Nancy Hildebrandt

On the structure of verbal short-term memory and its functional role in sentence comprehension: Evidence from neuropsychology.

Abstract We present a case of a patient with a disorder of short-term memory. BO has a reduced span (2 to 3 items), no recency effect in free recall, and rapid forgetting in Brown-Peterson tasks, establishing her as a patient with impaired short-term verbal memory functions. She shows no effect of either phonological similarity or word length in recall of auditory or written word lists, but some recency effect under recall-from-end conditions and better performance on Brown-Peterson tasks in an unfilled than in a filled condition. This pattern of performance is interpreted as being consistent with a primary disturbance of the articulatory rehearsal processes of S.T.M. and possibly some impairment of the phonological store (using Baddeleys 1986 terminology). Her aphasic disturbance—apraxia of speech—is also consistent with a disturbance of articulatory rehearsal. BO shows a retained ability to extract phonology from print, including an ability to apply sublexical grapheme-phoneme correspondences, thus ind...

Interaction of verb selectional restrictions, noun animacy and syntactic form in sentence processing

Abstract We report five experiments that deal with the role of verb selectional restrictions and the animacy of nouns in the construction and interpretation of syntactic structure. In the first two experiments, the effect of the selectional restriction requirements of verbs and the animacy of nouns on sentence comprehension was assessed in a speeded acceptability judgement task. Four sentence types were presented in which syntactic complexity (object vs subject relativisation) and number of propositions were orthogonally varied. Sentences contained verbs that required either animate subjects or animate objects, and unacceptable sentences were created by violating the selectional restriction requirements of the verb in the embedded clause. Analyses of both reaction time and accuracy data showed that there was an interaction between the selectional restriction requirements of verbs (which correlated perfectly with the animacy of nouns in subject or object position), and syntactic form, on these judgments. E...

Phonological processing of nonwords by a deep dyslexic patient: A rowse is implicitly a rose

Abstract Recent work has shown that implicit phonological knowledge plays a role in the word recognition performance of deep dyslexics [H ildebrandt , N. and S okol , S.M. Reading and Writing , 5 , 43–68, 1993; K atz , R.B. and L anzoni , S.M. Quarterly Journal of Experimental Psychology 45 , 575–608, 1992]. The results of the current study extend this examination to include the investigation of implicit knowledge of nonword phonology. The data from two lexical decision tasks indicate that nonword phonology is available for processing by a deep dyslexic patient in that she produced a significant pseudohomophone effect as well as semantic priming with pseudohomophone primes in lexical decision.

The mani left ti without a trace: A case study of aphasic processing of empty categories

Abstract We present the case of an aphasic patient who shows a selective impairment in interpreting syntactic structures on a test of sentence comprehension involving object manipulation. KG makes errors in assigning the antecedents of phonologically empty NPs called traces (Chomsky, 1982 a,b) in sentences like John seems to Bill to be shaving. He is significantly better at choosing the correct antecedent of another type of empty NP, namely subject- and object- controlled PRO (John persuaded Bill to shave, John promised Bill to shave). He has no trouble choosing the correct antecedents of overt pronouns and reflexives and shows no difficulty with syntactic structures that do not contain an empty category. His difficulty with trace is apparent in sentences which have a certain degree of complexity. He also misassigns the antecedent of subject-controlled PRO under one condition: when an overt reflexive or pronoun has PRO as its antecedent (John promised Bill to shave himself). The pattern of impairment sugg...

Phonological processing of nonwords in deep dyslexia: Typical and independent?

Abstract Patients with acquired deep dyslexia are unable to read nonwords aloud. The deficit has therefore been attributed to damage in nonlexical phonological processing. Buchanan, Hildebrandt and MacKinnon [5 Journal of Neurolingistics 8, 163–182, 1994] demonstrated that a deep dyslexic patient could process nonword phonology in two implicit tests. The generality of this claim is examined by replicating the Buchanan et al. experiments with two other deep dyslexic patients. Dissociations between lexical and nonlexical processing are examined by manipulating nonword phonology in a task that does not require lexical analysis. The results suggest that sensitivity to nonword phonology in deep dyslexia is common and is distinct from a purely lexical analysis.

Implicit sublexical phonological processing in an acquired dyslexic patient

We report a case study of an acquired dyslexic subject, who on tasks standardly used to assess acquired dyslexia showed no evidence of having any access to sublexical phonological information. However, on a lexical decision task, he showed normal effects of spelling regularity for low-frequency words. Since this effect is typically attributed to the use of sublexical phonological information in word recognition, it appears that sublexical phonological processing is occurring for this subject. The spelling regularity effect is discussed with respect to models of written word recognition and to acquired dyslexia. It is suggested that the reason for the discrepancy in test results may be that the types of explicit tasks previously used in the neuropsychological literature on dyslexia, which require conscious awareness of phonological representations, are not sensitive to implicit processing.

Lexical factors in the word-superiority effect

In the Reicher-Wheeler paradigm, fluent readers can identify letters better when they appear in a word than when they appear in either a pronounceable pseudoword (a lexicality effect) or a single letter (a word-letter effect). It was predicted that if both of these effects involve a lexical factor, then adult acquired dyslexic subjects whose deficit prevents access to visual word form should show disruptions of the normal effects on the Reicher-Wheeler task. The results were that dyslexic subjects as well as matched control subjects showed a lexicality effect; however, while the control subjects showed a normal word-letter effect, the dyslexic subjects showed a reverse letter-superiority effect. Both effects, however, showed a systematic variation: As performance on lexical decision improved, the subjects performance on words in the Reicher-Wheeler task was better than that for all the other conditions. These subject correlations were replicated by using data from a second lexical decision experiment, which utilized the same words and pseudowords that were used in the Reicher-Wheeler task. In addition, an item analysis showed that the words that the subjects had discriminated correctly in lexical decision showed a significant advantage over those that they had not, as well as an improvement relative to the other conditions. These results suggest that there is a lexical factor underlying the lexicality and word-letter effects, and it is proposed that the abnormal letter-superiority effect can be accounted for as the manifestation of other competing factors.

The Reicher-Wheeler effect and models of deep and phonological dyslexia

Abstract Current accounts of the functional impairment underlying phonological dyslexia (PD) do not postulate any disturbance of accessing the orthographic lexicon. For deep dyslexia (DD), only the righthemisphere hypothesis involves such a disturbance. However, neither PD nor DD subjects showed the normal word-superiority effects in a Reicher-Wheeler experiment (forced-choice identification of single letters that had been displayed briefly either as single letters or in words or nonwords with a backward mask). Since these word-superiority effects have been argued to lie at the word-specific level, the existing accounts cannot explain the observed results for both PD and DD subjects. Three other accounts are proposed. The most parsimonious account is a degradation hypothesis: as stress is placed on the reading system, reading performance will be seen to degrade gracefully across a number of different tasks and types of stimuli, resulting in symptoms of PD or DD and producing the correlated pattern of performance in oral reading, repetition, lexical decision, and the Reicher—Wheeler task, which was observed for the nine subjects reported here and which is consistent with many previously reported PD and DD subjects.