Signal detection (Psychology)

This research investigated whether choice reaction time (RT) measures and the P300 component of the event-related brain potential (ERP) could be employed to index the attentional resources associated with performing two near-simultaneous tasks. Specifically, this study investigated the effects of auditory tones on the ERPs and RTs associated with a visual stimulus when the stimuli in both modalities were presented in close temporal proximity. The hypothesis that the ERPs and RTs elicited by the deviant visual stimulus would index the processing demands associated with the auditory modality was confirmed. In general, greater P300 amplitude associated with one task indicates diminished P300 and poorer performance on a second task. The results indicate that P300 may be a sensitive indicator of shared processing resources when two tasks are performed near simultaneously.

The effect of alternating primary task stimulus modality on event-related brain potentials and secondary signal detection performance was examined in a dual-task paradigm. An odd-ball paradigm with alternating pairs of auditory tones and visual lights was employed as the primary counting task. Primary task stimuli were classified by previous trial modality (same vs different), previous trial stimulus type (standard vs deviant), and current trial stimulus type. A signal detection task in which an auditory tone followed the primary task stimuli by 120 ms on 50 percent of the trials served as the secondary task. For all but one condition, deviant stimuli produced large P300 and decreased signal detection performance. When a deviant stimulus preceded a deviant in the same modality, however, signal detection performance was better than on standard trials preceded by a deviant. These results were interpreted using a two-parameter model of stimulus probability and subjective value of the stimulus sequence. Also examined were other effects of alternating modality of the primary task stimulus and the sequences defined by the modality and stimulus type of the current and previous trial on the event-related potentials elicited by the primary task stimuli.

The relationship between P300 elicited on a primary counting task
and performance on a secondary signal detection task was examined in a
dual-task paradigm in which the secondary task followed the primary
task by 120 ms. An odd-ball paradigm, utilizing two auditory tones
(Standard and Deviant) was employed as the primary counting task in
order to elicit two states characterized by differences in P300
amplitudes. The standard trials were further categorized according to
their serial position in each series of trials. A signal detection
task in which an auditory tone followed the primary task tones on 50
percent of the trials served as the secondary task. The principal
hypothesis was that a decrease in sensitivity on secondary signal
detection task accompanied Deviant trials in which a P300 was elicited.
Results were consistent with the hypothesis and provided support for
both neural inhibition and cognitive resource allocation models.

The relationship between P300 elicited on a primary
counting task and performance on a secondary signal
detection task was studied in a dual task paradigm where
the secondary task followed the primary task by 300 msec.
A modified ("count both tones") oddball paradigm, utilizing
two auditory tones (Frequent and Rare) was used as the
primary counting task to elicit two states characterized by
differences in P300 amplitudes. An auditory signal detection
task presented on 50 percent of the trials following
the primary task tones served as the secondary task. Predictions
about performance on the secondary task were based
on a neural inhibition model of P300. It was hypothesized
that signal detection performance, as measured by detection
sensitivity (d') would be less on Rare tone trials than on
Frequent tone trials. Results were consistent with the
hypothesis and provided support for the neural inhibition
model of the P300.

Twenty-four naive human Ss were run in an auditory signal
detection task examining two hypotheses. 1) Naive Ss can
produce data consistent with the theoretical assumptions of
normality and equal variance of the underlying distributions. ROC curves on double-probability paper were found to be
generally supportive of these assumptions as indicated by their
linearity and slope. 2) The "trial-by-trial" method more
evenly distributes the effect of nonsensory variables, providing
less variable estimates of d' and S than does the "block"
method. No differences were found in mean d' values although
the "trial-by-trial" method produced less variable estimates.
The ''block" method produced somewhat better orderings of
individual, but not mean, beta values across probability levels. It is concluded that further use of naive Ss in signal detection paradigms permissible and that the "trial-by-trial"
method is preferable for obtaining stable estimates of d',
but not for obtaining appropriate orderings of beta.