Decomposing the reaction time distribution: Pure insertion and selective influence revisited

This paper investigates the consequences of extending the assumptions of pure insertion and selective influence (popular in RT theorizing) to the level of the distribution. In the case of pure insertion and under the additional assumption that the additive random variable is exponentially distributed, a solution is obtained which not only allows estimation of the exponential-rate parameter but also provides a test of the assumptions. The result is shown to be applicable not only when processing is serial but also for certain parallel models. In addition, discrimination between self-terminating and exhaustive search strategies is provided, and in the case of either, both parameter estimation and tests of the model are possible. Extensions to nonexponential models are investigated and a general method of moments solution is outlined. In the case of selective influence a general nonparametric alternative to Sternberg's additive factor method is developed. The problem of empirical estimation and application is then considered. Simulations which place bounds on the type I and II error are reported. Finally the first theorem is provided an illustrative application with data from a memory scanning experiment. The results provide some support for the double assumption of pure insertion and that the additive random variable is distributed exponentially.     

The emergence of functional play in infants: Evidence for a major cognitive transition

Sixty-four infants, eight boys and eight girls at each of four ages, $\text{9}\text{1}\text{2}\text{, 11}\text{1}\text{2}\text{, 13}\text{1}\text{2}\text{,}\text{and}\text{15}\text{1}\text{2}$ months, were observed during a 15-minute free play session. Three types of play (stereotypical, relational, and functional) and the number of appropriate uses for specific realistic toys were recorded. Stereotypical play (87% of total active play at $\text{9}\text{1}\text{2}$ months) gave way to relational (35% at $\text{13}\text{1}\text{2}$ months) and functional play (52% at $\text{15}\text{1}\text{2}$ months) as the dominant activity. Both functional play and the number of different appropriate uses of toys were rare at $\text{9}\text{1}\text{2}$ months, appeared reliably at $\text{11}\text{1}\text{2}$ months and increased lineraly through $\text{15}\text{1}\text{2}$ months. A change in the quality of play from indiscriminate mouthing, waving, banging, and fingering of objects to the matching of appropriate uses for a large array of toys indicates that the child's manipulations become more object specific and functional over this 6-month age span. Among possible explanations for the linear increase in the frequency and diversity of appropriate toy uses is the suggestion that an important cognitive change occurs toward the end of the first year of life. A case study is presented to illustrate the application of the play procedure for both assessment and treatment.     

The “lag effect” in dichoptic viewing

Ten subjects were asked to report both of two different consonant-vowels (CVs) presented to the same foveal area, but in different eyes (“dichoptically”). Stimuli were presented at stimulus-onset asynchronies (SOAs) ranging from 0 to 150 msec in 25-msec steps. Correct identifications were significantly depressed for the eye receiving the leading stimulus at SOAs of 25 to 75 msec. Monoptic data from three subjects indicated no significant reductions in correct identification as a function of SOA. The dichoptic results can be understood in terms of current theories of visual backward masking and are similar to the “lag effect” observed with dichotic listening to speech stimuli. Similarity of results for the two modalities suggests a similar “two-process” explanation may underlie both phenomena.     

Intelligence and short-term memory: A clandestine relationship

Five possible mechanisms are considered as being responsible for the systematic variation of serial STM with IQ, namely rehearsal maintenance, chunking, access, encoding of item and/or order information, and trace persistence. A STM/IQ correlational study is reported. It was concluded from analysis of a correlation matrix, and from earlier reported data, that the encoding of items-in-order into an already loaded store appears to be the critical mechanism in determining IQ-related individual differences in STM performance, at least in children. The implications of individual difference data for models of STM are also discussed.     

Happiness: When does it lead to self-indulgence and when does it lead to self-denial?

Previous research on self-gratification in children has found that happiness, compared to a neutral affective state, sometimes causes self-indulgence and sometimes causes self-denial. Review of this research led to the hypothesis that happiness leads to self-indulgence when children have no reason to believe that excessive self-gratification is morally wrong but that happiness promotes selfdenial when children fear that excessive self-gratification would violate a moral rule. In the present study, children were first placed in either a happy or neutral mood. They were then given an opportunity to help themselves freely to a reward supply, but half the children in each affect condition were warned that excessive self-gratification would violate a moral rule whereas the other half were not. In the absence of information that excessive self-gratification would violate a moral standard, happiness produced self-indulgence, but when children were told that excessive self-gratification would be wrong, happy children denied themselves significantly more than neutral-mood children. It was suggested that happiness motivates children to try to sustain their elevated mood; the behavioral route to maintaining positive mood, however, depends on how children perceive the moral implications of their actions.     

Cerebral lateralization for speech in deaf and normal children

The cerebral lateralization pattern for speech production in normal hearing and congenitally deaf children was studied using the dual-task paradigm. Performance under the verbal task conditions showed predicted left hemispheric dominance for speech production in the normal hearing children. No developmental trends in asymmetry were found, suggesting that speech lateralization is present in normal 3-year-old children. These data support the developmental invariance hypothesis of cerebral organization. Deaf children showed more symmetrical patterns of cerebral control for speech production. No developmental trends in functional brain organization were observed among prepubescent deaf children.     

A case of prosopagnosia with some preserved covert remembrance of familiar faces

This paper presents the detailed analysis of a case of prosopagnosia in a 54-year-old male farmer following bioccipital vascular disease. In-depth clinical investigations confirmed the diagnosis of prosopagnosia and revealed the absence of any associated defect, except for a slight aspecific disturbance of the short-term memory. Further study of this case indicated that the trouble was not concerned with the class of complex visual stimuli, was not even concerned with facial expressions or unknown faces, was not a perceptual defect, but was related mainly to the operation of individualization. The memory hypothesis was thus retained and supported. Moreover, exploration of the difficulty indicated that the deficiency was limited to defective access to conscious information concerning faces and information associated with these faces (name, context, etc.), effectively stored in memory.     

Perceptual categorization in the cerebral hemispheres

The suggestion of a functional hemispheric dissociation in performing perceptual categorization was examined in two tachistoscopic experiments with normal adults. Subjects were required to match physically identical or similar, but nonidentical, pictures of animals. The first experiment showed no hemispheric difference and indicated that both hemispheres could resort to two different types of categorization process as a function of the simultaneous or delayed mode of presentation of the stimuli. In the second experiment, the viewing conditions were manipulated so as to afford a reduced amount of stimulus energy, and a significant left-visual-field advantage was then obtained. The results are discussed with respect to models of information processing in the cerebral hemispheres, and in relation to impairments in object recognition following brain damage.