Interference in Short-Term Memory The Magical Number Two (or Three) in Sentence Processing ` (Sat.) / Chan-hoon Park Hypernetwork Models of Learning and Memory (Artificial Neural Networks)

© 2006 SNU CSE Biointelligence Lab 2 Contents Introduction Definition Parsing related problems Other STM Phenomena Limitation Conclusion

© 2006 SNU CSE Biointelligence Lab 3 Introduction The purpose of this chapter  Syntactic processing + Memory research  Limited syntactic working memory capacity – 2 (or 3)  Interference effects  Similarity-based interference  Within independently motivated architectural mechanisms and principles and their associated constants

© 2006 SNU CSE Biointelligence Lab 4 Definition (1/2) Problems to deal for the purpose  Center embedding  [The salmon that [the man that [the dog chased] smoked] fell.]  Almost every parsing theories about C.E. have No psychological motivation for structure or limit ex) Stack, Look-ahead buffers, 4, 2, 1 …  Interference in multifaceted working memory  Retroactive interference / Within-Category similarity effects  The independence of parsing from phonological STM

© 2006 SNU CSE Biointelligence Lab 5

6 Definition (2/2) An interference theory of syntactic working memory  NL-Soar : computational model of sentence comprehension (from Soar : a theory of the human cognitive architecture)  NL-Soar’s working memory : H/D Set – buffers partial constituents  X-bar position : Surface structure

© 2006 SNU CSE Biointelligence Lab 7

8 Parsing related problems (1/5) Embedded relative clauses  The boy that the man the woman hired hated cried.  What the woman that John married likes is smoked salmon.

© 2006 SNU CSE Biointelligence Lab 9 Parsing related problems (2/5) Center embedding or Gap-filling  Without Gap-filling  With Gap-filling  Fred is tough for the man to please.  Fred is easy for the woman who the man who hired me married to please.

© 2006 SNU CSE Biointelligence Lab 10 Parsing related problems (3/5) Embedding or stacking  Difficulty of C.E is  Consecutive occurrences of NPs (= Stacking ), rather than C.E. per se.  In head-final languages (Japanese, Korean...),

© 2006 SNU CSE Biointelligence Lab 11 Parsing related problems (4/5) Limitations on ambiguity resolution  At most two nodes are available to assign the same structural relation at any given time.  Amparo saw the dog under the box on the table in the room next to the library.  Closure principle  Keep a small set of syntactic nodes open for further attachment. Two most recent nodes

© 2006 SNU CSE Biointelligence Lab 12 Parsing related problems (5/5) Length effects in garden path structures  The horse (raced past the barn fell).  Distance to disambiguation  But,  Ron (believed the ugly little linguistics professor).  Ron (believed the ugly little linguistics professor he had met the week before in Prague disliked him).  A limited repair mechanism  Length-induced garden path effect in NL-Soar  The girls believe the man who believes the very strong ugly boys struck the dog killed the cats.

© 2006 SNU CSE Biointelligence Lab 13 In other STM phenomena Immediate verbal memory task  Average word span of 2.6  The limited capacity of human memory – 2~3 similar chunks

© 2006 SNU CSE Biointelligence Lab 14 Limitation Possibility of Three  Three NPs occupying spec-IP, but acceptable  Average span is more than just 2.  There are may be additional cost associated with adjuncts in general, regardless of whether they involve relativization.

© 2006 SNU CSE Biointelligence Lab 15 Conclusion Sentence processing theories can benefit from incorporating ideas from traditional work in short- term memory. NL-Soar’s working memory  The source of memory load is open or unsatisfied syntactic relations. This leads naturally to a focus on stacking, as a source of difficulty.  Increasing similarity makes things more difficult.