On the Relationship between Letter Names and Superordinate Categories

Selective Attention and Target Search with Brief Visual Displays

In a series of four experiments, subjects were presented with eight item arrays tachistoscopically. In two tasks, the subject was required to recall a digit presented among seven letters or a letter among seven digits. The remaining tasks required the subject to detect the presence of a specific letter either in the context of seven random letters or seven digits. An examination of the effects of a masking stimulus for various target positions suggested that subjects could attend selectively when the target was a different category than its context but had to process the entire array when the target was the same category as the context. The effects of selective attention and masking are explained in terms of parallel and sequential identification processes.

The Comparative Judgements of Generally and Specifically Gifted Children

Different groups of children were compared on sentence verification tasks. The children were either academically, musically or artistically gifted, and there were two forms of the task. In one, a picture was followed by a sentence, and in another, one sentence was followed by another. Subjects had to decide as quickly as possible whether or not the second proposition logically confirmed the first. In the picture-sentence condition results from all groups could be fitted to the constituent comparison model for sentence verification proposed by Carpenter and Just (1975). For the sentence-sentence condition, however, the observed results diverged from those predicted by the model. The results are explained in terms of different degrees of linguistic processing capacities of the subjects, and they demonstrate the importance which verbal-logical congruence has for children. Artistically able children had difficulties in processing subject/object incongruence in sentence pairs whereas musically able children had more problems in processing above/below incongruence.

Maintaining Recency despite a Stimulus Suffix

Two processes of information retrieval were considered in the context of the logogen model. The aim was to establish whether information about the final items of an auditory short-term memory list is held exclusively in precategorical acoustic storage at presentation or whether these items are automatically registered in a cognitive store as well. Error data for a final heterogeneous item in alphanumeric lists showed significantly better recall, despite the addition of a stimulus suffix. Although these results demonstrated that coding had proceeded further than a precategorical stage, which maintains only physical features, the possibility remained that the effect was due to a bias in focal attention and selective coding at list presentation. A second experiment increased the difficulty of the retrieval task, and effectively precluded the possibility of a bias in attention. The results confirmed the findings in the first experiment. It was concluded that information about the final item(s) is registered automatically in the cognitive system, and that responses are made available from this source when information about physical features of the item is degraded by a stimulus suffix.

Absence of distracting information explains the redundant signals effect for a centrally presented categorization task

The redundant signals effect, a speed-up in response times with multiple targets compared to a single target in one display, is well-documented, with some evidence suggesting that it can occur even in conceptual processing when targets are presented bilaterally. The current study was designed to determine whether or not category-based redundant signals can speed up processing even without bilateral presentation. Toward that end, participants performed a go/no-go visual task in which they responded only to members of the target category (i.e., they responded only to numbers and did not respond to letters). Numbers and letters were presented along an imaginary vertical line in the center of the visual field. When the single signal trials contained a nontarget letter (Experiment 1), there was a significant redundant signals effect. The effect was not significant when the single-signal trials did not contain a nontarget letter (Experiments 2 and 3). The results indicate that, when targets are defined categorically and not presented bilaterally, the redundant signals effect may be an effect of reducing the presence of information that draws attention away from the target. This suggests that redundant signals may not speed up conceptual processing when interhemispheric presentation is not available.

Word Processing and Effects of Variability in Type Fonts

Current models for reading words often assume the existence of features or shape characteristics for distinguishing one letter from another. However, the form of these features need not be invariant, particularly as one considers variations in type font or in handwriting. In this paper, we introduce the possibility of a two-level process with one level helping the viewer to identify the style or font being used at a given time. This first process leads to the activation of a decision tree that is specialized with respect to a particular set of characteristics while a second process makes use of this decision tree to identify the letter or word being presented. The results of an experiment designed to explore empirical implications of this two-level approach are described. Results are consistent with the model although additional experimentation is needed to explore more fully the implications for the processing of letters and words.

Redundant spoken labels facilitate perception of multiple items

Because of the strong associations between verbal labels and the visual objects that they denote, hearing a word may quickly guide the deployment of visual attention to the named objects. We report six experiments in which we investigated the effect of hearing redundant (noninformative) object labels on the visual processing of multiple objects from the named category. Even though the word cues did not provide additional information to the participants, hearing a label resulted in faster detection of attention probes appearing near the objects denoted by the label. For example, hearing the word chair resulted in more effective visual processing of all of the chairs in a scene relative to trials in which the participants attended to the chairs without actually hearing the label. This facilitation was mediated by stimulus typicality. Transformations of the stimuli that disrupted their association with the label while preserving the low-level visual features eliminated the facilitative effect of the labels. In the final experiment, we show that hearing a label improves the accuracy of locating multiple items matching the label, even when eye movements are restricted. We posit that verbal labels dynamically modulate visual processing via top-down feedback--an instance of linguistic labels greasing the wheels of perception.

