PIANTADOSI Steven Language, Rochester Feb 20 2013

He is a post-doc at U Rochester working with Dick Aslin in Brain/ Cog Sci.
worked with Ted Gibson and Josh Tenenbaum, MIT.

see Hockett 1960  language as a means of communic:
broadcast,  dies out  (unlike pheromones),
arbitary choice of topics (can discuss justice or  LEDs)
13 communication features...

OUTLINE:  rational language

word lengths...

optimized for communicative efficiency

word lengths 
sentence comprehension ambiguity....

What determines word lengths???

consider these:

a, to , in, on
apple, mother, chair
therefore, accordion, intersection

X-Y plot of   word freq  x-axis  vs word length...

Zipf  1935 and 1949...

word length is determined by frequency
minimize the total length of utterances...
(common words are SHORT)

u do not want to have to say velociraptor  everytime you want to say A is ON top of B...

words get worned down at the edges...(with use!)

so  minimize the total lenth of utterance  but
if language is trying to be concise... why not assign
meanings to  bim  boop, bup  etc...

but  maybe  words are chosen to be  an EFFICIENT CODE!!!

relative to our probabil expectations...

if  u say something  that is NOT predicted  velociraptor  then  
take ur time (cuz it has lots of surprisal)

THE is not very surprising

the senator once vandalized a neighbor's home

the is not surprising
senator moderate
once not surpriz.
vandalized  very very surprising...  carries all the contents...

how abt substituting  senator once IKED a neighbor's home..

NO

rather... make word length proportionate  to surprisal  (to   info content)

quantify info content... (shannon like eqn)

frequency and info content are  correleated

should be able to better predict  freq from  info content rather than word length...

result:  info content  better predicts word length than frequency...

Piantadosi, Tily, Gibson  2011  PNAS...

correl with word length is about  0.3  (? r or r**2)

long and short form mean same thing
 chimp vs chimpanzee  porn vs pornography
kilo  vs  kilogram...

information conveyed by long form is greater!! than short form
 (we use them in difft circumstances

he subtracts long and short form surprisals  and they are all above the line...

supportive context...
here it's predictable

Susan was v bad at algebra, so she hated math  (vs mathematics)

vs neutral context

Susan introduced herself to me as someone who loved...  (math vs mathematics... both equal freq)

u say don't  when its  more predicted  vs  do NOT.

so, it is NOT about  making the code as concise as possible.

(Zipf worked  BEFORE Claude Shannon)

summary word lengths...

a stitch in time  saves nine  vs

the number on my card is ... NINE   (in the first they really spit it out fast cuz its predicted)

****

Topic 2  Noisy Channel Sentence Comprehension
Gibson, Bergen, Piantadosi

shannon channel

Mi (i for intended) is the speakers meaning  gets encoded  into his sentence  Si  and goes thru the air
to me...  I hear  Sp  (sentence perceived) and get from it  Mp  (meaning perceived)

perceiver  picks a high prob meaning and  tries to  translate sentence into something that
the speaker may have said...

from work of roger levy in 2008...

do sentence processing mechanisms... employ efficient means  also..

Mary gave the candle the girl  (weird, but not impossible)
but might be corrupted form of 

Mary gave the candle TO the girl...
(much more plausible)

key feature... listeners might arrive at meanings other than what was literally uttered...

so  involves  sensible "decoding"

experiment:  with Mech Turk...
300 participants...

active vs passive

the girl kicked the ball   vs  the girl was kicked by the ball

onto the table jumped a cat  vs the table jumped onto a cat...

the tax law benefited the man  vs the tax law benefited from the man

the cook baked Lucy a cake  vs  the cook baked Lucy for a cake.

results
this is WRITTEN... not aural... and  they are on the screen as long as they want

mary gave the candle the girl  52% goes to mary gave the candle to the girl

vs

Mary gave the girl to the candle  only 38% goes to  Mary gave the girl the candle...
(low prob.  ... has an extra word... (to) and a weird meaning.

