Greg, I think one of your last comments here captures the issue: "We are dealing with the fact that Broca's area doesn't get involved with sentence processing unless the stims contain violations or things get really difficult (working memory? cognitive control?)." (March 14, 2011).My response was this:
If we want to learn about the processing of syntax, we need to make sure the brain is engaged in syntax analysis, and I guess there are two obvious cases in which this happens; 1. when syntax is violated and 2. when syntax analysis is needed in order to extract meaning from a sentence. So if a sentence is not attended and meaning does not need to be extracted, the auditory stimulus will flow into your brain but higher-order processing will not take place, which leaves an absence of syntax-related activation. Likewise, if a sentence has no meaning at all, as in your jabberwocky stimuli, syntax plays no role in understanding the sentence anymore, so your brain will just not bother. What I'm trying to say, I guess, is that syntax serves meaning (in good Chomskian tradition), and meaningful stimuli may just engage that syntax-processing unit we are thought to have.
As for music: same story? What do you think?
Jeroen,You seem to be suggesting that syntactic analysis may not be utilized for simple, grammatical sentences. I think there is a paradox hidden in there though. You suggest that one condition in which the brain is engaged in syntactic analysis is when syntax is violated. But presumably there has to be some mechanism in the brain telling you when a violation has occurred. This implies that syntactic analysis is being carried out even when no violation occurs. So even though, "The dog chased the cat" is simple and contains no violation, the fact that we readily detect a difference between that sentence and, "The dog chase the cat" means that syntactic analysis is being carried out, no?Jeroen countered:
Greg, You're right. A syntactic monitoring system must be active at all times. But don't you think that its activity will spike when a violation is detected? In neurolinguistics this seems to be a common paradigm: in both EEG and fMRI studies, conditions of no violation are often subtracted from conditions of violation to leave the activity that is specifically concerned with the analysis (or repair) of a syntax error. I think that with such an approach, we may be more successful in identifying a musical syntactic processing system, if there is one.
Your findings, of course, suggest that if any overlap is found in activity elicited by musical and linguistic syntax violations, this overlap is not a sign of a shared syntactic integration system, but rather of a general violation-activated system of some kind. This is contradicted by a couple of studies that found interactions specifically between syntax violating conditions in music and language, and not between other violation conditions, such as timbre-related surprises and semantic oddballs (c.f. Koelsch et al. (2005), Interaction between Syntax Processing in Language and Music: An ERP Study, J. Cogn. Neurosc. 17(10): 1565-77; and Slevc et al. (2009), Making psycholinguistics musical: Self-paced reading time evidence for shared processing of linguistic and musical syntax, Psychonomic Bulletin & Review 16(2): 374-81).
All in all, do you agree that a study comparing violation vs. control within-mode (language or music) and within-subjects with fMRI could provide useful insights?
Here's the issue I'd like to bring up for discussion here: "don't you think that [syntactic] activity will spike when a violation is detected?"
This is the underlying assumption of all the studies that use the violation paradigm, but it is an empirical question and I'm not convinced we have a clear answer on this. Does syntactic theory predict a spike in syntactic computation when a violation occurs? Not really. In fact, you might argue that the syntactic mechanism shuts down and something else takes over!
The problem I have with violation studies is that the occurrence of a violation is confounded with other processes, some of which may not be syntactic at all. E.g., conflict resolution, various forms of working memory, the probability of your subject talking to him/herself may increase ("Was that a violation? Should I push the button?), etc. In short, I don't know what is being measured in the response to a violation so I don't how to interpret a neurophysiological response triggered by such a violation. If you want to map the neural system involved in violation processing, then fine, study violations. But this that really what we're after here? Or are we trying to understanding the circuits involved in syntactic computations as they are normally carried out in grammatical sentences? I'm interested in the latter and so I'm not interested at all in the response to violations. I think it is misleading.
This is a theoretical concern but it is backed up by empirical results. I think we all agree that listening to structured sentences involves syntactic computation. If we look at that activation pattern associated with listening to sentences contrasted with rest or with listening to scrambled sentences or spectrally rotated versions of those sentences, we do not typically find activation differences in Broca's area. However, the most robust site of activation in violation studies is Broca's area. Given these two facts, how can we say that the violation response reflects syntactic computation?