We conducted two masked priming experiments to examine how the orthographic system processes words with mirrored letters. In both experiments, four different primes were used: an identity prime, an unrelated control prime, and two mirror-primes in which letters were either mirrored at their vertical or horizontal axis. Task was varied between experiments: In Experiment 1 we used a lexical decision task and in Experiment 2 we used a cross-case same-different match task. We expected to see priming effects in both mirror-conditions with stronger effects in the vertically than in the horizontally mirrored letters. In the lexical decision task, we observed only vertical priming effects for words whereas in the same-different task, priming effects were present in both mirror-conditions and for both words and non-words. We discuss the implications of our findings for extant models of orthographic processing.

This study examined the cognitive processes involved in reading vertically and horizontally mirrored text. We tracked participants’ eye movements while they were reading the Potsdam Sentence Corpus which consists of 144 sentences with target words that are manipulated for length and frequency. Sentences were presented in three different conditions: In the normal condition, text was presented with upright letters, in the vertical condition, each letter was flipped around its vertical (left-right) axis while in the horizontal condition, letters were flipped around their horizontal (up-down) axis. Results show that reading was slowed down in both mirror conditions and that horizontal mirroring was particularly disruptive. In both conditions, we found larger effects of word length than in the normal condition indicating that participants read the sentences more serially and effortfully. Similarly, frequency effects were larger in both mirror conditions in later reading measures (gaze duration, go-past time, total reading time) and particularly pronounced in the horizontal condition. This indicates that reading mirrored script involves a late checking mechanism that is particularly important for reading horizontally mirrored script. Together, our findings demonstrate that mirroring affects both early visual identification and later linguistic processes.

This study examined the cognitive processes involved in reading vertically and horizontally mirrored text. We tracked participants' eye movements while they were reading the Potsdam Sentence Corpus which consists of 144 sentences with target words that are manipulated for length and frequency. Sentences were presented in three different conditions: In the normal condition, text was presented with upright letters, in the vertical condition, each letter was flipped around its vertical (left-right) axis while in the horizontal condition, letters were flipped around their horizontal (up-down) axis. Results show that reading was slowed down in both mirror conditions and that horizontal mirroring was particularly disruptive.In both conditions, we found larger effects of word length than in the normal condition indicating that participants read the sentences more serially and effortfully. Similarly, frequency effects were larger in both mirror conditions in later reading measures (gaze duration, gopast time, total reading time) and particularly pronounced in the horizontal condition. This indicates that reading mirrored script involves a late checking mechanism that is particularly important for reading horizontally mirrored script. Together, our findings demonstrate that mirroring affects both early visual identification and later linguistic processes.