The relation between problem categorization and problem solving among experts and novices

These investigations were conducted to examine the relationship between problem-solving ability and the criteria used to decide that two classical mechanics problems would be solved similarly. We began by comparing experts and novices on a similarity judgment task and found that the experts predominantly relied on the problems' deep structures in deciding on similarity of solution, although the presence of surface-feature similarity had a clear adverse effect on performance. The novices relied predominantly on surface features, but were capable of using the problems' deep structures under certain conditions. In a second experiment, we compared groups of novices, at the same level of experience, who tended to employ different types of reasoning in making similarity judgments. Compared to novices who relied predominantly on surface features, novices who made greater use of principles tended to categorize problems similarly to how experts categorized them, as well as score higher in problem solving. These results suggest that principles play a fundamental role in the organization of conceptual and procedural knowledge for good problem solvers at all levels.     

Hefting for a maximum distance throw: a smart perceptual mechanism

Objects for throwing to a maximum distance were selected by hefting objects varying in size and weight. Preferred weights increased with size reproducing size-weight illusion scaling between weight and volume. In maximum distance throws, preferred objects were thrown the farthest. Throwing was related to hefting as a smart perceptual mechanism. Two strategies for conveying high kinetic energy to projectiles were investigated by studying the kinematics of hefting light, preferred, and heavy objects. Changes in tendon lengths occurring when objects of varying size were grasped corresponded to changes in stiffness at the wrist. Hefting with preferred objects produced an invariant phase between the wrist and elbow. This result corresponded to an optimal relation at peak kinetic energy for the hefting. A paradigm for the study of perceptual properties was compared to size-weight illusion methodology.     

Generativity and Erikson's “belief in the species”

Generativity is the concern for guiding and promoting the next generation through such creative behavior as parenting, teaching, mentoring, leading, and generating products and outcomes that benefit others. Erikson (1963) has argued that in order to be generative in adulthood, people must have a fundamental “belief in the species” or a faith that human progress is possible and worth working toward. The present study focuses on hope and trust concerning the self and others (Erikson's “belief in the species”). In addition, however, the study examines the relation between generativity and personality traits, in this case, dominance, leadership, self-absorption, and nurturance. A sample of 70 adults was administered (1) a series of self-report questionnaires converging on Erikson's idea of belief in the species, (2) a self-report scale assessing generativity, (3) measures of personality traits, and (4) two open-ended measures of generativity requiring subjects to describe life commitments and creative endeavors. The results provide modest support for Erikson's claim of a link between belief in the species and generativity, with significant positive correlations obtained (1) between self-report generativity and two measures of belief in species and (2) between generativity assessed through life commitments and one measure of belief in the species. In addition, the personality trait of nurturance was positively related to all three generativity measures. Problems and issues in the assessment of generativity are discussed.     

Contextual influences in aphasia: effects of predictive versus nonpredictive narratives

The influence of prior linguistic predictive and nonpredictive context on the comprehension of reversible passive sentences was investigated in 16 adults with aphasia. Eight subjects were classified as fluent and 8 as nonfluent. Subjects were presented with the sentences in isolation and preceded by nonpredictive and predictive contextual paragraphs. The overall results indicated that the subjects benefited significantly from the prior contextual narratives regardless of whether the paragraphs were predictive or nonpredictive. There were no significant differences between the two subject groups. The significant facilitation generated by the nonpredictive context suggests that redundancy of information may play a role in comprehension.     

Reading long words embedded in sentences: informativeness of word halves affects eye movements

The possibility was explored that the informativeness of a specific region within a word can influence eye movements during reading. In Experiment 1, words containing identifying information either toward the beginning or toward the end were displayed asymmetrically around the point of fixation so that the reader was initially presented with either the informative or noninformative zone. Words were read with shorter summed initial fixation time when the reading was started from the informative zone. In Experiments 2 and 3, the target words were presented in sentences that were to be comprehended. More attention was given to the informative endings of words than to redundant endings. The latter were also skipped more often. The duration of the first fixation was not affected by information distribution within the word, whereas the second fixation duration was. The results of these experiments lend good support to the hypothesis of immediate lexical control over fixation behavior and to the notion of a convenient viewing position.     

