Human Inferences about Sequences: A Minimal Transition Probability Model
Fig 3
The electrophysiological P300 response reflects the tracking of statistical regularities.
A) Data redrawn from Squires et al. (1976). Subjects passively listened to binary streams of auditory stimuli (denoted X and Y). Stimuli were generated randomly with global frequency p(X) = 0.5 (no bias), p(X) = 0.7 or p(X) = 0.3 (biased frequencies) in separate sessions. The P300 amplitude was averaged at the end of all possible patterns of 5 stimuli at most, and plotted as a “tree” whose branches show the possible extensions for each pattern. (B-C) Average theoretical levels of surprise for all possible patterns. For each model (i.e. each set of three trees), the theoretical surprise levels were adjusted for offset and scaling to fit the data. For local models with leaky integration (B), we show the trees corresponding to the best fitting value of the leak parameter ω. The insets show a direct comparison between data and best-fitting theoretical surprise levels, with the regression R2.