right toit without search; similarly, onecan reachfor thecoffee cup offin thecorner without really looking at it. Thus,
as in the case of sentences, a full visualfield provides a complex web of transient and novelrelationships that must be
put together out of familiar parts.
3.5.2 The Problem of 2
Inmuchworkonlanguage processing(e.g. Barsalou 1992; 1999; SmithandMedin1981; Caramazza and Miozzo1997;
Elman et al. 1996), the only mechanism availablefor constructing linguistic expressions is spreading activationamong
nodes connected in a semantic network or neural net. Thus it is assumed that“lexical retrieval”in processing—i.e.
identifying what word one is hearing or speaking—amounts to activating the nodes encoding (or instantiating) that
word in long-term memory. We have already seen that such an approach is silent about capturing the relations among
the words of a sentence. But there is an even simpler difficulty, which I will call the Proble mof 2.
Consider yet again sentence (23), in which there are two occurrences of the wordstar. If thefirst occurrence simply
activatesthe lexical entry in long-ter m me mory, what can the second occurrence do? It cannot just activatethe word a
second time,since—as just argued—thewordhas toremainactivatedthefirst time inorder for thesentencetoreceive
a full interpretation. Nor can the second occurrence just activate the word more strongly, because that leaves the two
occurrencesindistinguishable. Inparticular, thefirst occurrence isbound tolittleand thesecondtobig, so simultaneous
binding to both would lead to the contradictory concept of a little big star.
This proble mrecurs at every levelof linguisticstructure. For exa mple, inphonologicalstructure, ifthedetection ofthe
phoneme s consists simply of activatingan s-node (or a distributed complex of nodes that together instantiates), what
happens in a word with more than one such sound, saySisyphusorsassafras?^30 The same problem occurs in conceptual
structure when conceptualizing a relation involving two tokens of the same type (e.g. the meaning of (23)) and in
spatial structure when viewing or imagining two identical objects. It also occurs in understanding melodies: if the unit
of musical memory is the individual note, then every repetition of the same note raises the problem; if the unit is
COMBINATORIALITY 61
(^30) Rumelhart and McClelland(1986b) attempt to avoidthis problem by codingwords as“wickelphones,”overlappingsequencesof three phonemes. But thistoois subjectto
the Proble mof 2: how is the word detector to distinguishsassafrasfro mthe nonwordsassassafras, whichhas twooccurrences of the medial sequence...assa...—orgreat-
grandmother fromgreat-great-grandmother, which has two occurrences of the medial sequence...reatgr...? Pinker and Prince (1988) cite an Australian aboriginal language,
Oykangand, whose wordsalgal ‘straight’andalgalgal ‘ramrod straight’pose the same problem.