Written spelling agraphia

When a disorder of single word writing is seen in conjunction with preserved oral spelling and intact written grapheme formation ("written spelling agraphia"), the deficit may be presumed to lie somewhere between letter choice and written motor output. Two potential deficits are considered: (1) visual letter codes are not activated properly and (2) the information contained within properly activated visual letter codes fails to reach intact graphic motor patterns. Two patients with written spelling agraphia were each given a series of tests aimed at distinguishing between the two possibilities. Results suggest that the written spelling agraphia seen in these two patients arises from different underlying deficits. The results are discussed in terms of the patients' CT scan lesion sites, which were markedly different.     

Selective spatial attention and length representation in normal subjects and in patients with unilateral spatial neglect

The aim of this study was to assess whether perceptual representation along the horizontal axis is affected by hemispace position of the stimulus or by orienting attention to one side. Ten control subjects and 10 right brain damaged patients with left unilateral spatial neglect (USN) were asked to bisect lines of five lengths in three space positions (left, center, right) and under three cueing conditions (no cue, left cue, right cue). Normal controls showed significant displacement of bisection opposite to the side of hemispace presentation and toward the side of cueing. USN patients showed a bisection error toward the right end which increased with lines placed in the left hemispace and decreased with lines placed in the right hemispace and when attention was oriented toward the left side. We conclude that (1) In absence of cues normal subjects tend to overestimate the portions of space closer to their body midline; (2) both normal and USN patients tend to overestimate portions of space that they direct their attention to; (3) USN patients' performance without cueing is consistent with an attentional shift toward the right hemispace implying a gradient of overestimation of the right-most portions of space. A common neural substratum for directing attention and space representation can explain these findings.     

Chronic stress, leukocyte subpopulations, and humoral response to latent viruses

Psychological stress has been shown to affect immune system status and function, but most studies of this relationship have focused on acute stress and/or laboratory situations. The present study compared total numbers of leukocytes and lymphocyte subpopulations (determined by flow cytometry) and antibody titers to latent and nonlatent viruses among a group of chronically stressed individuals living near the damaged Three Mile Island (TMI) nuclear power plant with those of a demographically comparable control group. Urinary catecholamine and cortisol levels were also examined. Residents of the TMI area exhibited greater numbers of neutrophils, which were positively correlated with epinephrine levels. The TMI group also exhibited fewer B lymphocytes, T-suppressor/cytotoxic lymphocytes, and natural killer cells. Antibody titers to herpes simplex were significantly different across groups as well, whereas titers to nonlatent rubella virus as well as IgG and IgM levels were comparable.     

The dependence of lexical relatedness effects on syntactic connectedness

Context effects on lexical decision were analyzed by manipulating lexical relatedness and syntactic connectedness. Related and unrelated word pairs were embedded in syntactic (e.g., "the author of this book/floor") and in scrambled (e.g., "the author the and book/floor") phrases. The sequences were presented serially and subjects made lexical decisions to the terminal targets. In four experiments, relatedness effects were substantial in syntactic phrases but only marginal in scrambled sequences. This result was unaffected by presentation rate or by blocking manipulations. A fifth experiment showed that the relatedness effect in syntactic phrases involved both facilitation of responses to related words and inhibition of responses to unrelated words. These results argue against a role for intralexical priming in on-line reading. They highlight the role of syntactic connectedness and suggest that contextual facilitation depends on the ease of integration of new words with the current text-level representation.     

On the development of procedural knowledge

Amnesic patients demonstrate by their performance on a serial reaction time task that they learned a repeating spatial sequence despite their lack of awareness of the repetition (Nissen & Bullemer, 1987). In the experiments reported here, we investigated this form of procedural learning in normal subjects. A subgroup of subjects showed substantial procedural learning of the sequence in the absence of explicit declarative knowledge of it. Their ability to generate the sequence was effectively at chance and showed no savings in learning. Additional amounts of training increased both procedural and declarative knowledge of the sequence. Development of knowledge in one system seems not to depend on knowledge in the other. Procedural learning in this situation is neither solely perceptual nor solely motor. The learning shows minimal transfer to a situation employing the same motor sequence.