Discrepancies between orthographic and unrelated baselines in masked priming undermine a decompositional account of morphological facilitation.

This study uses the masked priming procedure to compare the decompositionality of regular with irregular English past tense forms relative to both an unrelated baseline and a baseline matched on orthographic similarity to the morphological prime. Morphological facilitation varies with the degree of similarity between related primes and targets. Discrepancies between unrelated and orthographic baselines arise when prime and target match in length and form overlap is high. The outcome demonstrates the key role of baselines in assessments of morphological facilitation and highlights problems of interpretation when evidence of morphological decomposition depends on meeting a statistical criterion for significant morphological facilitation.