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Friday, August 14, 2020

Wadley Pasturepedic®

Today, in Science, evidence that people were using grass bedding 200,000 YBP. I don't know if this marks the beginning of anatomically modern humans, but it certainly revises the date for the Great Sleep Forward. 

The FoLog has been on medical leave while I have been dealing with the consequences of a retinal detachment, but with the beginning of the semester I will try to post more regularly.

Bill

Tuesday, March 17, 2020

Recursion in the Time of Cholera

What better time to think about recursion as the COVID-19 virus is busy replicating itself all over the world?   

The big picture issues will come later—for the moment I will even use the term recursion loosely—because I think they become clear once we crack the empirical nut.  

Languages such as English allow infinite embedding of genitive possessors via the apostrophe -s (1a) but German, and most Germanic languages, typically allow only a single item that is a proper name or a handful of kinship terms (1b and 1c):

(1) a. Maria’s’s neighbor’s friend’s house
b. Marias Haus (Maria’s house)
c. *Marias Nachbars Freundins Haus (Maria’s neighbor’s friend’s house)

Such structures are all over language: the infinite use of finite means. One well-studied case is adjective embedding (aka stacking) in NPs as in the big red … car, which young children learn very early. Then there is the (in)famous Pirara debate on whether the language has clausal or any kind of recursive embedding. A principled solution to one of such cases has the potential of handling them all.

Before we look at how recursive embedding can be learned, let’s first look at how it can not be learned. First, deep embeddings are rare and deeper embeddings are rarer. There are very few triple possessive embeddings in child-directed English (about 20 in the entire CHILDES input of almost six million words) and no deeper ones whatsoever. Second, and more important, even if the child were to hear, say, 17-level embedding, there is no reason that infinite, or even 18-level, embedding should follow. Finally, it would not be wise to suppose that, perhaps by default, language recursively embeds across all domains. That would leave us with the huge question of reigning in numerous superset grammars all over the place. Plus, there is no evidence that German-learning children ever stray and stumble as in (1c), i.e., having to suppress the recursive rule. 

The proposal here is that recursive embedding is an instance of productivity.  The conventional notion of productivity is that it applies to a category of items without restrictions. A case in point is children’s knowledge of determiners, where productivity is defined as the interchangeability of the members in the determiner category—specifically, a/n and the—when used in combination with nouns. The recursive embedding of a rule merely has a different flavor: it applies irrespective of structural positions.   

Let me explain with the example of adjective stacking. We can view it as a case of productivity where the placement of adjectives takes place irrespective of their structural positions. For a noun phrase of the form A1A2N, if an adjective can appear in position A1, then it must be able to appear in position A2 as well, and vice versa. This conception of recursion as productivity enables us to apply learning models such as the Tolerance/Sufficiency Principle (TSP): a rule defined over N lexical items productively generalizes iff eN/lnN where e is the cardinality of the subset of items not attested under the rule in the input. A crucial property of the TSP is that N pertains to the child learner’s vocabulary, which is just a few hundred at age 2-3 when most of the recursive rules are learned. Thus, the evidence for rule productivity must come from a small set of early words, which can be approximated by examining the distributional properties of the most frequent types (here: adjectives) in child-directed input.

This idea has been explored in joint work (with Lydia Grohe and Petra Schulz) that is to appear, COVID19 permitting, at this year’s of GALANA conference in Iceland. For English, we focus on the 49 adjectives in the some 550 words known to typical 3-year-olds (found here). We use a part-of-speech tagger to extract “DA1A2N” sequences from a 5.5-million-word child- directed English corpus. All 49 adjectives appear in either A1 or A2 position, of which only 3 fail to appear in both, trivially clearing the TSP threshold (49/ln49=13). A1 and A2 are fully interchangeable: adjective stacking is productive and recursive. For German, we analyze five child-directed corpora of about 3.5 million words. We focus on the 40 most frequent adjectives and extract all “A1A2N” sequences. 38 of the 40 adjectives appear in either A1 or A2 position, of which only 7 fail to appear in both, also clearing the TSP threshold (38/ln38=10). Thus, the productivity of English and German adjective stacking can be rapidly acquired on a distributional basis.

