Syntactic processing is often considered a hallmark of human cognition. However, whether this ability relies on domain-specific or domain-general cognitive resources and mechanisms is a popular topic of ongoing research. Music, similar to language, has a complex hierarchical structure where discrete elements are organized into sequences governed by syntactic rules. Therefore, studying mechanisms involved in language syntactic processing and musical syntactic processing is an interesting approach to the domain-specific or domain-general debate. Slevc et al., with their results from a self-paced reading task accompanied by musical chords showed that music and language rely on shared, limited processing resources that activate separable syntactic representations.
The study examines how exposure to musical key structure interacts with a classic psycholinguistic phenomenon Garden-path effects. Garden-path effect refers to comprehenders’ temporary difficulty when encountering a phrase where the less likely interpretation of a local syntactic ambiguity seems to be the right one. For example, when you see the sentence The attorney advised the defendant… So far it is natural to interpret the defendant as the object of the action. However, if the sentence actually goes The attorney advised the defendant was guilty, you would later figure out that “defendant” is the subject of an embedded clause rather than the object of the action “advise”. The temporary parsing difficulty that happen right after you hear “defendant” is called garden-path effect. It is a case of syntactic unexpectancy during real-time processing, where you either need to abandon the initial analysis of the sentence and reanalyze, or take more time to evoke a less preferred analysis. Either way, it should take you more syntactic processing resources to parse that particular segment.
On the other hand, the unexpectancy in musical syntax is defined as naturalness of musical progression in the study. Even people who are not musically trained can certainly tell “natural” musical progression from “unnatural” ones. Those progressions that are perceived natural tend to follow certain underlying structural norms. Research has shown that chords from a key harmonically distant from the preceding chords are syntactically unexpected (Patel, 2008).
The current study is designed to ask whether common resources are used during processing musical syntax and syntax of language. During the experiment, participants are asked to read garden-path sentences one word by a time at their own pace. They control the pace by pressing a button to see the next word. Participants are instructed to read but carefully enough to answer the comprehension question at the end of each sentence. Meanwhile, accompanying each word is a chord presented through their headphones. As we have discussed above, there is a critical word at which, participants will experience syntactic unexpectancy in garden-path sentences. On critical trials, along with that critical word, either a natural chord fitting the progression or a “out of key” chord will be presented simultaneously. Time spent on each word is collected and used as an important measure.
The prediction is that if syntactic processing resources are shared between language and music, a harder linguistic parsing task requiring non-local analysis (garden path sentence) should be even harder to process while a harmonically unexpected chord employs some of the resources already.
The study also introduced a musical control and a linguistic control to address the possible confounding factors: How do we know it is not the case that unexpected chord is distracting, so it delayed participants' response on syntactic processing? To address this question, semantically surprising sentences are used as a control for garden-path sentences in the study. The researchers put different words in a sentence with varying real world likelihood in the sentence’s context. For example, it is conceivable that reader experience much more semantic unexpectancy right after the word “pig” in the sentence “The boss warned the mailman to watch for angry pigs when delivering mails” than if the word is instead “dog”.
How do we know it is specifically the violation of musical syntax that has an effect on syntactic parsing of the sentence instead of any other startling difference in music? The study crossed both syntactic and semantic expectancy in language with a non-syntactic musical unexpectancy - change in timbre. In the timbre control trials, along with the critical word, a natural chord in the same or different timbre from the preceding chords is played.
The results suggest that reading time is considerably longer right after the critical word in Garden-path sentences when the unnatural chord is played along with the critical word compared to when natural chord is played. People in general show prolonged reading time at critical words for the semantic anomalous sentences too. However, musical unexpectancy didn't bring about longer delays for the semantic trials. As for timbre manipulation, reading time is longer in both semantically anomalous sentences and garden path sentences (syntactic) when unexpected timbre is played at the critical word, especially so in the syntactic condition. But linguistic manipulation (syntactic or semantic) doesn't interact with the manipulation of musical timbre. Unlike the violation of progression, which affects syntax significantly but not semantics, timbre unexpectancy affects both types of processing equally. This result shows that effect of harmonic key unexpectancy on processing of linguistic syntax mentioned earlier is not merely due to attention-capturing nature of unexpected sounds, but instead suggests overlap in the syntactic processing resources between language and music.
The results suggest the resources that we employ in re-analyzing garden path sentences (linguistic syntactic processing) is shared with what we use to process musical syntactic unexpectancy. This study providence for the view that the syntactic processing ability we exhibit in language seems not to be specific to language.