PubMed Health⌕ Search

Biomedical subjects

B Espinoza-Varas

Publications and source records attributed to B Espinoza-Varas.

6 recordsLinked to original sources
PubMed1994

Effects of decision criterion on response latencies of binary decisions.

The effects of decision criterion on response latencies of binary decisions were examined. The stimuli comprised two, partly overlapping, "normal" distributions of either two-digit numbers or tonal frequencies. Individual stimuli were randomly sampled from the distributions, and subjects had to decide from which distribution the stimulus was sampled. The decision goal was to maximize the expected gain using three different payoff matrices. Decision latencies with and without prior knowledge of optimal decision criteria were measured. In a control task, subjects were asked only to label stimuli as being either above or below the optimal criteria (without regard for a posteriori probabilities or expected gain). The relation between criterion and latency was examined by means of a trial-by-trial analysis of the stimuli and the responses. Response latency was inversely related both to the distance between the stimulus and the decision criterion and to the probability of the response elicited by the stimulus. Response latencies showed a maximum at the criterion in all conditions. These results were obtained with different stimulus modalities (tones or numbers), different discriminability levels within the auditory modality, and different decision tasks. It is proposed that the decision criterion is the primary determinant of response latencies of binary decisions.

Acoustic Stimulation↗
PubMed1988

Modeling sensorineural hearing loss. I. Model and retrospective evaluation.

The present article describes an approach to the evaluation of psychoacoustic data from the hearing impaired. The results obtained from the hearing impaired in several studies of frequency resolution, temporal resolution, and speech recognition are compared to the results expected for noise-masked normal listeners. It is presumed in this approach that the hypothetical noise-masked normal listeners have masked thresholds that agree perfectly with the quiet thresholds of the hearing-impaired subjects. Using this approach, most of the results obtained from impaired ears on spectral-resolution and speech-recognition tasks could be accurately predicted, an exception being results from spectral-resolution paradigms using fixed-level signals. Some of the data from hearing-impaired listeners on temporal-resolution tasks, on the other hand, could not be adequately described with this approach. The latter data, however, were much more limited. Additional data are needed to better evaluate the adequacy of this approach in describing the performance of the hearing impaired on temporal-resolution tasks.

Adult↗
PubMed1986

Temporal discrimination for single components of nonspeech auditory patterns.

This paper extends previous research on listeners' abilities to discriminate the details of brief tonal components occurring within sequential auditory patterns (Watson et al., 1975, 1976). Specifically, the ability to discriminate increments in the duration delta t of tonal components was examined. Stimuli consisted of sequences of ten sinusoidal tones: a 40-ms test tone to which delta t was added, plus nine context tones with individual durations fixed at 40 ms or varying between 20 and 140 ms. The level of stimulus uncertainty was varied from high (any of 20 test tones occurring in any of nine factorial contexts), through medium (any of 20 test tones occurring in ten contexts), to minimal levels (one test tone occurring in a single context). The ability to discriminate delta t depended strongly on the level of stimulus uncertainty, and on the listener's experience with the tonal context. Asymptotic thresholds under minimal uncertainty approached 4-6 ms, or 15% of the duration of the test tones; under high uncertainty, they approached 40 ms, or 10% of the total duration of the tonal sequence. Initial thresholds exhibited by inexperienced listeners are two-to-four times greater than the asymptotic thresholds achieved after considerable training (20,000-30,000 trials). Isochronous sequences, with context tones of uniform, 40-ms duration, yield lower thresholds than those with components of varying duration. The frequency and temporal position of the test tones had only minor effects on temporal discrimination. It is proposed that a major determinant of the ability to discriminate the duration of components of sequential patterns is the listener's knowledge about "what to listen for and where." Reduced stimulus uncertainty and extensive practice increase the precision of this knowledge, and result in high-resolution discrimination performance. Increased uncertainty, limited practice, or both, would allow only discrimination of gross changes in the temporal or spectral structure of the sequential patterns.

Acoustic Stimulation↗
PubMed1984

Integration of spectral and temporal cues separated in time and frequency.

Subjects discriminated a "standard" pair of tone bursts (T1, T2) from a "comparison" pair (T1 + delta t, T2 + delta f), containing increments in the duration delta t of the first burst and/or the frequency delta f of the second burst. The threshold (d' = 2.0) for delta t was measured as a function of delta f, and the threshold for delta f as a function of delta t. The integration of increments in duration and frequency was studied as a function of the spectral and temporal separation between T1 and T2. A trade-off between the values of delta t and delta f required for d' = 2.0 performance was observed. This integration takes place when delta t, delta f occur simultaneously in the same spectral region, and when they occur separated by up to 120 ms, or by up to a full octave. The efficiency of integration was similar for all conditions of temporal and spectral separation studied, because the discriminability of delta t and of delta f is also nearly uniform across experimental conditions. The results from all experimental conditions are adequately described by a vector summation model derived from TSD. In a subsidiary experiment, subjects categorized pure tones varying in duration and frequency as "high" or "low" in pitch and "long" or "short" in duration. It was found that combined variations in duration and frequency result in essentially independent perceptual processes, although pitch has a small effect upon the perceived duration. It is concluded that spectral-temporal integration is a general ability operating in a variety of stimulus conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1983

Integration of spectral and temporal cues in discrimination of nonspeech sounds: a psychoacoustic analysis.

This study presents a psychoacoustic analysis of the integration of spectral and temporal cues in the discrimination of simple nonspeech sounds. The experimental task was a same-different discrimination between a standard and a comparison pair of tones. Each pair consists of two 80-ms, 1500-Hz tone bursts separated by a 60-ms interval. The just-discriminable (d' = 2.0) increment in duration delta t, of one of the bursts was measured as a function of increments in the frequency delta f, of the other burst. A trade off between the values of delta t and delta f required to perform at d' = 2.0 was observed, which suggests that listeners integrate the evidence from the two dimensions. Integration occurred with both sub- and supra-threshold values of delta t or delta f, regardless of the order in which the cues were presented. The performance associated to the integration of cues was found to be determined by the discriminability of delta t plus that of delta f, and thus, it is within the psychophysical limits of auditory processing. To a first approximation the results agreed with the prediction of orthogonal vector summation of evidence stemming from signal detection theory. It is proposed that the ability to integrate spectral and temporal cues is in the repertoire of auditory processing capabilities. This integration does not appear to depend on perceiving sounds as members of phonetic classes.

Adolescent↗