The Fishbein and Ajzen Theory of Reasoned Action Applied to Contraceptive Behavior: Model Variants and Meaningfulness1

Suggested modifications of the theory of reasoned action, which conceptualize the functional operation of the attitudinal and normative components in intention formation as separate, separate but contingent, and inseparable, are discussed. The model structures are examined with regard to the underlying psychological assumptions (psychological meaningfulness) and with regard to the required scale levels for the model variables, so that the results of model tests are invariant under the admissible scale transformations (formal meaningfulness). Using a procedure that combines “optimal scaling” with hierarchical regression analysis, the model variants are tested for women's (n= 89) and men's (n= 89) intentions to use contraceptive methods (pill, intrauterine device, condom, and natural methods) that require the model variables to be measured on interval scales. The results strongly favored the theory of reasoned action above the other model variants. Only for the subjective norm model was a better model fit found for a belief-only model compared to the original product-sum model. Gender differences were found with regard to the salient belief sets and the explanatory power of the normative model component.     

High-risk sexual behavior and knowledge of HIV antibody status in the San Francisco City Clinic Cohort

To evaluate the effectiveness of human immunodeficiency virus (HIV) testing and counseling among homosexual and bisexual men participating in the San Francisco City Clinic Cohort, compared behavioral data from 181 men who learned their HIV antibody status between 1985 and 1987 with data from 128 men who were tested but declined to receive their results. Overall, significant declines in risk indices for unprotected receptive and insertive anal intercourse occurred between 1983-1984 and 1986-1987, but these declines were independent of both knowledge of HIV status and actual serostatus. Those who chose to learn their HIV status were also no more likely to report depression or to learn their HIV status were also no more likely to report depression or anxiety subsequent to testing. Regression analyses showed no relationship between length of time since learning one's HIV status, mental health symptoms, and the persistence of high-risk behavior in 1986-1987. Although these results do not negate the value of HIV testing and counseling, they suggest that other motivating factors such as frequent access to risk-reduction information may provide sufficient impetus for behavioral change.     

Tracking of nociceptive thresholds using adaptive psychophysical methods

Psychophysical thresholds reflect the state of the underlying nociceptive mechanisms. For example, noxious events can activate endogenous analgesic mechanisms that increase the nociceptive threshold. Therefore, tracking thresholds over time facilitates the investigation of the dynamics of these underlying mechanisms. Threshold tracking techniques should use efficient methods for stimulus selection and threshold estimation. This study compares, in simulation and in human psychophysical experiments, the performance of different combinations of adaptive stimulus selection procedures and threshold estimation methods. Monte Carlo simulations were first performed to compare the bias and precision of threshold estimates produced by three different stimulus selection procedures (simple staircase, random staircase, and minimum entropy procedure) and two estimation methods (logistic regression and Bayesian estimation). Logistic regression and Bayesian estimations resulted in similar precision only when the prior probability distributions (PDs) were chosen appropriately. The minimum entropy and simple staircase procedures achieved the highest precision, while the random staircase procedure was the least sensitive to different procedure-specific settings. Next, the simple staircase and random staircase procedures, in combination with logistic regression, were compared in a human subject study (n = 30). Electrocutaneous stimulation was used to track the nociceptive perception threshold before, during, and after a cold pressor task, which served as the conditioning stimulus. With both procedures, habituation was detected, as well as changes induced by the conditioning stimulus. However, the random staircase procedure achieved a higher precision. We recommend using the random staircase over the simple staircase procedure, in combination with logistic regression, for nonstationary threshold tracking experiments.     

Role of surface roughness in hysteresis during adhesive elastic contact

In experiments that involve contact with adhesion between two surfaces, as found in atomic force microscopy or nanoindentation, two distinct contact force (P) versus indentation-depth (h) curves are often measured depending on whether the indenter moves towards or away from the sample. The origin of this hysteresis is not well understood and is often attributed to moisture, plasticity or viscoelasticity. Here we report experiments which show that hysteresis can exist in the absence of these effects, and that its magnitude depends on surface roughness. We develop a theoretical model in which the hysteresis appears as the result of a series of surface instabilities, in which the contact area grows or recedes by a finite amount. The model can be used to estimate material properties from contact experiments even when the measured P–h curves are not unique.     

How the Learning Path and the Very Structure of a Multifloored Environment Influence Human Spatial Memory

Few studies have explored how humans memorize landmarks in complex multifloored buildings. They have observed that participants memorize an environment either by floors or by vertical columns, influenced by the learning path. However, the influence of the building’s actual structure is not yet known. In order to investigate this influence, we conducted an experiment using an object-in-place protocol in a cylindrical building to contrast with previous experiments which used rectilinear environments. Two groups of 15 participants were taken on a tour with a first person perspective through a virtual cylindrical three-floored building. They followed either a route discovering floors one at a time, or a route discovering columns (by simulated lifts across floors). They then underwent a series of trials, in which they viewed a camera movement reproducing either a segment of the learning path (familiar trials), or performing a shortcut relative to the learning trajectory (novel trials). We observed that regardless of the learning path, participants better memorized the building by floors, and only participants who had discovered the building by columns also memorized it by columns. This expands on previous results obtained in a rectilinear building, where the learning path favoured the memory of its horizontal and vertical layout. Taken together, these results suggest that both learning mode and an environment’s structure influence the spatial memory of complex multifloored buildings.     

Testing a new cognitive behavioural treatment for obesity: A randomized controlled trial with three-year follow-up

It is remarkably difficult for people with obesity to maintain a new lower weight following weight loss. The aim of the present study was to examine the immediate and longer-term effects of a new cognitive behavioural treatment that was explicitly designed to minimise this post-treatment weight regain. One hundred and fifty female participants with obesity were randomized to the new treatment, behaviour therapy (the leading alternative psychological treatment) or guided self-help (a minimal intervention). Both of the main treatments resulted in an average weight loss of about ten percent of initial weight whereas weight loss was more modest with guided self-help. The participants were subsequently followed-up for three years post-treatment. The great majority regained almost all the weight that they had lost with the new treatment being no better than the behavioural treatment in preventing weight regain. These findings lend further support to the notion that obesity is resistant to psychological methods of treatment, if anything other than a short-term perspective is taken. It is suggested that it is ethically questionable to claim that psychological treatments for obesity “work” in the absence of data on their longer-term effects.     

Seeing is believing: Trustworthiness as a dynamic belief

Recent efforts to understand the mechanisms underlying human cooperation have focused on the notion of trust, with research illustrating that both initial impressions and previous interactions impact the amount of trust people place in a partner. Less is known, however, about how these two types of information interact in iterated exchanges. The present study examined how implicit initial trustworthiness information interacts with experienced trustworthiness in a repeated Trust Game. Consistent with our hypotheses, these two factors reliably influence behavior both independently and synergistically, in terms of how much money players were willing to entrust to their partner and also in their post-game subjective ratings of trustworthiness. To further understand this interaction, we used Reinforcement Learning models to test several distinct processing hypotheses. These results suggest that trustworthiness is a belief about probability of reciprocation based initially on implicit judgments, and then dynamically updated based on experiences. This study provides a novel quantitative framework to conceptualize the notion of trustworthiness.