In signal detection theory, sensitivity can be indexed as either the distance between distributions or the area under the isosensitivity curve. The statistic d′ is usually identified as a distance measure of sensitivity, while A′ is an estimate of the area. This article considers both statistics as estimates. As such, they can be evaluated against actual distances and areas calculated under specific assumptions about the variances of the distributions. The analysis shows that d′ is a better estimate of distance than A′ is of area only under the assumption that the variances of the hypothetical distributions are equal (i.e., the slope of the z-coordinate ROC is 1.0). When the slope takes on values other than 1.0, A′ is generally a more accurate estimate of area than d′ is of distance.
The Journal of Statistics Education (JSE) is a new electronic journal on postsecondary statistics education.(See the December Amstat News
In a recent article, Ferrand and Grainger (1992) reported that briefly presented, forward-masked, nonword primes that share letters with a target word facilitate lexical decision performance at prime exposures of 33 msec, but no longer affect performance at 67-msec exposures. In the same experiment, nonword primes that were homophonic with targets did not affect performance relative to orthographic controls at 33-msec prime exposures, but produced facilitatory priming effects at prime exposures of 67 msec. In the present study, we extend these results, varying prime exposures from 17 msec to 100 msec. Orthographic facilitation was found with prime exposures from 17 msec to 50 msec, whereas phonological facilitation only started to emerge at exposures of 50 msec. The results demonstrate a distinct time course for the buildup of orthographic and phonological information during the processing of pronounceable strings of letters.
The Journal of Statistics Education (JSE) is a new electronic journal on postsecondary statistics education.(See the December Amstat News
Some events in musical sequences are not performed as indicated in the score, but rather undergo systematic timing and intensity variations (played louder/softer and longer/shorter). Traditionally, these performance variations are considered to be related to a musician’s desire to transmit a particular musical interpretation to the listener. We suggest an alternative perceptual explanation that considers that the performance variations may result from constraints of the auditory system, with some events played louder and/or longer because they are heard softer and/or shorter. Two experiments are presented to distinguish between these two explanations. Subjects heard short musical sequences containing rhythmic grouping and melodic accents. Their task was to detect and identify the position of one event that was either slightly longer/shorter (Experiment 1) or louder/softer (Experiment 2) than other events in the sequence. Sensitivity to intensity changes was unaffected by the physical characteristics of the events in the sequences, but sensitivity to duration changes varied in relation to both rhythmic grouping and melodic accents. Thus, these results provide support for the perceptual hypothesis in the case of timing changes, but not for intensity changes.
Despite much disagreement regarding how probabilistic information is best communicated, virtually no research has been done to determine what communication modes people prefer or what factors affect their communication preferences. To address these issues, we did a survey of 442 graduate and undergraduate students in several specialties and universities. Some group differences emerged, but overall, 34% expressed preference for both conveying and receiving information about uncertainty in numerical rather than verbal form, 30% expressed the opposite preferences, and 35% indicated that they preferred to receive such information numerically but to convey it verbally. Generally, respondents who endorsed the use of verbal information said that it is easier to use, as well as more natural and personal. Those preferring numerical information said that it is more precise. Virtually all respondents, however, evidenced a willingness to use the opposite of their initially preferred mode if the situation should warrant it. The willingness to switch from one mode to another was said to depend on the level of precision implied by the data and the importance of the issue, as was suggested by Budescu and Wallsten (1987). These results may be helpful in structuring risk communication strategies.
This study was conducted to compare responses to stimuli presented in three different modalities: olfactory, visual, and lexical (the written name of the object). Cognitive aspects of these responses as well as affective components were examined. The subjects were placed at random into one of three experimental groups and were tested individually. Each subject was asked to smell, to view, or to see the name of six common items and to write whatever immediately came to mind after each stimulus presentation. The results indicate that the olfactory mode produced the shortest answers, with the largest amount of affect. The results are discussed in terms of their implications about the structure and nature of concepts and how such concepts interrelate with different sensory modalities.
University-We provide evidence that the decelerative portion of rapid reaching is visually guided .We describe optical information that may be used to guide reaching .The strategy entails the use of two variables .T4> specifies the time to close the gap between target and hand; TR specifies the time to reach target distance .The strategy is to use TR ~constant T4> .We present evidence from rapid targeted reaches of 4 subjects perturbed via a displacement prism .
Several months prior to the availability of a now-common blood test, homosexual volunteers, in a longitudinal study of their health, and typical college students were questioned about their attitudes toward early detection of acquired immunodeficiency syndrome (AIDS) and toward receiving information about desirable or fear-worthy hypothetical events. Generally, the homosexual volunteers were more interested in receiving information than were the students. Most homosexual volunteers desired human immunodeficiency virus (HIV) antibody test results, which could indicate infection, and indicated that receiving them would affect their behavior. However, all the subjects showed a preference for information on most questions, especially when the information could be used in guiding behavior change and was not virtually certain to be unfavorable. We are unaware of controlled evidence assessing whether or how knowledge of infection influences the imminent health risk of people who are asymptomatic, but prior to learning their HIV status, the homosexual volunteers who at the time had antibody in their sera were less concerned in knowing the test results of hypothetical future sexual partners than those without antibody.
Adult age differences in frequency-of-occurrence memory for actions performed zero, one, or two times in the laboratory were investigated shortly after the actions had been performed and after a retention interval of 24 h. A moderate age difference in accuracy of frequency judgments was found on the immediate retention test. Forgetting over 24 h was moderate for both young adult and elderly adult subjects. A negligible interaction between age and retention interval suggested comparable forgetting rates for young and elderly subjects, at least over 24 h.
