On the study of statistical intuitions

The study of intuitions and errors in judgment under uncertainty is complicated by several factors: discrepancies between acceptance and application of normative rules; effects of content on the application of rules; Socratic hints that create intuitions while testing them; demand characteristics of within-subject experiments; subjects' interpretations of experimental messages according to standard conversational rules. The positive analysis of a judgmental error in terms of heuristics may be supplemented by a negative analysis, which seeks to explain why the correct rule is not intuitively compelling. A negative analysis of non-regressive prediction is outlined.     

Developmental differences in the allocation of processing capacity

Recently psychologists have formulated a comprehensive view of attention involving allocation of processing capacity. Although developmental changes in processing capacity have been proposed as one source of age differences in certain cognitive skills, there has been little systematic investigation of this hypothesis. In the present study, second and sixth graders and adults (8, 12, and 20 years of age, respectively) performed a letter-matching task (primary task) concurrently with an auditory detection task (secondary task). Changes in reaction time in the secondary task as a function of manipulations of the primary task were used to estimate capacity allocation to the primary task. Primary task variables included stage of processing (alerting, encoding, rehearsing, responding) and matching condition (physical-identity vs name-identity matching). Age differences in secondary task performance were found to be related to stage of processing but not to matching condition. Earlier stages of the letter match task (alerting, encoding) required somewhat more capacity allocation in younger subjects. Later stages (rehearsing, responding) made substantially higher demands on capacity in children. Capacity allocation may be an important cognitive variable mediating developmental differences in basic information processing skills, and may underlie age trends found in performance of certain complex cognitive tasks.     

Semantic aphasia: A neglected entity

Three cases of semantic aphasia are reported. Computerized brain tomography showed bilateral temporo-parieto-occipital junction hemorrhages in one patient, and left parieto-occipital junction infarctions in the other two patients. The auditory comprehension defect of the three patients was characterized by preserved understanding of single words and impaired understanding of grammatically complex constructions. It is suggested that this comprehension defect reflects an inability to fully grasp the meaning of words and grammatical constructions imbued with spatial or quasi-spatial significance. Each of the three patients showed a complex spatial disorder that included constructional apraxia, spatial agnosia, and elements of Gerstmann's syndrome. The aphasic as well as the spatial disorder of semantic aphasics may be manifestations of a common defect in the perception of spatial relationships produced by left temporo-parieto-occipital region damage.     

Possible psychometric problems in a test for selective deficits of conceptualization

We administered a modified version of the test of Semenza, Denes, Lucchese, and Bisiacchi (Brain and Language, 10, 243-248 (1980)) for selective deficits in conceptualization to a group of normals and psychiatric patients. Analysis of the results obtained with the normal sample revealed several psychometric problems. The two components of the test (one for thematic and one for class relationships) each had poor internal consistency and were significantly different from each other on a measure of discriminating power. It is not clear if our results are related to difficulty in applying the test to an English-speaking population or reflect inherent psychometric problems.     

Intrusions and perseverations

Twenty-two subjects with presumed senile dementia of the Alzheimer's type (SDAT), twenty-two with dementia other than SDAT, twenty with aphasia, and seventeen healthy controls over 50 years of age were examined for intrusions and perseverations. Perseverations were defined as the immediate inappropriate repetition of a prior response whereas intrusions were defined as the inappropriate repetition of prior responses after intervening stimuli. Intrusions and perseverations occurred in demented and aphasic subjects, but were rare in controls. Intrusions occurred most often in SDAT or Wernicke aphasia, but also in dementia other than SDAT. Intrusions were not correlated with dementia severity. Intrusions are a useful sign of dementia, but they cannot be considered pathognomonic of SDAT. They appear to arise when subjects are unable to access correct responses from long-term memory and instead substitute erroneous responses selected from short-term memory. Perseverations were most common in the Wernicke aphasics and subjects with dementia due to communicating hydrocephalus. Although frontal lobe dysfunction is prominent in communicating hydrocephalus, it is absent in cases of Wernicke aphasia. Thus, we have confirmed prior suggestions that perseveration can occur in the absence of frontal lobe injury. Failure to self-monitor speech as well as an inability to change mental set probably plays an important role in the genesis of perseverations. There was no statistically significant correlation between dementia severity and number of perseverations. Low correlations were found between intrusions and perseverations suggesting that these seemingly similar behaviors are distinct and are probably produced by separate neuropsychological mechanisms.     

