Perceptual centres for Dutch digits

In two experiments, analogous to those reported by Marcus (1976) with English words and subjects, we determined the psychological moment of occurrence (p-centre) of Dutch digit names. In the first experiment we determined the p-centres for the digits 1 through 10 and compared the empirical results with values calculated from the formula that Marcus defines over the acoustic characteristics of stimulus words. We found good agreement between empirical and predicted values. In a second experiment we studied the effect of cycle time and repeated measurement on perceptual centres. The results confirm the independence of the p-centre phenomenon from practice and periodicity. A comparison of ‘identical’ and ‘non-identical’ stimulus pairs shows that larger variances are associated with the former condition.     

Short-term consolidation of individual identities leads to Lag-1 sparing

A rapid serial visual presentation (RSVP) technique was used to investigate the role of the nature of processing carried out on targets in the Lag-1 sparing phenomenon. Lag-1 sparing refers to a higher accuracy in the task associated with the 2nd target when the 2 targets are immediately successive in the RSVP stream relative to when there are 1 or 2 intervening items between the targets. In 5 experiments, 0, 1, or 2 digits were embedded with equal probability in RSVP streams of letter distractors. In 4 of the experiments, subjects identified the digits in some blocks of trials, and they counted the number of presented digits in other blocks. In a 5th experiment, the counting task was replaced with a digit-sum task. The most interesting results were those from trials with 2 digits. Lag-1 sparing was always evident when the task involved the explicit identification of the digits. In addition, Lag-1 sparing was evident when subjects were required to sum 2 digits or to count digits of a prespecified parity subclass (e.g., count only even digits). In striking contrast, Lag-1 sparing was absent when subjects were required to count the digits independent of their parity subclass. These results suggest that the occurrence of Lag-1 sparing depends on the type of mental representation that must be generated on the basis of target information.     

Perception of signals presented in the periphery of the visual field

Two experiments were performed which tested the type of information that can be extracted from the periphery of the visual field, i.e. content information or position information. In both studies two digits were compared, one presented at the left and one at the right of the subject's meridian, seperated by a binocular visual angle, comprising either an eye-field (45°) or a head-field display (100°). In the first experiment the right signal was presented in separate blocks of either degraded or undegraded digits. In the case of undegraded digits, processing efficiency was better in the eye-field than in the head-field. With degraded digits this eye-field advantage was significantly smaller, but did not altogether disappear, suggesting that information about both the content and the position of digits in the periphery is acquired in the eye-field as opposed to the head-field. In the second experiment degraded and undegraded digits occured randomly within the same block of trials. This was done to investigate whether peripheral information is acquired automatically or through controlled processing. The results indicate a small eye-field advantage, about equal for both degraded and undegraded digits. This supports the controlled processing hypothesis, at least with regard to the acquisition of content information from the periphery.     

Sequential effects in number comparison

The modular framework of number processing (e.g., S. Dehaene & R. Akhavein, 1995) was applied to study sequential trial-to-trial effects in a number comparison task. In Experiment 1, numbers were always presented as digits. Responses were faster when the same number was repeated, but this effect was additive with the numerical distance effect. In Experiment 2, numbers were presented either as digits or as words. The authors found significant effects of repeating (a) the same physical stimulus, (b) the same number but in a different notation, and (c) the same notation but a different number. Again, all 3 effects were additive with the numerical distance effect. The authors' results provide strong evidence against accounts according to which, on stimulus repetition trials, the comparison stage is bypassed (as proposed by S. Dehaene, 1996), and the results clearly favor an early, precomparison locus of repetition effects.     

