On estimating the difference limen in duration discrimination tasks: a comparison of the 2AFC and the reminder task

This article assesses whether the two-alternative forced-choice (2AFC) and the reminder tasks (i.e., method of constant stimuli) yield identical estimates of the difference limen (DL). In a series of six experiments, participants discriminated between two duration stimuli. Experiments 1-5 employed auditory stimuli, and Experiment 6 employed visual stimuli. Experiments 1 and 2 combined each of the two tasks with an adaptive and a nonadaptive procedure for threshold estimation. Experiment 3 varied the distribution of the comparison levels, whereas Experiment 4 employed random interstimulus intervals. Experiments 5 and 6 examined the influence of the presentation order of the standard and comparison stimuli. Results indicate that both the adaptive and the nonadaptive procedures yield virtually identical DL estimates; yet, the 2AFC task produces consistently larger DLs than does the reminder task. In addition, DL increases when the standard occurs in the second rather than in the first stimulus position. In order to account for these results, we assume that participants use an internal standard instead of the actually presented standard as a reference for their judgment.     

Interval bias in 2AFC detection tasks: sorting out the artifacts

Proportion correct in two-alternative forced choice (2AFC) detection tasks often varies when the stimulus is presented in the first or in the second interval. Reanalysis of published data reveals that these order effects (or interval bias) are strong and prevalent, refuting the standard difference model of signal detection theory. Order effects are commonly regarded as evidence that observers use an off-center criterion under the difference model with bias. We consider an alternative difference model with indecision whereby observers are occasionally undecided and guess with some bias toward one of the response options. Whether or not the data show order effects, the two models fit 2AFC data indistinguishably, but they yield meaningfully different estimates of sensory parameters. Under indeterminacy as to which model governs 2AFC performance, parameter estimates are suspect and potentially misleading. The indeterminacy can be circumvented by modifying the response format so that observers can express indecision when needed. Reanalysis of published data collected in this way lends support to the indecision model. We illustrate alternative approaches to fitting psychometric functions under the indecision model and discuss designs for 2AFC experiments that improve the accuracy of parameter estimates, whether or not order effects are apparent in the data.     

Measuring the difference limen for identification of order of onset for complex auditory stimuli

The approximately 20-msec perceptual threshold for identifying order of onset for components of auditory stimuli has been considered both as a possible factor contributing to the perception of voicing contrasts in speech and as no more than a methodological artifact. In the present research, we investigate the identification of the temporal order of onset of spectral components in terms of the first of a sequence of thresholds for complex stimuli (modeled after consonant-vowel [CV] syllables) that vary in degree of onset. The results provide clear evidence that the difference limen (DL) for discriminating differences in onset time follows predictions based on a fixed perceptual threshold or limit at relatively short onset differences. Furthermore, the DL seems to be a function of context coding of stimulus information, with both the DL and absolute threshold probably reflecting limits on the effective perception and coding of the short-term stimulus spectrum.     

Estimating long-range dependence in time series: An evaluation of estimators implemented in R

Recent studies have shown that many physiological and behavioral processes can be characterized by long-range correlations. The Hurst exponent H of fractal analysis and the fractional-differencing parameter d of the ARFIMA methodology are useful for capturing serial correlations. In this study, we report on different estimators of H and d implemented in R, a popular and freely available software package. By means of Monte Carlo simulations, we analyzed the performance of (1) the Geweke—Porter-Hudak estimator, (2) the approximate maximum likelihood algorithm, (3) the smoothed periodogram approach, (4) the Whittle estimator, (5) rescaled range analysis, (6) a modified periodogram, (7) Higuchi’s method, and (8) detrended fluctuation analysis. The findings—confined to ARFIMA (0, d, 0) models and fractional Gaussian noise—identify the best estimators for persistent and antipersistent series. Two examples combining these results with the step-by-step procedure proposed by Delignières et al. (2006) demonstrate how this evaluation can be used as a guideline in a typical research situation.     

Ratio and difference comparisons of expected reward in decision-making tasks

Several models of choice compute the probability of selecting a given option by comparing the expected value (EV) of each option. However, a subtle but important difference between two common rules used to compute the action probability is often ignored. Specifically, one common rule type, the exponential rule, compares EVs via a difference operation, whereas another rule type, the power rule, uses a ratio operation. We tested the empirical validity of each rule type by having human participants perform a choice task in which either the difference or the ratio between the reward values was altered relative to a control condition. Results indicated that participants can compare expected rewards by either ratio or difference operations but that altering the ratio between EVs produces the most dramatic changes in behavior. We discuss implications for several related research fields.     

