Priming T2 in a visual and auditory attentional blink task

Participants performed an attentional blink (AB) task including digits as targets and letters as distractors within the visual and auditory domains. Prior to the rapid serial visual presentation, a visual or auditory prime was presented in the form of a digit that was identical to the second target (T2) on 50% of the trials. In addition to the "classic" AB effect, an overall drop in performance on T2 was observed for the trials on which the stream was preceded by an identical prime from the same modality. No cross-modal priming was evident, suggesting that the observed inhibitory priming effects are modality specific. We argue that the present findings represent a special type of negative priming operating at a low feature level.     

Are spatial selection and identity extraction separable when attention is controlled endogenously?

Visual search for a target involves two processes: spatial selection and identity extraction. Ghorashi, Enns, and Di Lollo (2008) found these processes to be independent and surmised that they were carried out along distinct visual pathways: dorsal and ventral, respectively. The two experiments that are described in the present article evaluated this hypothesis. Attentional-blink methodology was combined with voluntary spatial cuing in a visual search task: Intertarget lag was used to manipulate identity extraction; predictive cues were used to signal target locations. Central digit cues in Experiment 1 required participants to identify digits before voluntarily directing attention to a corresponding location, whereas flashed dots in Experiment 2 (indicating an opposite location) required attentional redeployment without prior cue identification. Consistent with the dual-pathway hypothesis, cuing was impaired only when the first target and the number cue competed for ventral-pathway mechanisms. Collectively, the results support the dual-pathway account of the separability of spatial selection and identity extraction.     

Evidence that fixation digits can contribute to visual field asymmetries in lateralized tachistoscopic tasks

Fixation point digits have been widely used in tachistoscopic laterality studies as a simple and convenient means of ensuring unihemispheric projection of stimulus materials to the hemispheres. Previous findings demonstrate that fixation digits do not influence asymmetries in recognition accuracy studies with adult Ss. Present results, comparing four conditions differing in their use of fixation digits, show that in the naming latency paradigm the requirement to remember and report fixation control digits significantly augments RVF superiority. Implications for other latency tasks are discussed.     

The differential influence of decades and units on multidigit number comparison

What role do the magnitudes of the constituent digits play in three-digit number comparison (e.g., choosing the larger one of two numbers)? The present study addressed this question by examining compatibility effects between hundred and decade digits and between hundred and unit digits. For example, the number pair 372-845 is hundred-decade incompatible because the larger number contains the smaller decade digit, but hundred-unit compatible because the larger number contains the larger unit digit. We obtained significant effects ofhundred-decade and hundred-unit compatibility on number comparison times. However, the effect of hundred-unit compatibility was largely restricted to the hundred-decade-compatible condition. These results suggest that place-value information, through decomposition, is automatically taken into account when multidigit numbers have to be compared. Implications of our findings for models of number processing are discussed.     

The differential influence of decades and units on multidigit number comparison

What role do the magnitudes of the constituent digits play in three-digit number comparison (e.g., choosing the larger one of two numbers)? The present study addressed this question by examining compatibility effects between hundred and decade digits and between hundred and unit digits. For example, the number pair 372–845 is hundred–decade incompatible because the larger number contains the smaller decade digit, but hundred–unit compatible because the larger number contains the larger unit digit. We obtained significant effects of hundred–decade and hundred–unit compatibility on number comparison times. However, the effect of hundred–unit compatibility was largely restricted to the hundred–decade-compatible condition. These results suggest that place-value information, through decomposition, is automatically taken into account when multidigit numbers have to be compared. Implications of our findings for models of number processing are discussed.     

Ensemble size and selective response times with a constant signal rate

Using a selective response task in which subjects were required to respond only to one of a number of alternative digits, although signal rate was held constant, the latency of selective responses was found to lengthen as the number of alternatives increased. This finding does not support the inference drawn from the work of Mowbray (1960) that, with signal rate held constant, there should be no significant lengthening of reaction times as the ensemble of digits increases.     

Arousal and the Bakan vigilance task: The effects of noise intensity and the presence of others

The joint effects of social setting and loud noise on task performance are examined. In a modified version of the Bakan vigilance task subjects were required to detect a sequence of two identical even digits and to report the two digits preceding the signal. Two types of acoustic environment were compared: loud noise at 90 dBC and quiet noise at 60 dBC. Two types of social setting were employed: “pair” where two subjects worked in the same room on similar tasks, and “single” where a subject performed the task alone. The effects of noise and the presence of another did not interact. Loud noise increased the speed of responses to signals early in the task. This effect is attributed to noise-induced arousal. There was a higher incidence of recall errors in pre-signal digits when subjects were in pairs. This effect is attributed to distraction. This research was part of a series of studies sponsored by the Social Science Research Council (Grant HR 5563 awarded to Dr. A.J. Chapman and Dr. D.M. Jones).     