汉字刺激质量与语义启动间的交互作用

本研究探讨汉字刺激质量与语义启动的相互作用,深入考察汉字识别的内在机制。实验采用真假字判断范式,实验1使用语义相关词对比率较高的实验材料,实验2使用语义相关词对比率较低的实验材料,结果发现：（1）无论语义相关词对比率高还是低,均存在语义启动效应和刺激质量效应,且汉字刺激质量与语义启动之间均存在交互作用;（2）轻度模糊刺激较重度模糊刺激受到的语义启动效应更大。结果表明,即使排除了额外反馈的作用,汉字刺激质量与语义启动之间仍存在交互作用,进一步支持交互激活模型。     

Isolation of items and the stimulus suffix effect

Thirty Ss heard and serially recalled 36 different nine-digit series. The recall cue was a buzzer, the wordzero read in the same voice that read the first seven digits, or the wordzero read in a voice different from the one that read the first seven digits. In half the series, all nine digits were read in the same voice. The final two digits of the remaining series were isolated by having them read in a voice different from the one that read the first seven digits. Zero suffixes disrupted recall of the terminal digits more than the buzzer (the stimulus suffix effect) and had a greater degrading effect when they were in the same voice as the final two digits than when the zero suffixes and the final digits were read in different voices. Isolated digits were more likely to be recalled than nonisolated digits. Results suggest the importance of perceptual analysis in both the stimulus suffix effect and the isolation effect.     

Dissociative effects of stimulus quality on semantic and morphological contexts in visual word recognition.

Semantic and morphological contexts were manipulated jointly with stimulus quality under conditions where there were few related prime-target pairs (i.e., low relatedness proportion) in a lexical decision experiment. Additive effects of semantic context and stimulus quality on RT were observed, replicating previous work. In contrast, morphological context interacted with stimulus quality. This dissociation is discussed in the context of Besner and colleagues' evolving multistage framework. The essence of the account is that 1) stimulus quality affects feature and letter levels, but not later levels, 2) feedback from semantics to the lexical level is inoperative under low relatedness proportion conditions (hence stimulus quality and semantic context yield additive effects), whereas 3) feedback from the lexical level to the letter level is intact, hence stimulus quality and morphological context produce an interaction by virtue of them affecting a common stage of processing.     

Why is it difficult to see in the fog? How stimulus contrast affects visual perception and visual memory

Processing visually degraded stimuli is a common experience. We struggle to find house keys on dim front porches, to decipher slides projected in overly bright seminar rooms, and to read 10th-generation photocopies. In this research, we focus specifically on stimuli that are degraded via reduction of stimuluscontrast and address two questions. First, why is it difficult to process low-contrast, as compared with high-contrast, stimuli? Second, is the effect of contrastfundamental in that its effect is independent of the stimulus being processed and the reason for processing the stimulus? We formally address and answer these questions within the context of a series of nested theories, each providing a successively stronger definition of what it means for contrast to affect perception and memory. To evaluate the theories, we carried out six experiments. Experiments 1 and 2 involved simple stimuli (randomly generated forms and digit strings), whereas Experiments 3–6 involved naturalistic pictures (faces, houses, and cityscapes). The stimuli were presented at two contrast levels and at varying exposure durations. The data from all the experiments allow the conclusion that some function of stimulus contrast combines multiplicatively with stimulus duration at a stage prior to that at which the nature of the stimulus and the reason for processing it are determined, and it is the result of this multiplicative combination that determines eventual memory performance. We describe a stronger version of this theory— the sensory response, information acquisition theory—which has at its core, the strong Bloch’s-law-like assumption of a fundamental visual system response that is proportional to the product of stimulus contrast and stimulus duration. This theory was, as it has been in the past, highly successful in accounting for memory for simple stimuli shown at short (i.e., shorter than an eye fixation) durations. However, it was less successful in accounting for data from short-duration naturalistic pictures and was entirely unsuccessful in accounting for data from naturalistic pictures shown at longer durations. We discuss (1) processing differences between short- and long-duration stimuli, (2) processing differences between simple stimuli, such as digits, and complex stimuli, such as pictures, (3) processing differences between biluminant stimuli (such as line drawings with only two luminance levels) and multiluminant stimuli (such as grayscale pictures with multiple luminance levels), and (4) Bloch’s law and a proposed generalization of the concept ofmetamers.     

