Attentional deficit in learning-disabled children: evidence from visual half-field asymmetries

The structural theory of cerebral lateralization has been typically used to explain hemispheric asymmetries. However, the attentional model of brain functioning may help resolve some of the inconsistent findings with groups of learning-disabled children. To test this hypothesis, a visual half-field paradigm for word recognition was employed in a group of 26 learning-disabled and 26 normal children matched for sex, chronological age, and handedness. Three experimental conditions (unilateral, cued unilateral, and bilateral) and two word error types (visually and acoustically confusable words) were analyzed. The results indicated that normals produced the expected RVHF superiority under all experimental conditions, but the learning-disabled produced the expected RVHF superiority only under the cued unilateral condition. Learning-disabled children also made significantly more visually and acoustically confusable errors than normals and unlike normal children increased the number of acoustic errors in the RVF under bilateral stimulation. These results provide evidence that learning-disabled children may process information inefficiently and have brain activation patterns that are more susceptible to attentional effects.     

Neuropsychological assessment of learning disabilities: a discriminant analysis

The neuropsychological test scores of 23 learning disabled children were compared with those of a matched population of normal children in the 9-1 to 13-1 age range. All children were administered the Wechsler Intelligence Scale for Children-Revised (WISC-R), a dichotic listening task involving both free and directed recall conditions, a handedness inventory, the Tactile Performance Test and the Category Test from the Halstead-Reitan Neuropsychological Test Battery. A multivariate analysis of variance resulted in a significant separation between groups (p less than .001) using these procedures. A stepwise discriminant function analysis revealed that both of the directed dichotic tasks contributed the most of all 13 measures to the significant group separation. In addition, other cognitive tasks found to discriminate normal from learning disabled children include general verbal processes, concept formation, and tactile memory. These findings suggest that the directed dichotic listening procedure and the WISC-R Verbal IQ measure are reasonably valuable clinical tools in the classification of learning disabilities.     

Development of cerebral dominance: dichotic listening asymmetry in normal and learning-disabled children

The magnitude of the dichotic right-ear advantage was assessed in 48 normal and 48 learning-disabled children representing an age range of approximately 5 years. All subjects were matched according to age, sex, and handedness. An analysis of results indicated a significant right-ear advantage in both the normal and learning-disabled children, but revealed no developmental trends for either group. Differences observed in the performance of the learning-disabled and normal children may reflect variability in selective attention rather than differences in the degree of cerebral lateralization. These results suggest a need for a reconceptualization of the causative factors affecting children with learning disorders and lend support to the notion that cerebral lateralization is not a developmental phenomenon.     

Information processing and speech lateralization in learning-disabled children

The relationship between information processing and speech lateralization was investigated in learning-disabled children. The Kaufman Assessment Battery for Children (K-ABC) assessed simultaneous and successive processing while a dichotic listening paradigm with free recall and directed attention conditions assessed speech lateralization. A three-factor ANOVA design conducted on the dichotic data revealed that normal children demonstrated stronger right ear advantage (REA); whereas learning-disabled showed weaker right ear advantage. Further, lambda analyses conducted on individual subjects revealed that the learning-disabled did not demonstrate the REA, were not biased attenders, and did not get more right ear than left ear items when attention was directed to one ear. Multiple-regression analysis was used to predict sequential processing from the dichotic data for both groups. Learning-disabled children demonstrated a substantial deficit in sequential processing as compared to normal children. These results indicate that learning-disabled children may not have adequate cerebral lateralization of receptive speech processes, shift their attention more readily, and are more inadequate in sequential processing that presumably subserves language functioning. Perhaps learning-disabled children have deficiencies of processor capacity of salient areas of the left (language) hemisphere.     

Hemispheric specialization in learning disabled readers' recall as a function of age and level of processing

This study was designed to test the inadequacy of two theoretical accounts of learning disabled readers' memory deficiencies. Two age groups of learning disabled and nondisabled readers were compared on diotic and dichotic listening recall tasks for semantically organized, phonemically organized, and categorically unrelated word lists presented in either the left, right, or both ears. Dependent measures were free recall, serial recall, recall organization, and hierarchical organization. As expected, recall increases were a function of age, group, and level of word processing. However, the results clearly demonstrated that age and group recall differences were an interaction of both mode of presentation and level of processing. The recall differences between reading groups were attributed to word knowledge (superordinate categorization) rather than recall organization within cerebral hemispheres or differences in hemispheric capacity, per se.     

