Comparison of Absolute Thresholds Derived from an Adaptive Forced-Choice Procedure and from Reaction Probabilities and Reaction Times in a Simple Reaction Time Paradigm

Abstract

An understanding of the auditory system's operation requires knowledge of the mechanisms underlying thresholds. In this work we compare detection thresholds obtained with a three-interval-three-alternative forced-choice paradigm with reaction thresholds extracted from both reaction probabilities (RP) and reaction times (RT) in a simple RT paradigm from the same listeners under otherwise nearly identical experimental conditions. Detection thresholds, RP, and RT to auditory stimuli exhibited substantial variation from session to session. Most of the intersession variation in RP and RT could be accounted for by intersession variation in a listener's absolute sensitivity. The reaction thresholds extracted from RP were very similar, if not identical, to those extracted from RT. On the other hand, reaction thresholds were always higher than detection thresholds. The difference between the two thresholds can be considered as the additional amount of evidence required by each listener to react to a stimulus in an unforced design on top of that necessary for detection in the forced-choice design. This difference is inversely related to the listener's probability of producing false alarms. We found that RT, once corrected for some irreducible minimum RT, reflects the time at which a given stimulus reaches the listener's reaction threshold. This suggests that the relationships between simple RT and loudness (reported in the literature) are probably caused by a tight relationship between temporal summation at threshold and temporal summation of loudness.

Simple reaction time to the onset of time-varying sounds

“…This lies in the larger ranges already obtained by Raab (1962) and Ulrich et al (1998). It is considerably shorter than the CD for loudness and underscores the requirement of a constant duration if RT is taken as a correlate of loudness, as Heil et al (2006) pointed out. An explanation why the CDs for loudness and RT are different might be difficult.…”

“…The effects observed are difficult to explain by what is known about temporal integration of loudness. It appears that, in order for RT to be a correlate of loudness, all stimuli must have the same normalized envelope (see Heil et al, 2006). When using stationary sounds which do not contain very low frequencies, and when keeping the rise time constant, this is not a problem.…”

“…That is why Heil et al (2006), focusing on RT near the threshold in quiet, suggested that two necessary conditions for RT to be a correlate of loudness are that stimulus durations and temporal envelopes are the same across the conditions being studied. The present work will investigate these two stimulus features in more detail; however, it shall focus on sounds well above threshold.…”

Towards a Unifying Basis of Auditory Thresholds: Binaural Summation

“…All stimuli had a carrier frequency of 3.125 kHz, as in some previous studies from this lab (e.g., Heil et al 2006;Tiefenau et al 2006;Heil et al 2013a;Zoefel and Heil 2013). The stimuli, however, differed substantially in temporal envelope (Fig.…”

“…The arithmetic mean of the remaining five single-track thresholds (in decibel SPL) for each condition was defined as the threshold for that subject, stimulus, and condition, and the corresponding standard deviation (SD, in decibels) served as a measure of the reliability of the threshold estimate. Because the thresholds for the B, the L, and the R condition were all measured on the same day, effects of possible dayto-day variation in sensitivity (Hempstock et al 1966;Heil et al 2006) are ruled out. The justification for arithmetically averaging single-track thresholds in decibel SPL, rather than in pascals, is the observation that the distribution of threshold estimates obtained repeatedly from a given subject to the same stimulus is approximately normal when thresholds are expressed in decibel SPL, and consequently log-normal when expressed in pascals (H. Neubauer, personal communication).…”