Channels and order of report in dichotic memory*

Experiments were conducted in which Ss received to-be-remembered sequences of two, three, or four simultaneous pairs of digits. Both digits of each pair were recorded by the same male speaker and both were presented binaurally, thus eliminating cues of spatial location and voice by which Ss could “channel” their reports. Even in the absence of these stimulus channels, Ss reported the digits sequentially. High bias ratings in the first experiment suggested the possibility that sequential reports were induced by uncontrolled stimulus characteristics (e.g., temporal synchrony, intensity, and pitch). Pulse-coded speech stimuli, which provided greater control over nonlinguistic stimulus features, were used in the terminal experiment. Bias ratings were reduced, but the majority of Ss continued to report sequentially. These results suggest that the presence of stimulus channels is not a necessary condition for the occurrence of sequential reporting.     

Switching attention within and between categories: Evidence for intracategory inhibition

In a variation of the Posner and Snyder (1975b) paradigm, subjects made speeded “same” or “different” responses to pairs of digits or letters on the basis of name identity (Experiment 1) or physical identity (Experiment 2). Each target pair was preceded by an informative (letter or digit) or noninformative (plus-sign) warning signal. The letter or digit represented by an informative warning signal had a high probability of appearing in the subsequent target pair (expected condition). On trials in which the expected stimulus did not appear in the target pair, the target pair belonged with equal probability to either the same category (either letters or digits) as the expected stimulus or to the opposite category (unexpected-similar and unexpected-opposite conditions, respectively). The pattern of “benefits” and “costs” of attentional expectancy found by Posner and Snyder for “same” responses was replicated: Subjects were faster and more accurate in the expected condition than in the neutral (uninformative warning signal) condition, but slower and less accurate in the unexpected conditions. Present theoretical interest concerns “same” response times and accuracy for the two unexpected conditions. Under instructions emphasizing accuracy as well as speed (Experiments 1 and 2), performance was worse in the unexpected-similar condition than in the unexpected-opposite condition. Only when instructions deemphasized accuracy (Experiment 2) was performance better in the unexpected-similar condition than in the unexpected-opposite condition. The fact that subjects may have more difficulty switching attention within a category than between categories (at least when instructions emphasize accuracy as well as speed) contrasts sharply with current theoretical emphasis on intracategorical facilitation effects in the priming paradigm. The results are interpreted within the framework of a model of attention (Keele & Neill, 1978) in which the activation of associates to the focus of attention is actively and optionally suppressed so as to reduce present or potential interference with the focal information processing.     

Task requirement and hemifield asymmetry in tachistoscopic partial report performance

It was hypothesized that the amount and direction of differences in tachistoscopic recognition accuracy for the right and the left visual hemifield should depend on the degree to which a partial report task requires exhaustive processing of the test stimulus. Position curves for single-item report were examined using four different tasks. In the Arrow task, Ss had to report a letter which was designated by a bar marker. In the Number task, the position of the critical letter was indicated by the digits 1–8. In the Letter task, the cue stimulus was a letter, and Ss were required to report its position in the test stimulus. In the Alphabetic task, a report on the alphabetically first letter of the test stimulus was required. The tasks were designated to encourage either selective processing (Arrow and Number tasks) or exhaustive processing (Letter and Alphabetic tasks). Right-hemifield superiority was predicted for selective processing, and left-hemifield superiority for exhaustive processing. The predictions were confirmed for the Arrow and Alphabetic tasks. A complete account of the position curves in the Number and Letter tasks required a consideration of the effects of the semantic nature of the cue stimulus and/or the spatial arrangement of cue stimulus and test stimulus. It was concluded that the processing operations underlying partial report are more complex than had been assumed previously.     

