Performance on paced serial addition tasks indicates an associative network for calculation

Although paced serial addition (PSA) tasks are considered to be tests of general information-processing capacity, recent work suggests that performance on such tasks is influenced by arithmetic-specific variables. We designed two visual PSA experiments to determine whether the performance of normal adults would support predictions derived from the cognitive psychology of calculation. Experiment 1 showed that mixing familiar (Arabic numeral) and less familiar (Roman numeral) stimulus formats reduced scores below the averaged scores for pure Arabic and Roman lists. The Roman-Arabic order of addends was more difficult than the Arabic-Roman order. Experiment 2, which involved only Arabic numerals as addends, showed that performance could be impaired by constraining the trial-to-trial variability of sums. The results of both experiments confirm the importance of arithmetic-specific variables in PSA and provide support for an associative network model of calculation. In addition, the findings implicate interference from extraneous addends and responses as the performance-limiting factor.     

Paced Serial Addition: Modality-Specific and Arithmetic-Specific Factors

Tests of paced serial addition are used to detect diminished information-processing capacity. Nonetheless, performance might be influenced by modality-specific interference or by variables that specifically affect numerical processing. In a series of three experiments with normal adults, we manipulated, respectively, the modality in which addends were presented, the modality in which responses were produced, and the format in which visual addends were displayed. Performance was enhanced when stimuli were presented visually and when responses were made manually. When visual addends were used, Arabic numerals were processed more effectively than number words. Thus, performance was influenced by modality-specific interference and by presentation format. We conclude that paced serial addition tasks may not provide a pure measure of general information-processing capacity.     

Remediation of arabic numeral processing in a case of developmental dyscalculia

In this case study we investigated numeral transcoding in CM, a young man with developmental dyscalculia. Our initial assessment revealed that CM's difficulties in numeral transcoding occurred mainly on tasks requiring the production of Arabic numerals. His errors on these tasks were most often syntactically ill-formed strings in which the basic lexical elements are retained, but the overall structure is incorrect (e.g. nine hundred two thousand seventy → 92,70). We then implemented a training programme designed to overcome CM's syntactic impairment. Pre-training/post-training comparisons revealed significant improvement on the trained written-verbal-to-Arabic task as well as on an untrained spoken-verbal-to-Arabic task presumed to share the same Arabic numeral production process. A comparison of CM's numeral transcoding performance with control children showed that CM's performance improved from a third-grade level to approximately a fourthgrade level (i.e. the grade in which most children begin to display proficient number transcoding skills). Further analyses revealed that the syntactic errors produced by CM and the control subjects were inconsistent in terms of length, a finding that contrasts with the results of previous studies of numeral transcoding in children. In the general discussion we mention possible reasons for the discrepant outcomes across studies.     

Bilateral processing of redundant information: the influence of stimulus notation and processing speed in number comparison

Improved performance is generally observed when identical copies of a stimulus are presented bilaterally to both visual half fields (VHFs), relative to unilateral single presentations. We investigated the influence of stimulus notation and processing speed on this bilateral redundancy gain (B-RG) in number comparison. Two experiments were performed with consistent (i.e., two identical copies of Arabic digits or word numerals) and inconsistent (i.e., an Arabic digit in one VHF with a word numeral of the same value in the other VHF) displays (see also Marks and Hellige, 2003 for a similar design in number naming). In Experiment 1, the processing speeds of the Arabic digits were faster than the ones of the word numerals while in Experiment 2, the processing speeds of the two stimulus notations were kept equal. A significant difference between consistent and inconsistent conditions was restricted to Experiment 1 in which the processing speeds of the two stimulus notations diverged. These results are discussed in the framework of a simple race model in which two independent hemispheric processes compete for the control of response, and the faster process wins.     

Object Recognition in the Cerebral Hemispheres as Revealed by Visual Field Experiments

Visual object recognition contains several stages of information processing carried out along the ventral visual pathway. Brain imaging and behavioural studies have suggested hemispheric asymmetries in object recognition, but the results do not provide a coherent view about the direction of the asymmetries or about the processing stage at which the asymmetries emerge. In order to clarify the contribution of the hemispheres to object recognition, two visual field experiments using normal participants were conducted. Experiment 1 used five different decision-making tasks to study processing at different stages of object recognition. The results showed that familiar objects were recognised faster when presented to the left visual field (LVF) than to the right visual field (RVF) in tasks requiring decisions between familiar objects vs scrambled objects or between familiar objects vs coherent novel objects, suggesting that the right hemisphere is superior in matching visual stimuli to stored representations. Experiment 2 replicated the LVF advantage in object decisions with the novel objects from Experiment 1 that had an unfamiliar overall shape but basic features similar to those of familiar objects. In addition, a RVF advantage emerged with chimeric objects composed by changing parts of familiar objects. The results suggest that the right hemisphere is superior at accessing the overall shape of objects from memory whereas the left hemisphere is superior at analysing whether the parts of objects match to memory representations.     

