Simon Fischer-Baum

Modality and Morphology What We Write May Not Be What We Say

Written language is an evolutionarily recent human invention; consequently, its neural substrates cannot be determined by the genetic code. How, then, does the brain incorporate skills of this type? One possibility is that written language is dependent on evolutionarily older skills, such as spoken language; another is that dedicated substrates develop with expertise. If written language does depend on spoken language, then acquired deficits of spoken and written language should necessarily co-occur. Alternatively, if at least some substrates are dedicated to written language, such deficits may doubly dissociate. We report on 5 individuals with aphasia, documenting a double dissociation in which the production of affixes (e.g., the -ing in jumping) is disrupted in writing but not speaking or vice versa. The findings reveal that written- and spoken-language systems are considerably independent from the standpoint of morpho-orthographic operations. Understanding this independence of the orthographic system in adults has implications for the education and rehabilitation of people with written-language deficits.

Representation of item position in immediate serial recall: Evidence from intrusion errors.

In immediate serial recall, participants are asked to recall novel sequences of items in the correct order. Theories of the representations and processes required for this task differ in how order information is maintained; some have argued that order is represented through item-to-item associations, while others have argued that each item is coded for its position in a sequence, with position being defined either by distance from the start of the sequence, or by distance from both the start and the end of the sequence. Previous researchers have used error analyses to adjudicate between these different proposals. However, these previous attempts have not allowed researchers to examine the full set of alternative proposals. In the current study, we analyzed errors produced in 2 immediate serial recall experiments that differ in the modality of input (visual vs. aural presentation of words) and the modality of output (typed vs. spoken responses), using new analysis methods that allow for a greater number of alternative hypotheses to be considered. We find evidence that sequence positions are represented relative to both the start and the end of the sequence, and show a contribution of the end-based representation beyond the final item in the sequence. We also find limited evidence for item-to-item associations, suggesting that both a start-end positional scheme and item-to-item associations play a role in representing item order in immediate serial recall.

Representation of letter position in single-word reading: Evidence from acquired dyslexia

Visual word recognition requires information about the positions as well as the identities of the letters in a word. This study addresses representation of letter position at prelexical levels of the word recognition process. We present evidence from an acquired dyslexic patient, L.H.D., who perseverates letters in single-word reading tasks: Far more often than expected by chance, L.H.D.s reading responses include letters from preceding responses (e.g., SAILOR read as SAILOG immediately after FLAG was read correctly). Analyses carried out over two large data sets compared the positions of perseverated letters (e.g., the G in SAILOG) with the positions of the corresponding “source” letters (e.g., the G in FLAG). The analyses assessed the extent to which the perseverations preserved source position as defined by various theories of letter position representation. The results provided strong evidence for graded both-edges position representations, in which the position of each letter is encoded coarsely relative to both the beginning and the end of the word. Alternative position representation schemes, including letter-context and orthosyllabic schemes, were not supported.

Time, Space and Memory for Order

Information about the order of items in a sequence can be conveyed either spatially or temporally. In the present investigation, we examined whether these different modes of presentation map onto compatible mental representations of serial order. We examined this issue in three immediate serial-recall experiments, in which participants recalled lists of letters in the temporal order in which they had appeared. Each letter in a to-be-remembered sequence was presented in a unique spatial position, with the order of these spatial positions progressing from either left to right or right to left. In this way, the visually presented lists contained both temporal and spatial order information. Recall of the temporal order information was more accurate with congruent spatial order information—that is, when the letters progressed from left to right, following the typical reading direction of English—than when the spatial order information was incongruent. These results suggest compatible representations of serial order when sequences are conveyed spatially and temporally.

Perseveration during verbal fluency in traumatic brain injury reflects impairments in working memory.

OBJECTIVE Previous studies of verbal fluency have reported higher rates of perseverative responses in both Alzheimers disease (AD) and traumatic brain injury (TBI) relative to control groups. These perseverations could arise from a number of impairments-for example, failures in working memory, inhibitory control, or word retrieval-and different clinical populations may show an increase in perseveration because of different underlying deficits. The objective of the current report is to investigate the cause of perseveration in verbal fluency in individuals with TBI and compare those results to a recent study of individuals with AD. METHOD In a previous study, conducted by Miozzo, Fischer-Baum, and Caccappolo-van Vliet (2013), perseveration errors produced by individuals with AD were shown to have long lags between the 1st occurrence of a word and its repetition in verbal fluency, suggesting that perseverations were caused by a failure of the working memory mechanisms that control response monitoring. In the present investigation, we applied the same analysis to the perseveration errors produced during 197 administrations of the verbal fluency task with 143 individuals with TBI. RESULTS The perseverations of individuals with TBI showed a lag distribution similar to that of the AD population, with the lag between the 1st occurrence of a word and its repetition systematically longer than would be expected by chance. CONCLUSIONS These results suggest that the perseverations produced during verbal fluency in individuals with TBI stem from the same working memory mechanism proposed in AD, rather than inhibitory control or word retrieval deficits. (PsycINFO Database Record