Hemispheric emotional asymmetry in a dichotic listening task.

In a dichotic listening experiment white noise was played to one ear and either music or poetry to the other ear. Subjects rated the stimuli on each of three dimensions. The results showed that both music poetry were judged as more pleasant when heard at the left than the right ear. In addition the music, but not the poetry, was perceived as more soothing at the left ear. The findings are discussed in relation to other indications in the literature that left and right cerebral hemispheres differ in their emotional make-up.     

Spatial perspective taking in young children.

Four- and five-year-old children were tested in a spatial perspective task employing a production format. They were shown a photograph of an aspect of a doll house and asked to generate the view on the photograph for a puppet that served as the observer. The house was mounted on a lazy Susan and could be rotated freely by the children. Puppet line of regard (to a corner, side, or rear of the house) and photograph type (fron, corner, side, or rear) constituted within-subject factors. Puppet position, photograph type, and age affected patterns of errors and proportion of correct responses. It was concluded that perspective taking is highly task dependent as well as dependent upon developmental status.     

A model of problem solving with incomplete constraint knowledge

The problem-solving behavior of subjects presented with a series of Tower of Hanoi problems is examined. A production system model which incorporates elements of domain-specific knowledge into a general problem-solving framework is presented. Other models developed for the task are based on understanding of complete solution strategies and are not satisfactory models of nonexpert human performance. The current model discriminates between problem-solving behavior based on constraint knowledge and behavior based on nonspecific general search strategies. A variety of move choice and latency measures are used to compare the performance of the model to human subject performance.     

Determinants of infant visual fixation: evidence for a two-process theory

Three experiments were conducted to investigate the dynamics of the human infant's (4 months old) visual fixation. The general finding that, over a series of trials, infants fixate longer to a complex than to a simple stimulus was replicated. The function relating fixation time to trials was shown to be nonmonotonic when the stimulus was complex (fixation time increased between Trials 1 and 2 and then decreased), but was monotonic when the stimulus was simple (it decreased systematically over trials). Additional experiments indicated that (a) the nonmonotonic function associated with the complex stimulus was eliminated when the interval separating Trials 1 and 2 was increased from 10 to 20 or 30 s (Experiment 2), and (b) the difference in fixation time between the complex and the simple stimulus was eliminated by controlling their effects in a within-subjects design (Experiment 3). These data challenge the prevailing cognitive-schema theories as a complete account of the dynamics of the infant's visual fixation. A two-process theory that accounts for these data was proposed.     

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.     

Pupillary changes during recall in children

Seven children aged 7–9 years were auditorily presented five-digit numbers for retention intervals of 0 and 10 sec. Pupil size was recorded during stimulus presentation, retention interval, and recall of items. Findings indicate that pupil dilation occurs during encoding and retrieval of stimulus items with pupillary constriction occurring during retention of the items. The pupillary change functions obtained with children were found to be very similar to those obtained with older subjects.     

Lateral asymmetry of personal optimism

By combining models of cerebral emotional asymmetry and unilateral hemispheric activation, it was hypothesized that orienting to the right would produce greater personal optimism about future events than would orienting toward the left. This was supported significantly in two experiments which differed from each other in their manipulations, hypothetical future events, means of responding, and settings. The results supported previous research on unrealistic optimism and extended the concept to show the effect of induced lateral orientation. It was proposed that this effect is mediated by mood, and possibly by perceived control, and that this methodology can be extended to other behaviors which have proven amenable to mood manipulation.     