Possessor embedding can be handled similarly. The rule has the form of “X’s Y” where X is the possessor and Y is the possessee. Productivity of recursive embedding means that nouns appearing in the X position can also appear in the Y position, and vice versa. Again, this only needs to be true of a relatively small number of highly frequent nouns in a young child learner's vocabulary. I have not run the numbers for English but Daoxin Li, a graduate student at Penn, has checked Chinese, which has the identical structure (just replace ’s with , the possessor marker). Even in a smaller corpus, 40 out of top 50 nouns appear in both X and Y positions, again meeting the productivity criterion (50/ln50=13): young children learning Chinese do know this recursive rule very early And given the state of German, there is no way for the structure to be productive: the child will not generalize the rule to all nouns but only learn the specific lexical class of items that does appear in the possessor position. 

Yes, the same argument carries over the CP embedding. Almost all of the top 10 recursively embedding verbs (think, know, say, tell, believe, etc.) that young children know and use, which all express propositional attitudes, are robustly attested in both matrix and embedded clause positions, often together, in child-directed English input (e.g., ".. think ... [CP that .. think]", "... know [CP ...  think ... ]", "told .. [CP.. said ...]"

A couple of general remarks before I finish.

  1. If correct, recursive embedding can be learned distributionally; no need to rig a theory of linguistic structures to do so.
  2. It is theoretically possible for a language, or a stage of language development, to have no recursive embedding rules at all. (NB: productive rules needn't be recursive but recursive rules must be productive.)
  3. The current proposal implies that embedding is either infinite (as in most cases) or restricted to level one (as in German possessives). There is nothing in between. This is analogous, in my view, to the nature of counting systems and the knowledge of natural numbers (I believe) it entails: productivity is a categorical notion. 
  4. Recursion, as conceived here, is somewhat independent of representational structure. That is, a linear structure that iterates (e.g., a A* finite state language) can be learned by the same mechanism, provided that the learner treats A as a discrete category of elements. The learning theory applies to linear positions as well as hierarchical positions, where interchangeability appears to the key. The origin of hierarchy, a la Merge, remains as mysterious as ever.
Take good care, everyone. Better: recursively!

Thursday, December 12, 2019

200k, 27M YBP?

In The Atlantic today, a summary of a new article in Science Advances this week about speech evolution:

https://www.theatlantic.com/science/archive/2019/12/when-did-ancient-humans-start-speak/603484/?utm_source=feed

https://advances.sciencemag.org/content/5/12/eaaw3916

I think Greg Hickok had the most trenchant comment, that people are hoping “that there was one thing that had to happen and that released the linguistic abilities.” And John Locke had the best bumper sticker, “Motor control rots when you die.”

As the authors say in the article, recent work has shown that primate vocal tracts are capable of producing some vowel sounds:

https://advances.sciencemag.org/content/2/12/e1600723

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0169321

This is certainly interesting from a comparative physiological perspective, and the article has a great summary of tube models for vowels. But I don't think that "producing vowel sounds" should be equated with "having speech" in the sense of "having a phonological system". My own feeling is that we should be looking for a couple of things. First, the ability to pair non-trivial sound sequences (phonological representations) with meanings in long term memory. Some nonhuman animals (including dogs) do have this ability, or something like it, so this isn't the lynch pin.

http://science.sciencemag.org/content/304/5677/1682.short

Second, the emergence of speech sound sequencing abilities in both the motor and perceptual systems. That is, the ability to perform computations over sequences; to compose, decompose and manipulate sequences of speech sounds, which includes concatenation, reduplication, phonotactic patterning, phonological processes and so on. The findings closest to showing this for nonhuman animals (birds in this case) that I am aware of are in:

https://www.nature.com/articles/ncomms10986

https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.2006532

In those papers the debate is framed in terms of syntax, which I think is misguided. But the experiments do show some sound sequencing abilities in the birds which might coincide with some aspects of human phonological abilities. But, of course, this would be an example of convergent evolution, so it tells us almost nothing about the evolutionary history in primates.

