Why long words take longer to read: the role of uncertainty about word length

Some of the most robust effects of linguistic variables on eye movements in reading are those of word length. Their leading explanation states that they are caused by visual acuity limitations on word recognition. However, Bicknell (2011) presented data showing that a model of eye movement control in reading that includes visual acuity limitations and models the process of word identification from visual input (Bicknell & Levy, 2010) does not produce humanlike word length effects, providing evidence against the visual acuity account. Here, we argue that uncertainty about word length in early word identification can drive word length effects. We present an extension of Bicknell and Levy’s model that incorporates word length uncertainty, and show that it produces more humanlike word length effects.