Toddler fearfulness is linked to individual differences in error-related negativity during preschool.

We investigated associations between early fearfulness and error-related negativity (ERN) in preschoolers. Children were classified as low, moderate, or high in fearfulness based on observations at age 2 years. ERN was measured at age 4.5 years. ERN was visible in preschoolers who were moderate or high in fear during toddlerhood, but was characterized differently in children based on associations with fearfulness during toddlerhood. A non-localized ERN was visible across midline electrodes in high-fear children and an adult like ERN distribution was visible in moderately fearful children. In contrast, low-fear children showed no evidence of ERN at 4.5 years of age.