In this paper, we describe a study in which we attempted to autoshape three horses to make a leverpress response. This study was motivated by observations made during earlier studies (Dougherty & Lewis, 1991b, 1992) in which we observed horses directing consummatory behaviors toward stimuli signaling the availability of reinforcers. The procedure was similar to that of other autoshaping procedures. Horses received forward conditioning trials in which stimuli (an illuminated panel and a retractable response lever) were periodically presented together for 10 sec and followed by a grain reinforcer. Each horse's stall served as an experimental chamber. A response panel was positioned in the stall's doorway, and a computer located nearby controlled and monitored experimental events. Each day, for 14 days, 100 stimulus-reinforcer pairings were presented. Despite 1,400 stimuli-reinforcer presentations, none of the horses were autoshaped. A few possible reasons for these results are discussed.
Taste preferences for representatives of the four taste qualities and the taste of MSG were assessed for Long-Evans rats (Rattus norvegicus) and Egyptian spiny mice (Acomys cahirinus). The rats preferred hedonic concentrations of all salty and sweet tastants, as well as the taste of MSG, and rejected sour and bitter tastants. The spiny mice preferred water to salty tastants, approached some concentrations of sweet tastants, and rejected all others—including those readily ingested by rats.
Many studies have investigated judgment and decision making under uncertainty (i.e., when the possible outcomes of a given alternative occur with some known exact probability between 0 and 1). Fewer studies, however, have investigated judgment and decision making in which the probabilities associated with different outcomes are ambiguous (i.e., known to be in a certain interval such as.40–.60, rather than known to be a specific value such as.50). Judgment under both uncertainty and ambiguity was investigated by having subjects evaluate two-outcome prospects that varied in expected value, level of probability ambiguity, and the center of the ambiguous probability range. Results indicated a preference for unambiguous probabilities when the probability of obtaining the better outcome was.50 or greater and a preference for a small amount of ambiguity when the probability of obtaining the better outcome was moderately low (.30).
Tversky & Hemenway's (1984) claim that parts are central to basic-level categorization suggests that parts should play an important role in the formation of basic-level categories by young children. There is, however, a prevailing claim that young children do not attend to parts, but treat objects as integral wholes. The present study attempted to compare children's ability to categorize at the basic level and their sensitivity to parts and part-whole relations. Nursery school children, kindergarteners, first- and second-graders performed three tasks: (1) sorting objects into basic-level categories, (2) sorting parts that belong to the same object, and (3) matching parts with basic-level objects. Children's performance on parts sorting and part-object matching lagged behind their objects sorting, suggesting that attention to parts per se does not seem to be essential for children's basic-level categorization. Also, by 5 years of age, children showed sensitivity to parts and to part-whole relations, and this sensitivity improved with age.
The perception of speech rate was examined as a function of the gender of the speakers and listeners and the speech rate of the listeners. In the first experiment, the stimuli were moderately paced speech samples from women, with males and females as listeners. The results indicated that although the speech rates of the female listeners were positively related to perceived speech rate, the rates of the male listeners were negatively related. In the second experiment, the stimuli were comparably paced samples of male and female speech, again with men and women as the listeners. The results indicated that the women judged the speech rates of all the speakers to be faster than did the men, and that all the listeners believed that the men talked faster than the women. The results of both studies suggest that gender plays an influential role in the perception of speech rate.
Two experiments were run in which subjects judged the sizes of stimuli that moved toward and away from them in total darkness by varying a comparison stimulus. In Experiment 1, the target was centered with respect to eye level in the first condition, extended upward from the eye level in the second condition, and extended downward from eye level in the third condition. The subjects were instructed to maintain a level gaze in all conditions. All targets changed in apparent size as a function of varying distance, but the type of change was contingent upon the egocentric location of the stimulus. In Experiment 2, the point at which subjects fixated the stimuli was manipulated. Varying fixation had no effect upon apparent visual size. These data were interpreted as supporting an egocentric explanation of size perception.
In the first of three experiments, we found that 26% of our subjects reversed the mental image of Jastrow’s (1900) duck/rabbit figure. We speculated that the remaining 74% did not perform the reversal in imagination because they were unable to maintain an accurate image of the figure sufficiently long to allow for the reversal to occur. Therefore, in a second experiment, subjects attempted to reverse the memory image of the duck/rabbit, while simultaneously feeling an embossed version of the figure. This resulted in a 66% reversal rate, suggesting that the haptic form allowed for a greater number of reversals by preventing the mental image of the duck/rabbit from becoming distorted or decaying over time. Because a good portion of these reversals may have been tactual and not imaginai, a fragmented haptic form was used in a third experiment. A 50% reversal rate was obtained, even though this form could not be reversed by touch alone.
Cataract removal from the left eye resulted in color distortion in that eye; the entire visual world seemed to be bathed in blue light. Reasoning that this may have been due to a conditioned color aftereffect, a perceptual adaptation procedure was devised to correct the problem. Normal color vision was restored in the eye after six 10-min adaptation sessions.
Fifteen subjects participated in a study designed to record event-related potentials (ERPs) to various concentrations of the odorant n-butyl alcohol. Subjects pressed a response key upon detection of the odor, while ERPs were recorded from nine electrode positions. Results indicated a concentration-dependent increase in amplitude of a P300-like component 320–520 msec following the stimulus onset. Correlations between subjects’ sensory thresholds and activity at frontal electrode sites were also found. The absence of early ERP components is discussed.
