2/28/2012

It is an indubitable fact that, once they have reached a certain maturational stage, the members of the human species, barring any serious impairment, are able to produce and comprehend sentences of the language that they are exposed to. The existence of the language faculty has been assumed by many and it has been the point of departure of Chomsky's research program although there is also a contrary view accepted by many, as indicated in N. J. Enfield's recent (2010) review article in Science "Without Social Contexts?."^FN1 Chomsky has maintained over the years that we should approach the language faculty just as natural scientists approach their subject matters. It has, however, remained unclear how hypotheses about the language faculty can be put to rigorous empirical test. The problem manifests itself most acutely once we consider how the hypothetico-deductive method―the most commonly acknowledged hypothesis-testing "method" in a mature science such as physics―can be applied to language faculty science.

　　　In my ongoing work, I try to articulate how predictions about the language faculty can be deduced from our hypotheses, how such predictions can be tested against experimental results, what should count as the relevant data in language faculty science, how such data can be of a categorical nature, what kind of experimental design would maximize the significance of the experimental results, how we can make various aspects of experimental devices maximally effective, how rigorous a match we could expect between the prediction and the experimental results, along with many other related issues. I try to pursue and defend the thesis that it is possible to investigate the language faculty by applying the hypothetico-deductive method, i.e., by rigorously comparing the predictions deduced by our hypotheses with experimental results and observations. Insofar as we can carry this out successfully, with compelling empirical demonstration, that will constitute support for the existence of the language faculty.

　　　In physics, what is predicted and compared with experimental results (or observations) is something that is measurable (ultimately in terms of temporal and spatial values). The measurability of the relevant "data" is what makes it possible to compare a prediction with an experimental result and also to determine how much reproducibility there is to the experimental results and observations. Given that reproducibility and measurability are two prerequisites for effectively adopting the hypothetico-deductive method, it follows that predictions in language faculty science must be about something reproducible and measurable as long as we adopt the hypothetico-deductive method.

　　　One may wonder whether it is reasonable to apply the hypothetico-deductive method to research concerned with the language faculty. After all, it is commonly understood that the "predictions" in fields outside the extremely limited domains of inquiry including physics are about differences and tendencies and that it is not possible to deduce point-value predictions in such fields. One may thus object that physics is not the right field for us to turn to as a model of our research program. One may also point out that the hypothetico-deductive method is not the only method adopted even in physical sciences. My response, briefly put, is: if it is possible to get to know something by following the hypothetico-deductive method, why would one want to adopt a less rigorous method?^FN2

　　　There are various types of evidence that we can in principle bring to bear on the validity of our hypotheses. Some are "experimental" while others are not.^FN3 Whatever type of evidence one wishes to consider, it has to be articulated how the predicted "value" can be deduced from a set of hypotheses, how a particular experimental result or an observation can be understood as a reflection of properties of the language faculty, and finally, how we can rigorously compare the prediction and the experimental result or the observation. Without minimally satisfactory answers to such questions, it remains unclear what significance can be assigned to the experimental result or the observation in a research program that is concerned with a discovery of properties of the language faculty.

　　　Given the assumption that the language faculty underlies our ability to relate a sequence of sounds/signs to a "meaning," it makes sense to ask informants, including ourselves, about possible correspondences between sounds/signs and "meanings." However, in light of the fact that the informant judgments, especially when "meanings" are involved, have been known to be extremely slippery, one should naturally wonder how we can justify the use of informants' introspective judgments as crucial evidence, let alone the use of the researcher's own judgments. The present work proposes a specific way to make informant judgments qualify as evidence in language faculty science, as something measurable and reproducible.

　　　My main concern is how we can deduce definite predictions and test them experimentally in accordance with the research heuristics in (1).

(1)　a.　Secure testability.
　　b.　Maximize testability.
　　c.　Maximize the significance of the experimental result.^FN4

　　　I take it for granted that, regardless of the object of inquiry, one should like to adopt the research heuristics in (1) if it is at all possible to do so. The methodology I am proposing in my ongoing work is a consequence of having the language faculty as the object of inquiry and adopting (1). Unless we start accumulating results in language faculty science based on research that rigorously pursues testability, the research program initiated by Chomsky in the mid-1950s will most likely remain to be regarded as a metaphysical speculation, at least by those outside the field. The goal of my current work is to articulate how it is possible to pursue language faculty science as an exact science^FN5, by providing a conceptual basis for how that is possible in principle and empirical illustration of how that has actually been done.^FN6


　　FN1: See Chomsky's response to it in his lectures in April and June of 2011, available at the following sites:
(i)a."Language and the Cognitive Science Revolution(s)" http://www.youtube.com/watch?v=XbjVMq0k3uc (at Carleton University, April 8, 2011)
b."Language and other cognitive systems: What is special about language?" http://www.youtube.com/watch?v=2v6XFkSwVys. (at the University of Cologne, June 6, 2011)
　　FN2: Social and behavioral sciences adopt a method of evaluating hypotheses where the significance test on the so-called null hypotheses plays an enormous role. That is because it is deemed impossible in such fields to deduce point-value predictions.
　　FN3: "Experimental" evidence is based on various types of reactions by the informants (e.g., introspective judgments, reading time, eye movement, etc.) to stimuli (typically a sentence (with a specified intended interpretation)). "Non-experimental" evidence is based on observations of (linguistic) behavior of the subjects, without involving any stimuli provided by the experimenter.
　　FN4: The heuristic in (1c) subsumes the "Maximize our chances of learning from errors" heuristic.
　　FN5: As I noted above, what is meant by an "exact science" is a research program in which we can deduce definite predictions and rigorously compare them with experimental results (and expect them to be supported experimentally).
　　FN6: For further remarks/discussion, please see my "Hypothesis testing in generative grammar: Evaluation of predicted schematic asymmetries" Journal of Japanese Linguistics vol. 26, pp. 25-52, available here, and the postings in the Methodology board.