Semantic and visual memory codes in learning disabled readers

Two experiments investigated whether learning disabled readers' impaired recall is due to multiple coding deficiencies. In Experiment 1, learning disabled and skilled readers viewed nonsense pictures without names or with either relevant or irrelevant names with respect to the distinctive characteristics of the picture. Both types of names improved recall of nondisabled readers, while learning disabled readers exhibited better recall for unnamed pictures. No significant difference in recall was found between name training (relevant, irrelevant) conditions within reading groups. In Experiment 2, both reading groups participated in recall training for complex visual forms labeled with unrelated words, hierarchically related words, or without labels. A subsequent reproduction transfer task showed a facilitation in performance in skilled readers due to labeling, with learning disabled readers exhibiting better reproduction for unnamed pictures. Measures of output organization (clustering) indicated that recall is related to the development of superordinate categories. The results suggest that learning disabled children's reading difficulties are due to an inability to activate a semantic representation that interconnects visual and verbal codes.     

Motor and visual codes interact to facilitate visuospatial memory performance

The spatial working memory system constantly updates spatial representations and many studies have focused on the underlying principles of the encoding and maintenance of visual information. Here we investigated the question of how the production of actions influences spatial working memory. Participants were given a task that required concurrent maintenance of two spatial arrays, one encoded by visual observation accompanied with pointing movements, the other by only visual observation. Across two experiments, movement during encoding was found to facilitate recognition of spatial arrays in a load-dependent manner. The results suggest an action-based encoding principle within the working memory system, and possible underlying action-related mechanisms are discussed.     

Development of visual,name, and conceptual memory codes for pictures

In a recognition memory task, 4-, 8-, and 16-year-olds quickly decided whether or not probe pictures were identical to remembered study pictures. Conceptual and visual, but not acoustic, confusion were evidenced by the longer latencies when probes were visually or conceptually related to study items than when unrelated or rhyming. Visual confusion arose only when seven or fewer pictures intervened between study and probe items, and the kinds of visual similarity that produced confusion changed with age. Conceptual confusion resulted only at longer lags, and the same kinds of conceptual relationships produced confusion at all ages. These findings are discussed in terms of the development of visual and semantic encoding processes.     

The size illusion: visual and kinaesthetic information in size perception

Earlier studies have shown the size of kinaesthetically presented two-dimensional movement patterns to be significantly overestimated. Whether this size overestimation is characteristic of the kinaesthetic system alone has not been established. Two experiments are reported which were designed to investigate size judgment made after kinaesthetic and visual pattern presentation and the effect of environmental cues on the perception of movement patterns. In experiment 1 patterns were presented kinaesthetically (experimenter guided hand movements around the outline of the pattern) or in combination with visual information given by a moving light (pinpoint light attached to the stylus which was moved around the pattern); visual and kinaesthetic cues were either congruent or conflicting with each other; and environmental cues were either present or absent. In experiment 2 static visual display was compared with visually traced pattern presentation, again with or without environmental cues. Overall the results showed that, regardless of experimental manipulation, in all cases where the information was given over time the subject perceived the pattern larger than reality. After static visual display, overestimation of size did not occur.     

Influence of short-term memory codes on visual image processing: evidence from image transformation tasks.

Three experiments showed that phonological recording of visual stimuli in short-term memory (STM) affects coding in long-term memory (LTM) and therefore performance on tasks involving generation and manipulation of visual images of the stimuli. An image transformation task was devised. It consists of mentally subtracting a part of an image to discover in the remainder another object. In Experiment 1, Ss were required to learn a set of easily nameable visual stimuli and then perform the subtraction task on images retrieved from LTM. Performance was significantly better when initial learning was accompanied by articulatory suppression (AS). Experiment 2 confirmed that AS had no effect when the task was performed on an image of a just-presented stimulus. In Experiment 3, the nameability of the stimuli was manipulated. The results replicated the effect of AS for items that were easy to name but showed no effect of AS for stimuli that were difficult to name.     

Age related changes in the effectiveness of name and visual codes in recognition memory

In the first of three studies college, third grade, and kindergarten Ss were able to determine that two stimuli presented 700 msec apart were the same more quickly if they were visually identical than if they shared the same name. If 3000 msec elapsed between stimulus presentations third grade and college Ss responded at the same rate in making both types of matches, whereas kindergarten Ss appeared to continue to respond more quickly in making visual matches. Study II was an unsuccessful attempt to replicate the kindergarten finding. A warning signal, presented 500 msec prior to the second stimulus, reduced RTs at both interstimulus intervals, but no significant differences in making visual and name matches occurred. In Study III first-graders, responding either with or without a warning signal, were found to respond like the older Ss in Study I. The warning signal again reduced RT at both intervals. The results suggest that Ss across a wide age range are able to use the visual properties of a stimulus for only a very brief period as the basis for making matching judgments.     

