Hypotheses

• The neuromodulator norepinephrine (NE) level rises when cue-predicted events do not occur

• The NE level drops back down to near baseline when a cue-predicted event occurs

• When the NE level exceeds a given threshold, the cue is abandoned as an event predictor

• To prevent premature abandonment, cues with less reliability have higher thresholds

• The neuromodulator acetylcholine (ACh) level determines the cue abandonment threshold