Multiple roles for time in short-term memory: evidence from serial recall of order and timing

Three experiments are reported that examine the relationship between short-term memory for time and order information, and the more specific claim that order memory is driven by a timing signal. Participants were presented with digits spaced irregularly in time and postcued (Experiments 1 and 2) or precued (Experiment 3) to recall the order or timing of the digits. The primary results of interest were as follows: (a) Instructing participants to group lists had similar effects on serial and timing recall in inducing a pause in recall between suggested groups; (b) the timing of recall was predicted by the timing of the input lists in both serial recall and timing recall; and (c) when the recall task was precued, there was a tendency for temporally isolated items to be more accurately recalled than temporally crowded items. The results place constraints on models of serial recall that assume a timing signal generates positional representations and suggest an additional role for information about individual durations in short-term memory.     

The influence of string length and repetition on chunking of digit strings

This study examined the effects of string length and repetitions on number processing with a data entry task. Participants read and entered strings of between three and eight digits and then typed them on the keypad of a computer. Chunking effects were found for all string lengths, with chunk sizes of as small as two digits. Chunk boundary placement varied depending on the length of a digit string, and chunking was avoided at positions between digit repetitions, even when those positions were otherwise common chunk boundaries. Digit repetitions significantly reduced the study time required to process a string prior to its entry. These results are interpreted as showing that flexible chunking strategies and the presence of repetitions are used to facilitate number processing.Means with an asterisk correspond to repeated digits     

Focal spatial attention can eliminate inhibition of return

Inhibition of return (IOR) is an orienting phenomenon characterized by slower responses to spatially cued than to uncued targets. In Experiment 1, a physically small digit that required identification was presented immediately following a peripheral cue. The digit could appear in the cued peripheral box or in the central box, thus guaranteeing a saccadic response to the cue in one condition and maintenance of fixation in the other. An IOR effect was observed when a saccadic response to the cue was required, but IOR was not generated by the peripheral cue when fixation was maintained in order to process the central digit. In Experiment 2, IOR effects were observed when participants were instructed to ignore the digits, whether those digits were presented in the periphery or at fixation. These findings suggest that behaviorally manifested, cue-induced IOR effects can be eliminated by focal spatial attentional control settings.     

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.     

Temporal Grouping Effects in Immediate Recall: A Working Memory Analysis

The presence of temporal pauses during list presentation can markedly improve immediate memory for a sequence of verbal items. A series of experiments analysed this effect using Baddeley's (1986) model of working memory. Experiment 1 showed that the effect of temporal grouping on memory for visual sequences was removed by either articulatory suppression or reciting random digits. Experiment 2 indicated that effects of temporal grouping were insensitive to the word length of the items. Experiment 3 showed that articulatory suppression did not remove the temporal grouping effect for auditory lists. Experiment 4 showed that the temporal grouping effect was insensitive to the phonemic similarity of the items. The effects of concurrent articulation suggest that grouping influences the phonological loop component of working memory. However, the working memory model is insufficiently well specified to account for the insensitivity of grouping effects to word length and phonemic similarity. The main findings could be simulated by a connectionist model of the phonological loop, which invokes a context timing signal (Burgess & Hitch, 1992, in press), This assumed that pauses during list presentation affect the timing signal in a similar way to the pause before list presentation and made some novel predictions.     

Synesthetic color experiences influence memory

We describe the extraordinary memory of C, a 21–year–old student who experiences synesthetic colors (i.e., photisms) when she sees, hears, or thinks of digits. Using three matrices of 50 digits, we tested C and 7 nonsynesthetes to evaluate whether C's synesthetic photisms influence her memory for digits. One matrix consisted of black digits, whereas the other two matrices consisted of digits that were either incongruent or congruent with the colors of C's photisms. C's recall of the incongruently colored digits was considerably poorer than her recall of either the black or the congruently colored digits. The 7 nonsynesthetes did not show such differences in their recall of the matrices. In addition, when immediate recall of the black digits was compared with delayed recall of those digits (48 hr), C showed no decrease in performance, whereas each of the nonsynesthetes showed a significant decrease. These findings both demonstrate C's extraordinary memory and show that her synesthetic photisms can influence her memory for digits.     

