A comparison of six methods to estimate thresholds from psychometric functions

There are many ways in which to estimate thresholds from psychometric functions. However, almost nothing is known about the relationships between these estimates. In the present experiment, Monte Carlo techniques were used to compare psychometric thresholds obtained using six methods. Three psychometric functions were simulated using Naka-Rushton and Weibull functions and a probit/logit function combination. Thresholds were estimated using probit, logit, and normit analyses and least-squares regressions of untransformed orz-score and logit-transformed probabilities versus stimulus strength. Histograms were derived from 100 thresholds using each of the six methods for various sampling strategies of each psychometric function. Thresholds from probit, logit, and normit analyses were remarkably similar. Thresholds fromz-score- and logit-transformed regressions were more variable, and linear regression produced biased threshold estimates under some circumstances. Considering the similarity of thresholds, the speed of computation, and the ease of implementation, logit and normit analyses provide effective alternatives to the current “gold standard”—probit analysis—for the estimation of psychometric thresholds.     

Effects on pupil size of manual and verbal indicators of cognitive task fulfillment

A total of20 Ss attempted to generate images to concrete and abstract stimulus words while pupillary activity was continuously photographed. One group (N =5) was required to press a key when an image occurred, a second to describe the image, and a third to press a key as well as describe the image. No overt indicator was required of a fourth group. Results showed that greater dilation occurred during the imagery task than during a control period only in those conditions in which an overt response indicated task fulfillment. Consistent with earlier findings significantly greater dilation occurred to abstract than concrete stimulus words in the key press condition.     

The step method: a new adaptive psychophysical procedure

A new adaptive psychophysical method, the step method, is introduced. Simulations show the method to be less biased and more efficient than constant stimuli or Pentland's adaptive method for fewer than 40 trials. An experiment using discrimination of dot number, however, failed to find any differences among the three methods in either bias or efficiency.     

Reliability of a Measure of Temporal Discounting

The Psychological Record - Participants (N = 17) chose between smaller, immediate and larger, delayed hypothetical money amounts in two laboratory sessions separated by 1 week. The choice procedure...     

TESTIMONY AND SINCERITY

Is there a justified presumption that a speaker is testifying sincerely? Anti‐reductionism about testimony claims that there is, absent reasons to the contrary. Yet why believe this, given the actuality and prevalence of lies and deception? I examine one argument that may be appropriated to meet this challenge, David Lewis's claim that truthfulness is a convention. I argue that it fails, and that the supposition that there is a presumption of sincerity remains unsupported. The failure of Lewis's argument is instructive, however, for it shows us a better way of approaching language use than the standard anti‐reductionist treatment. As speech is an intentional action, so a presumption of the sincerity or otherwise of others' testimony must be explicable in the terms we normally use to explain action.     

Sleep deprivation and stressors: Evidence for elevated negative affect in response to mild stressors when sleep deprived

Stress often co-occurs with inadequate sleep duration, and both are believed to impact mood and emotion. It is not yet known whether inadequate sleep simply increases the intensity of subsequent stress responses or interacts with stressors in more complicated ways. To address this issue, we investigated the effects of one night of total sleep deprivation on subjective stress and mood in response to low-stress and high-stress cognitive testing conditions in healthy adult volunteers in two separate experiments (total N = 53). Sleep was manipulated in a controlled, laboratory setting and stressor intensity was manipulated by changing difficulty of cognitive tasks, time pressure, and feedback about performance. Sleep-deprived participants reported greater subjective stress, anxiety, and anger than rested controls following exposure to the low-stressor condition, but not in response to the high-stressor condition, which elevated negative mood and stress about equally for both sleep conditions. These results suggest that sleep deprivation lowers the psychological threshold for the perception of stress from cognitive demands but does not selectively increase the magnitude of negative affect in response to high-stress performance demands. (PsycINFO Database Record (c) 2012 APA, all rights reserved).     

Comparability of Self‐Reported Conscientiousness Across 21 Countries

In cross‐national studies, mean levels of self‐reported phenomena are often not congruent with more objective criteria. One prominent explanation for such findings is that people make self‐report judgements in relation to culture‐specific standards (often called the reference group effect), thereby undermining the cross‐cultural comparability of the judgements. We employed a simple method called anchoring vignettes in order to test whether people from 21 different countries have varying standards for Conscientiousness, a Big Five personality trait that has repeatedly shown unexpected nation‐level relationships with external criteria. Participants rated their own Conscientiousness and that of 30 hypothetical persons portrayed in short vignettes. The latter type of ratings was expected to reveal individual differences in standards of Conscientiousness. The vignettes were rated relatively similarly in all countries, suggesting no substantial culture‐related differences in standards for Conscientiousness. Controlling for the small differences in standards did not substantially change the rankings of countries on mean self‐ratings or the predictive validities of these rankings for objective criteria. These findings are not consistent with mean self‐rated Conscientiousness scores being influenced by culture‐specific standards. The technique of anchoring vignettes can be used in various types of studies to assess the potentially confounding effects of reference levels. Copyright © 2011 John Wiley & Sons, Ltd.