Dissociating subjective and objective awareness reports using priming

Goal: Phenomenal awareness is the first-person experience we have of seeing something. Although subjective awareness reports and objective performance often correspond, they can sometimes dissociate, presenting opportunities to identify mechanisms specific to each. Priming occurs when exposure to a stimulus facilitates subsequent processing of similar stimuli. Here we asked whether dissociations of subjective and objective measures of awareness can be obtained using priming. Methods: Observers performed a simultaneous detection and orientation discrimination task on a grating target that appeared on half of the trials. The grating target was tilted ±45 degrees from vertical and presented foveally at threshold and near-threshold contrasts. On each trial, observers reported 1) whether or not they saw the target and 2) the target tilt (regardless of whether they saw the target). Before the target, observers were exposed to either a “high awareness” or “low awareness” priming block, in which a stream (60 s initial exposure with 10 s top-ups) of vertical gratings was presented peripherally at mostly high or low (including zero) contrasts, respectively. Results: We assessed subjective and objective reports using signal detection theory, which separates objective sensory processing, measured as perceptual sensitivity, from subjective phenomenal or decisional processing, measured as response criterion. Target contrasts at floor or ceiling performance were excluded from analysis. Following high vs. low awareness exposure, detection criterion was lower (i.e., observers were more likely to report seeing the target) while detection sensitivity remained unchanged (i.e., observers were no better at distinguishing between target present and target absent trials). Awareness exposure also did not significantly affect orientation discriminability, though for most observers, discriminability improved following high vs. low awareness exposure. Conclusion: Recent visual exposure makes detection criterion more liberal but does not change detection sensitivity. Subjective and objective measures of awareness can therefore be dissociated using priming.