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. Author manuscript; available in PMC: 2019 Jul 1.
Published in final edited form as: Conscious Cogn. 2018 Apr 30;62:34–41. doi: 10.1016/j.concog.2018.04.009

Figure 1. Signal detection theoretic framework for the simulated spatial 2AFC task.

Figure 1

For a given subject s, each stimulus presentation (either ◼◆or ◆◼) caused an internal response value (x), with X◼◆ ~ N(d’/2, 1) and X◆◼ ~ N(-d’/2, 1), and the subject then indicated which of the two shape configurations appeared. If x exceeds the subjects Type 1 criterion (cs,1), then the subject responded “◼◆;” otherwise the subject responded “◆◼.” Objective performance capacity (d’) is the normalized distance between the two distributions. The subject then indicated how clearly/confidently they saw the stimulus, based on a comparison between x and the Type 2 criterion (-cs,2 and cs,2). If x < cs,1 or x > cs,2 the subject responded “clear”; otherwise the subject responded “unclear.” If TMS is present and assumed to degrade metacognitive sensitivity, noise (σs,TMS) is added for the Type 2 responses, such that the relevant computations are whether x < cs,1 + εtrial or x > cs,2 + εtrial, with εtrial ~ N(0,σs,TMS) and resampled on each trial (see Supplementary Materials for more details).