Figure 2.

Novelty manipulations and the surprise signal (noveltysurprise.jpg). The brain constantly generates prediction errors as the expectations generated by its inner model are compared to its actual inputs. These prediction errors are summed to judge the necessity of updating the inner model. If the sum of the prediction errors is high enough, it results in the surprise response—the focusing of attention and enhanced learning. Stimulus novelty manipulations usually fail to elicit this response, while it is frequently evoked by contextual, associative and spatial novelty manipulations [Modified figure; Patrick J. Lynch, medical illustrator (https://commons.wikimedia.org/wiki/File:Brain_human_lateral_view.svg), “Brain stem normal human”, added features by R. Reichardt, https://creativecommons.org/licenses/by/2.5/legalcode].