demonstrate that a manipulation of stimulus novelty can alter age-related associative deficits.     

Sublexical processing in visual recognition of Chinese characters: evidence from repetition blindness for subcharacter components

Repetition blindness (RB) refers to the failure to detect the second occurrence of a repeated item in rapid serial visual presentation (RSVP). In two experiments using RSVP, the ability to report two critical characters was found to be impaired when these two characters were identical (Experiment 1) or similar by sharing one repeated component (Experiment 2), as opposed to when they were different characters with no common components. RB for the whole character occurred when the exposure duration was more than 50 ms with one intervening character between the two critical characters (lag=1), whereas RB for subcharacter components was more evident at exposure durations shorter than 50 ms with no intervening character (lag=0). These results provide support for the model of sublexical processing in Chinese character recognition.     

A model for the time-order error in contrast discrimination

Trials in a temporal two-interval forced-choice discrimination experiment consist of two sequential intervals presenting stimuli that differ from one another as to magnitude along some continuum. The observer must report in which interval the stimulus had a larger magnitude. The standard difference model from signal detection theory analyses poses that order of presentation should not affect the results of the comparison, something known as the balance condition (J.-C. Falmagne, 1985, in Elements of Psychophysical Theory). But empirical data prove otherwise and consistently reveal what Fechner (1860/1966, in Elements of Psychophysics) called time-order errors, whereby the magnitude of the stimulus presented in one of the intervals is systematically underestimated relative to the other. Here we discuss sensory factors (temporary desensitization) and procedural glitches (short interstimulus or intertrial intervals and response bias) that might explain the time-order error, and we derive a formal model indicating how these factors make observed performance vary with presentation order despite a single underlying mechanism. Experimental results are also presented illustrating the conventional failure of the balance condition and testing the hypothesis that time-order errors result from contamination by the factors included in the model.     

Preferential processing of threatening facial expressions using the repetition blindness paradigm

Background: Neuroanatomical evidence suggests that the human brain has dedicated pathways to rapidly process threatening stimuli. This processing bias for threat was examined using the repetition blindness (RB) paradigm. RB (i.e., failure to report the second instance of an identical stimulus rapidly following the first) has been established for words, objects and faces but not, to date, facial expressions. Methods: 78 (Study 1) and 62 (Study 2) participants identified repeated and different, threatening and non-threatening emotional facial expressions in rapid serial visual presentation (RSVP) streams. Results: In Study 1, repeated facial expressions produced more RB than different expressions. RB was attenuated for threatening expressions. In Study 2, attenuation of RB for threatening expressions was replicated. Additionally, semantically related but non-identical threatening expressions reduced RB relative to non-threatening stimuli. Conclusions: These findings suggest that the threat bias is apparent in the temporal processing of facial expressions, and expands the RB paradigm by demonstrating that identical facial expressions are susceptible to the effect.     

Effects of Auditory/Visual and Lexical/Non-lexical Comparisons on Event-related Potentials in a Memory-scanning Task

A late parietal positivity (P3) and behavioural measures were studied during performance of a two-item memory-scanning task. Stimuli were digits presented as memorised items in one modality (auditory or visual) while the following probe, also a digit, was presented in the same or the other modality. In a separate set of experiments, P3 and behaviour were similarly studied using only visual stimuli that were either lexical (digits) or non-lexical (novel fonts with the same contours as the digits) to which subjects assigned numerical values. Reaction times (RTs) and P3 latencies were prolonged to non-lexical compared to lexical stimuli. Although RTs were longer to auditory than to visual stimuli, P3 latencies to memorised items were prolonged in response to visually compared to auditorily presented memorised items, and were further prolonged when preceding visual probes. P3 amplitudes were smaller to auditory than to visual stimuli, and were smaller for the second memorised item when lexical/non-lexical comparisons were involved. The most striking finding was scalp distribution variations indicating changes in relative contributions of brain structures involved in processing memorised items, according to the probes that followed. These findings are compatible, in general, with a phonological memorisation, but they suggest that the process is modified by memorising the item in the same terms as the expected probe that follows.     

Memory-conjunction errors: Miscombination of stored stimulus features can produce illusions of memory

We demonstrate that subjects will often claim to have previously seen a new stimulus if they have previously seen stimuli containing its component features. Memory for studied stimuli was measured using a "yes"/"no" recognition test. There were three types of test stimuli: target stimuli, which had been presented during study, conjunction stimuli, constructed by combining the features of separate study stimuli, and feature stimuli, in which studied stimulus features were combined with new, unstudied, features. For both nonsense words and faces, the subjects made many more false alarms for conjunction than for feature stimuli. Additional experiments demonstrated that the results were not due to physical similarity between study and test stimuli and that conjunction errors were much more common than feature errors in recall. The results demonstrate that features of stored stimuli maintain some independence in memory and can be incorrectly combined to produce recognition errors.     

Hemispheric differences in stimulus identification

Subjects were presented with either verbal (letters) or nonverbal (outline forms) stimuli to their left or right cerebral hemispheres. Verbal items presented with a lateral masking stimulus were identified more quickly and accurately when presented to the right hemisphere rather than to the left. When the letters were presented without a masking stimulus, weak hemispheric effects were obtained. Nonverbal forms demonstrated faster reaction time and fewer errors for right-hemisphere presentations under both masked and unmasked conditions. Retinal locus of the display item was also varied and produced faster responding with fewer errors when the stimulus was presented foveally rather than peripherally under all display conditions. These effects were attributed to the use of a manual response procedure that effectively reduced the ability of subjects to employ names for the stimulus objects.     

Task difficulty and visual similarity increase a distractor's effects on random shapes

Recognition of random shapes followed by a visual distractor is altered by the type of distractor and whether the distractor needs to be attended. Three experiments tested which characteristics modify a visual distractor's effect on random target shapes presented for 75 to 150 msec. Exp. 1 showed that increasing the number of digits to be remembered (1, 3, or 8) increased the effectiveness of digits as distractors. Exeir effect as visual distractors for random target shapes. Random shapes were highly effective as distractors, while pictures of faces or comples colored pictures had a relatively small effect. In Exp. 3 decreasing the presentation time for novel visual distractors decreased recognition of the distractors but not of random target shapes. However, adding a three-digit distractor after the novel visual distractor did decrease recognition of target shapes. Exps. 2 and 3 showed that the order of the recognition tests of the target and distracting stimuli altered target recognition if and only if subjects did know which was to be reported first. These experiments indicate that the effect of a visual distractor depends on both the extent to which it is allotted attention and its visual similarity to the target stimulus.     

The effect of emotional faces on eye movements and attention

Using a rapid serial visual presentation (RSVP) paradigm, response times to a previously ignored item occurring after a target were measured. Using this procedure, it was possible to plot the time course of inhibition following target selection. Results showed that post-target distractors produce negative priming for at least 270 ms after target presentation. It is suggested that stimuli presented immediately after a target may be inhibited in order to prevent temporal binding errors. The results are discussed in relation to two selective attention paradigms: negative priming and the attentional blink.