Memory scanning for words in visual images

This study attempts to replicate an experiment reported by Seamon (1972). In the present investigation, as in the study by Seamon, the scanning of short-term memory was compared when its contents were rehearsed words vs. a mental image. Memory sets were composed of either one, two, or three words. In the relational imagery group, subjects were required to form a single interactive mental scene of the entities which the memory set words represent. Nonimagery subjects were given instructions to covertly rehearse the memory set. In both groups, the usual memory set size (m) effect was obtained, i.e., reaction time (RT) increased linearly with m. Moreover, the set size effect was the same for both groups. This latter finding stands in marked contrast to the result obtained by Seamon; he found no effect of set size when subjects were given interactive imagery instructions. Because of the failure to replicate Seamon, an additional group of subjects were given imagery instructions. For this latter group, some of the procedural discrepancies between the relational imagery group of the present study and the corresponding group in Seamon’s study were resolved. Also, in this additional group, the set size effect was examined as a function of the subjects’ ratings of the quality of the images which they had formed. The same set size effect was found for this additional group, and the effect was independent of image quality.     

Directional scanning of remembered visual patterns

We report a set of experiments that helps to define the conditions under which mental image scanning may be used spontaneously for specific, practical purposes. Subjects were shown a dot pattern, followed by an arrow, and their task was to say whether the arrow was pointing at any of the previously seen dots. When no advance information was provided about the arrow's location, reaction time for correctly verifying that an arrow was pointing at a dot increased linearly with increasing arrow-dot distance, and the subjects almost always reported scanning a mental image in order to make their judgments. However, when a cue for the arrow's location was presented 2 sec beforehand, reaction time was uncorrelated with distance, and most of the subjects reported using an alternative strategy based on the determination in advance of correct directions from that location to the dots. When given only 1 sec of advance information about arrow location, most subjects reported using a combined image-scanning and advanced determination strategy, resulting in a reaction time function that increased only for the farthest distances. Because in each of these experiments instructions to form or to scan mental images were never given, these findings address the most common criticisms of the image-scanning paradigm.     

Peripheral-foveal scanning and the identification of heteropalindromes in the visual half-fields

The possible identifying properties of the peripheral-field-to-foveal-field (PFTFF) scan, thought to precede the left-to-right reading scan of English alphabetical arrays, were investigated. Heteropalindromes, letter strings that spell one word when read from left to right but another word when read from right to left, were tachistoscopically exposed in the left or right visual fields of 16 male, dextral college students in each of two experiments. The results support Schissler and Baratta's idea that the scan does not appear to yield detailed stimulus information. We suggest that the direction of this scan is well suited to the requirements of encoding horizontally aligned words, given the acuity/information gradient produced when such stimuli are exposed unilaterally. The direction and operation of the scan prior to the left-to-right reading scan are discussed in terms of an earlier account of the encoding of unilaterally exposed, horizontally aligned English words.     

Parallel scanning of auditory and visual information

Two experiments involving memory retrieval of auditorilv and visually presented materials were performed. In Experiment I, subjects were presented with memory sets of 1, 2, or 4 stimuli and then with a test item to be classified as belonging or not belonging to the memory set. In Condition 1, each memory stimulus was a single, auditorily presented letter. In Condition 2, each memory stimulus was a visually presented letter. In Conditions 3 and 4, each memory stimulus was a pair of letters, one presented visually and the other auditorily. Mean reaction time (RT) for the classification task increased as a function of number of memory stimuli at equal rates for all four conditions. This was interpreted as evidence for a parallel scanning process in Conditions 3 and 4 where the auditory item and visual item of each memory stimulus pair can be scanned simultaneously. Experiment II compared memory retrieval for a simultaneous condition in which auditory and visual memory items were presented as pairs with a sequential condition in which mixed auditory-visual memory sets were presented one item at a time. RTs were shorter for the simultaneous condition. This was interpreted as evidence that parallel scanning may depend upon memory input parameters.     

Location cuing and response time distributions in visual attention

The allocation of visual attention was investigated in two experiments. In Experiment 1 (n = 24), a peripheral cue was presented, and in Experiment 2 (n = 24), a central cue was used. In both experiments, cue validity was 90%, and the task was four-choice target identification. Response time distributions were collected for valid trials over five cue-target stimulus onset asynchronies (SOAs), and ex-Gaussian parameters were extracted. In both experiments, only the mean of the Gaussian component decreased as a function of cue-target SOA, which implied a strict time axis translation of the distributions. The results were consistent with sequential sampling models featuring a variable delay in the onset of information uptake.     

