Monday, April 30, 2012

Some thoughts on Bouchard (2012)

I think Bouchard (2012) actually takes a similar approach to Perfors et al. (2011) with respect to solving the structure-dependence problem, in the sense of redefining what the problem is and then stating that the solution to this problem does not involve UG learning biases.  It's at this point that the two studies part ways, but there is, in fact, the fundamental similarity.  Bouchard does believe that meaning is inextricably tied to the problem, but rejects the transformational approach that's traditionally assumed by Chomsky and colleagues.  Instead, meaning is more foundational in how the structures are generated.  One thing that isn't clear to me at all is whether the UG problem is solved, as the title would suggest.  It seems to me that the components that Bouchard assumes involve a lot of knowledge about interpretation (ISSUE and its structural relationship to Tense, incompleteness relating to a non-tensed utterance, etc.), and it's unclear where this knowledge comes from, if it's not meant to be innate.  Maybe "solving the UG problem" is just supposed to be about providing a complete specification of what's in UG?

Some more targeted thoughts:

- One of Bouchard's issues with the current ideas about UG is that the components of UG seem hard to explain evolutionarily.  That is, if we accept the current UG formulation, it's hard to explain why this would come to be for any kind of adaptive reasons.  This is a fair point, but I'm not sure the UG Bouchard proposes gets around this either.

- I think Bouchard does a nice review of the current approach to UG that's motivated by efficient computation.  In particular, it's fair to ask if "efficiency" is really the crucial factor - maybe "effectiveness" would be better, if we're trying to relate this to some kind of evolutionary story.

- I'm not sure it's fair to criticize the transformational account by saying that children may not encounter declarative utterances before they encounter interrogative utterances.  It should be enough that children recognize the common semantics between them, and assume they're related.

- I appreciate Bouchard's effort to specify the exact form of the rule that relates declarative and interrogative utterances (the four constraints on the rule).  This is useful if we were ever interested in making a hypothesis space of rules, and having the child learn which one is the right one (it reminds me a bit of Dillon, Dunbar, & Idsardi (2011), with their rule-learner).  Anyway, the main point is clear: The issue is that the actual rule is one of many that could be posited, even given the four constraints Bouchard describes, and we either need the right rule to fall out from other constraints or we need it to be learnable from the available possibilities.

- I agree with the basic point that "with a different order comes different meaning", but the point is that it's a related meaning.  Even in example (21), the utterances are still about the event of seeing and involve the actors Mary and John.

- "Question formation is not structure dependent, it is meaning dependent" - Well, sure, but meaning dependent, especially as it's described here, is all about the structure.  So "meaning dependent" is the same as saying "structure dependent", isn't it?

- The Coherence Condition of Conindexation (example 30): This sounds great, but don't we then need to specify what "coherent" means?  This seems to be an example of describing what's going on, rather than explaining what's going on.  For example, for (29), why do those two elements get coindexed, out of all the elements in the utterance?  Presumably, this has to do with the structure of the utterance...  This relates to a point slightly later on: "...due to the lexical specifications that determine which actant of the event mediates the link between the event and a point in time" - Where do these lexical specifications come from?  Are they learned?  This seems more a description than an explanation.

- p.25: "Whatever Learning Machine enables them to learn signs also enables them to learn combinatorial signs such as dedicated orders of signs" - This seems like a real simplification.  The whole enterprise of syntax is based on the idea that meaning is not the only thing determining syntactic form (otherwise, how do you get ungrammatical utterances that are intelligible, like "Where did Jack think the necklace from was expensive?").  So the Learning Machine needs to have something explicit in there about how combinatorial meaning links to form.

Wednesday, April 18, 2012

Next time on May 2: Bouchard (2012)

Thanks to everyone who was able to join us for an informative discussion of Perfors et al. (2011), along with the reply piece in Berwick et al. (2011)!  Next time on May 2, we'll be looking at a different approach to addressing the same problem in language acquisition (structure-dependent rules) by Bouchard (2012). Interestingly, Bouchard is coming from a very different perspective, where the issue is not that too much has been assumed to be part of UG, but rather that not enough has.

Bouchard, D. (2012). Solving the UG Problem. Biolinguistics, 6(1), 1-31.

