Is letter position coding a unique skill for developing and adult readers in early word processing? Evidence from masked priming.

Reading words in alphabetic scripts requires encoding the relative order of the letters. This process of letter position coding is known to be flexible. For instance, the masked transposed-letter prime jugde activates the word JUDGE to a greater degree than a replacement-letter prime like jupte, a phenomenon known as the transposed-letter effect. In this study, we investigated whether the transposed-letter effect in masked priming is related to reading skills (as measured by a standardized reading test) in a sample of sixth-grade children. Targets (e.g., RITME: Catalan for rhythm) were preceded by identity primes (ritme), transposed-letter primes (rimte), or replacement-letter primes (risle) in a sandwich priming paradigm. Results showed that transposed-letter primes were more effective than replacement-letter primes but less effective than identity primes. More importantly, while the readers' reading skills modulated overall latency and accuracy, we found no evidence that the participants' reading skill modulated the size of the priming effects. This outcome prompted us to re-analyze analogous conditions in a masked priming mega-study with approximately 1000 adult participants (Adelman et al. Behav Res Methods 46(4):1052-1067, 2014), where we found a near-zero correlation between the size of transposed-letter priming and spelling and vocabulary tests. These findings suggest that if there are individual differences in the first moments of word processing, these are not detectable for neurotypical readers in laboratory tasks.