Interhemispheric cooperation of left- and right-handers in mental calculation tasks

Relations between handedness and interhemispheric processing in cognitive tasks were examined. Thirty six right-handers and thirty left-handers (familial and nonfamilial left-handers) were asked to add two numbers which were presented tachistoscopically. Two numbers were displayed either to one visual field, or one to the left and one to the right visual field simultaneously. In Experiment 1, the numbers were displayed in Arabic numerals, and in Experiment 2 one of the numbers was displayed in Kanji and one in Arabic numerals. The results of Experiment 1 showed a bilateral advantage, however no subject group difference was shown in the performance of the three (left unilateral, right unilateral, and bilateral) presentation conditions. Though familial left-handers showed a weaker tendency to different patterns than right and non-familial left-handers, the results of Experiment 2 were largely similar to those of Experiment 1. These findings suggest that interhemispheric processing may not differ between left- and right-handers.     

Interhemispheric Cooperation of Left- and Righthanders in Mental Calculation Tasks

Relations between handedness and interhemispheric processing in cognitive tasks were examined. Thirty six right-handers and thirty left-handers (familial and nonfamilial left-handers) were asked to add two numbers which were presented tachistoscopically. Two numbers were displayed either to one visual field, or one to the left and one to the right visual field simultaneously. In Experiment 1, the numbers were displayed in Arabic numerals, and in Experiment 2 one of the numbers was displayed in Kanji and one in Arabic numerals. The results of Experiment 1 showed a bilateral advantage, however no subject group difference was shown in the performance of the three (left unilateral, right unilateral, and bilateral) presentation conditions. Though familial left-handers showed a weaker tendency to different patterns than right and non-familial left-handers, the results of Experiment 2 were largely similar to those of Experiment 1. These findings suggest that interhemispheric processing may not differ between left- and righthanders.     

Serial order short-term memory capacities and specific language impairment: No evidence for a causal association

This study re-explored the nature of verbal short-term memory (STM) deficits in children with specific language impairment (SLI), by distinguishing item and serial order STM processes. Recent studies have shown serial order STM capacity to be a critical determinant of language development, relative to item STM. In Experiment 1, 12 children with SLI, 12 age-matched children and 12 language-matched children were administered serial order recognition and reconstruction tasks. Experiment 2 assessed implicit serial learning abilities via a Hebb learning task. The SLI group showed impaired performance for the serial order reconstruction and recognition tasks, relative to language-matched and/or age-matched control groups. However, normal serial position effects were observed in all SLI children in the serial order reconstruction task, suggesting normal coding of serial position information. Similarly, performance on the Hebb serial learning task was at chronological age appropriate levels. Experiment 3 showed that the group differences observed for the serial order STM tasks in Experiment 1 disappeared when the SLI group was compared to a mental age-matched control group. Experiment 4 showed similar performance levels in the SLI group and the mental age-matched control group for a nonword recognition task assessing item STM capacities. This study shows that children with SLI have no specific impairments for serial order and item STM components but that poorer general cognitive efficiency is related to functional limitations in verbal STM tasks. The data are in line with limited information processing accounts of SLI.     

Selective impairment for reading numbers and number words: a single case study

The article reports the case of a patient who showed a selective inability in reading multi-digit numbers following recovery from aphasic disorders. Although his ability to read words, non-words, syntagms and sentences was almost preserved, he made errors with Arabic numerals and number words. Different types of errors with alphabetic material were also observed: he made only rare phonological substitutions with linguistic stimuli, whereas errors were almost always lexical in reading number words. A series of experiments showed that his ability to access number semantics was intact. In contrast, he selectively failed in all production tasks (including calculation), but only when the required response was in the oral output modality. This pattern was interpreted in terms of a selective deficit to the spoken number name production system. Furthermore, the different types of errors made with alphabetic materials belonging to the two classes of stimuli (numerical versus non-numerical) further support the hypothesis of a categorical organisation in the lexical-semantic system.     

