Second Language Learning and Language Teaching

Box 7.2 Bottom-up parsing
Step 1: the
 man
➞
(the man)
article
 noun  noun phrase
Step 2: ate
 breakfast
➞
verb
 noun  verb phrase
(ate breakfast)
Step 3: (the man)
 (ate breakfast) 
noun phrase
 verb phrase
➞ 
(the man ate breakfast)
 sentence
Box 7.3 Top-down parsing
➞
? sentence The man ate breakfast
[means: is there a noun phrase plus a verb phrase?]
➞
? a noun phrase
➞
? an article
the
✓
➞
? a noun
man
✓
➞
✓a noun phrase (the man)
[means: yes, there is a noun phrase consisting of article
 noun (the man)]
➞
? a verb phrase
➞
? a verb ate
✓
➞
? a noun phrase
➞
? an article 
✗
➞
? a noun
breakfast
✓
➞
✓ a noun phrase (breakfast)
➞
✓ a verb phrase (ate breakfast)
[means: yes, there is a verb phrase verb
 noun phrase (ate breakfast)]
➞
✓ a sentence 
[means: yes, there is a sentence because there is a noun phrase plus a verb
phrase (the man)(ate breakfast)]
‘Top-down’ parsing, on the other hand, means breaking down the whole sentence
into smaller and smaller bits, that is, going from the top of the tree to the bottom, as
represented in Box 7.3. Given ‘The man ate breakfast’, the top-down process tries to
find the whole structure of an SVO sentence. It first tries to find a noun phrase, which
in turn means trying to find, first, an article ‘the’, and then a noun, ‘man’. If it suc-
ceeds, the next step is to find a verb phrase, which means trying to find a verb ‘ate’
and a noun phrase ‘breakfast’. If the quest to find a noun phrase and a verb phrase
succeeds, it has parsed the whole sentence, complete with its structure. The list in the
figure is in fact a mirror of a computer program to parse sentences in a computer lan-
guage like Prolog. The schema theories mentioned earlier are top-down in that they
see how the sentence fits in with whole patterns in the mind.

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In principle, the mind could parse the sentence in either direction, bottom-up or
top-down. In practice, listeners use both types of process. Features such as the into-
nation pattern allow them to fit words and phrases within an overall structure, a
top-down process. Particular words such as articles indicate the start of a phrase
and allow them to build it up word by word, a bottom-up process. The top-
down/bottom-up dichotomy, then, is only true in ideal terms. Some parsing
experts talk in terms of left-corner parsing, that is to say, starting with the lowest
word in the left corner of the tree, then going up to the first branching node and
down to the next word, up the next node, then down again, rather like a yoyo. 
J. Michael O’Malley and his colleagues (1985) found that effective L2 learners used
both top-down strategies listening for intonation or phrases and bottom-up strate-
gies listening for words, while ineffective listeners concentrated on the bottom-up
process. When parsing failed, they fell back on a range of other strategies, the least
effective being translation.