Biomedical subjects

Andreas Tiefenau

Publications and source records attributed to Andreas Tiefenau.

2 recordsLinked to original sources

PubMed2006

Correcting for false alarms in a simple reaction time task.

Simple reaction times (RTs) constitute an important source of information and tool in human and animal psychophysics, in cognitive neuroscience, and in the clinic. We measure simple RTs to auditory stimuli, in a high signal rate vigilance design, to examine the possibility that simple RT may be used as a tool to study mechanisms of temporal summation at absolute threshold. By means of catch trials, we monitor the subjects' tendencies to produce false alarms, that is reactions not controlled by the reaction stimulus. Here we examine the possibility that a model of a race between a stimulus-controlled reaction process and a false alarm process can account for the numbers as well as for the timing of early and late RTs on stimulus trials in our experiments. We show that the responses in both tails of our empirical RT distributions on stimulus trials are indeed correctly predicted by the race model and can be considered false alarms. This suggests that the race model might also provide a reasonable description of the way in which false alarms and stimulus-controlled reactions combine when they overlap in time. We examine the magnitudes of the estimated effects of false alarms on several parameters of the RT distributions by application of the race model. The analyses reveal that the effects not only vary with false alarm rate but also with stimulus parameters. Our data suggest that the race model may provide a theoretically reasonable and easy means of correcting for false alarms in simple RT paradigms and thus may constitute a useful alternative to the common practice of truncation.

Adult↗

PubMed2006

Comparison of absolute thresholds derived from an adaptive forced-choice procedure and from reaction probabilities and reaction times in a simple reaction time paradigm.

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.

Adult↗