The rapid extraction of numeric meaning

Several kinds of statistical properties can be rapidly extracted from visual displays (e.g., luminance and roughness, Olive, A., & Torralba, A. (2001). Modeling the shape of the scene: a holistic representation of the spatial envelope. International Journal of Computational Vision, 42, 145-175). Here, we investigate whether this phenomenon extends to meaning contained in Arabic numerals. Observers were shown brief displays containing two sets of numerals and asked to determine which contained the largest average value. Comparisons were made more quickly and accurately between displays of digits than between displays of letters and shapes; this effect could not be attributed to task instructions. When numeric meaning could be used in a classification task, performance was better for digits than for letters, but when numeric meaning could not be used as a basis of classification, performance was approximately equal across stimulus types, suggesting that numeric meaning is rapidly extracted only when it is task-relevant. The digit advantage was eliminated with unlimited viewing time, suggesting that this process is used when counting is not possible. Dual-task methodology revealed that this process requires limited-capacity attentional resources.

Preservation of cognitive function after long-term tetraplegia

The claim of a significant relationship between pulmonary peak expiratory flow rate and cognitive decline in normal aging is bound to raise the question of whether accelerated cognitive decline would be an automatic consequence of long-term tetraplegia, with its significant effects on normal respiratory function. We present a case series of three persons with long-term tetraplegia (11, 15, and 21 yr) comparing their cognitive test results (short-term and working memory, the ability to inhibit interference, and cognitive processing speed) with scores for age-matched noninjured adults. Results showed that long-term tetraplegia, even with compromised respiration, does not inevitably lead to decline in fundamental cognitive functions relative to age-matched noninjured controls.

Taking attention to task: P300, task response probability, and within-category deviation detection

Previously, we reported enhanced P3 amplitudes to between-category deviations among high and low probability events. Here, we tested the effects of a within-category difference. Subjects performed a go/no-go button press task as they viewed repeated, randomly-ordered presentations of nine double-digit numbers. Eight numbers fell within a prescribed range (42-49, standards); prior to testing, subjects selected one standard number for later recall. A ninth, out-of-range (91, deviant) number was also included. Subjects were tested under two conditions, in which they responded either to one (low response probability) or to seven (high response probability) standard nonselected numbers, designated as targets. Relatively larger P3s were consistently apparent only when the deviant nontarget was associated with a low probability response to a nontarget. There was a selective effect of nontarget response probability on P3 amplitude to the deviant nontarget. Our results indicate that within-category deviation detection is facilitated by "controlled" attention to the structure of the stimulus field.

Filtering versus parallel processing in RSVP tasks

An experiment of McLean, D. E. Broadbent, and M. H. P. Broadbent (1983) using rapid serial visual presentation (RSVP) was replicated. A series of letters in one of 5 colors was presented, and the subject was asked to identify the letter that appeared in a designated color. There were several innovations in our procedure, the most important of which was the use of a response menu. After each trial, the subject was presented with 7 candidate letters from which to choose his/her response. In three experimental conditions, the target, the letter following the target, and all letters other than the target were, respectively, eliminated from the menu. In other conditions, the stimulus list was manipulated by repeating items in the series, repeating the color of successive items, or even eliminating the target color. By means of these manipulations, we were able to determine more precisely the information that subjects had obtained from the presentation of the stimulus series. Although we replicated the results of McLean et al. (1983), the more extensive information that our procedure produced was incompatible with the serial filter model that McLean et al. had used to describe their data. Overall, our results were more compatible with a parallel-processing account. Furthermore, intrusion errors are apparently not only a perceptual phenomenon but a memory problem as well.

Classification without identification in visual search

Six subjects scanned displays of random consonants for a single target which was (a) another consonant; (b) a given number; or (c) any number. A second group of six subjects took part in three comparable conditions with number displays, and letters or numbers as targets. Scanning time for a number in a letter display or a letter in a number display was more rapid than scanning for a target drawn from the same set as the background. Several unpractised subjects, and all the subjects who practised the task, were able to scan as fast through letters for “any number” as for a specific number, or conversely through digits. The finding of different scanning rates for two precisely physically specified targets, depending on which class they were drawn from, runs counter to an explanation of high-speed scanning in terms of the operation of visual feature analysers. It is suggested that familiar categorization responses may be immediate and may provide the basis for the discrimination of relevant from irrelevant items in rapid visual scanning.