Influence of stimulus symmetry on visual scanning patterns

Eye movements of four Ss performing a complexity rating task in which the stimuli consisted of random shapes differing in symmetry, number of turns (sides) in the perimeter, and structural angularity were examined. It was found that for both symmetrical and asymmetrical shapes, the number of fixations and fixation time increased directly with structural complexity (number of sides). Distributions of fixations for symmetrical shapes clustered in one-half of the shapes, while the distributions of fixations for asymmetrical shapes did not exhibit this one-sided bias. No differences were found in the distributions of fixation time to either half of asymmetrical or symmetrical shapes. The findings suggest that S utilizes an organizing code in addition to the featural code in characterizing a given shape. The organizing code permits S to generate the feature code for a gwen shape on the basis of partial information.     

Developmental aspects of auditory and visual scanning.

60 Ss from Grades 1 through 6 were administered an auditory and visual scanning procedure and 27 of those Ss were given arithmetic and reading achievement tests. Data indicated scanning ability increases linearly with grade in school and the relationship between the scanning measures also increases sharply with grade. Auditory scanning was related to academic achievement; visual scanning only approached significance with arithmetic achievement but was unrelated to reading achievement.     

Developmental differences in cognitive scanning and encoding of visual information

Report accuracy of horizontally arranged letter sequences was measured for second-grade children and adults using a tachistoscopic single report procedure. Results indicated age differences in both the amount of information encoded out of visual sensory store and in the magnitude of left-right visual field differences. However, large age differences in amount of encoded information were also present under conditions which served to reduce left-right visual-field asymmetries in report accuracy. These findings are discussed in terms of their implications for using a left-to-right cognitive trace scanning explanation to account for age differences in encoding efficiency.     

Sex differences during visual scanning of occlusion events in infants

A growing number of sex differences in infancy have been reported. One task on which they have been observed reliably is the event-mapping task. In event mapping, infants view an occlusion event involving 1 or 2 objects, the occluder is removed, and then infants see 1 object. Typically, boys are more likely than girls to detect an inconsistency between a 2-object occlusion event and a 1-object display. The current research investigated underlying reasons for this sex difference. Three eye-tracking experiments were conducted with infants at 9 and 4 months (mean age). Infants saw a ball-box or ball-ball occlusion event followed by a 1-ball display; visual scanning of the occlusion event and the 1-ball display was recorded. Older boys were more likely than older girls to visually track the objects through occlusion and more likely to detect an inconsistency between the ball-box event and the 1-ball display. In addition, tracking objects through occlusion was related to infants' scanning of the 1-ball display. Both younger boys and girls failed to track the objects through occlusion and to detect an inconsistency between the ball-box event and the 1-ball display. These results suggest that infants' capacity to track objects through occlusion facilitates extraction of the structure of the initial event (i.e., the number of distinct objects involved) that infants can map onto the final display and that sex differences in the capacity emerge between 4 and 9 months. Possible explanations for how the structure of an occlusion event is extracted and mapped are considered.     

The pigeon's discrimination of visual entropy: a logarithmic function

We taught 8 pigeons to discriminate 16-icon arrays that differed in their visual variability or "entropy" to see whether the relationship between entropy and discriminative behavior is linear (in which equivalent differences in entropy should produce equivalent changes in behavior) or logarithmic (in which higher entropy values should be less discriminable from one another than lower entropy values). Pigeons received a go/no-go task in which the lower entropy arrays were reinforced for one group and the higher entropy arrays were reinforced for a second group. The superior discrimination of the second group was predicted by a theoretical analysis in which excitatory and inhibitory stimulus generalization gradients fall along a logarithmic, but not a linear scale. Reanalysis of previously published data also yielded results consistent with a logarithmic relationship between entropy and discriminative behavior.     

