Pre-activation negativity (PrAN)
The pre-activation negativity (PrAN) is an electrically negative brain potential discovered in our lab. It shows the predictive strength of phonological cues. Already at word onset, PrAN has higher amplitude for word beginning that have few possible word continuations of high lexical frequency (Söderström, Horne, Frid & Roll, 2016; Roll, Söderström, Frid, Mannfolk, & Horne, 2017).
PrAN and cohort size
The number of possible word continuations is also referred to as the word beginning's cohort size. Thus, word beginnings with smaller cohort sizes have a larger PrAN (Söderström et al., 2016). PrAN amplitude is also larger if the words of the cohort have high lexical frequency (Roll et al., 2017). Since PrAN is a negative component, its decrease with cohort size is positive and its increase with lexical frequency is negative:
PrAN = k (cohort size) – c (lexical frequency)
where k and c are constants.