Timeout postponement without increased reinforcement frequency

Three experiments were conducted to examine pigeons' postponement of signaled extinction periods (timeouts) from a schedule of food reinforcement when such responding neither decreased overall timeout frequency nor increased the overall frequency of food reinforcement. A discrete-trial procedure was used in which a response during the first 5 s of a trial postponed an otherwise immediate 60-s timeout to a later part of that same trial but had no effect on whether the timeout occurred. During time-in periods, responses on a second key produced food according to a random-interval 20-s schedule. In Experiment 1, the response-timeout interval was 45 s under postponement conditions and 0 s under extinction conditions (responses were ineffective in postponing timeouts). The percentage of trials with a response was consistently high when the timeout-postponement contingency was in effect and decreased to low levels when it was discontinued under extinction conditions. In Experiment 2, the response-timeout interval was also 45 s but postponement responses increased the duration of the timeout, which varied from 60 s to 105 s across conditions. Postponement responding was maintained, generally at high levels, at all timeout durations, despite sometimes large decreases in the overall frequency of food reinforcement. In Experiment 3, timeout duration was held constant at 60 s while the response-timeout interval was varied systematically across conditions from 0 s to 45 s. Postponement responding was maintained under all conditions in which the response-timeout interval exceeded 0 s (the timeout interval in the absence of a response). In some conditions of Experiment 3, which were designed to control for the immediacy of food reinforcement and food-correlated (time-in) stimuli, responding postponed timeout but the timeout was delayed whether a response occurred or not. Responding was maintained for 2 of 3 subjects, suggesting that behavior was negatively reinforced by timeout postponement rather than positively reinforced by the more immediate presentation of food or food-correlated (time-in) stimuli.     

Risk-sensitive choice in humans as a function of an earnings budget

Risky choice in 3 adult humans was investigated across procedural manipulations designed to model energy-budget manipulations conducted with nonhumans. Subjects were presented with repeated choices between a fixed and a variable number of points. An energy budget was simulated by use of an earnings budget, defined as the number of points needed within a block of trials for points to be exchanged for money. During positive earnings-budget conditions, exclusive preference for the fixed option met the earnings requirement. During negative earnings-budget conditions, exclusive preference for the certain option did not meet the earnings requirement, but choice for the variable option met the requirement probabilistically. Choice was generally risk averse (the fixed option was preferred) when the earnings budget was positive and risk prone (the variable option was preferred) when the earnings budget was negative. Furthermore, choice was most risk prone during negative earnings-budget conditions in which the earnings requirement was most stringent. Local choice patterns were also frequently consistent with the predictions of a dynamic optimization model, indicating that choice was simultaneously sensitive to short-term choice contingencies, current point earnings, and the earnings requirement. Overall, these results show that the patterns of risky choice generated by energy-budget variables can also be produced by choice contingencies that do not involve immediate survival, and that risky choice in humans may be similar to that shown in nonhumans when choice is studied under analogous experimental conditions.     

HUMAN RESPONDING ON RANDOM‐INTERVAL SCHEDULES OF RESPONSE‐COST PUNISHMENT: THE ROLE OF REDUCED REINFORCEMENT DENSITY

An experiment with adult humans investigated the effects of response‐contingent money loss (response‐cost punishment) on monetary‐reinforced responding. A yoked‐control procedure was used to separate the effects on responding of the response‐cost contingency from the effects of reduced reinforcement density. Eight adults pressed buttons for money on a three‐component multiple reinforcement schedule. During baseline, responding in all components produced money gains according to a random‐interval 20‐s schedule. During punishment conditions, responding during the punishment component conjointly produced money losses according to a random‐interval schedule. The value of the response‐cost schedule was manipulated across conditions to systematically evaluate the effects on responding of response‐cost frequency. Participants were assigned to one of two yoked‐control conditions. For participants in the Yoked Punishment group, during punishment conditions money losses were delivered in the yoked component response independently at the same intervals that money losses were produced in the punishment component. For participants in the Yoked Reinforcement group, responding in the yoked component produced the same net earnings as produced in the punishment component. In 6 of 8 participants, contingent response cost selectively decreased response rates in the punishment component and the magnitude of the decrease was directly related to the punishment schedule value. Under punishment conditions, for participants in the Yoked Punishment group response rates in the yoked component also decreased, but the decrease was less than that observed in the punishment component, whereas for participants in the Yoked Reinforcement group response rates in the yoked component remained similar to rates in the no‐punishment component. These results provide further evidence that contingent response cost functions similarly to noxious punishers in that it appears to suppress responding apart from its effects on reinforcement density.     

