David LaBerge

Toward a theory of automatic information processing in reading

Abstract A model of information processing in reading is described in which visual information is transformed through a series of processing stages involving visual, phonological and episodic memory systems until it is finally comprehended in the semantic system. The processing which occurs at each stage is assumed to be learned and the degree of this learning is evaluated with respect to two criteria: accuracy and automaticity . At the accuracy level of performance, attention is assumed to be necessary for processing; at the automatic level it is not. Experimental procedures are described which attempt to measure the degree of automaticity achieved in perceptual and associative learning tasks. Factors which may influence the development of automaticity in reading are discussed.

Spatial extent of attention to letters and words

The spatial extent of attention to visually presented letters and words was investigated using a probe technique. The primary task required subjects to categorize (a) five-letter words, or to categorize the middle letter of (b) five-letter words or (c) five-letter nonwords. The probe task required the subjects to respond when the digit 7 appeared in one of the five letter positions. Probe trials were inserted at the onset of letter and word processing in Experiment 1 and 500 msec after letter and word processing in Experiment 2. In both experiments, probe trials produced a V-shaped function of reaction times across probe positions for the letter-categorization task for word and nonword stimulus conditions. In contrast, a relatively flat reaction time function was found for the word-categorization tasks. An analysis of the data based on a quantitative model of attentional spotlight distributions suggests that the spotlight width in the letter tasks is one letter space, and the spotlight width in the word task is typically five spaces.

Thalamic and cortical mechanisms of attention suggested by recent positron emission tomographic experiments

An attention mechanism in the pulvinar nucleus of the thalamus appears to be involved in the filtering of a location in a cluttered visual field, according to recent PET data. The mechanism in the pulvinar is assumed to be a particular type of circuit that reciprocally connects thalamic relay cells to cortical cells. This circuit, which is characteristic of thalamic nuclei in general, appears to embody an algorithm that enhances firing in a target set of cells while inhibiting firing in the surrounding set of cells. Recent PET studies have also identified specific areas of cortex that show increased blood flow when humans expect to process particular aspects of visual objects, such as location, shape, color, and movement velocity. An expectation for a particular feature can be regarded as a peaked activity distribution across cortical synaptic space that increases the effectiveness (accuracy and speed) of the perception of that feature and features similar to that feature. The expectation process is assumed to be generated by a thalamic enhancement circuit, which in turn is driven by a cognitive procedure, apparently located in the anterior cingulate area of the cortex. The selection of a particular cognitive procedure is assumed to depend on the momentary relative motivational value associated with it by means of connections to deeper limbic structures. Under usual conditions, the procedure having the dominant motivational value is the one selected.

A recruitment theory of simple behavior

A statistical theory of choice is developed using a sequential sampling assumption. Response latency distributions for certain simple reaction-time situations are derived and tested. Both response probability and response latency measures are developed for a two-alternative judgment situation and the relationship between the two measures explored. The sampling parameter is proposed as a means of representing incentive conditions in choice situations and ROC curves are obtained by appropriate manipulations of this parameter. A solution to the overlap problem in simple discrimination-learning situations is also derived.

Variations in size of the visual field in which targets are presented: an attentional range effect.

In Experiment 1, subjects responded with a buttonpress to a target letter O embedded in a pair of vertical lines. A flanker control method was used to constrain the location and size of the initial attentional focus. The target could appear in one of five locations within a particular horizontal range. There were five ranges, varying from 1.7° to 8.6° in visual angle. Reaction time measures to the target exhibited V-shaped curves, with the lowest reaction time corresponding to the location of the initial focus of attention. The slopes of the curves decreased monotonically with target ranges. Reaction time measures at the extreme locations of the five ranges showed no significant increase with eccentricity, indicating that the influence of retinal sensitivity is negligible in this identification task as compared with the influence of other, presumably attentional, processes. Experiment 2 indicated that within a given range the slopes of the reaction time curves are independent of the number of locations probed. Additional evidence for the attentional range effect was given in Experiments 3 and 4, in which the tasks were detection of an asterisk both with and without flanking vertical lines and identification of the letter O with and without flanking lines. These results do not conform to predictions of a shifting focus theory of attention with the velocity of the focus assumed to be constant, or to the predictions of a gradient theory with total processing capacity assumed to be fixed.

Attention, Awareness, and the Triangular Circuit☆

It is proposed that attention to an object requires the simultaneous activity of three brain regions that are interconnected by a triangular circuit. The regions are the cortical site of attentional expression, the thalamic enhancement structure, and the prefrontal area of control. It is also proposed that awareness of an object requires the additional component of attention directed to a representation of the self. The expression of attention to a self-representation may involve activations of cortical sites corresponding to the body landscape and/or verbal-based memories of autobiographical episodes. As in the case of attention to objects, attention to the self is presumed to involve a triangular circuit. The proposed triangular circuit of attention is shown to be generally consistent with current knowledge of brain structures and with data from a broad range of experiments concerned with the functions of neurons in these structures.

Automatic semantic processing of unattended words

In a two-choice reaction time experiment, subjects identified single words as belonging to one of four semantic categories. Each target word had flanking words placed above and below it which belonged to the same or a different category as the target. Response latencies were elevated when the category of the flanking words was assigned to a response different than the target category, replicating the pattern reported by Eriksen and Eriksen (1974) in a letter identification task. It is concluded that semantic information of the flanking words is processed automatically. The data also suggest that some interference may occur at an earlier categorization stage independent of response assignment.

Attention and the measurement of perceptual learning.

Novel and familiar letters were presented to Ss under conditions which controlled momentary attention states. The latencies of letter matching for the novel and familiar letters did not differ when Ss were expecting the particular letters which were presented. However, latencies to the two types of letters differed significantly when Ss were not expecting the particular letters which were presented. Additional exposures significantly reduced this difference, thereby generating a perceptual learning curve in terms of response latency. The main findings were interpreted in terms of a model of perceptual processing which involves mechanisms for hierarchical coding, selective attention, and automatic processing.

The modification of short-term memory through instructions to forget

This study was designed to investigate whether Ss could reduce the proactive interference of a first verbal item (CCCC) if they were signalled just prior to the presentation of a second item that they could forget the first item. Recall of the second of two CCCC items inserted in a series of digits was better when Ss were told to “drop” the first item than when there was no such instruction, but it was not as good as recall when only one item was presented.

Reducing the effects of adjacent distractors by narrowing attention

Three experiments explored the gradual narrowing of visual attention to a letter target when other letters were positioned close by. The method by which attention was narrowed involved presenting a digit target immediately prior to the latter target and in the same location for progressively shorter durations and requiring the subject to identify both the digit target and the letter target before responding. The response time data from the first 2 experiments indicated that shorter durations of the digit reduced the amount of information processed from noise letters positioned on either side of the letter target. In the third experiment, in which separation of letters was increased slightly, the response times indicated that the information from flanking noise letters may have been virtually eliminated.