A psychophysical measure of visual and kinaesthetic spatial discriminative abilities of adults and children

Quantitative estimates of the spatial discriminative capacities of the visual and kinaesthetic systems in adults and children were obtained. Intersensory integration was investigated by including spatial discriminations based on congruent visual plus kinaesthetic reafference. The psychophysical method of adjustment was used with simultaneous comparisons of a fixed and a variable stimulus. The subject's task was to estimate when the variable stimulus (ellipse) was identical to the standard one (circle), under one of three modality conditions: vision, kinaesthesis, and vision plus kinaesthesis. After a pilot study with adults, children (aged 8, 10, and 12 years) and adults were both tested. Subjects from each age group were randomly allocated to each of the three experimental conditions. Results show that the visual and kinaesthetic estimates of the 8- and 10-year-old subjects did not differ significantly, but the visual responses of the adults and 12 year olds were significantly more accurate than corresponding kinaesthetic estimates. Bisensory estimates were significantly more accurate than visual responses only for the 8- and 10-year-old age groups. Intramodal comparisons showed the kinaesthetic estimates of the 8, 10, and 12 year olds to be significantly more accurate than the corresponding adult performance. Adult visual estimates were significantly more accurate than those made by 8 year olds, but were not significantly different from the visual responses of 10 and 12 year olds. Estimates based on bisensory reafference did not differ from each other across the four age groups. It is concluded that modality adeptness and dominance are task dependent and empirically determined rather than being innate properties of sensory systems. The data indicate that intersensory differentiation rather than integration occurs with maturity.     

Visual memory and visual perception: when memory improves visual search

This study examined the relationship between memory and perception in order to identify the influence of a memory dimension in perceptual processing. Our aim was to determine whether the variation of typical size between items (i.e., the size in real life) affects visual search. In two experiments, the congruency between typical size difference and perceptual size difference was manipulated in a visual search task. We observed that congruency between the typical and perceptual size differences decreased reaction times in the visual search (Exp. 1), and noncongruency between these two differences increased reaction times in the visual search (Exp. 2). We argue that these results highlight that memory and perception share some resources and reveal the intervention of typical size difference on the computation of the perceptual size difference.     

Phenobarbitone and kinaesthetic after-effect

The effect of phenobarbitone (phenobarbital), predominantly a central depressant, on kinaesthetic after-effect was examined. The subjects were selected after a preliminary testing with the Maudsley Personality Inventory. They were classified into two groups: extraverts and introverts. The drug was used at different dose levels. A 2 × 4 randomized block design was replicated ten times. The study supports the following conclusions: (a) the extraverted subjects show larger kinaesthetic after-effect than introverted subjects under placebo condition; (b) phenobarbitone has no effect on kinaesthetic after-effects in extraverted subjects except in small doses (30 mg) which reduce the size of the effect; (c) the drug in larger doses (60 mg and 100 rng) produces a significant increasing effect in the introverted group.     

Training of fast tapping with reduction of kinaesthetic, tactile, visual and auditory sensations

Five subjects were trained to tap on a light Morse-key during nerve compression block. The training sessions lasted for 40 sec., with a 5 sec. rest after the first 20 sec. work period. The group learning curve reached 89.5 per cent. level of normal performance by the eighth training session. In the ninth, the testing session, subjects tapped with visual and auditory sense reduction superimposed on the kinaesthetic and tactile impariment of the training condition. Performance in the testing session reached 40.9 per cent. of normal.

The sixth subject was trained in the same task as the other five subjects, but the training condition included elimination of cues from all four sensory channels. He reached 79.09 per cent. of his normal tapping performance in the seventh session.

These results show that the motor skill of tapping can be relearned in the absence of kinaesthetic cues. Furthermore when the subject has no conscious knowledge of any peripheral sensory cues connected with the ongoing motor activity, learning can nevertheless take place. These findings lead to the hypothesis, that skilled motor activity can be monitored by central processes alone.

During the training sessions subjects showed a tendency of tapping in groups of gradually increasing length. It is hypothesized that increased number of taps forming a group gives an indication to the possible mode of action of these central processes.     

Two-channel visual memory

Ss attempted immediate recall of word and color attributes of series of three “Stroop” words (Experiments I and 2) or three colored number words (Experiments 3 and 4), presented either at 2 words/sec or I word/2 sec. They were instructed to give either channel-by-channel recall, grouping words and colors together, or temporal recall, in which the two attributes of each item were to be reported together. In Experiments I and 3, in which words were to be reported before colors, channel-by-channel recall was rather better than temporal recall, especially at the fast rate. In Experiments 2 and 4, the colors were to be reported before the words, and channel-by-channel recall tended to be worse than temporal recall. In all four experiments serial position data suggested that the channel-by-channel strategy was to attend to one attribute (either words or colors) during presentation and hold the other in preattentive storage. By contrast, when instructed to give temporal report, Ss apparently alternated attention between attributes during presentation.     

