Does the semantic content or syntactic regularity of masker speech affect speech-on-speech recognition?

Speech-on-speech recognition differs substantially across stimuli, but it is unclear what role linguistic features of the masker play in this variability. The linguistic similarity hypothesis suggests similarity between sentence-level semantic content of the target and masker speech increases masking. Sentence recognition in a two-talker masker was evaluated with respect to semantic content and syntactic structure of the masker (experiment 1) and linguistic similarity of the target and masker (experiment 2). Target and masker sentences were semantically meaningful or anomalous. Masker syntax was varied or the same across sentences. When other linguistic features of the masker were controlled, variability in syntactic structure across masker tokens was only relevant when the masker was played continuously (as opposed to gated); when played continuously, sentence-recognition thresholds were poorer with variable than consistent masker syntax, but this effect was small (0.5 dB). When the syntactic structure of the masker was held constant, semantic meaningfulness of the masker did not increase masking, and at times performance was better for the meaningful than the anomalous masker. These data indicate that sentence-level semantic content of the masker speech does not influence speech-on-speech masking. Further, no evidence that similarities between target/masker sentence-level semantic content increases masking was found.