Vocher-based reinforcement of opiate plus cocaine abstinence in treatment-resistant methadone patients: Effects of reinforcer magnitude.

The study tested a voucher-based abstinence reinforcement procedure for reducing opiate and cocaine use in a population of treatment-resistant opiate- and cocaine-abusing methadone patients. Vouchers exchangeable for goods and services were contingent on abstinence from both opiates and cocaine. In two conditions, participants could earn up to $374 or $3,369 in vouchers for providing opiate- and cocaine-free urine samples. Participants received a daily 60-mg dose of methadone. The dose was increased in a second phase, and the voucher conditions were replicated. Analyses of both phases revealed trends toward greater abstinence under the high voucher condition and suggested that higher doses may enhance the efficacy of voucher reinforcement. The results show that reinforcement for abstinence from 2 drugs simultaneously can be effective even in a treatment-resistant population. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Computer-based task representation: a methodology for improving system design

Task analysis procedures can be used in all stages of system development to examine the nature and severity of performance demands placed upon human operators. Task analyses involve considerable effort in obtaining a detailed set of measurements that represent the behavioural and cognitive tasks performed by the operators; these measures are referred to as task representation. The present article describes a flexible method for incorporating task representation data into an electronic spreadsheet. Such a computer-based procedure has many advantages over the more traditional paper and pencil approaches to task representation and analysis, including greater flexibility in data analysis and the inclusion of both objective and subjective measures of workload. Portions of an illustrative task representation and task analysis are presented along with a discussion of the strengths of computer-based task representation and analysis.     

Dietary protein effects on gallstone formation

Semipurified lithogenic diets for hamsters contain casein as the protein source. Since substitution of soy protein isolate for casein reduces serum cholesterol concentrations in several species, we studied replacement of casein by soy protein for effects on gallstone formation. Feeding soy protein consistently resulted in a significantly reduced incidence of gallstones. Switching to a soy-based diet after induction of gallstones resulted in dissolution of a significant percentage of the stones. Partial substitution of soy for casein gave results intermediate between 100% casein and 100% soy. The lysine/arginine ratio of the proteins may be responsible for the observed differences in cholelithiasis. The reduction in lithogenicity associated with feeding soy protein appears to be mediated primarily through decreased secretion of cholesterol into bile.     

Contingent take-home incentive: Effects on drug use of methadone maintenance patients.

Examined contingent methadone take-home privileges for effectiveness in reducing on-going supplemental drug use of methadone maintenance patients. 53 new intakes were randomly assigned to begin receiving take-home privileges after 2 consecutive weeks of drug-free urines or to a noncontingent procedure in which take-homes were delivered independently of urine test results. The contingent procedure produced more individuals with at least 4 consecutive weeks of abstinence (32 vs 8%); 28% of noncontingent Ss also achieved abstinence after shifting to the contingent procedure. Lower baseline rate of drug-free urines was strongly associated with successful outcome, whereas the type of drug abused (cocaine vs benzodiazepines) did not influence outcomes. Findings support a recommendation for using contingent take-home incentives to motivate abstinence during methadone maintenance treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chemically mediated interactions among juvenile mosses as possible determinants of their community structure

A field study of the distribution patterns of six closely related species of mosses along a complex altitudinal gradient found evidence suggesting differential aggressiveness among juveniles rather than evidence of differential competitive abilities among adults of the species. Work by Bopp (1963, 1968) on the moss phytohormone, factor H, suggests a means by which such interactions might be mediated. An experimental system is proposed through which the effect of patterns of early moss development upon the determination of moss community structure may be assessed.