Serial position encoding of signs

Reduced short-term memory (STM) capacity has been reported for sign as compared to speech when items have to be recalled in a specific order. This difference has been attributed to a more precise and efficient serial position encoding in verbal STM (used for speech) than visuo-spatial STM (used for sign). We tested in the present investigation whether the reduced STM capacity with signs stems from a lack of positional encoding available in verbal STM. Error analyses reported in prior studies have revealed that positions are defined in verbal STM by distance from both the start and the end of the sequence (both-edges positional encoding scheme). Our analyses of the errors made by deaf participants with finger-spelled letters revealed that the both-edges positional encoding scheme underlies the STM representation of signs. These results indicate that the cause of the STM disadvantage is not the type of positional encoding but rather the difficulties in binding an item in visuo-spatial STM to its specific position in the sequence. Both-edges positional encoding scheme could be specific of sign, since it has not been found in visuo-spatial STM tasks conducted with hearing participants.

How much better? The challenge of interpreting interactions in intervention studies

The weighted statistics (WEST) approach recommended by Howard, Best, and Nickels (2014) provides a simple, statistically rigorous method for comparing the size of a treatment effect that can be used for comparisons across conditions (e.g., trained vs. untrained items), time (e.g., improvement during baseline testing vs. preto post-treatment improvement), participants, or intervention method. The approach analyses the change in per cent correct between preand post-intervention for each item used in the study by subtracting the per cent correct between the two conditions, using item-to-item variability to assess statistical significance. The recommendations made by Howard and colleagues will undoubtedly strengthen the inferences that can be drawn from single-case intervention studies. However, I have some concerns with the statistical approach they suggest. While using difference scores is a convenient way to measure the size of an effect, alternative measures may better capture the goals of an intervention study. The choice of effect size can have serious consequences for the statistical inferences drawn from a study, particularly when the central question relies on the interpretation of an interaction. Furthermore, there are serious statistical problems with comparing differences in per cent correct using parametric statistics like t-tests and analyses of variance (ANOVAs) as suggested by the WEST approach (e.g., Jaeger, 2008). I believe that consideration of these statistical issues will further strengthen single-case design intervention studies.

The analysis of perseverations in acquired dysgraphia reveals the internal structure of orthographic representations.

At a minimum, our long-term memory representations of word spellings consist of ordered strings of single letter identities. While letter identity and position must certainly be represented, it is by no means obvious that this is the only information that is included in orthographic representations, nor that representations necessarily have a one-dimensional “flat” structure. Evidence favours the alternative hypothesis that orthographic representations, much like phonological ones, are internally rich, complex multidimensional structures, though many questions remain regarding the precise nature of the internal complexity of orthographic representations. In this investigation, we test competing accounts of the internal structure of orthographic representations by analysing the perseveration errors produced by an individual with acquired dysgraphia, L.S.S. The analysis of perseveration errors provides a novel and powerful method for investigating the question of the independence of different representational components. The results provide clear support for the hypothesis that letter quantity and syllabic role information are associated with, but separable from, letter identity information. Furthermore, the results indicate that digraphs—letter pairs associated with a single phoneme (e.g., the SH in FISH)—are units of orthographic representation. These results contribute substantially to the further development of the multidimensional hypothesis, providing both new and converging evidence regarding the nature of the internal complexity of orthographic representations.

Orthographic units in the absence of visual processing: Evidence from sublexical structure in braille.

Reading relies on the recognition of units larger than single letters and smaller than whole words. Previous research has linked sublexical structures in reading to properties of the visual system, specifically on the parallel processing of letters that the visual system enables. But whether the visual system is essential for this to happen, or whether the recognition of sublexical structures may emerge by other means, is an open question. To address this question, we investigate braille, a writing system that relies exclusively on the tactile rather than the visual modality. We provide experimental evidence demonstrating that adult readers of (English) braille are sensitive to sublexical units. Contrary to prior assumptions in the braille research literature, we find strong evidence that braille readers do indeed access sublexical structure, namely the processing of multi-cell contractions as single orthographic units and the recognition of morphemes within morphologically-complex words. Therefore, we conclude that the recognition of sublexical structure is not exclusively tied to the visual system. However, our findings also suggest that there are aspects of morphological processing on which braille and print readers differ, and that these differences may, crucially, be related to reading using the tactile rather than the visual sensory modality.

How modality-specific is morphology?

ABSTRACT Writing has long been considered to be dependent on speaking. However, modality-specific dissociations between written and spoken word production imply that word production is supported by distinct neural mechanisms in writing, which can be impaired or spared regardless of the intactness of spoken word production. Rapp et al. (2015). Modality and morphology: What we write may not be what we say. Psychological Science, 26, 892–902 documented a double dissociation where problems with regular inflections were selectively restricted to writing or speaking. We report on two English-speaking aphasic individuals who exhibit this same modality-specific dissociation of inflectional processing, replicating the original findings. We expand on Rapp et al.’s study by examining whether the dissociations observed with regular inflections extend to other morphological forms, such as derivation and irregular inflection. Results showed that the dissociation holds for derivation; however, both participants were impaired with irregular inflections in both output modalities. Implications of these findings for morphological processing and the independence of the orthographic system are discussed.