Category-level contributions to the alphanumeric category effect in visual search

Do letter and digit recognition depend on the same or different cognitive mechanisms? Letters are detected more quickly among digits than among letters; likewise, digit search is facilitated when distractors are letters, as opposed to digits. This effect suggests that different mechanisms underlie recognition of these two categories. There are, however, systematic physical differences between letters and digits that might account for the effect. We used target and distractor stimuli that facilitated within-category search when inverted, and category identity was, thereby, attenuated. However, in conditions of upright search, in which category identity was more salient, between-category search was more efficient for the same stimuli. These findings suggest that letter and digit recognition are, at least to a degree, functionally independent.     

EEG correlates of sustained attention: Hemispheric and sex differences

Subjects were presented with sets of four digits, and had to respond only when all the digits in a set were odd. The EEG was measured from occipital-parietal derivations over the left and right hemispheres, and the energy within each of five frequency bands was integrated over 3-sec epochs corresponding to the presentation of individual sets of digits. The EEG abundance was found to be lower the more a digit set resembled a signal, but hemisphere differences in this effect tended to be small and to occur only in certain frequency bands. The effect for stimulus type changed over time in some frequency bands, but there were no differences between the hemispheres in this change. Nor were sex differences in lateralization found. Reaction time was found to correlate positively with (a) EEG abundance, and (b) EEG differentiation of stimuli, in the theta and low alpha frequency bands.     

A memory-based account of automatic numerosity processing

We investigated the mechanisms responsible for the automatic processing of the numerosities represented by digits in the size congruity effect (Henik & Tzelgov, 1982). The algorithmic model assumes that relational comparisons of digit magnitudes (e.g., larger than {8,2}) create this effect. If so, congruity effects ought to require two digits. Memory-based models assume that associations between individual digits and the attributes "small" and "large" create this effect. If so, congruity effects ought only to require one digit. Contrary to the algorithmic model and consistent with memory-based models, congruity effects were just as large when subjects judged the relative physical sizes of small digits paired with letters as when they judged the relative physical sizes of two digits. This finding suggests that size congruity effects can be produced without comparison algorithms.     

亮度对空间-数字反应编码联合效应的影响

本研究探讨亮度对空间-数字反应编码联合效应（Spatial-Numerical Association of Response Codes,简称SNARC效应）的影响及其机制。通过三个实验设计不同的亮度对比水平,要求被试对阿拉伯数字1~9（5除外）进行奇偶判断。实验一将数字亮度设为最高值255时,结果出现了数字的SNARC效应。实验二将数字的亮度值分别设为255和213时,结果仍存在SNARC效应。实验三将亮度值分别设置为213和42时,数字的SNARC效应却消失了。这些结果表明亮度会激活或抑制数字的空间表征,可能与亮度对比值的高低及所消耗认知资源的多少有关。     

Processing of geometrical dimensions in a binary classification task: Evidence for a dual process model

Confirming the findings in search tasks with letters and digits, the typical RT_same < RT_diff result was obtained in a matching paradigm requiring the classification of geometrical stimuli that were given in pairs. The study supports a dual process model that is based on an identity reporter for the faster “same” response and a difference detector for the slower “different” responses, both operating with equal accuracy. Subjects appeared to perceive outline aspects of figures, formed by size and form, holistically. An internal characteristic, such as an interior line, was apparently processed as a separate attribute. However, the outlines of the stimulus configurations appeared to be much more salient and interfered with the judgment of the orientation of the interior line. Moreover, the latter stimulus aspect could be easily ignored as the task required.     

Synaesthetic photisms guide attention

We evaluated whether synaesthetic colour experiences (i.e., photisms) guide or attract attention. An alphanumeric-colour synaesthete, J, and seven non-synaesthetes searched for target digits presented against backgrounds that were either congruent or incongruent with the colours of J's photisms for the target digits. For J, the slope of the search function for detecting the target digits on incongruent trials was shallower than the slope of the search function for detecting the target digits on congruent trials. In contrast, for the seven non-synaesthetes, the slopes of the search functions for detecting the target digits on congruent and incongruent trials were equivalent. These findings suggest that synaesthetic colour experiences influence the efficiency of visual search by guiding or attracting attention.     

Differences between digit naming and number word reading in a flanker task

Numbers can be represented as number words or as digits, but are the two notations processed differently? Two experiments in which a flanker paradigm with a naming task was used were conducted, with digits and number words as targets and flankers. Reaction times were shortest when the flanker denoted the same numerical value as the target. The numerical distance between the target and a numerically different flanker modulated reaction times in all conditions, except for number word targets with digit flankers. The direction of this effect—targets were named faster when the flanker was numerically close than when it was far—indicates that the numerical magnitude representations of numbers are associatively connected. When the target and the flanker were presented in the same format, no difference was observed in the distance effects for the two formats. This indicates that number words activate the abstract representation of their numerical value in a way that is very similar to that for digits.