Tuesday, August 20, 2019

□ modal conference, ◊ you attend

Endless Possibilities: The Development of Possibility and Necessity in Cognition, Language, and Society

Anna Papafragou (Linguistics, University of Pennsylvania)
Ailís Cournane (Linguistics, New York University)
Jonathan Phillips (Psychology, Harvard)
Nicolò Arlotti (Psychological & Brian Sciences, Johns Hopkins)
Lucas Butler (HDQM, UMD)
Valentine Hacquard (Linguistics, UMD)

Friday September 27th from 9:15 to 4 in the UMD Language Science Center (2130 HJ Patterson Hall)

Register here.

Monday, August 19, 2019

Herb Terrace on Nim and Noam

From my colleague Greg Ball, news about a new blog and book by Herb Terrace which will ask how words evolved (as opposed to grammar).

Monday, July 8, 2019

Interesting Post Doc possibility for linguists with cogneuro interests

William Matchin sent me this post doc opportunity for posting on FoL

A Postdoctoral Fellow position is available at the University of South Carolina, under the direction of Prof. William Matchin in the NeuroSyntax laboratory. The post-doc will help develop new projects and lead the acquisition, processing, and analysis of behavioral and neuroimaging data. They will also assist with the organization of the laboratory and coordination of laboratory members. We are particularly interested in candidates with a background in linguistics who are interested in projects at the intersection of linguistics and neuroscience. For more information about our research program, please visit www.williammatchin.com.

Salary and benefits are commensurate with experience. The position is for one year, renewable for a second year, and potentially further pending the acquisition of grant funding.

The postdoctoral associate will work in close association with the Aphasia Lab (headed by Dr. Julius Fridriksson) as part of the NIH-funded Center for the Study of Aphasia Recovery (C-STAR). The NeuroSyntax lab is also part of the Linguistics program, the Neuroscience Community, and the Center for Mind and Brain at UofSC.

The University of South Carolina is in historic downtown Columbia, the capitol of South Carolina. Columbia is centrally located within the state, with a two-hour drive to the beach (including historic Charleston, SC) and the mountains (including beautiful Asheville, NC).

If you are interested in this position, please send an email to Prof. William Matchin matchin@mailbox.sc.eduwith your CV and a brief introduction to yourself, your academic background, and your research interests. You can find more details and apply online: https://uscjobs.sc.edu/postings/60022.

Wednesday, July 3, 2019

Postdoc position at South Carolina

A Postdoctoral Fellow position is available at the University of South Carolina, under the direction of Prof. William Matchin in the NeuroSyntax laboratory. The post-doc will help develop new projects and lead the acquisition, processing, and analysis of behavioral and neuroimaging data. They will also assist with the organization of the laboratory and coordination of laboratory members. We are particularly interested in candidates with a background in linguistics who are interested in projects at the intersection of linguistics and neuroscience. For more information about our research program, please visit www.williammatchin.com.

Salary and benefits are commensurate with experience. The position is for one year, renewable for a second year, and potentially further pending the acquisition of grant funding.

The postdoctoral associate will work in close association with the Aphasia Lab (headed by Dr. Julius Fridriksson) as part of the NIH-funded Center for the Study of Aphasia Recovery (C-STAR). The NeuroSyntax lab is also part of the Linguistics program, the Neuroscience Community, and the Center for Mind and Brain at UofSC.

The University of South Carolina is in historic downtown Columbia, the capitol of South Carolina. Columbia is centrally located within the state, with a two-hour drive to the beach (including historic Charleston, SC) and the mountains (including beautiful Asheville, NC).

If you are interested in this position, please send an email to Prof. William Matchin matchin@mailbox.sc.edu with your CV and a brief introduction to yourself, your academic background, and your research interests. You can find more details and apply online: https://uscjobs.sc.edu/postings/60022.