Abstract
Motivated by Signal Detection Theory (SDT), we developed a family of novel adaptive methods that estimate the sensitivity threshold—the signal intensity corresponding to a pre-defined sensitivity level (d′ = 1)—in Yes-No (YN) and Forced-Choice (FC) detection tasks. Rather than focus stimulus sampling to estimate a single level of %Yes or %Correct, the current methods sample psychometric functions more broadly, to concurrently estimate sensitivity and decision factors, and thereby estimate thresholds that are independent of decision confounds. Developed for four tasks—(1) simple YN detection, (2) cued YN detection, which cues the observer's response state before each trial, (3) rated YN detection, which incorporates a Not Sure response, and (4) FC detection—the qYN and qFC methods yield sensitivity thresholds that are independent of the task's decision structure (YN or FC) and/or the observer's subjective response state. Results from simulation and psychophysics suggest that 25 trials (and sometimes less) are sufficient to estimate YN thresholds with reasonable precision (s.d. = 0.10–0.15 decimal log units), but more trials are needed for FC thresholds. When the same subjects were tested across tasks of simple, cued, rated, and FC detection, adaptive threshold estimates exhibited excellent agreement with the method of constant stimuli (MCS), and with each other. These YN adaptive methods deliver criterion-free thresholds that have previously been exclusive to FC methods.
Highlights
The measurement of detection thresholds, which characterize the sensitivity of sensory systems and concisely, provides the foundation of many perceptual studies
We develop, test, and validate a family of sensitivity-based Bayesian adaptive methods, which consists of the (1) quick Yes-No, (2) quick Yes-No Cuing, (3) quick Yes-No Rating, and (4) quick Forced-Choice methods
As reported in previous studies, and seen for the quick Yes-No (qYN) in simple detection, (1) the convergence of precise threshold estimates is more rapid in YN tasks, relative to FC tasks, and (2) in YN tasks, threshold convergence is most rapid for relatively conservative response states
Summary
The experiment was conducted on a Windows-compatible computer running PsychToolbox extensions (Brainard, 1997; Pelli, 1997). The stimuli were displayed on a Dell 17-inch color CRT monitor updating at a 120 Hz refresh rate. A special circuit changed the display to a monochromatic mode, with high grayscale resolution (14 bits) and luminance levels linearized via a lookup table (Li et al, 2003). Stimuli were viewed binocularly with natural pupil at a viewing distance of approximately 72 cm in dim light
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