*Continuation:* * RPEs in classical and instrumental conditioning and reinforcement learning (RL) * With regard to the involvement of RPE in RL, one key observation was that, if the PE is absent, learning does not occur even when a cue is strongly associated with an outcome. This is famously demonstrated in Kamin’s blocking effect, in which a previously learned cue-outcome association (A → X) blocks the acquisition of learning when a new cue is added (AB → X). In this case, there is no PE to AB-X because A already predicts X and so, though B is associated with X, the association is not reinforced. This remarkable observation underpins formal RL models * Reward value typically increases as the magnitude, probability, and temporal proximity increase, the weighting of each of these reward attributes varies across time and individuals. Reward preferences vary across individuals, and depend on personality characteristics such as attention, motivation, patience and willingness to take a gamble. In general, people are risk avoidant, that is, they prefer smaller “safe” rewards over a gamble that can result in a larger, risky reward, but preference varies both across individuals and conditions (e.g., we are more likely to take a gamble when the amount of money at stake is small). * Novel and physically salient stimuli might be inherently rewarding as they provide unexpected, new information, that might be of value for adaptive behavior * **Dopamine** neurons increase their responses in the face of novelty; once novel stimuli become familiar and are not reinforced, **dopamine** responses habituate. However, no such effect could be found for other types of salience, including rareness and negative emotional valence, suggesting that **dopamine** might be particularly responsive to novelty. * Surprise (or unsigned) PE signal indicates the degree to which an outcome is unexpected, independent of its sign, and thereby controls the rate of learning, whereas the signed RPE signals the extent to which an outcome is better or worse than expected * Using sensory preconditioning (associations between different neutral stimuli), research showed that the acquisition of information about transitions between non-rewarding events is also driven by PEs and that, **dopamine** transients were sufficient to support this type of learning * Clinical intervention: Target the (surprise) stimuli by improving one’s “model of the world” and by those actions that have predictable outcomes. Perception and action can minimize exteroceptive and proprioceptive PEs. This helps individuals to avoid exchanges with the environment that might be harmful. Also, neural systems encoding predictions errors respond more strongly when new information is more reliable (i.e., minimizing surprise) and hence more informative.