Skip to main content

Currently Skimming:

APPENDIX B: DETECTION SENSITIVITY AND RESPONSE BIAS
Pages 37-43

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.


From page 37...
... It was further realized that estimates of thresholds made using any of the three classical psychophysical methods confounded the sensitivity of the sensory process with the response criterion of the decision process. In order to measure these two separate characteristics, one needs two measures of detection performance.
From page 38...
... This curve, which one actually obtains in experiments is quite different from the straight line relationship predicted by the high threshold model and is one of the bases for rejecting that model. SIGNAL DETECTION THEORY A widely accepted alternative to the high threshold model is the signal detection model.
From page 39...
... Another measure is xc, the critical value of the sensory process output used as the decision criterion. If one assumes that the probability distributions describing the output of the sensory process are normal Gaussian distributions of equal variance, then d• and xc are calculated from the HR and FAR in the following way: FIGURE 17 Hit rate as a function of false alarm rate.
From page 40...
... The ROC curve predicted by the signal detection model is shown in Figure 18 along with the empirical data shown in the previous figure. The signal detection prediction is in accord with the observed data.
From page 41...
... Figure 20 shows the high threshold sensitivity index, p, for different values of decision criteria, for an observer having constant sensitivity. The detection FIGURE 19 Z-score of the hit rate as a function of the Z-score of the false alarm rate.
From page 42...
... It is now understood, however, that detection performance in the 2AFC paradigm is equivalent to an observer using an unbiased decision criterion and that the percentage correct performance can be predicted from signal detection theory. Specifically, the percentage correct in a 2AFC detection experiment corresponds to the area under the ROC curve obtained if the same stimulus were used in the yes-no signal detection paradigm (Green and Swets, 1974; Egan, 1975)
From page 43...
... The second method is based on signal detection theory and requires that there be two types of detection trials: some containing the signal and some containing no signal. Both detection sensitivity and response criterion may be calculated from the hit rates and false alarm rates resulting from the performance in these experiments.


This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More information on Chapter Skim is available.