how noisy is the channel... 2 string errors are really unlikely... 44% vs 7% likelihood..

depends on peoples belief about syntactic error vs  implausible (semantic)  weirdness...

asks a Q... did the girl receive a candle  or  was there the girl kicked?

sensitive to factors like  plausability;  how strings get corrupted   how likely;
base rates of anomalous syntax and semantics...

future work.. the full model...

other work:
phonological  forms  (choose phonemes which are discriminable)

syllable stress patterns... eg  REcord  vs  rec-ord  to  emphasize difft meanings...

stress syllables: are louder, longer  and contain more info... help u communicate robustly...

************************
Next topic;  AMBIGUITY

a puzzle for language  (his intro  was this paper:  Wasow, Perfors, Beaver  2005...)

Smoking warning labels will help save lives  Philip Inquirer  Aug 29 2012...

(2 meanings!)

Coach charged with battery   NYT  7/11/2012...

if your dog does a POO  put it in the litter bin...  what does it mean?
(why should language have  it, you, I.... so ambiguous)

every sailor loves a farmers daughter... what is the meaning  (one girl  vs the notion)

ambiguity could be there to make it short and simple
  (cuz context already provides the meaning)
ie  u do not have to say what the context already provides...

baba  is a stocking run
bako  is  running
koba  is a coffee cup
koko is the act of robbing someone with a gun...

but in english  :  can use MUG for both the latter and 
RUN for both of the former... cause  meaning is unambiguous...

so,.... ambiguity is  predicted by EFFICIENT DESIGN,

he shows  apple  warranty... total legal gobbledigook...

prediction:  ambiguity should rarely cause communicative problems...

see Wasow, Perfors, Beaver  2005  for examples of problems

Ambiguity and confusion

SWITCHBOARD...  naturalistic conversations btwn 2 stranger... give them a random topic
and record the whole conversaiton...

ambiguity in the wild..

what did u do last weekend...

proprotion of question types in 
70%  information
20%  soical
10%  rhetorical
5%  vagueness
4%  speech signal
2%  ambiuity... abt once vevery 12000 word sin the corpus...

ambig  in the wild  (on switchboard)

B  You call, we sold a a refirgetror  thru it and it took us all of 12 hours

A  to sell the frig?  (he tries to resolve ambig)

his thesis...  ambiguity is used for good  (is used to  shorten  communic where more is not needed)

ambiguity in lexical design...

y axis  mean number of homophones  (one word with mult  meanings)

longer words  have  fewer and fewer extra meanings...

Don't communicate info that the context provides  (c.f.  GRICE)

but why not make the short words distinct

mug(cup)  vs mug to steal  how abt
muc(cup and WUG  (for to steal)  why not just do that...

why is that?

one answer:  might just be easier to reuse  one word  for mult meanings...

might be easier to reuse words...

expt...

15 common nous and 15  matched words  non-words

fox  vs  heen  for new object...

people learn  new meanings for existing words better than for  nonsense words

GENERAL SUMMARY:

features of language:  pressures for raitonal, commun  optimizaiton..

word freq distrib  (Zipf)

word form/lengths...

Evelina Fedorenko...

Anthony:   a fox wrapped in foil 
 (ie  perhaps u  re-use the meaning of fox to map to
a new meaning...

Barabara T :  I went with a friend  (diplomatic.. don't want to specify identity, man vs woman etc)

Barb T:  really likes ambiguity...

Jay Q:   might use  chimpanzee if room is really noisy  (rather than chimp)  cuz it contains more info...

(or perhaps cud be audience designed... word choice)  I'm slowing down for you or for me...

Q   about the cost of extra  words  vs  the cost of being unambiguous...

Barbara T:  may just be saying... I like you.. or ... this is fun  and not actually communicating meaning at all...
barb... conversations with babies and small kids... its like  being affectionate: 
Main meaning is "I like you.".