Sampling the favorite bias at Task Stage 2.

<p>If subjects choose to sample at Task Stage 1, they enter Task Stage 2. If this is on an AB trial, they then may sample again from row A, or from row B, or make a guess. <b>(A)</b> Model predictions. The relative expected value (in points) of sampling from row A versus sampling from row B in the MULTIPLY conditions. It is generally more valuable to sample from the row that currently has the higher-valued card (e.g., the 7, in the example shown). Crucially, this prediction is the same in both MULTIPLY BIG and MULTIPLY SMALL conditions. <b>(B)</b> Subject behavior. Subjects show a propensity to sample from the row containing the high-valued card in MULTIPLY BIG, but this trend is reversed in MULTIPLY SMALL. Subjects are therefore inclined to sample the option that is currently most likely to be approached. <b>(C)</b> Sampling the favorite bias is revealed by subtracting MULTIPLY SMALL trials from MULTIPLY BIG trials. The normative model predicts this heat map to show no difference between conditions, yet there is a clear tendency to sample the currently favored row. See also <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.2000638#pbio.2000638.s006" target="_blank">S6 Fig</a> and <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.2000638#pbio.2000638.s007" target="_blank">S7 Fig</a> for other conditions, and <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.2000638#pbio.2000638.s008" target="_blank">S8 Fig</a> for relative value of guessing versus sampling across all six conditions. Data for reproducing all analyses is freely available for download from Dryad.