Self-rated imagery and encoding strategies in visual memory.

The value of self-rated vividness of imagery in predicting performance was investigated, taking into account the mnemonic strategies utilized among subjects performing a visual-memory task. Subjects classified as 'good' or 'poor' imagers, according to their scores in the Vividness of Visual Imagery Questionnaire (VVIQ; Marks, 1972), were to detect as rapidly as possible differences between pairs of similar pictures presented consecutively. No coding instructions were given and the mnemonic strategies used were analysed by studying subjective reports and objective performance measurements. The results indicated that the subjects utilized two main strategies--a detail or an image strategy. The detail strategy was the more efficient. In accordance with a previous study (Berger & Gaunitz, 1977), it was found that the VVIQ did not discriminate between performance by 'good' and 'poor' imagers. However, among subjects who used the image strategy, 'good' imagers performed more rapidly than 'poor' imagers. Self-rated imagery may then have some value in predicting performance among individuals shown to have utilized an image strategy.     

Initial codes for order in memory

The roles of positional and associative information in preserving the order of short sequences of items were investigated either by presenting an item in the same serial position on successive trials (position transfer), or by presenting the same pair of items in adjacent but shifted positions on successive trials (association transfer). While Experiment I found that positive transfer of position information occurred after just one repetition of an item in the same serial position, Experiment II found no evidence for association transfer after a single trial. If an item is presented in the same position, or if a pair of items are presented in adjacent positions on several successive trials, position transfer effects built up more rapidly than association transfer effects (Experiments III and IV). However, the rate at which association transfer effects are established depends on the type of item used, with lists of concrete words showing rapid establishment of associations (Experiment V) but lists of digits showing only slow development of associations (Experiment IV). It was concluded that serial order may be preserved both by positional and associative codes, but the establishment of an associative code is linked to the extraction of information about the items themselves.     

Enduring visual memory despite forced verbal rehearsal.

The ability to decide rapidly that two visual stimuli are nominally the same when they are also visually the same (the Posner effect) was examined for stimuli of increasing visual complexity (Experiment 1) and when a greater variety of visual differences between the two stimuli was employed (Experiment 2). When the two stimuli each consisted of a pair of letters or when to single-letter stimuli sometimes differed in both case and style, the Posner effect occurred even though subjects made overt verbal rehearsals of the first stimulus. The results suggest that losses of the Posner effect found under simpler circumstances are not attributable to a switch from visual to exclusively verbal coding.     

Semantic and phonetic memory codes in beginning readers

In two experiments a group (N=15) of poor beginning readers and of good readers (N=15) were auditorily presented with continuous item lists. The children were asked to indicate whether each item had occurred previously in the list. In Experiment 1, using real words, later items were related either semantically or as rhymes to earlier ones. False positives to each item type were taken as indices of memory coding and showed that good readers encoded both semantic and surface aspects of items. In contrast, poor readers made a large number of meaning-based confusions (saying “old” tohouse whenhome had been presented earlier) but almost none based on rhyme (home/comb confusions). In a second experiment, with phonetically legal nonwords as items, poor readers made a significant number of phonetic false positives, although the good reader controls made more. The results are interpreted as confirming that poor readers are relatively insensitive to surface features of language but that this weakness is most marked when sound and meaning are both available as memory codes.     

Movement imagery in rock climbing: patterns of interference from visual,spatial and kinaesthetic secondary tasks

Climbers were trained on two routes on a climbing wall, one vertical and one horizontal. The routes differed in the amount that could be seen from the start position, in the visibility of the holds (both of which were greater in the vertical climb), and in the need to use a range of hand and body configurations during the climb (which was greater in the horizontal climb); also the vertical climb was shorter than the horizontal climb. After training, subjects imagined climbing the routes under control conditions and with one of three secondary tasks derived from the working memory literature. The secondary tasks were dynamic visual noise, spatial tapping, and kinaesthetic suppression. Spatial tapping increased the duration of both routes; dynamic visual noise increased the duration on the vertical route, and kinaesthetic suppression increased duration on the horizontal route. The results are discussed in terms of the multiple forms of representation for action and the complexity of imagery for skilled movement. It is suggested that these working memory tasks may have a role in elucidating the demands of movement imagery under different conditions. © 1998 John Wiley & Sons, Ltd.     

Individual differences in reported visual imagery and memory performance.

Seventy high school students completed the Vividness of Visual Imagery Questionnaire (VVIQ). Two months later, the 16 highest scores (low visualizers) and the 16 lowest scores (high visualizers) took part in a memory experiment involving abstract words, concrete words and pictures. Analyses of variance showed that high visualizers were superior to low visualizers on all three kinds of item in short-term recall, whereas they were only superior on the concrete words and pictures in long-term recall. Finally, both groups performed equally well on a subsequent recognition test. The results were interpreted as providing support for the validity of the VVIQ.