Treating number transcoding difficulties in a chronic aphasic patient

Background : Number transcoding comprises the ability to read and write Arabic numerals and number words. Although number transcoding and counting are frequently impaired in aphasic patients, little attention has been given to the development of specific treatment methods and the evaluation of their efficiency. We report the treatment of the chronic aphasic patient PK who had severe difficulties in reading Arabic numerals. Number words could only be produced with an automatic counting strategy, always beginning with one. Aims : The therapy study was aimed at examining whether PK's numeral transcoding abilities could be improved by an intensive remediation programme that comprised tasks in which Arabic numerals had to be transcoded into number words. Methods & Procedures : Treatment consisted of specific training blocks of gradually increasing complexity. Therapy started with reading one-digit Arabic numerals, followed by teens, decades, and two- to five-digit numerals, which were divided into different subgroups according to complexity. Outcomes & Results : After an 8-week therapy period significant improvement in the processing of one- to five-digit numbers was observed. PK was able to read 49.4% of the Arabic numerals as compared to 2.2% before treatment. Performance was influenced significantly by number length and number word structure. Transcoding abilities improved remarkably for two- and three-digit numbers containing a zero or ending with two zeros. Stability of the treatment effects was assessed in a follow-up study 6 months after termination of the treatment programme. PK was still able to read 48.3% of the Arabic numerals successfully. Conclusions : In a single-case study of patient PK, suffering from chronic severe aphasia that was also characterised by severe transcoding and calculation impairments it could be demonstrated that these transcoding problems could be remedied to a substantial degree when employing a carefully graded intensive retraining programme for Arabic number naming.     

Rapid acquisition of emotional information and attentional bias in anxious children

This study reports on the relationship between evaluative learning (EL) and attentional preference in children with varying degrees of anxiety, as measured by the Multidimensional Anxiety Scale for Children, and varying degrees of parental anxiety, as measured by scores on the Beck Anxiety Inventory (BAI). In the first experiment, 3 age groups (7-8, 10-11 and adults with mean age 26.8 years) were compared on a novel EL method, in which neutral images "morphed" over 1s into either smiling or angry adult faces. There were no differences in EL between the age groups-each showing a strong EL effect. In 2 subsequent experiments, we examined learning and attention to stimuli following EL trials in 7- to 8-year olds. In Experiment 2, panic/separation anxiety (PSA) and the mothers' BAI predicted the overall magnitude of EL. In addition, high PSA children were more likely to attend to a neutral stimulus previously paired with a negative stimulus than were low PSA children. In Experiment 3, only PSA was positively associated with the magnitude of EL. In the attention trials, high PSA children had longer fixation times on frowning faces than did low PSA children but unlike Experiment 2 PSA was not associated with preferential attention towards stimuli with acquired negative valence. These results indicate that associations between learning, attention and emotional information can be influenced by separation anxiety and maternal anxiety.     

Number processing and calculation in a case of visual agnosia

We describe the performance of a brain-damaged subject who suffered from visual agnosia leading to major difficulties in generating and exploiting visual representations from long-term memory. His performance in a physical judgement task in which he was required to answer questions about the visual shapes of Arabic numerals reflected his agnosic problems. However, he showed no impairment in usual number processing and calculation tasks. This case shows that, despite some commonalities in number and object processing, actual numerical processes are not affected by visual agnosia and can be preserved even when fine visual processes are impaired.     

Discrimination, reversal, and shift learning in Huntington's disease: mechanisms of impaired response selection

In a series of three experiments, we investigated different aspects of response selection in early-stage clinically symptomatic Huntington's disease (HD) patients in the context of discrimination learning. A series of structurally related response selection tasks involving discrimination, reversal, and shift learning were employed. In Experiment 1, the mechanisms of our previously reported [37] finding of impaired extra-dimensional shift learning were explored. The results suggested that impaired shift learning in HD is a result of perseverative responding. In Experiment 2, performance on a concurrent-pair (CP) discrimination and reversal task was examined. HD patients showed no deficits in CP discrimination learning or reversal. In Experiment 3, the performance of HD patients on a probabilistic discrimination and reversal task was examined. HD patients were impaired in the learning of a probabilistic discrimination, and also its reversal. This reversal deficit was again the result of perseverative responding. In addition, there was a strong correlation between HD patients' activities of daily living scores and reversal errors. The result are consistent with current theories of the role of the basal ganglia in cognition, and suggest specific impairments in response selection mechanisms in HD, in particular, in overcoming selection biases based on prior reinforcement.     

