An experimental investigation into the effects of uncertainty on rational behaviour in two person symmetric games

This paper reports the results of two experiments to investigate the effects of payoff alterations in two-person symmetric games. The initial experiment involved 60 subjects, each of whom could earn from £0 to £15, depending on the interaction of their decisions and the unknown decisions of one other person. All decisions were made without feedback to isolate the impact on subjects' behaviour of the game's parameters. A primary aim was to see if the games had strategically distinct structures, or whether uncertainty over the choice rule of others would influence choice behaviour and lessen this independence. An alternative model of rational choice, making allowance for uncertainty in the decision environment, was proposed to capture subjects' behaviour. The results indicated that the frontiers of most of the games had no impact on choice behaviour other than through the magnitude of the change in payoffs. The model received strong support across an identifiable set of ‘frontierless’ games. However, the variety of games was not sufficient to provide a comprehensive test. A second experiment was recently held to close these gaps. Fifty subjects took part, each of whom earned from A$0 to A$24, averaging A$17. The findings provided broad additional support for the theory.     

An investigation of DIF mechanisms in the context of differential testlet effects

This study investigated differential item functioning (DIF) mechanisms in the context of differential testlet effects across subgroups. Specifically, we investigated DIF manifestations when the stochastic ordering assumption on the nuisance dimension in a testlet does not hold. DIF hypotheses were formulated analytically using a parametric marginal item response function approach and compared with empirical DIF results from a unidimensional item response theory approach. The comparisons were made in terms of type of DIF (uniform or non‐uniform) and direction (whether the focal or reference group was advantaged). In general, the DIF hypotheses were supported by the empirical results, showing the usefulness of the parametric approach in explaining DIF mechanisms. Both analytical predictions of DIF and the empirical results provide insights into conditions where a particular type of DIF becomes dominant in a specific DIF direction, which is useful for the study of DIF causes.     

An experimental investigation of the relative effectiveness of two techniques for structuring multiattributed hierarchies

An experiment was performed to evaluate the relative effectiveness of a top-down approach and bottom-up approach to structuring multiattributed hierarchies. It was hypothesized that the top-down approach would result in both (1) a more accurate hierarchy and (2) a deeper hierarchy than the bottom-up approach. Although the latter hypothesis was supported, the former was not. Implications for further research are discussed.     

An experimental investigation of thought suppression

An experiment investigating the hypothesis that trying to suppress a thought will lead to an immediate and/or delayed increase in its occurrence is reported. Normal subjects listened to a taped story and then verbalized their stream of consciousness during two consecutive time periods. During the first period, one group (suppression) were asked not to think about the tape while two other groups (controls) were asked to think about anything or think about anything including the tape. During the second period, all three groups were instructed to think about anything. Results from the first period failed to support the immediate enhancement hypothesis as the suppression group reported less thoughts about the tape than the controls. However, results from the second period supported the delayed (rebound) hypothesis as subjects who had previously suppressed reported more thoughts about the tape than subjects who had not. The theoretical, methodological, and clinical implications of these results are discussed.     

Comparison of positive and negative intrusive thoughts and experimental investigation of the differential effects of mood.

The similarity between positive and negative intrusive thoughts is considered for both recently occurring, personally relevant intrusions and for the same intrusions occurring during an experimental task involving self-monitoring. The results indicate that positive and negative intrusions differ in most respects. There was evidence that increasing the frequency of negative thinking is associated with a deterioration of mood. In a subsequent experiment, induced happy and sad moods were shown to differentially affect frequency of intrusions in a fashion consistent with mood congruency effects previously found in experiments on the effect of mood on memory. The implications of these findings for disorders involving the experience of intrusive thoughts such as OCD and depression are discussed.     

Relative reinforcing effects of different oral ethanol doses in rhesus monkeys

The relative reinforcing effects of different doses of orally delivered ethanol were evaluated. Mouth-contact responding by rhesus monkeys was measured under concurrent fixed-ratio fixed-ratio schedules of liquid delivery (0.67 ml/delivery) from each of two spouts during daily 3-hr sessions. Experiment 1 examined persistence of responding with ethanol (2%, 8%, and 32% wt/vol) and water available. When fixed-ratio values from 8 to 128 were tested, the number of ethanol deliveries obtained per session decreased as the response requirement increased. The decrease in deliveries was less at higher than at lower ethanol concentrations, however. Experiment 2 examined choice between two ethanol concentrations under concurrent fixed-ratio 16 schedules (4% vs. 8%, 4% vs. 16%, 8% vs. 16%, 2% vs. 8%, 2% vs. 32%, 8% vs. 32%). Higher concentrations (16%, 32%) generally maintained more responding than concurrently available concentrations of 8% or less. An exception was the observation of a preference for 8% over 32% ethanol. When the fixed-ratio value was increased, however, the relative preference for these two doses was reversed so that 32% ethanol maintained more responding than 8% ethanol. Thus, the direction of the preference depended on the size of the response requirement. These results indicate that the reinforcing effects of ethanol increase with dose.     

Time management: An experimental investigation

Four groups of preservice teachers participating in student teaching seminars were randomly assigned to one of three conditions to test the effectiveness of brief training in time-management techniques. A control group received no training. Experimental Group 2 received basic training in time management, whereas Experimental Group 1 received the same training and, in addition, implemented two specific time- management procedures (written planning and self-monitoring) under the supervision of the experimenters. Significant differences among the groups were observed in the expected direction on measures of promptness in completing tasks during student teaching and on self-ratings of proficiency in time management.     

An evaluation of stimulant medication on the reinforcing effects of play

Although a vast literature has indicated that stimulant medications are effective for reducing inappropriate behavior in children with attention deficit hyperactivity disorder (ADHD), the effects of stimulant medication on ancillary behaviors (e.g., play) have yet to be investigated with the same rigor. We used a reinforcer assessment procedure to evaluate the effects of medication on the play and social behavior of 5 preschool children who had been diagnosed with ADHD. Conditions included (a) social reinforcement (i.e., playing with friends), (b) alone play, and (c) quiet time (i.e., resting). Results indicated that 1 of the 5 participants selected fewer social reinforcers and more nonsocial reinforcers (alone play or quiet time) while on medication. The findings indicate that the reinforcer assessment procedure may be a viable way to evaluate medication effects on an ongoing basis and to inform treatment decisions.     

An experimental treatment using verbal punishment with two preschool stutterers

A multiple base-line experimental treatment was conducted with two preschool stuttering children. Each child conversed 20 min with the experimenter for 20 sessions. Treatment consisted of the presentation of the verbal stimulus “slow down” contingent upon a stuttering response. The percentage of words stuttered by both children decreased during the treatment sessions. Probe tape recordings conducted in each child's home revealed a decrease in stuttering frequency.