Criticism: The Nim Chimpsky project (Terrace et al., 1979)
Most-frequent sign combinations:
|2 signs||#||3 signs||#||4 signs||#|
|play me||375||play me Nim||81||eat drink eat drink||15|
|me Nim||328||eat me Nim||48||eat Nim eat Nim||7|
|tickle me||316||eat Nim eat||46||banana Nim banana Nim||5|
|eat Nim||302||tickle me Nim||44||drink Nim drink Nim||5|
|more eat||287||grape eat Nim||37||banana eat me Nim||4|
Nim's MLU (mean length of utterance) did not increase with age, as a child's would.
Semantic limitations: 99% of beneficiaries in Nim's utterances were 'Nim' and 'me'
Also, 76% of agents in agent-object combos were 'you'
Nim did not take turns in the conversation the way children do
39% of Nim's utterances were imitations or reductions of what had just been signed to him; only 18% of a comparable child's utterances were imitations or reductions.
Nim expanded on what had just been signed only 7% of the time; children do so 21% of the time.
A full 71% of Nim's utterances were interruptions.
Terrace et al. claimed that previous researchers had not convincingly shown that chimps' "linguistic" abilities couldn't be explained with reference to simpler, non-linguistic processes. For instance,
"The function of the symbols of an ape's vocabulary appears to be not so much to identify things or to convey information as it is to satisfy a demand that it use that symbol in order to obtain some reward."
(There were no "tacts"--there were only "mands".)