Evidence for scanning with unilateral visual presentation of letters

When letters and words are presented tachistoscopically, material from the right visual field (RVF) can be reported more accurately than that from the left visual field (LVF). The RVF superiority may reflect either left hemispheric dominance for language or directional scanning. Previous studies have deliberately focused on the cerebral asymmetry factor while "controlling" scanning and, thus, have cast some doubt on the potency of the scanning factor. Two experiments were conducted to show that scanning can induce a RVF superiority comparable to that often associated with cerebral asymmetry. The first experiment required bilingual subjects to report six English or six Hebrew letters, shown briefly in either the LVF or RVF, with order of report controlled. A RVF superiority found with English characters was matched by an equal but opposite LVF effect with Hebrew. In a second experiment, five English characters were shown briefly in either the LVF or RVF, and subjects had to identify a single character indicated by a post exposural cue. Using a spatial cue to by pass scanning, there were no field differences; with an ordinal position cue--a procedure thought to force scanning--there was a strong RVF superiority. The results show clearly that scanning can induce visual field differences.     

Directional scanning and cerebral asymmetries in processing visual stimuli.

A perceptual exploration task involving three horizontal linear arrays of stimuli was administered to 167 children ranging in age from 3 to 7 yr. It was found that the well organized, predominantly right-to-left responses of very young children were eventually replaced by left-to-right patterns. A tachistoscopic test showed that Ss who gave right-to-left responses to the linear arrays showed hemispheric asymmetry of perception. The results were interpreted as supporting the view that directional response tendencies are related to hemispheric asymmetry.     

Methylphenidate increases selectivity of visual scanning in children referred for hyperactivity

Visual scanning patterns were investigated in 32 children referred for symptoms of hyperactivity in a doubleblind crossover comparison of methylphenidate and placebo treatments. Total errors, response latency, and visual fixations were recorded as the child scanned computer-generated visual matching-to-sample problems. Results indicated that the number of fixations on the standard stimulus in the matching task was significantly larger in the methylphenidate state. Drug treatment also resulted in a significant increase in the number of systematic comparisons between the standard and the variants in the task. However, the increased selectivity of attention to the standard stimulus was not accompanied by a reduction of total errors. It was suggested that the stimulant drug may increase attentional selectivity even when such a shift fails to produce improvement in task performance.This research is based in part upon a master's thesis completed by the first author in the department of Psychology, University of Guelph. The authors are indebted to Dean H. Owen for providing the random polygons used in the experiment. The research was supported by grants from the Ontario Mental Health Foundation and the Medical Research Council of Canada to James M. Swanson.     

Associations between the developmental trajectories of visual scanning and disengagement of attention in infants

The relation between the developmental trajectories of visual scanning and disengagement of attention and gaze were examined throughout early infancy. A sample of 10 infants carried out a scanning and a disengagement task with the same visual stimuli six times between 6 and 26 weeks of age. Frequency and latency measures were analyzed using multivariate multilevel models and Monte Carlo analyses. The results suggest that the ability to scan a face or an abstract stimulus evolves slightly earlier than the ability to shift gaze to a newly appeared target in the periphery. This is consistent with the account that the parvocellular stream becomes functional slightly before the magnocellular stream. The study revealed no indications of a positive association between the development of scanning and disengagement on the level of the individual infant. Scanning and disengagement change scores contrasted more with one another than could be expected on the basis of chance. This implies that the magnocellular and the parvocellular stream develop rather independently up to the age of 26 weeks.     

Finding lung nodules with and without comparative visual scanning

The effect of a pretarget (TS1) masked by a noise mask (MS) upon the recognition of a posttarget (TS2) was examined in a TS1-MS-TS2 paradigm. The results clearly showed that the presentation of TS1 masked completely by MS reduced the recognition of a subsequent TS2 to a much greater extent if TS2 was the same as TS1 than when it was not. The results suggest that a TS1 that is perceptually masked by an MS nevertheless continues to have an effect within the visual system. A possible explanation of this reductive effect is described briefly.     

The use of visual and name codes in scanning and classifying colors

The effect of incongruent color words on speed of classifying ink colors was measured in visual scanning tasks and in card sorting tasks. In both cases, little or no interference effects were noted when the classification allowed focusing on a single ink color or a set of highly similar colors (adjacent hues). Substantial interference occurred when the task required grouping of three dissimilar colors (nonadjacent hues). These findings suggest that the relative efficiency of name and visual codes in making perceptual classifications is largely dependent upon the memory requirements imposed by the task.