生活医学化与健康恐慌的关系及其反思*--论Michael Fitzpatrick《健康的暴政：医生及生活方式的控制》

迈克尔·菲茨帕特里克的《健康的暴政：医生及生活方式的控制》一书,以健康干预为主线,以健康政治化、生活医学化、疾病道德化为主题,论述了生活医学化的不同方面和形成过程,并力图揭示医学化背后隐含着的医学对社会的干预和控制。其中作者关于生活医学化和健康恐慌的一些哲学思考,尤其是生活医学化与健康恐慌的内涵及特点、生活医学化与健康恐慌的关系以及对生活医学化的审视与反思,在一定程度上蕴涵着对当今社会发展的启示。     

Traffic-entry behavior and crash risk for older drivers with impairment of selective attention

Current research suggests that older drivers with declines in selective attention would make more unsafe traffic-entry judgments than would older drivers with normal attention. This hypothesis was tested using an instrumented vehicle and a LIDAR speed and range detector. Participants were 20 older drivers: 10 (M=72.0 yr.) had impairments of selective attention, measured with the Visual Attention Analyzer, Model 3000, and 10 were nonimpaired (M=71.2 yr.). Drivers pressed a button to indicate the last possible moment they could safely cross a road in front of an oncoming vehicle. The speed and distance of the oncoming vehicles were measured and time-to-contact was calculated. Each driver's time-to-cross the roadway was independently measured. Attention-impaired drivers showed shorter time-to-contact values (5.60 sec. versus 6.86 sec.), took longer to cross the roadway (5.41 sec. versus 4.84 sec.), and had shorter safety cushions (the difference between time-to-contact and time-to-cross the roadway). Monte Carlo simulation showed that these performance differences increased the crash risk of the impaired group by up to 17.9 times that of the nonimpaired group.     

Human risky choice under temporal constraints: tests of an energy-budget model

Risk-sensitive foraging models predict that choice between fixed and variable food delays should be influenced by an organism's energy budget. To investigate whether the predictions of these models could be extended to choice in humans, risk sensitivity in 4 adults was investigated under laboratory conditions designed to model positive and negative energy budgets. Subjects chose between fixed and variable trial durations with the same mean value. An energy requirement was modeled by requiring that five trials be completed within a limited time period for points delivered at the end of the period (block of trials) to be exchanged later for money. Manipulating the duration of this time period generated positive and negative earnings budgets (or, alternatively, "time budgets"). Choices were consistent with the predictions of energy-budget models: The fixed-delay option was strongly preferred under positive earnings-budget conditions and the variable-delay option was strongly preferred under negative earnings-budget conditions. Within-block (or trial-by-trial) choices were also frequently consistent with the predictions of a dynamic optimization model, indicating that choice was simultaneously sensitive to the temporal requirements, delays associated with fixed and variable choices on the upcoming trial, cumulative delays within the block of trials, and trial position within a block.     

Situation awareness as a function of frame of reference, computer-graphics eyepoint elevation, and geometric field of view

The purpose of this study was to determine how 3 variables for the design of a "heads-down" spatial display--the frame of reference (pilot's eye vs. God's eye), geometric field of view, and elevation of the computer graphics eyepoint--influenced situation awareness. Thirteen flight-naive subjects each flew a simulated F-16 over a computer-generated flight environment to lock onto and intercept a series of sequentially appearing targets. The flight scene consisted of both an "out-the-window" view and a computer-generated heads-down spatial display showing an airplane symbol superimposed on a perspective view of the flight environment. During the interactive phase of the experiment, root mean square flight-path error, target lock-on time, and target acquisition time were measured. After the interactive phase of the study was completed, subjects were required to mark the location of the targets from memory on a computer-generated top-down view of the flight scene in an attempt to reconstruct the spatial mental model which subjects formed of the flight environment. The results for the interactive phase of the study indicated that performance was superior using the pilot's-eye display. However, for the spatial reconstruction task, performance was better using the God's-eye display. It was also shown that the ability to maintain the optimal flight-path using the more top-down view of the scene (600 eyepoint) was superior to the 300 eyepoint elevation. Implications of the results for the design of spatial instruments are discussed.