This paper investigates the processing of lexical causative verbs in English as a means to provide insight into long-standing debates in this domain and to explore methods for comparison of words which are phonologically-identical but vary at other levels of representation. Verbs such as melt can be used in both transitive and intransitive contexts, which have been argued to vary not only in the number of thematic arguments, but also in semantic, morphological, and syntactic representation. Hypothesizing that the transitive variants contain additional causativity, we predicted that they would induce greater processing cost that could be attributed to greater lexical semantic complexity. In order to test this prediction, we included in each study pairs of activity verbs which alternate in transitivity but not causativity. Two self-paced reading studies confirmed our prediction, demonstrating an interaction such that transitive verbs in the causative condition took significantly longer to process than intransitive verbs, a pattern that was not reflected in the activity condition. A further magnetoencephalography study tested for neural activity associated with different levels of linguistic processing and provides insight into the nature of the behavioral delay. The behavioral findings suggest that the transitive variants in the lexical causative alternation are more complex than the intransitives at some level of representation, despite their phonological identity. The MEG study provides a profile which is suggestive of a link with lexical or morphological complexity.