Signal detection theory in the study of nociceptive and pain perception processes
Citation
Tan, C. (2008) Signal detection theory in the study of nociceptive and pain perception processes, no. 248.
Abstract
Signal detection theory (SDT) measures (discriminability and response bias) have
been proposed to be valid for determining pain perception changes. The construct
validity of SDT measures applied to pain perception studies has been questioned on
three grounds: interpretation, methodology and theory.
Multiple interpretations are possible for the combinations of discriminability and
response bias change when the magnitude-rating scale is used for pain perception
studies. This is resolved by utilising the confidence-rating scale. The problem of
comparability of results between the two scales is bridged by Irwin & Whitehead's
(1991) common analytical framework. The results of this thesis supported the
framework's prediction that both scales are comparable. Therefore, the confidencerating
scale was used for all studies within this thesis for interpretational clarity.
Response bias data were not analysed in this thesis due to data artefacts created by
correction methods for zero proportions in response categories.
Methodologically, the construct validity of discriminability is influenced by the
research design and procedures. Therefore, the following procedures were adopted to
address weaknesses in previous studies. The one-interval confidence-rating task was
used with a six-category confidence-rating scale and post-trial feedback. Based on a
methodological study conducted within this thesis, the trial number was pragmatically
reduced from 40 trials to 17 trials per stimulus intensity. This trial number reduction
would not alter the mean and variance of the data sufficiently to influence the
outcome of inferential statistical testing performed. Due to the novel use of the
Quantitative Sensory Testing machine for the signal detection study procedures,
accuracy and precision study on the machine was performed. This thesis found that
the accuracy, repeatability and reproducibility of the machine in generating noxious
thermal stimuli is excellent for the purposes of this thesis. Machine error is eliminated
as a major source of variance for the thesis results.
Theoretically, critics have challenged the construct validity of discriminability as an
indicator of pain perception alteration. This thesis examined this issue in two separate
contexts: 1) discriminability change as a correlate of local anaesthesia and, 2)
discriminability as a correlate of psychological factors (depression and anxiety) in
chronic low back pain (CLBP) sufferers. The results failed to establish the construct
validity of discriminability for both contexts. However, the higher discriminability in
CLBP sufferers compared to healthy individuals is in contrast to past research and
warrant further investigation.
This thesis addressed the construct validity issues through theoretical, methodological
and interpretational modifications. A more robust analysis of the construct validity
issue was facilitated. Caution is recommended on the use of discriminability as a pain
perception measure until the construct validity issue has been satisfactorily resolved.