Collocations, semi-productive lexical combinations with one figurative and one literal word, are said to be a “pain in the neck” for researchers and L2 learners. The present study aims: (i) to conceptually replicate the processing costs incurred by L1 speakers when processing collocations using a larger and more diverse set of items, (ii) to use literalness judgements to test whether L1 speakers are aware of the semi-transparent meaning of a collocation, and (iii) to test whether the presence of processing costs associated with collocations can be predicted from literalness judgements. If so, we propose that literalness judgements could be used as a diagnostic for reliably identifying collocations. We replicate the L1 processing costs with a larger stimulus set and demonstrate that speakers are aware of the semi-transparent meaning of the collocation. We further show that L1 speaker judgements about the literalness of a word combination can be used to predict its status as a collocation.