Counting Back from a Visually Presented Digit Increases Recall Asymmetries Between Hemispheres: A Brown-Peterson Experiment with Lateral Projection of Trigrams

The effect of a verbal distracting activity on memory performance of the left and right hemisphere was investigated in normal subjects by showing the time course of laterally presented consonant trigrams in the Brown-Peterson paradigm. Experiment 1 showed that delay alone, with no interpolated activity, did not produce significant hemispheric asymmetries. In Experiment 2 a verbal interfering task produced a significant greater memory impairment for LVF/RH inputs. In order to test some hypotheses fitting the data of these 2 experiments, 2 parameters were altered. Increasing the exposure time (Experiment 3) and reducing the amount of information to be recalled (Experiment 4) reduced the RVF/LH advantage. As in Experiments 3 and 4 the verbal features of both the laterality and the interpolated task were not modified, this result lends support to a dual code model rather than to a selective activation model.     

Hemispheric specialization of abacus experts in mental calculation: Evidence from the results of time-sharing tasks

Hemispheric specialization for mental calculation and verbal tasks in abacus (Soroban in Japanese) experts and control subjects was tested using time-sharing tasks. In Experiment 1, the effects of auditorily presented mental calculation and news-listening tasks on sequential finger tappings were examined. The results revealed that in the mental calculation condition, abacus experts showed greater interference effects on left hand tapping, whereas control subjects showed greater interference effects on right hand tapping (as compared to left hand). In the news-listening condition, abacus experts showed no hand difference while the controls showed greater interference effects on the right hand. In Experiment 2, the effects of visually presented mental calculation and word-reading tasks on sequential finger tapping were examined. The results revealed that in the mental calculation condition, abacus experts showed a non-significant tendency towards greater interference in the left hand whereas the controls showed no hand difference. In the word-reading condition, both abacus experts and controls showed greater interference in the right hand than in the left hand. In Experiment 3, intermediate and upper-rank abacus experts performed a similar task to Experiment 1 under two instruction conditions. The results of this control experiment confirmed that a greater left hand reduction in calculation of abacus experts is not due to subject's cognitive mode but due to the amount of abacus learning experience. These data suggest that (1) learning experiences can affect the pattern of cerebral specialization through the change of approaches to perform cognitive tasks, and (2) the right hemisphere engages in mental calculation for the abacus experts whereas the left hemisphere contributes to mental calculation in ordinary people having no experience of abacus learning.     

Residual Difficulties with Categorical Induction in Children with a History of Autism

In two experiments, typically developing (TD) children, high-functioning children with autism (HFA) and children with a history of autism who have achieved optimal outcomes (OOs), matched on age (M = 13 years) and nonverbal IQ, were asked to extend properties of categories to new items (categorical induction). All groups demonstrated some knowledge of category structure by extending at above-chance levels; however, the TD group extended more consistently than the OO and HFA groups. More consistent extenders had higher lexical and nonverbal IQ scores (Experiment 1) or higher pragmatics scores (Experiment 2). Thus, even very high functioning individuals with autism, or with an OO, still exhibit residual difficulties with category knowledge and extension; moreover, category tasks relate to a variety of verbal and nonverbal abilities. The difficulty these groups had with categorical induction may be related to their difficulty with generalization more widely; future research should investigate this possibility.     

Phonological short-term store impairment after cerebellar lesion: a single case study

The cerebellum is a recent addition to the growing list of cerebral areas involved in the multifaceted structural system that sustains verbal working memory (vWM), but its contribution is still a matter of debate. Here, we present a patient with a selective deficit of vWM resulting from a bilateral cerebellar ischemic lesion. After this acute event, the patient had impaired immediate and delayed word-serial recall and auditory-verbal delayed recognition. The digit span, however, was completely preserved. To investigate the cerebellar contribution to vWM, four experiments addressing the function of different vWM phonological loop components were performed 18 months after the lesion, and results were compared with normative data or, when needed, with a small group of matched controls. In Experiment 1, digit span was assessed with different presentation and response modalities using lists of digits of varying lengths. In Experiment 2, the articulatory rehearsal system was analyzed by measurement of word length and articulatory suppression effects. Experiment 3 was devoted to analyzing the phonological short-term store (ph-STS) by the recency effect, the phonological similarity effect, short-term forgetting, and unattended speech. Data suggested a possible key role of the semantic component of the processed material, which was tested in Experiment 4, in which word and nonword-serial recall with or without interpolating activity were analyzed. The patient showed noticeably reduced scores in the tasks that primarily or exclusively engaged activity of the ph-STS, namely those of Experiment 3, and good performance in the tests that investigated the recirculation of verbal information. This pattern of results implicates the ph-STS as the cognitive locus of the patient's deficit. This report demonstrates a cerebellar role in encoding and/or strengthening the phonological traces in vWM.