The role of fundamental frequency and temporal envelope in processing sentences with temporary syntactic ambiguities

While natural speech prosody facilitates sentence processing, unnatural or misleading prosody decreases speed and accuracy in resolving syntactic ambiguities. This study investigated how, and to what extent, fundamental frequency (F0) and the temporal envelope (E) contribute to processing garden-path sentences that provide misleading grammatical interpretations. Signal processing methods degraded either F0 or E in 120 garden-path sentences (e.g. While the man hunted the deer ran into the woods). Twenty-two participants listened to natural and acoustically modified garden-paths. For each sentence, participants answered a comprehension question and repeated the sentence. Results demonstrated that degrading E consistently affected sentence comprehension, with a different effect observed for degrading F0. The nature of this difference varied with the plausibility of the postverbal noun. For example, in the E-modified condition, plausible sentences resulted in productions that reconstructed the original prosody of the sentence less accurately than those resulting from natural sentences. These findings suggest that E plays a greater role, compared to F0, in processing garden-path ambiguities. However, how listeners use prosody may vary based on context. This suggests that prosodic information can interact with cognitive processing load.