Syntacticians often act like parochial snobs. They are snobs in that some (e.g. me) believe that the kinds of data and explanations offered within syntax are deeper than those offered in other domains. There really is non-trivial syntactic theory and a whole budget of effects that these theories explain. Syntacticians (e.g. me) can be parochial in believing that only these kinds of questions are worth asking and investigating. A consequence of this is the oft-exhibited habit of evaluating the interest of other linguistic questions in terms of how much they address questions in syntax. This habit can be especially pronounced when syntacticians consider work in psycholinguistics. When evaluating psycho work, it is not uncommon for syntacticians to expect psycholinguists to provide evidence/methods for helping to choose among competing cutting edge syntactic alternatives. As this rarely happens, syntacticians often come to have jaundiced views about the intellectual contributions of psycholinguistic research.
This is clearly a rather perverse way of evaluating psycho research. The issue is not whether psycholinguistics can answer syntactic questions but whether they have their own interesting questions concerning the form and function of FL. Over the years I have made it a habit to sit in on lab meetings of my psycho colleagues and two things have struck me. First, that wrt syntactic theory, to date, psycho techniques have contributed little that purely syntactic methods have not delivered more cleanly and quickly (but see below) and, second, that psycholinguists have found fascinating effects and have developed interesting theories of these effects that greatly expand our understanding of how FL is used in real time, both learning and processing. Let me elaborate each point just a bit.
A good deal of the questions in language processing and acquisition can proceed just fine in blissful ignorance of the latest findings in syntax. For example, studying the acquisition or processing of long distance dependencies will not be greatly affected by whether one assumes that movement is actually an expression of Merge (I-merge) or an independent operation in its own right. The differences between these two conceptions is too fine grained to be captured by (at least current) psycho methods. However, this does not mean that there is nothing worth studying. For example, regardless of how a WH gets to clause initial position, we have an interesting question: how eagerly does the parser try to find the gap the WH is related to? One possibility is that it waits to find a gap and then tries to relate the WH to it. A second option is that it tries to link the WH immediately on sighting a theta marking host predicate without waiting to see if there is a gap after the predicate to fill. Thus in a sentence like (1), we can ask if the parser tries to interpret who as complement of tell after/before seeing if there is a gap there.
(1) Who did you tell Bill about
So given the question ‘how “eager” is the parser?’, the next question is how to study its eagerness? Via a very interesting phenomenon discovered in the 1980s (Laurie Stowe in 1984), the so-called “Filled Gap Effect” (FGE). If you put people in front of a computer and have them read a sentence word by word and measure how they doe this, it turns out that in a sentence like (1) readers will pause longer at Bill than they would in reading a sentence like (2):
(2) Who did you tell about Bill
This is a very reliable effect. Interpretation? Readers are trying to thematically interpret who when they get to tell and must rescind this when they get to Bill in (1) but not in (2). In other words, readers “prefer” giving a thematic role to who even at the cost of having to rescind this assignment soon after over waiting to see if there is an available role to assign, even if this means just waiting one word. Conclusion: parsers are very eager to interpret uninterpreted material. And this eagerness can be measured and used to probe how parsers use grammars to construct sentence interpretations in real time, i.e. FGE is a marvelous tool for probing the relation between grammars and parsers.
Let me give an illustrative example. Consider the following question: Given that parsers use grammars what is the relation between competence grammars (ones beloved of syntacticians) and parsing grammars? A strong position is that there is a very high level of “transparency” between the two. What’s this mean? Well, that the categories and relations that the grammar specifies are identical to those that the parser exploits/respects in real time. For example, the categories that grammars deploy (e.g. DP, VP, CP) are what the parser tries to recover and the conditions the grammar respects (e.g. minimality, c-command, subjacency) the parser does as well. A good deal of work in parsing over the last 15 years has been aimed at specifying the degree of transparency between competence grammars and parsing grammars. For example, psycholinguists have investigated whether parsers respect c-command in trying to find a bound anaphors possible antecedents and whether parsers display cross-over effects. My colleague, Colin Phillips, has a really beautiful set of results bearing on how parsers “do” movement, particularly does gap filling “obey” islands (see here). The answer is “yes.” How does he know? Building on earlier work by others, he shows that the FGE only appears if the “gap” sits in a possible movement site. Gaps within islands do not trigger FGEs (unless they are licensable parasitic gaps (this is Colin’s great find)). Gaps generable by movement do trigger FGEs. The argument is subtle and well worth reading (if you’ve read it already, read it again to your kids; it makes for a lively bedtime experience!). All this makes sense if parsing grammars and competence grammars are (largely) the same. Ergo…
Note that these psycho results build on what syntactic research has revealed about competence. It uses these results to address a related very interesting question, viz. the Transparency Thesis (TT) and it does so by exploiting a psycho probe, viz. FGE, manifest in online reading tasks. Most interestingly in my view, as TT becomes more and more empirically grounded (and the evidence in its favor is already pretty good IMO), syntacticians may finally get what they’ve been asking for: psycholinguistic constraints on adequate competence theories (Syntacticians, careful what you ask for lest you get it!). After all, if TT is right, then syntactic theories that fail to support transparent parsing grammars should be less valued than those that do. In other words if TT proves empirically tenable, then online psycho results will prove highly relevant to evaluating the empirical adequacy of proposed competence grammars.
How far away is this day? Well, I want to end by presenting a possible glimpse of the future. In some recent work Shevaun Lewis, Dave Kush and Brad Larson (LKL) have used FGEs to probe the syntactic derivation of constructions like (3) (see here for some slides):
(3) What and when will we eat
Not surprisingly, these coordinated WH questions have rather elaborate syntactic properties. I will not detail them for you (read the slides), except to say that LKL are led to analyze these by treating the two WHs rather differently. LKL propose that the inner WH lands in clause initial position via movement while the outer one is base generated there. The evidence for this conclusion is two-fold. First, there is an acceptability contrast between (4a) and (4b), the latter being quite a bit worse than the former (and yes they ran the relevant acceptability judgment studies to show this). Second, the what in (4a) fails to induce an FGE. If FGEs are diagnostic of movement dependencies (as above) then the absence of these in (4a) is just what we would expect, and apparently receive. To my knowledge this is the first time a technique borrowed from psycho has been pressed into service to support a novel syntactic conclusion. Terrific!
(4) a. What and when will we eat something
b. When and what will we eat something
It is the sign of a progressing research program that novel questions and techniques keep springing up. The aim is to conciliate these producing a bigger and bigger coherent picture. To date, in my view, a great deal of what we have discovered about how FL does syntax has come from the careful analysis of natural language grammars. The LKL results are signaling a slightly different future: I have a dream that is deeply rooted in the Generative enterprise. I have a dream that one day linguistics will rise up and live the true meaning of its biolinguistic roots. I have a dream that one day syntacticians and psycholinguists (and eventually neuroscientists) will use each other’s work to strongly constrain their common research project of understanding how FL is structured and how it is used. I have a dream, and LKL provides a glimpse of that wonderful and glorious future.