Figure 3. Evidence for lateralization of effect valence.

Collapsing across the effect type for all subjective experiences (n = 30), valence was mostly negative (n = 11) or neutral (n = 15), with a handful of positive effects (n = 4; right panel). Montreal Neurological Institute (MNI) coordinates were available for electrode sites for 22 of these effects (see Methods for details of missing data). Of these 22 electrodes sites, neutral effects (n = 13) showed evidence of right-hemisphere preference (mean x = 21, light green diamond), whereas negatively valenced effects (n = 9) showed a tendency toward left lateralization (mean x = −9, dark green diamond; left panel). This difference was significant (t[20] = 2.998, p = 0.007), and the size of the effect was large (Cohen d = 1.3). In contrast, the difference in the anterior-posterior position (mean y-coordinates) was not significant (p = 0.21). Coordinates are in standard (MNI) space; the orbitofrontal surface is shown for illustrative purposes only, and electrode locations are not exact (see figure 2 for precise locations). Note that it was not possible to visualize electrode location data from 4 of 22 patients; for details of missing data, see Methods.