In an earlier post I discussed a nice little piece by Geoff Pullum (GP) on Aspects after 50 years (here). GP has a second interesting post (here) that discusses a central distinction highlighted in Aspects; the competence-performance distinction (CPD). As he rightly notes, this distinction has caused endless cognitivist’s dissonance. Like GP, I don’t really understand why. It’s a distinction that is rampant, for example, in statistical conceptions of cognition. The trivial distinction between the structure of the hypothesis space and the actual distributions over that space is a version of the CPD. Nobody takes this to be a controversial distinction. If so, we can take a theory of the hypothesis space (what’s its geography?) to be a theory of competence and a theory of how this space gets filled probabilistically to be a theory of performance. This common distinction then provides a first okish pass at the CPD. It is not perfect, but it gets you a lot of the way there.
Another useful explication is that a theory of competence aims to limn the limits of the possible. In syntax we aim to describe the possible sentences of a language in terms of the unbounded products of a given G. We aim to describe the possible Gs in terms of the products of FL/UG. We aim to describe the possible FLs… The sentences/ Gs/FLs we actually encounter are points in a space of sentences/Gs/FLs that could exist. Theories of what could be are theories of competence.
Ontologically, theories of competence ground theories of performance. This is why the CPD is rife with Empiricist/Rationalist (E/R) baggage, which chapter 1 of Aspects elaborates on. This is also why, IMO, it has proven to be so difficult a concept to get across. Empiricists treat competence as a conceptually derivative notion. First there is performance. Competence, on the E view, is smoothed performance, performance with the variance squeezed completely out, non-noisy performance. This, however, is not what the CPD demarcates. It is essentially a Rationalist notion, pointing to hidden structure, which actual linguistic items can be used to reveal.
I mention this because, this seems quite different from the way that GP frames matters in his post. For GP, following Edward Lorenz, competence is “what you expect,” and performance is “what you get.” He then elaborates this in terms of what we will find if we squeeze out all the “sporadic and unintended mistakes” of performance. So competence is cleaned up performance. But it isn’t. For example, many many G products will never be performed, (im)perfectly or otherwise, yet they are explanada of a competence theory of G. Humans may fail to internalize many many Gs, yet these Gs may be possible and Gs that at theory of FL/UG should permit. So, what we see, even in statistically cleaned up form (i.e. with all the nosiy variance squeezed out) is not what competence is about.
Of course, we hope that we can get a window into the possible by investigating what is actually deployed. Thus, actual performances are the source of our linguistic data. What people say, how they judge things we present to them, etc. These data are used to plumb the limits of the possible. And some data is perhaps better than others for this purpose. So, if you are interested in what linguistic knowledge consists in (i.e. knowledge of a G) then some data might be better suited than others for probing this. What kind? Well, those that do not run afoul of factors such as limited memory, slips of the tongue, etc. that we think might confuse matters. So, we clean up the relevant data we use to plumb G competence. These gussied up linguistic objects are not themselves the targets of explanation. Rather they act as probes into the structure of a G or of FL/UG. In other words, the target of a theory of competence in linguistics (i.e. what we want a theory of competence to explain the properties of) is a G or FL/UG. The intuitions we harvest and the utterances we track are what we use to investigate these structures. The point that Chomsky makes in Aspects concerning the ideal speaker-hearers simply adverts to the fact that some data (e.g. those that abstract away from performance factors like memory and attention limitations) are nosier than others and so less useful as probes of the G and FL/UG systems. In other words, Aspects makes the undeniably correct point so some data are plausibly more useful than others if one’s aim is to discern the structure of linguistic knowledge.
GP interprets the discussion in Aspects quite differently. He understands Chomsky to have been proposing that the “subject matter” of linguistics was “speaker intuitions about sentence structure.” These intuitions are purer than linguistic performances (e.g. utterances) in that they abstract away from (and here GP quotes Chomsky) “grammatically irrelevant conditions as memory limitations, distractions, shifts of attention and interest, and errors (random or characteristic) in applying his knowledge of this language in actual performance.” However, even if we grant this (which we should), this does not make these intuitions the subject matter of linguistics. No! These intuitions are simply data, evidence that linguists can use effectively to understand the structure of Gs and FL/UG. Chomsky does claim that such intuitions are rich sources of information about the structure of G knowledge and might suggest that they are superior data to corpora data (i.e. recorded speech of actual utterances). Moreover, he clearly thinks that we should dump the prejudice against speakers’ judgments that behaviorism saddled us with. However, Chomsky does not argue in Aspects (so far as I can tell) that intuitions are epistemologically or ontologically privileged data, just that they don’t suffer from some of the problems we might think would mislead investigation.
This is almost certainly correct, and it is not the same as suggesting that these data are the subject matter of linguistics. The subject matter, (aka aim of inquiry) is, as Chomsky puts it, to describe “the mental reality underlying actual behavior.”
I should add that the idea that intuitions are privileged in some way leads to all sorts of misconceptions that psychologists then spend so much time lecturing linguists about. Such judgments are themselves complex performances, with all the problems that performances entail. The most that can be said for intuitions is that have proven to be excellent probes and that they are very stable, robust, and easy to gather. These are important virtues, but they don’t argue for intuitions as such being privileged, as would be the case were intuitions the subject matter of linguistics.
In sum, if I got GP right here (but see note 2), then I think he gets the CPD wrong. What he presents is the Eish version of the CPD. Aspects takes an irreducibly Rish conception of the aim of inquiry and the CPD is intended to highlight this approach. If this is right, then the main problem with getting others to understand the competence/performance distinction lies in them getting to see how closely it is related to an Rish conception of mind (and science actually (see here)). But Rationalism is largely anathema to many practicing neuro-cog types and so the distinction is hard for them to understand (and accept). This is to be expected. On an Eish conception, the most one can make of the notion lies in the quality of data. It marks a distinction between types of data: Performance data is “messy” “competence” data is not. The latter is privileged for that reason. However, this is not the point that the CPD is intended to highlight. It highlights the difference between the products of an underlying mechanism and the mechanism itself. In other words, it highlights the claim that the subject matter of linguistics is Gs and FL. In other words, the CPD carries within itself the project of modern Generative Grammar, and that’s why understanding it is so very important.
 I say “might be” because it is possible to read GP as making the same point as I am making here. If so, great. However, there is another reading where he sees competence as non-noisy performance. But, I may be misreading him here and if so my sincere apologies to GP. That said, the two ways of interpreting the CPD are important so I will continue putting my own construal on GP’s elaboration.