Estimating discrimination performance in two-alternative forced choice tasks: Routines for MATLAB and R

Ulrich and Vorberg (Attention, Perception, & Psychophysics 71: 1219–1227, 2009) introduced a novel approach for estimating discrimination performance in two-alternative forced choice (2AFC) tasks. This approach avoids pitfalls that are inherent when the order of the standard and the comparison is neglected in estimating the difference limen (DL), as in traditional approaches. The present article provides MATLAB and R routines that implement this novel procedure for estimating DLs. These routines also allow to account for processing failures such as lapses or finger errors and can be applied to experimental designs in which the standard and comparison differ only along the task-relevant dimension, as well as to designs in which the stimuli differ in more than one dimension. In addition, Monte Carlo simulations were conducted to check the quality of our routines.     

An improved technique for monitoring fixation in tachistoscopic tasks

A monocular lens mounted behind a stimulus screen was used to monitor fixation in a tachistoscopic recognition task. This technique was found superior to the often used “sideview technique” and as accurate as the method involving identification of a fixation stimulus. It was found that the “telescope technique” is preferable in those studies where presentation of a fixation stimulus might interfere with recognition or report of the experimental stimulus.     

Factorial design in the determination of differential limen values

This paper discusses the application of the principles of factorial design to an experiment in psychology. For the purpose of illustrating the principles, a simple experiment was designed dealing with the determination of the differential limen values of subjects for weights increasing at constant rates. The factorial design was of the type: 4 rates × 7 weights × 2 sexes × 2 sights × 2 dates. The appropriate statistical analysis for this type of design is the analysis of variance. The mathematical formulation of the problem was specified and the appropriate solution for the specific problem was obtained. Greater precision results from this type of design, in comparison with the traditional psychological experiment dealing with a single factor, in that measures are obtained of the effect of each of a number of factors together with their interactions.This is one of a number of studies on modern principles of experimental design. For the research grant to finance these studies, grateful acknowledgment is given to the Graduate School, the University of Minnesota.     

Respecting difference and moving beyond regulation: tasks for U.S. bioethics commissions in the twenty-first century

This article focuses on two possible missions for a national bioethics commission. The first is handling differences of worldview, political orientation, and discipline. Recent work in political philosophy emphasizes regard for the dignity of difference manifested in "conversation" that seeks understanding rather than agreement. The President's Council on Bioethics gets a mixed review in this area. The second is experimenting with prophetic bioethics. "Prophetic bioethics" is a term coined by Daniel Callahan to describe an alternative to compromise-seeking "regulatory bioethics." It involves a critique of modern medicine. In the contemporary context, the areas of biotechnology and access to health care cry out for prophetic attention. The Council has addressed biotechnology; unfortunately, that experience suggests that the kind of prophecy that it practices poses risks to conversation. With regard to access issues, the article proposes an effort that unites themes of human dignity, solidarity, and limits in support of reform, while highlighting, rather than papering over, differences.     

An improved measurement technique for human operator stability in aiming tasks

A technique is presented for field measurement of human operator stability in an aiming task. The small angular displacements of the aiming axis are measured by photographing a part of the target as reflected by a mirror mounted on the aiming device.     

Stuttering and anxiety: The difference between stutterers and nonstutterers in verbal apprehension and physiologic arousal during the anticipation of speech and non-speech tasks

To test if stressful anticipation of speech situations is a factor in eliciting stuttering behavior, the difference between 24 stutterers and 24 nonstutterers in verbal apprehension and physiologic activity was studied before and during speech tasks (reading and conversation), and nonspeech tasks (motor and intelligence task).Results indicate that the difference between stutterers and nonstutterers mainly were restricted to anxiety ratings assessed after each task. Heart rate, vasomotor responses, and electrodermal activity recorded before and during speech tasks were higher compared with the physiologic activity before and during nonspeech tasks but, unexpectedly, this was also the case for nonstutterers. It is concluded that stuttering is not elicited by anxiety.     

Comparison of inhibition in two timed reaction tasks: the color and emotion Stroop tasks

The authors examined the cross-task consistency of the ability to inhibit the processing of irrelevant information. They compared interference scores on 2 widely used inhibition tasks and found that color word Stroop interference scores correlated with emotion word Stroop interference scores. An examination of physiological reactivity showed that, in general, the color Stroop was more arousing than was the emotion Stroop, most likely due to increased response conflict.     

Scale convergence as a criterion for rescaling: Information integration with difference,ratio, and averaging tasks

Ss lifted pairs of weights simultaneously, one in each hand, and judged either the difference, ratio, or average heaviness of the two weights. Data for the difference and ratio tasks were in general agreement with subtractive and ratio models, but the averaging data showed discrepancies from the constant-weight averaging model similar to those reported in previous psychophysical research. Rescaling was ruled out for the averaging data, because responses to pairs of equal weight were a linear function of subtractive model scale values derived from the difference task data. Scale values for the ratio and difference task data were related exponentially, as were the responses to the pairs, consistent with Torgerson’s conjecture that Ss do not distinguish “differences” from “ratios.” They appear to use the same composition rule but different output functions, depending on the procedures for responding. The scale convergence criterion can thus prevent inappropriate rescaling when a model fails and can dictate rescaling even when a model fits.     

