Thomas C. Lorsbach

Encoding and contextual components of word recognition in good and poor readers

Good and poor readers from the third and sixth grades (9- and 12-year-olds, respectively), named visually presented words as rapidly as possible. Words were in clear or degraded form, and were preceded by related or unrelated words. Poor readers were hurt more by degradation than were good readers, and showed greater benefit from context. In general, the contextual benefit was greater with degraded words than with intact, and this interaction was especially pronounced in the poor readers. The results are consistent with an interactive-compensatory model of word recognition. Under conditions in which stimulus encoding is slow, contextual factors may compensate for this encoding deficit.

Definition for Definitions of Learning Disabilities

This article examines the problem of definition in learning disabilities. First, the focus is on the nature of definition. It is suggested that available definitions of LD are not real in the Aristotelian sense of providing an essence. Rather, they are best viewed as providing stipulative meaning by representing information agreed upon by particular groups. What is stipulated, however, cannot be considered either true or false but only useful for practical purposes. Practice requires operational definitions, which are also fraught with conceptual difficulties. Such difficulties are illustrated in a discussion of discrepancy. It is also suggested that operational definition is too narrowly focused and should be expanded by considering operational interpretations, based on the best available knowledge. Finally, an example is provided of how operational interpretations may be combined into a more comprehensive operational definition for classifying learning disabilities.

The development of explicit and implicit forms of memory in learning disabled children

Abstract Cognitive theorists have recently described two forms of memory. One is termed “explicit” memory and requires the conscious reinstatement of episodic memories, while the other form of memory is referred to as “implicit” (e.g., Graf & Schacter, 1985 ). The present study tested the hypothesis that tasks requiring the use of explicit forms of memory are sensitive developmental and individual differences, whereas tasks requiring implicit memory are not. Learning disabled children enrolled in the third and sixth grades were compared with third and sixth grade nondisabled children on a series of picture memory tasks. The original hypothesis was confirmed, with significant effects of grade and subject group being observed with explicit memory tasks (naming speed, free recall, and cued recall), but no differences on a fragment completion task.

Dual-task performance as a function of adult age and task complexity.

A dual-task procedure was used to examine capacity demands of letter-matching in younger and older adults. Older subjects generally were slower on both tasks than were younger adults, but this difference was especially pronounced for the late stages of category matching, suggesting that retrieval and comparison of category information is particularly demanding for older adults.

Context Processing and Cognitive Control in Children and Young Adults

T. S. Braver and colleagues (e.g., T. S. Braver, J. D. Cohen, & D. M. Barch, 2002) have provided a theory of cognitive control that focuses on the role of context processing. According to their theory, an underlying context-processing mechanism is responsible for the cognitive control functions of attention, inhibition, and working memory. In the present study, the authors examined whether T. S. Braver et al.s theory can account for developmental differences in cognitive control. The authors compared the performance of children (M age = 11.9 years, SD = 0.43 years) with that of young adults (M age = 21.7 years, SD = 3.61 years) on a continuous performance task (AX-CPT) that placed demands on context processing. The results suggest that developmental differences in the cognitive control functions of attention, inhibition, and working memory may be based on age-related changes in an underlying context-processing mechanism.

Developmental Differences in Cognitive Control: Goal Representation and Maintenance During a Continuous Performance Task

The present study examined whether younger and older children differ in the use of the goal-related information in a continuous performance task (AX-CPT), and if so, whether those age differences are due to the ability to represent and/or maintain goal information. Experiment 1 compared third- and sixth-grade children in their ability to transform the identity of letter cues into goal representations, as well as to sustain those goal representations during a long (5,500 ms) cue-probe delay in the AX-CPT. Experiment 2 used a short cue-probe delay (1,000 ms) and thereby eliminated the demands of maintaining goal representations in working memory. In addition, Experiment 2 varied the level of demand that was placed on the ability to represent context information by varying the features of letter cues. The combined results of these experiments indicated that sixth graders were superior to third graders in cognitive control under conditions that placed demands on either the ability to represent or maintain goal-related information.

Automatic semantic feedback during visual word recognition

Four experiments were conducted to determine whether semantic feedback spreads to orthographic and/or phonological representations during visual word recognition and whether such feedback occurs automatically. Three types of prime-target word pairs were used within the mediated-priming paradigm: (1) homophonically mediated (e.g., frog-[toad]-towed), (2) orthographically mediated (e.g., frog-[toad]-told), and (3) associatively related (e.g., frog-toad). Using both brief (53 msec; Experiment 1) and long (413 msec; Experiment 3) prime exposure durations, significant facilitatory-priming effects were found in the response time data with orthographically, but not homophonically, mediated prime-target word pairs. When the prime exposure duration was shortened to 33 msec in Experiment 4, however, facilitatory priming was absent with both orthographically and homophonically mediated word pairs. In addition, with a brief (53-msec) prime exposure duration, direct-priming effects were found with associatively (e.g., frog-toad), orthographically (e.g., toad-told), and homophonically (e.g., toad-towed) related word pairs in Experiment 2. Taken together, these results indicate that following the initial activation of semantic representations, activation automatically feeds back to orthographic, but not phonological, representations during the early stages of word processing. These findings were discussed in the context of current accounts of visual word recognition.

Direct and Indirect Testing of Picture Memory in Second and Sixth Grade Children.

Abstract Recent studies have found that a developmental dissociation may be observed between direct and indirect tests of memory. Although older children perform significantly better than younger children on direct tests of memory, these developmental differences are often absent when memory is tested indirectly. The present investigation further examines whether such a developmental dissociation is obtained between a direct and an indirect test of picture memory. Recognition memory provided the direct measure, whereas the magnitude of naming facilitation that accompanied “old,” relative to “new,” pictures provides the indirect measure of memory. Second and sixth grade children were asked to study a set of pictures, and on the following day measures of recognition accuracy and naming facilitation were obtained. Although older children performed significantly better on the recognition task, the two age groups were comparable in their degree of naming facilitation.

Individual Differences in Semantic Encoding Processes

A Type I incidental learning paradigm was used to examine the manner in which learning disabled children and non-learning-disabled children responded to systematic variations in the semantic elements of words. Accuracy of performance on word categorization tasks did not differentiate the two subject populations. However, the LD subjects categorized words less rapidly and recalled fewer words on a subsequent free recall task than the non-LD subjects. The results suggested that semantic encoding and retrieval processes occur with less automaticity in learning and reading disabled children. Less rapid and inefficient use of the semantic content of words appears to be a contributing factor in the reduced performance of LD children on verbal learning tasks.

The dissociation of repetition priming and recognition memory in language/learning-disabled children

Recent research has found that the performance of learning-disabled and non-disabled children is dissociated on explicit and implicit tests of memory (Lorsbach & Worman, 1989). The current study further examined this phenomenon by comparing language/learning-disabled (L/LD) and nondisabled children (NLD) on tasks measuring primed picture-naming and item recognition. Included within the design of the experiment was the manipulation of both presentation format (pictures or words) and retention interval (immediate or 1 day). Children were initially presented with pictures and words. Performance was measured both immediately and following a 1-day retention interval on a picture naming task, an item recognition task, and a supplementary measure of memory for presentation format. The magnitude of facilitation associated with primed picture-naming was found to be independent of item recognition performance. In addition, the effects of population (L/LD and NLD) and retention interval (immediate test or 1 day) each produced dissociations between the magnitude of naming facilitation and item recognition performance. Results were discussed in terms of their implications for our understanding of the nature of memory difficulties in L/LD children.