X线碘对比剂过敏试验的价值

讨论当前X线碘对比剂过敏试验存在的争议和问题,并提出修改意见,以明确指导临床正确使用,规避医疗风险,保障患者安全。针对碘对比剂有关过敏试验的相关文件规定及部分产品说明书的相关内容进行深入解读,对碘过敏试验是否应进行及其试验方法进行讨论并提出修改建议。根据我国现行卫生行政法规要求,目前碘对比剂应进行碘过敏试验。建议相关政...     

Generalization in a child's oppositional behavior across home and school settings

A 9-year-old clinic-referred boy, his mother, and his teacher were observed in 38 home and 38 school sessions on the same days. Categories of the boy's oppositional behavior and the inappropriate social attention of his mother and teacher were graphed to visually inspect changes during baseline, a parent-training phase, a follow-up phase, and a final parent-training booster phase. Parent-training phases produced reductions in the mother's inappropriate attention and in the boy's oppositional behavior, whereas the follow-up and baseline phases were associated with higher rates of these categories. Generalization occurred in the school across these home phases, as seen in the increase in rates of the boy's problem behavior, despite the lack of change in his teacher's attention. Correlational analyses of proportion scores reflecting the boy's home-school oppositional behavior and mother-teacher social attention suggested his responsiveness to relative changes in adult social contingencies across settings.     

Projection, Double Bind, and Demonic Possession: Some Common Elements in Three Theories of Psychosis

A desirable goal in science is to identify points at which theories converge. Three theories of psychosis are addressed with respect to three elements they share. The theories are (1) projection, (2) double bind, and (3) demonic possession. The points of convergence are (1) negative injunction, (2) persecutory belief, and (3) obedience to a transcendental command. Implications of the linkage between the elements and theories are drawn.     

Effects of different accessibility of reinforcement schedules on choice in humans

Based on the delay-reduction hypothesis, a less profitable schedule should be rejected if its duration exceeds the mean delay to reinforcement. It should be accepted if its duration is shorter than the mean delay. This was tested for humans, using a successive-choice schedule. The accessibility of the less profitable (variable-interval 18 s) schedule was varied by changing the duration (in terms of a fixed interval) of the waiting-time component preceding its presentation. Forty-eight students were randomly assigned to three groups. In Phase 1, the duration of the less profitable schedule equaled the mean delay to reinforcement in all groups. In Phase 2, waiting time preceding the less profitable schedule was reduced in Group 1 and increased in Group 2. Thus, the schedule was correlated either with a relative delay increase (Group 1) or a delay reduction (Group 2). In Group 3, conditions remained unchanged. As predicted, acceptance of the less profitable schedule decreased in Group 1 and increased in Group 2. The increased acceptance in Group 2 was accompanied by a decreased acceptance of the more profitable (variable-interval 3 s) schedule, resembling a pattern of negative contrast. Response rates were higher under the component preceding (a) the more profitable schedule in Group 1 and (b) the less profitable schedule in Group 2. Implications for the modification of human choice behavior are discussed.     

Contrast and undermatching with regular or irregular alternation of components

Behavioral contrast and response-ratio sensitivity to reinforcement were compared in multiple schedules in which components alternated strictly or according to a pseudorandom sequence. Average component durations in the two regimes were always 60 s, and order of presentation of component alternation regimes was counterbalanced across subjects. In Part 1, the reinforcer rate in one component was reduced from 60 per hour to zero, while that in the other component was unchanged. Positive behavioral contrast occurred in the constant component in that response rates increased, but neither the reliability nor the magnitude of contrast was affected by the manner in which components alternated. Part 2 was similar, except that a number of different reinforcer rates were used in the varied component. Neither contrast nor sensitivity of response ratios to changes in reinforcer ratios depended on the regime of component alternation. Thus, the predictability in time of future reinforcement conditions, which is a feature of regular multiple scheduling, does not appear to be a determinant of multiple-schedule performance.     