See you then!

Monday, April 16, 2012

Some thoughts on Perfors et al. (2011) + Berwick et al. (2011)

I really like how straightforward Perfors et al's (2011) Bayesian model is - it's very easy to see how and why they get the results that they do from child-directed speech.  They're very careful to say precisely what their model is doing: Assuming there are hierarchical representations in the child's hypothesis space already, these representations can be selected as the ones that best match the child-directed input.  In addition, I think they highlight how previous approaches to this problem have tended to split along two distinct dimensions: domain-specific vs. domain-general, and structured vs. unstructured.  It's always useful to figure out where the current approach is adding to the existing discussion.

The only real issue I see is the one Berwick et al. (2011) pointed out: The (infamous) poverty of the stimulus (PoS)  problem relating to structure dependence is not the one Perfors et al. (2011) are addressing.  In particular, the traditional PoS problem has to do with hypothesizing what kind of rules will relate a declarative utterance (e.g., "I can have an opinion") to its interrogative equivalent (e.g., "Can I have an opinion?"). This relationship isn't addressed in Perfors et al.'s model - all that model is concerned with is the ability to assign structure to these utterances.  As far as it knows, there's no relationship between the two.  And this is where we see the real divergence from the traditional PoS problem, where it was assumed that the child is trying to generate an interrogative using the same semantic content that would be used to make the declarative.  This is why the "rules of transformation" were hypothesized in the first place (granted, with the assumption that the declarative version was more basic, and the interrogative version had to be created from that basic version).  So, long story short, the Perfors et al. model is learning something that is different from the original PoS problem.

However, it's fair to assume that knowing there are hierarchical structures is a prerequisite for creating rules that use those hierarchical structures.  In this sense, what Perfors et al. have shown is really great - it allows the building blocks of the rules (hierarchical structures) to be chosen from among other representations.  However, as Berwick et al. point out, it still remains to be shown how having structures building blocks leads you to create structure-dependent rules.  Perfors et al. assume that this is an automatic step: [end of section 1.2] "...any reasonable approach to inducing rules defined over constituent structure should result in appropriate structure-dependent rules".  Phrased that way, it does sound plausible - and yet, I think there's a real distinction, especially if we're concerned about relating the declarative and interrogative versions of an utterance.  Making a structure-dependent rule requires using the available structure as the context of the rule.  So this means you could make a structure-independent rule just by not using structure in the context of the rule - even if your building blocks are structured.

Example of a structure-independent rule using structure building blocks:
Move the auxiliary verb after the first NP.
Building blocks: auxiliary verb, NP (structured)
Context: first (not structured)

So again, I think that what Perfors et al. have shown is great in terms of understanding the stages of learning - it's important to know that the preference for hierarchical structure in language doesn't have to be innate (even if the ability to consider hierarchical structure in the hypothesis space may be).  However, I do think it falls short of addressing the PoS problem that linguists typically associate with structure dependence.  This isn't a failing of Perfors et al. - it just means that people really have to be careful about how they interpret these results.  It's very tempting to say that the structure-dependence PoS problem has been solved if you don't give this a very careful read and know what linguists think the problem actually is.

Wednesday, April 4, 2012

Next time on April 18: Perfors et al. (2011)

We'll have our first meeting of the CoLa Reading Group for this quarter on Wednesday April 18 at 10:30am in SBSG 2221. You can check out the schedule at 

for the rest of this quarter's meetings.  

For our first article of the quarter, we'll be looking at Perfors, Tenenbaum, & Regier (2011), who use hierarchical Bayesian modeling to examine structure dependence in syntax, which has often been used as an example of an induction problem (or poverty of the stimulus) in language acquisition.  I also recommend looking at a section in a recent response to this article by Berwick, Pietroski, Yankama, & Chomsky (2011), since it explicitly addresses the results of Perfors et al. (2011).

Perfors, A., Tenenbaum, J., & Regier, T. (2011). The learnability of abstract syntactic principles. Cognition, 118, 306-338.

Berwick, R., Pietroski, P., Yankama, B., & Chomsky, N. (2011). Poverty of the Stimulus revisited. Cognitive Science, 35, 1207-1242. [Section 4.2]

See you then!