Position-invariant letter identification is a key component of any universal model of reading.

A universal property of visual word identification is position-invariant letter identification, such that the letter "A" is coded in the same way in CAT and ACT. This should provide a fundamental constraint on theories of word identification, and, indeed, it inspired some of the theories that Frost has criticized. I show how the spatial coding scheme of Colin Davis (2010) can, in principle, account for contrasting transposed letter (TL) priming effects, and at the same time, position-invariant letter identification.