Looking where you listen: visual cues and auditory attention

In the non-laboratory environment, we are generally able to see the source of the sounds to which we are attending. In a preliminary examination of how and to what degree we might use this visual information, subjects shadowed one of two female voices when able to see the persons speaking (Experiment I) or when able to see, and thus precisely localize, the auditory loudspeakers (Experiment II). Selective performance was improved by being able to see the lip movements of the people whose voices were heard, and by being able to localize visually the sources of the voices.     

CONSCIOUS OBJECTIONS: GOD AND THE CONSCIOUSNESS DEBATES

Abstract. Consciousness studies are dogged with religious overtones, and many researchers fight hard against Christian ideas of soul or anything supernatural. This gives many studies on consciousness a particular relevance to religious belief. Many writers assume that, if consciousness can be explained physically, religious belief in a soul—and perhaps religious belief itself—must be false. Theorists of consciousness grapple with questions of materialism and reduction in trying to understand how the physical brain can produce the bizarre sensations that we call ourselves. In this essay I discuss the problems in trying to separate religion from science in such a “fuzzy” area as consciousness. I look at the question of what precisely theories of consciousness are trying to explain. I consider theories from David Chalmers, Daniel Dennett, and Roger Penrose as examples of different approaches. Although all of these are materialistically based, I argue that they do not necessarily demonstrate the nonexistence of a soul and also that religious belief does not necessarily require belief in a nonmaterial soul. I conclude with a discussion of why a physical/ materialist explanation of consciousness is desired and how religious bias is still a problem in this scientific/philosophical field.     

“P300” and memory: Individual differences in the von Restorff effect

Event-related brain potentials (ERPs) were elicited by words in a free recall paradigm that included a novel item. The P300 component of the ERP is elicited by novel, task-relevant events, and we tested the hypothesis that P300 is a manifestation of the cognitive processing invoked during “context updating.” If the degree to which current representations in working memory need revision is related to P300 amplitude, then the P300 elicited by a given item should be related to the ability to recall that item on a subsequent test. Forty lists were presented to 12 subjects in each of two sessions. The lists were 15 words long, and 1 word, in position 6 through 10, was “isolated” by changing its size. Most subjects recalled these isolated words more often than other words in the same positions (von Restorff effect), and these words also elicited larger P300s than other words. Analysis of variance on the component scores from a principal components analysis revealed that words recalled had a larger amplitude P300 (on initial presentation) than words not recalled. Striking individual differences emerged, and there were strong relationships between the von Restorff effect, overall recall performance, mnemonic strategies, and the association between components of the ERP and recall performance. The overall recall performance of subjects who reported simple (rote) mnemonic strategies was low, but they showed a high von Restorff effect. For these subjects the amplitude of the P300 elicited by words during initial presentation predicted later recall. In contrast, subjects who reported complex mnemonic strategies remembered a high percentage of words and did not show a von Restorff effect. For these subjects P300 did not predict later recall, although a later “slow wave” component of the ERP did. The initial response to isolated items was the same for all subjects (a large P300), and all subjects recognized the isolates faster than other words in a recognition test given at the end of each session. The subjects in whom P300 did not predict recall reported mnemonic strategies that involved organizing the material. These strategies continue long after the time period reflected by P300 (600 msec). Because they were so effective they may have overshadowed the relationship between P300 and recall, which is based on the initial encoding of an event. Our interpretations were further confirmed and clarified from data obtained in a final grand recall and in the recognition test.