Knowledge structures and the acquisition of a complex skill.

The purpose of this study was to examine the viability of knowledge structures as an operationalization of learning in the context of a task that required a high degree of skill. Over the course of 3 days, 86 men participated in 9 training sessions and learned a complex video game. At the end of acquisition, participants' knowledge structures were assessed. After a 4-day nonpractice interval, trainees completed tests of skill retention and skill transfer. Findings indicated that the similarity of trainees' knowledge structures to an expert structure was correlated with skill acquisition and was predictive of skill retention and skill transfer. However, the magnitude of these effects was dependent on the method used to derive the expert referent structure. Moreover, knowledge structures mediated the relationship between general cognitive ability and skill-based performance.

Motor vehicle crash involvement and moving violations: convergence of self-report and archival data.

In the crash involvement literature, it is generally assumed that archival and other "objective" criterion data are superior to self-reports of crash involvement. Using 394 participants (mean age = 36.23 years), the present study assessed the convergence of archival and self-report measures of motor vehicle crash involvement and moving violations. We also sought to determine whether predictor/criterion relationships would vary as a function of criterion type (i.e., archival vs. self-report), and if a combination of both criteria would result in better prediction than would either by itself. The degree of agreement between the two criterion sources was low, with participants self-reporting more crashes and tickets than were found in their state records. Different predictor/criterion relationships were also found for the two criterion types; stronger effects were obtained for self-report data. Combining the two criteria did not result in relationships stronger than those obtained for self-reports alone. Our findings suggest that self-report data are not inherently inferior to archival data and, furthermore, that the two sources of data cannot be used interchangeably. Actual or potential applications include choosing the appropriate criterion to use, which, as the finding of this study reveals, may depend on the purpose of the investigation.

Social identity and individual productivity within groups.

The purpose of the present research was to show how social identity theory can be applied to enhance individual productivity within groups. Three experiments manipulated in-group identifiability and importance of the group for one's social identity, and compared individual's productivity when working alone to when working in a group setting. The group setting in the first study involved either a collective of unrelated individuals, a group of participants expecting future interaction, or a group working for a group reward. The second study compared productivity in groups with four differing interdependent reward structures. The final study examine the impact of group members wearing a common uniform (vs. no uniform) and the presence (or absence) of an out-group. Results supported the general prediction that group productivity would be enhanced by factors that increase group categorization and the importance of the group to members' social identities (future interaction, interdependent reward structure and uniform/outgroup present). However, productivity in groups was not influenced by perceptions of the task or identifiability of performance. These findings extent social identity theory by suggesting that group members will increase their in-group position through individual work efforts.

Gallstone ileus. Review of the literature and presentation of thirty-four new cases.

An analysis of thirty-four patients with gallstone ileus is integrated with a review of the literature on the subject. Surgical treatment was carried out in thirty-two patients, with an overall operative mortality of 19 per cent. Three patients were treated by one stage enterolithotomy, fistula repair, and cholecystectomy without operative mortality, emphasizing the merit of one stage treatment in selected, well prepared patients. A 6 per cent incidence of carcinoma of the gallbladder was noted in this series of patients.

The lactone precursor in fresh milk fat: Identification of the hydroxy fatty acids.

A series of hydroxy fatty acids was identified from a polar glyceride milk-fat fraction. These acids were identified as trimethylsilyl (TMS) ether methyl ester derivatives. Identification was achieved by mass spectral analysis and comparison of gas chromatographic retention times with authentic compounds. Mass spectral fragmentation patterns of the TMS ether methyl esters were obtained, and correlation of important ions for structural identifications were made. In addition, semiquantitative data are presented.

Acetaldehyde utilization by Leuconostoc species.

Single-strain cultures of Leuconostoc dextranicum and L. mesenteroides were found to be capable of utilizing acetaldehyde in both acidified and nonacidified milk cultures at 21 and 30 C. L. dextranicum utilized acetaldehyde more rapidly than L. mesenteroides when the pH of the medium was near that of normal ripened lactic dairy cultures. Acetaldehyde production and utilization varied widely among different two-strain cultures of lactic streptococci and leuconostocs. The concentration of acetaldehyde in ripened single-strain lactic streptococcal cultures was lowered by adding a large inoculum of ripened L. citrovorum culture and continuing incubation at 21 or 5 C.