Developmental dyslexia: the visual attention span deficit hypothesis

The visual attention (VA) span is defined as the amount of distinct visual elements which can be processed in parallel in a multi-element array. Both recent empirical data and theoretical accounts suggest that a VA span deficit might contribute to developmental dyslexia, independently of a phonological disorder. In this study, this hypothesis was assessed in two large samples of French and British dyslexic children whose performance was compared to that of chronological-age matched control children. Results of the French study show that the VA span capacities account for a substantial amount of unique variance in reading, as do phonological skills. The British study replicates this finding and further reveals that the contribution of the VA span to reading performance remains even after controlling IQ, verbal fluency, vocabulary and single letter identification skills, in addition to phoneme awareness. In both studies, most dyslexic children exhibit a selective phonological or VA span disorder. Overall, these findings support a multi-factorial view of developmental dyslexia. In many cases, developmental reading disorders do not seem to be due to phonological disorders. We propose that a VA span deficit is a likely alternative underlying cognitive deficit in dyslexia.     

Division of attention: The single-channel hypothesis revisited

Two experiments are reported in which subjects performed two forced-paced serial reaction time tasks separately and together at their maximum sustainable rates of information processing. Experiment 1 investigated the effects on the relationship between single- and dual-task performance of using tasks with the same or different input and output modality characteristics; an additional condition tested the effects on this relationship of using tasks with higher S-R compatibility. Experiment 2 investigated the effects on the relationship between single- and dual-task performance of varying information load (number of S-R alternatives). No significant differences were found in subjects' capacities to process information in single- and dual-task conditions. This finding was unaffected by: (a) the absolute information levels of the tasks, (b) whether inputs and/or outputs involved the same or different modalities, or (c) the level of S-R compatibility. The data from both experiments provide strong support for the single-channel hypothesis.     

Study of the single channel hypothesis and input regulation within a continuous, simultaneous task situation

Subjects performed simultaneously on an auditory tracking and an auditory discrimination task, with each, task presented to a separate ear. Information transmitted on the tasks was measured as a function of ability to predict task characteristics, input information-rate, and input discriminability. Based on comparison of single-versus simultaneous-task performance, support was found for a single, central decision-type channel in information processing, having as one primary limit the rate at which information can be accepted. Discriminability of inputs also was found to be a limit on information processing rate. Although ability to predict a task's characteristics facilitated performance on that task, in this experiment it did not result in facilitation of performance on the second task. Relevance of these findings to certain aspects of Broadbent's information-processing model is discussed.     

Information integration in multiple cue judgment: a division of labor hypothesis

There is considerable evidence that judgment is constrained to additive integration of information. The authors propose an explanation of why serial and additive cognitive integration can produce accurate multiple cue judgment both in additive and non-additive environments in terms of an adaptive division of labor between multiple representations. It is hypothesized that, whereas the additive, independent linear effect of each cue can be explicitly abstracted and integrated by a serial, additive judgment process, a variety of sophisticated task properties, like non-additive cue combination, non-linear relations, and inter-cue correlation, are carried implicitly by exemplar memory. Three experiments investigating the effect of additive versus non-additive cue combination verify the predicted shift in cognitive representations as a function of the underlying combination rule.     

A critical analysis of the attention hypothesis of Zeaman and House: problems of parameter interactions in multiparameter models

The attention hypothesis of Zeaman and House [in N. R. Ellis (Ed.), Handbook of mental deficiency. New York: McGraw-Hill, 1963] was examined through a systematic, computer-simulation analysis of the parameter interactions found in the One-Look model. The hypothesis states that mental retardates and normals differ in their initial attention habits but not in their learning rates in the context of discrimination learning. The analysis showed that possible differences in the learning rates cannot be ruled out. The result was used to suggest how shift designs can unconfound the effect of the attention habits from the effect of the learning rates and maximize chances of observing possible differences in the learning rates between retarded and normal children.     

Testing the dorsal stream attention hypothesis: Electrophysiological correlates and the effects of ventral stream damage

The roles of dorsal and ventral processing streams in visual orienting and conscious perception were examined in two experiments. The first employed high density EEG with source localization. The second comprised a neuropsychological case study. Visual orienting was assessed with an attention procedure, where peripheral letters cued participants towards a target location. In the perception procedure participants responded to the same letters by performing an explicit conscious discrimination. In Experiment 1, the peripheral letters elicited rapid dorsal stream activation in the attention procedure, and this activation preceded top-down enhancement of target processing in occipital cortex. In the perception procedure early ventral stream activation was seen. In addition, peripheral letters elicited an “early directing attention negativity” (EDAN) over parietal recording sites in the attention procedure, but not in the perception procedure. In Experiment 2, a patient with a bilateral ventral stream lesion but preserved dorsal stream function showed clear disruption to performance in the perception procedure, whilst exhibiting a normal visual orienting effect in the attention procedure. Taken together these findings (1) highlight the distinct roles of the dorsal and ventral streams in attention and perception, and (2) suggest how these streams might interact, via reentrant effects of attention on perceptual processing.     

Psychopathy, risk taking, and attention: a differentiated test of the somatic marker hypothesis

A. R. Damasio's (1994) somatic marker hypothesis relates psychopathy to deficits in the ventromedial prefrontal cortex. Using the gambling task (A. Bechara, A. R. Damasio, H. Damasio, & S. Anderson, 1994), the authors tested this premise and the role of attention as a moderator. Forty-nine male prison inmates were assessed with the Psychopathy Checklist--Revised (R. D. Hare, 1991), the gambling task, and standardized tests on attention-concentration, and intelligence. Results revealed no general relation between psychopathy and gambling task performance. However, psychopathic inmates with low attention scores gambled worse than did the attentive ones. They also had more previous convictions. In nonpsychopathic individuals, attention had no impact. Different processing strategies for psychopathic and nonpsychopathic individuals are proposed to explain these findings.     

