When does rotation disrupt letter encoding? Testing the resilience of letter detectors in the initial moments of processing

Previous research has reported that both letter and word identification are slower when the stimuli are presented at rotations above 45 degrees than when presented in their canonical horizontal view. Indeed, influential models of word recognition posit that letter detectors in the visual word recognition system are disrupted by rotation angles above 40 degrees or 45 degrees (e.g., Local Combinations Detector model; Dehaene, Cohen, Sigman, & Vinckier, 2005, Trends in Cognitive Sciences). However, recent experiments have shown robust masked identity/form priming effects for 90 degrees rotated words, thus calling into question this assumption. Here we aimed to isolate the degree to which letter detectors are disrupted when manipulating letter rotation in three masked identity priming letter match experiments. Probes and targets were always presented in the canonical upright position, whereas forwardly masked primes were rotated in different angles. The rotation angles were 0 degrees versus 45 degrees (Experiment 1), 22.5 degrees versus 67.5 degrees (Experiment 2), and 45 degrees versus 90 degrees (Experiment 3). Results showed a sizeable masked identity priming effect regardless of the rotation angle, hence demonstrating that letter detectors are not disrupted by rotations smaller than 90 degrees in the early moments of letter processing. This pattern suggests that letter detectors are more resilient to changes in visual form than predicted by the LCD model.