Type 2 tasks in the theory of signal detectability: Discrimination between correct and incorrect decisions

It has been known for over 40 years that there are two fundamentally different kinds of detection tasks in the theory of signal detectability. The Type 1 task is to distinguish between events defined independently of the observer; the Type 2 task is to distinguish between one’s own correct and incorrect decisions about those Type 1 events. For the Type 1 task, the behavior of the detector can be summarized by the traditional receiver operating characteristic (ROC) curve. This curve can be compared with a theoretical ROC curve, which can be generated from overlapping probability functions conditional on the Type 1 events on an appropriate decision axis. We show how to derive the probability functions underlying Type 2 decisions from those for the Type 1 task. ROC curves and the usual measures of performance are readily obtained from those Type 2 functions, and some relationships among various Type 1 and Type 2 performance measures are presented. We discuss the relationshiPbetween Type 1 and Type 2 confidence ratings and caution against the practice of presenting transformed Type 2 ratings as empirical Type 1 ratings.     

Bizarreness effects in verbal tasks and subject-performed tasks

Abstract

Recognition and cued recall of ordinary action phrases (e.g. “open the book”) and bizarre ones (e.g. “plant the hammer”) were compared under two encoding conditions: in verbal tasks (VTs), subjects learned the phrases by simply listening to them; in subject-performed tasks (SPTs), subjects learned the phrases by performing the denoted actions (without real objects). Memory performance was better after SPTs than after VTs in recognition and cued recall. In addition to this already established finding, it was observed that recognition was better for bizarre phrases than for ordinary ones after VTs and that bizarreness was unrelated to recognition after SPTs. Cued recall, on the other hand, depended on bizarreness after VTs as well as after SPTs and, in contrast to the recognition findings, ordinary phrases were recalled better than bizarre phrases. This pattern of findings was explained by the assumptions that lexical and conceptual information is encoded after VTs and motor information is additionally encoded after SPTs, and that different kinds of information are used in recognition and cued recall, and after VTs and SPTs.     

Serial and free recall in children can be improved by training: evidence for the importance of phonological and semantic representations in immediate memory tasks

Children were assigned to three groups given training on unfamiliar words--phoneme-awareness training, rhyme training, and vocabulary training--and an untrained control group. Before and after training, we assessed the children's performance on serial- and free-recall tasks with these words, as well as their ability to define the words, manipulate phonemes in them, and generate rhymes for them. We found that phoneme-awareness training improved serial recall substantially and improved free recall to a lesser extent. In contrast, vocabulary training produced a substantial increase in free recall and a lesser increase in serial recall. These effects on recall were specific and did not generalize to untrained words. Rhyme training produced increases in rhyming skills but no increase in either serial or free recall. We argue that serial and free recall depend on common memory mechanisms, but serial recall relies more on phonological codes and free recall relies more on semantic codes.     

Item and order information in subject-performed tasks and experimenter-performed tasks

This study investigated the enactment effect from the perspective of the item-order hypothesis (e.g., M. Serra & J. S. Nairne, 1993). The authors assumed that in subject-performed tasks (SPTs), item encoding is improved but order encoding is disrupted compared with experimenter-performed tasks (EPTs), that order encoding of EPTs is only better in pure lists, and that the item--order hypothesis is confined to short lists. Item information was tested in recognition memory tests, order information in order reconstruction tasks, and both item and order information in free-recall tests. The results of 5 experiments using short (8 items) and long lists (24 items) in a design with list type (pure, mixed) and encoding condition (EPT, SPT) as factors supported the hypotheses.     

The Unseen Spouse: Pitfalls and Possibilities for the Individual Therapist

Individual therapists often hear a great deal about our patients' spouses or partners, and naturally develop ideas and beliefs about that unseen other and about the causes of any relationship difficulties the patient reports. Not uncommonly, therapists can lose touch with the fact that their impressions of an unseen spouse are constructions that have emerged from the transference/countertransference field, based on only partial or limited information—not veridical truths. They can then talk with the patient about his or her partner or relationship issues in ways that can ultimately do both patient and spouse a significant disservice and perhaps distract from the patient's own issues and analytic goals. This paper discusses several factors that seem to contribute to the development of this problematic dynamic, including various qualities of the transference/countertransference field, and offers suggestions for avoiding or reducing it. Clinical material is used to illustrate key points.