Laterality differences in speaker and consonant identification in dichotic listening

Two dichotic listening experiments assess the lateralization of speaker identification in right-handed native English speakers. Stimuli were tokens of /ba/, /da/, /pa/, and /ta/ pronounced by two male and two female speakers. In Experiment 1, subjects identified either the two consonants in dichotic stimuli spoken by the same person, or identified two speakers in dichotic tokens of the same syllable. In Experiment 2 new subjects identified the two consonants or the two speakers in pairs in which both consonant and speaker distinguished the pair members. Both experiments yielded significant right-ear advantages for consonant identification and nonsignificant ear differences for speaker identification. Fewer errors were made for speaker judgments than for consonant judgments, and for speaker judgments for pairs in which the speakers were of the same sex than for pairs in which speaker sex differed. It is concluded that, as in vowel identification, neither hemisphere clearly dominates in dichotic speaker identification, perhaps because of minor information loss in the ipsilateral pathways.     

Ambiguous-cue learning in preschool children: A test of the dimensional characteristics of task stimuli

Sixteen preschool children were administered a two-choice discrimination problem consisting of three stimulus compounds: the consistently rewarded stimulus, the consistently nonrewarded stimulus, and the ambiguous stimulus which was nonrewarded when paired with the positive, but rewarded when paired with the negative. When both pair of stimuli, positive-ambiguous and negative-ambiguous, were presented together the subject was required either to choose or to avoid the ambiguous stimulus depending upon the stimulus with which it was paired. In Experiment 1, when each of three stimuli (positive, negative, ambiguous) varied along one nonspatial cue dimension (color), performance was better on negative-ambiguous trials than positive-ambiguous trials. In Experiment 2, when the positive and negative stimuli varied along three nonspatial cue dimensions (colors and form) and the ambiguous stimulus varied along one of these dimensions (color), superior positive-ambiguous over negative-ambiguous performance was obtained. These findings complement those reported for other subjects and confirm Berch's (D. B. Berch, Learning and Motivation, 1974, 5, 135–148) predictions regarding use of differential numbers of cue dimensions.     

A process model for water jug problems

We develop and evaluate a model for the water jug task in which a subject is required to find a sequence of moves (pouring operations) which produce a specified amount of water in each jug. Experiment 1 was designed to evaluate the meansends, move selection heuristics that are assumed by the model. Experiment 2 tested the model's predictions concerning those aspects of the water jug task that determine problem difficulty.A three stage process model incorporating GPS-like, means-ends heuristics and assumptions concerning the utilization of short- and long-term memory was able to account for differences across problems as well as details of the performance of subjects solving a given problem. We conclude that a GPS-like model that only selects one move at a time (no forward planning of move sequences or setting up of subgoals) can provide a good account of solution behavior in the water jug task.     

Habituation in children within a behavior suppression paradigm

Using an instrumental response suppression paradigm, Experiment 1 demonstrated habituation and long-term retention of habituation to a tone stimulus in third-grade children, but specificity of habituation was not obtained when a new tone stimulus was presented. In Experiment 2 first graders showed specificity of habituation to auditory stimuli on the response suppression measure whereas fifth graders did not. However, both age groups evidenced specificity when a skin conductance measure was employed. In addition, specificity of habituation was not affected by amount of training at either age level. Experiment 3 demonstrated specificity of habituation in fifth graders on the response suppression measure when a cross-modality stimulus change was introduced. Implications of these data for analyses of habituation and traditional learning are discussed.     

Therapy and immunization of long-term analgesia in rats

Three experiments are reported which examine the effects of experience with escapable shock either subsequent to (Experiment 1) or prior to (Experiments 2 and 3) a session of inescapable shock on the subsequently produced long-term analgesic reaction in rats. Experment 1 demonstrated that experience with escapable shock 4 hr after a session of inescapable tail shock completely reverses the analgesic response that is normally observed 24 hr later upon reexposure to shock. The escapability of the shock was shown to be the important factor in reversing the analgesic reaction, since subjects given inescapable shock in amounts equivalent to escape subjects exhibited no reduction in analgesia. Experiment 2 showed that experience with escapable shock 4 hr prior to a session of inescapable tail shock could also completely eliminate the long-term analgesic reaction. Experiment 3 replicated the results of Experiment 2, but employed a different escape task and temporal parameters in order to extend the generality of the findings, and to more closely match the procedures employed in behavioral experiments reported by J. L. Williams and S. F. Maier (Journal of Experimental Psychology: Animal Behavior Processes, 1977, 3, 240–253). The implications of these results for the areas of pain control and learned helplessness were discussed.