Mental comparison of size and magnitude: size congruity effects

Paivio (1975) found that the latency to choose the larger of two named objects does not depend on congruity between the object sizes and the sizes of the object names. Because size congruity does affect latencies for pictorially presented objects, Paivio interpreted this result as support for the dual coding hypothesis. However, Experiment 1 demonstrated that Paivio's results were an artifact of his experimental design. Size congruity does affect latencies to choose the larger of two named objects when object pairs are not repeated. When the same object pairs are used repeatedly, as in Paivio's experiment, the effect disappears. In this case the response is probably remembered, so that the objects need not be compared. To determine the processing stages affected by size congruity, both the distance between stimulus sizes and the size congruity were manipulated in Experiment 2. Three groups of subjects chose either the greater Arabic digit, the greater named digit, or the larger named object. Size congruity interacted with distance only for Arabic digits. For both Arabic digits and named digits, the interference caused by size incongruity was greater than the facilitation caused by size congruity, whereas for object names, the facilitation was greater than the interference. A model of the interaction between physical size comparisons and conceptual size comparisons is proposed to account for these results.     

Auditory versus visual processing of three sets of simultaneous digit pairs.

Two experiments were conducted to determine whether the auditory and visual systems process simultaneously presented pairs of alphanumeric information differently. In Experiment 1, different groups of subjects were given extensive practice recalling pairs of superimposed visual or auditory digits in simultaneous order (the order of arrival) or successive order (one member of each digit pair in turn, followed by the other pair member). For auditory input, successive order of recall was more accurate, particularly for the last two of three pairs presented, whereas for visual input, simultaneous order of recall was more accurate. In Experiment 2, subjects were cued to recall in one or the other order either immediately before or after stimulus input. Recall order results were the same as for Experiment 1, and precuing did not facilitate recall in either order for both modalities. These results suggest that processing in the auditory system can only occur successively across time, whereas as in the visual system processing can only occur simultaneously in space.     

Articulatory organization in digit perception and recall

In two experiments, tape-recorded strings of seven recall digits were preceded by a redundant stimulus prefix containing either one or three digits. The prefix and recall digits (1) were articulatorily continuous, or (2)were made discontinuous by tape-splicing, or (3)were made discontinuous by deliberately spoken prosodic contour. Subjects were instructed to ignore the redundant prefixes and report only the recall digits. The main results were: (1)Compared to strings preceded by no prefix, all prefix conditions reduced recall. (2)Three-digit prefixes reduced recall less than one-digit prefixes. (3) In most cases, spliced prefixes reduced recall less than intact prefixes. Acoustic waveform measurements are presented to provide a partial account for the results.     

Time-course of Spatial-attentional Focusing in the Case of High Processing Demand on the Peripheral Precue

Subjects had to identify pairs of spatially overlapping or neighbouring letters exposed successively at various locations around the central fixation. The first letter (S1) in a pair acted both as a physical precue to indicate the S2 location and as a stimulus letter to be identified. The second letter (S2) in a pair acted only as a letter to be identified. The SOA was varied between 0 and 320 ms in different experiments. Comparison of the time-course functions of S2 identification in the conditions of (1) single pair presentation and (2) presentation of the letter pairs in the context of distractor letters that accompanied S2 in time, but occupied alternative spatial positions, revealed that S2 processing from the covert spatial-attentional focus was open to non-decreasing interference from the distractor letters up to 240 ms SOAs. An unexpected result consisted in equal level of S2 identification regardless of whether S1 had to be identified or not. This shows that if the peripheral precue has to be processed with higher processing demands at the identification level beyond simple location processing (which by itself is sufficient to fulfil the spatial orienting function), then the narrowing down or zooming-in of the attentional area in response to a physical precue can take place as effectively as in the case of a lesser processing demand on that precue. By comparing the relative time-course functions of S1 and S2 identification, it was found that S2 identification gained significant advantage over S1 identification at intermediate SOAs even if the intensity of S1 exceeded that of S2. The results of this investigation refer to the spontaneous, automatic nature of spatial attentional focusing that is evoked by spatially localised transient signals, but also to the possibility of interference between the targets and distractors in the working memory representation.     