Choice performance in several concurrent key-peck treadle-press reinforcement schedules

Five pigeons were exposed to several concurrent variable-interval food reinforcement schedules. For three subjects, one component of the schedule required a key-pecking response, the other a treadle-pressing response. For the other two subjects, both schedule components required treadle-pressing responses. The relative probability of reinforcement associated with the manipulanda was varied from 0 to 1.0 in 13 experimental conditions for the Key-Treadle subjects and nine conditions for the Treadle-Treadle subjects. The results indicated that the logarithms of relative time spent responding, and the logarithms of relative number of responses emitted on a manipulandum, approximated direct linear functions of logarithms of the relative frequencies of reinforcement associated with that manipulandum. No systematic bias in favor of time spent key pecking over time spent treadle pressing was apparent for the Key-Treadle subjects. All subjects exhibited undermatching, in that the ratios of time and response allocation at the alternatives systematically differed from the ratios of reinforcers obtained from the alternatives in the direction of indifference. Key pecking appeared to have no special link to food beyond treadle pressing or what would be expected on the basis of the reinforcement dependencies alone.     

Negative behavioral contrast on multiple treadle-press schedules

Eight pigeons pressed treadles for food reinforcers delivered by several multiple variable-interval schedules. The rate of reinforcement for responding during one component schedule was held constant at 30 reinforcers per hour. The rate of reinforcement for responding during the other component varied from 0 to 120 or 240 reinforcers per hour. The schedules were presented in different orders for different subjects. The rate of responding emitted during the variable component schedule varied directly with the rate of reinforcement it provided. The rate of responding during the constant component did not increase consistently when the rate of reinforcement obtained from the variable component decreased from 30 to 0 reinforcers per hr. The rate of responding emitted during the constant component decreased when the rate of reinforcement obtained from the variable component increased from 30 reinforcers per hour to a higher rate. That is, negative but not positive behavioral contrast occurred. The failure to find positive contrast is consistent with one of the predictions of the additive theories of behavioral contrast. Finding negative contrast has ambiguous implications for the additive theories.     

A company-based lottery to reduce the personal driving of employees

A company-based lottery was used to reduce the number of nonessential miles employees drove their personal cars each day and thereby save gasoline. Employees were divided into an experimental and a contrast group. The experimental design involved two conditions: (a) a baseline in which no consequences were attached to driving behavior, and (b) a month-long lottery in which the experimentals were rewarded for decreasing their percentage of average miles driven per day relative to their initial baseline average. The experimentals received an ABA order of conditions while the contrast group remained in baseline. The lottery condition consisted of four weekly lotteries and one grand drawing held at the end of the month. During the lottery condition, the experimentals reduced their average daily mileage by 11.6% relative to their initial baseline (7.85 miles per employee per day) while the contrast employees increased their average mileage by 21.2%. Both groups exceeded their initial baseline averages in the return to baseline. The study was almost cost-effective because the experimentals' gas savings ($75) was within $4 of the cost of motivating them to reduce their mileage ($79).     

Behavioral contrast and the automaintained key peck

In two experiments behavioral contrast was demonstrated during discrimination training in a positive automaintenance procedure. During the baseline condition in each experiment, a key was transilluminated for eight seconds by one of two colors (CS) following a variable intertrial interval signaled by a dark key. Keylight transillumination terminated with a response-independent food presentation. In the first experiment, food was eliminated during one CS for up to fifty sessions. After reinstatement of food following each CS, the discrimination was reversed. Six of the eight subjects showed positive behavioral contrast, i.e., response rates increased during the CS associated with food as they decreased during the CS associated with no food. The effect was replicated in Experiment II, but it did not occur when both the food and its associated CS were eliminated. These results were comparable to those obtained with operant discrimination training procedures (behavioral contrast) and with Pavlovian discrimination training. The results suggest that additivity theories of behavioral contrast may be insufficient to account for these data.     

A molecular analysis of multiple schedule interactions: negative contrast

The present experiments investigated the relationship between changes in the relative reinforced interresponse-time distributions and the occurrence of positive and negative contrast in multiple variable-interval—variable-interval and multiple variable-interval—extinction schedules of reinforcement. Experiment I demonstrated that changes in the interresponse-time distributions were consistently correlated with response-rate changes referred to as positive and negative contrast. Corresponding changes in the reinforced interresponse-time distributions suggested that negative contrast resulted as an inductive effect of selectively reinforcing long interresponse times in the altered component at the moment the baseline schedule was reintroduced. Experiment II demonstrated that the magnitude of the negative-contrast effect could be significantly decreased if the altered component schedule was modified in order to prevent the reinforcement of these interresponse times during the first few sessions of baseline recovery. The results supported a proposal that interresponse time—reinforcer relations may act as amplifiers or attenuators of negative contrast.