Human choice behaviour in a frequently changing environment

The present experiment provided a replication in humans of an experimental procedure that has been used frequently with nonhumans to investigate choice behaviour in a changing environment. Six volunteers played a computer game, which required tracking of a moving balloon on two simultaneously available response panels for monetary reinforcers. Each of the 15 sessions randomly arranged the following concurrent variable-interval reinforcement schedules, which were in effect until six reinforcers had been obtained: 27:1, 9:1, 3:1, 1:1, 1:3, 1:9, and 1:27. Although many aspects of human performance appeared to be qualitatively similar to that of nonhumans on this procedure, such as the rapid preference shifts towards the within-session reinforcer ratios and the presence of local effects of reinforcers, values of sensitivity to reinforcement were very variable in the present study, as commonly reported in human choice studies. Future variations and refinements of the experimental methods are needed to explore how this variability may be reduced.     

不同放化疗模式治疗中晚期非小细胞肺癌的疗效分析

目的:探讨同步和序贯放疗联合不同化疗方案对治疗中晚期非小细胞肺癌近期疗效、远期生存及毒性反应的影响。方法:将45例III-IV期非小细胞肺癌患者随机归入两组,同步放化疗组22例;序贯放化疗组23例。全组病例依据病情分别选择艾素和顺铂、吉西他滨和顺铂、长春瑞滨和顺铂或培美曲塞和顺铂方案化疗。比较两组近期疗效、远期生存率及毒性反应。结果:同步组近期有效率为81.8%高于序贯组73.9%,但无统计学差异(P0.05);两组均有随放疗剂量增加有效率升高趋势。NP和TP方案两组近期疗效相近(P0.05)。同步组和序贯组1年生存率分别为90.9%和86.9%(P0.05);2年生存率分别为72.7%和52.2%(P0.05)。毒性反应主要为骨髓抑制、放射性食管炎和肺炎。同步组毒副反应发生率高于序贯组,但无统计学差异(P0.05)。结论:同步放化疗治疗中晚期非小细胞肺癌近期疗效及远期生存率有优于序贯放化疗的趋势,但毒副反应发生相对增多。联合治疗模式下,分期越早,患者远期生存时间越长。近期疗效有随放疗剂量增高而提高趋势,但放疗剂量、病理类型、化疗方案等对患者远期生存无明显统计学差异。     

Trichinella spiralis and Strongyloides ratti: immune interaction in adult rats.

The consequences of prior and concurrent infection with two species of nematodes were studied in rats. Primary infection with Strongyloides ratti adversely affected the development of a secondary Trichinella spiralis infection. Both immediate and delayed challenge with T. spiralis, following the expulsion of the previous S. ratti infection, reduced the percentage of worm recovery of the former as well as their fecundities and lengths. It is suggested that nonspecific inflammation produced by one species, during the peak period of worm expulsion, was not responsible for the accelerated rate of expulsion of the other; instead a direct, specific cross-immunity was probably operative affecting the survival of the challenge species. The response elicited by previous experience of the intestinal phase was reciprocal, but there was evidence of an enhancing effect by the muscle larval stages of T. spiralis on S. ratti. Rats concurrently infected with both species expelled S. ratti more rapidly than T. spiralis. Possible mechanisms underlying the interaction between the two species are suggested and discussed.     

Choice between contingencies of variation: Effects of the requirement of variation upon preference

The present study investigated whether choices between contingencies of variation are affected by the degree of variability required. For such, five pigeons were exposed to a concurrent chain schedule. In the initial links, responses in one key initiated the terminal link with the most stringent variation requirement while responses in the other key initiated the terminal link with the least stringent variation requirement. In both terminal links, four-responses sequences were reinforced according to a variation criterion, which favored less frequent and less recent sequences. The probability of reinforcement in the terminal link with the least stringent criterion was manipulated in order to generate similar percentage and rate of reinforcers in both terminal links. Choices for the terminal link with the least stringent criterion were more frequent than choices for the terminal link with the most stringent criterion. It is possible that situations that demand lower levels of behavior variability are chosen due to the lower response cost correlated to those situations.