Reaching towards an end: Numerical end and distance effects in motor movements

Numerical comparisons are affected by the distance between the numbers and by the presence of an end stimulus. In line with embodied cognition approaches, past studies found evidence for the distance effect in continuous motor movements. The present study is the first to provide evidence for the end effect (i.e., faster comparisons for pairs that include an end stimulus of a set) using continuous motor movements. Two digits were presented horizontally on a screen and participants reached towards the larger one using a computer mouse cursor. Response trajectories were straighter (1) when the number pair included the end stimulus of 1, and (2) when the numerical distance between the numbers was large. Importantly, the end effect appeared earlier in the motor trajectory than the distance effect. The implications of this pattern for the cognitive processes underlying the end and the distance effects are discussed.     

Comparing two-digit numbers: the importance of being presented together

The effect of presentation mode on magnitude comparisons of two-digit (2D) numbers was examined using the stimuli set developed by Nuerk, Weger, and Willmes (2001). In Experiment 1, only number pairs from difference decades were presented either simultaneously or sequentially. In the former case there was evidence for the parallel processing of both the units and decades digits and for a components representation, consistent with previous findings. In contrast, in the latter case there was evidence for the processing of mainly the decades digits. In Experiment 2, within-decade number pairs were added to make both digits task relevant. The results from the simultaneous condition were again consistent with a components representation, while results from the sequential presentation were in line with a holistic representation, in line with Zhang and Wang's (2005) research. Results therefore suggest that the processing of 2D numbers depends on the way they are presented.     

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).     

Articulatory organization in the prefix effect

Neisser, Hoenig, and Goldstein (1969) reduced the “stimulus prefix effect” (diminished recall of seven digits preceded by a redundant prefix) when the redundant prefix and the recall digits were produced by different speakers. In the present studies, similar results were obtained using one speaker only, but with the prefix and recall digits spoken separately in different utterances and combined by tape splicing. The results support a hypothesis concerning the perception of intact, wholistically organized articulatory units. A second hypothesis, also based on the idea of intact articulatory units, was tested.     

Sources of Intertrial Proactive Interference in Rats’ Short-Term Memory in a Delayed Successive Matching-to-Sample Modality Discrimination

Rats were trained on a delayed successive matching-to-stimulus modality task consisting of onset of chamber lights or a tone for the sample stimulus, S1, and a comparison stimulus, S2. Lever pressing to S1 was reinforced as was lever pressing to its matching S2 (light–light or tone–tone pairs) but not to its mismatching S2 (light–tone, tone–light pairs). The interval between S1 and S2 within a trial, the retention interval (RI), was varied between 1 and 6 s within sessions while the interval between S2 and the next S1, the intertrial interval (ITI), was reduced from 24 to 12 s and finally to 6 s over blocks of sessions. In Experiment 1, where S1 was kept at 2 s and S2 at 10 s, rats’ matching accuracy declined over the longer RI, was slightly disrupted as ITIs were reduced to 6 s only over 1-s RIs, and was generally poorer to the tone than light S1. In Experiment 2, where both stimuli were 10 s increasing RIs caused steeper declines in matching accuracy to the tone S1 than light S1 and decreasing ITIs to 6 s disrupted rats performance over both RIs. Matching accuracy to the tone but not to the light S1 was also poorer when a preceding trial's S2 was a light S2 than when it was a tone S2 only during Experiment 2. Thisintertrial stimulus disagreementeffect was not influenced by ITI duration. These results suggest that intertrial proactive interference in delayed matching tasks consists of two separate and independent processes in rats similar to those found in pigeons (Edhouse & White, 1988).