Negative mood, self-focused attention, and the experience of physical symptoms: the joint impact hypothesis

A joint impact hypothesis on symptom experience is introduced that specifies the role of negative mood and self-focus, which have been considered independently in previous research. Accordingly, negative affect only promotes symptom experience when people simultaneously focus their attention on the self. One correlational study and 4 experiments supported this prediction: Only negative mood combined with self-focus facilitated the experience (see the self-reports in Studies 1, 2a, & 2b) and the accessibility (lexical decisions, Stroop task in Studies 3 & 4) of physical symptoms, whereas neither positive mood nor negative mood without self-focus did. Furthermore, the joint impact of negative mood and self-focused attention on momentary symptom experience remained significant after controlling for the influence of dispositional symptom reporting and neuroticism.     

On recognizing proper names: the orthographic cue hypothesis

Five experiments investigated the recognition of proper names and common nouns using the lexical decision paradigm. In Experiments 1-3 the case of the initial letter of written stimuli was systematically varied. An advantage was consistently found for proper names written with the first letter in capital. Crucially, response times to proper names with the first letter in lowercase and to common nouns irrespective of the case of the first letter did not differ from each other. No difference between proper names and common nouns emerged in Experiment 4 where the stimuli were presented auditorily, and in Experiment 5 where a visual lexical decision task was performed with illegal non-words. The pattern of results shows that the proper name advantage is orthographic in nature and rules out an account in terms of semantic, morphological or other lexical variables. A model is proposed in which information about the case of the first letter is specified in the abstract multidimensional orthographic representation mediating written word recognition.     

On the Bradley hypothesis concerning agrammatism: the nonword-interference effect

In 1980, D. C. Bradley, M. F. Garrett, and E. B. Zurif (in D. Caplan (Ed.), Biological studies of mental processes, Cambridge, MA: MIT Press) have proposed a lexical hypothesis on agrammatism. The theoretical background of this hypothesis is described. Then two experiments are reported with normal speakers on the so-called nonword-interference effect that has been one of the two major sources of experimental evidence for this hypothesis. The first experiment replicates the original finding that the interference effect is found when the nonword starts with a content word but not when it starts with a function word. In the second experiment, it is shown that this contrast is due to an artifact of the composition of the word list. When this list contains both content and function words, rather than only content words--as in Bradley's experiments and our Experiment I--both content and function nonwords show an equally sized interference effect. The consequences for the lexical hypothesis are discussed.     

On varying the span of visual attention: Evidence for two modes of spatial attention

Three experiments investigated whether subjects could selectively attend to a target item presented in close spatial proximity to a distractor element. Typically, the display consisted of two curved lines, one a target and the other a distractor. The task was to judge the direction of curvature of the target. When subjects attended to a target away from fixation, performance was affected by the presence of a distractor within an area of 1° around the target. In contrast, the distractor did not influence target processing when subjects fixated on the target location. Two modes of visual attention are proposed. When a target is located away from fixation, a “wide” attentional span is employed. With the present stimuli, this led to the detailed processing of items within 1° of the attended position. However, when targets are at fixation a “narrow” span can be adopted, with the result that there is differential processing of attended items even within the formerly critical area.     

Contextual assimilation and its effect on the division of attention between nonverbal signals

Subjects performed a recognition task in which a low or a high frequency signal was presented simultaneously with a dim or a bright intensity one. The independent variable was the degree of association between the signals on the two dimensions. Unknown to the subjects four levels were tested in separate conditions, 1.0, 0.8, 0.5 and 0.2. Increasing the positive association improved overall sensitivity as measured by d' on both dimensions, but left contingent sensitivity unchanged. Changing the association did not affect overall bias, as measured by Beta. However, holding context constant by analysis produced significant differences between individual measures of contingent bias in the direction of assimilation, for example “low” responses tended to accompany dim signals and “dim” responses. The differences were unaffected by the changes in association. The results are interpreted as favouring models of contextual assimilation which assume that biasing at some level of processing depends upon the mutually contingent interaction of discrete events rather than on memory and expectation of the relative frequency of conjoint events. Further support for this conclusion comes from previous studies which indicate that assimilation occurs with separate responses but not with unitary ones. The implications of the findings for research on the division of attention are discussed, particularly the need to control variability in measured bias to establish a true change in the allocation of attention. Two generalized models of contextual assimilation are proposed, one based on “object” and the other on “lexical” assimilation. The possible application of these models to synaesthesia is considered.     

Affection and attention: On the phenomenology of becoming aware

Addressing the matter of attention from a phenomenological perspective as it bears on the problem of becoming aware, I draw on Edmund Husserl's analyses and distinctions that mark his “genetic” phenomenology. I describe several experiential levels of affective force and modes of attentiveness, ranging from what I call dispositional orientation and passive discernment to so-called higher levels of attentiveness in cognitive interest, judicative objectivation, and conceptualization. These modes of attentiveness can be understood as motivating a still more active mode of reflective attention, i.e., philosophical attentiveness, and to this extent, even it would be subject to varying influences of affection. What role, if any, does affection play in a peculiar kind of reflective attention that is phenomenological? I conclude by briefly considering phenomenological reflective attentiveness and its relation to affection.