244 Speech Production and Perception
summer when meaning to say winter) and form-based
(sayingequivocal when meaning to say equivalent). These
observations suggested to Garrett (1980) that two broad
phases of planning occur. At a functional level, lemmas (that
is, words as semantic and syntactic entities) are slotted into a
phrasal structure. When movement errors occur, lemmas
might be put into the wrong phrasal slot, but because their
syntactic form class determines the slots they are eligible for,
when words anticipate, perseverate, or exchange, they are
members of the same syntactic category. Semantic substitu-
tion errors occur when a semantic neighbor of an intended
word is mistakenly selected. At a positional level, planning
concerns word forms rather than their meanings. This is
where sound-based word substitutions may occur.
For their part, phonological segment errors also have
highly systematic properties. They are not sensitive, as word
movement errors are, to the syntactic form class of the words
involved in the errors. Rather, they are sensitive to phonolog-
ical variables. Intended and erroneous segments in errors
tend to be featurally similar, and their intended and actual
slots are similar in two ways. They tend to have featurally
similar segments surrounding them, and they come from
the same syllable position. That is, onset (prevocalic) conso-
nants move to other onset positions, and codas (postvocalic
consonants) move to coda positions.
These observations led theorists (e.g., Dell, 1986; Shattuck-
Hufnagel, 1979) to propose that, in phonological planning, the
phonemes that compose words to be said are slotted into syl-
labic frames. Onsets exchange with onsets, because, when an
onset position is to be filled, only onset consonants are candi-
dates for that slot. There is something intuitively displeasing
about this idea, but there is evidence for it, theorists have of-
fered justifications for it, and there is at least one failed attempt
to avoid proposing a frame (Dell, Juliano, & Govindjee, 1993).
The idea of slotting the phones of a word into a structural
frame is displeasing, because it provides the opportunity for
speakers to make errors, but seems to accomplish little else.
The phones of words must be serially ordered in the lexical
entry. Why reselect and reorder them in the frame? One justifi-
cation has to do with productivity (e.g., Dell, 1986; Dell,
Burger, & Svec, 1997). The linguistic units that most fre-
quently participate in movement errors are those that we use
productively. That is, words move, and we create novel sen-
tences by selecting words and ordering them in new ways.
Morphemes move, and we coin some words (e.g.,videocas-
sette) by putting morphemes together into novel combinations.
Phonemes move, and we coin words by selecting consonants
and vowels and ordering them in new ways (e.g.,smurf). The
frames for sentences (that is, syntactic structure) and for sylla-
bles permit the coining of novel sentences and words that fit
the language’s constraints on possible sentences and possible
words.
Dell et al. (1993; see also Dell & Juliano, 1996) developed
a parallel-distributed network model that allowed accurate
sequences of phones to be produced without a frame-content
distinction. The model nonetheless produced errors hitherto
identified as evidence for a frame. (For example, errors were
phonotactically legal the vast majority of the time, and con-
sonants substituted for consonants and vowels for vowels.)
However, the model did not produce anticipations, perse-
verations, or exchanges, and, even with modifications that
would give rise to anticipations and perseverations, it would
not make exchange errors. So far, theories and models that
make the frame-content distinction have the edge over any
that lack it.
Dell (1986) more or less accepted Garrett’s (1980) two-
tiered system for speech planning. However, he proposed
that the lexical system in which planning occurs has both
feedforward (word to morpheme to syllable constituent to
phone) links and feedback links, with activation of planned
lexical units spreading bidirectionally. The basis for this idea
was a set of findings in speech error corpora. One is that, al-
though phonological errors do create nonwords, they create
words at a greater than chance rate. Moreover, in experi-
mental settings, meaning variables can affect phonological
error rates (see, e.g., Motley, 1980). Accordingly, when
planning occurs at the positional level, word meanings are
not irrelevant, as Garrett had supposed. The feedforward
links in Dell’s network provide the basis for this influence.
A second finding is that semantic substitutions (e.g., the
summer/wintererror above) tend to be phonologically more
related than are randomly re-paired intended and error
words. This implies activation that spreads along feedback
links.
In the last decade, researchers developed new ways to
study phonological planning. One reason for these develop-
ments is concern about the representativeness of error cor-
pora. Error collectors can only transcribe errors that they
hear. They may fail to hear errors or mistranscribe them for a
variety of reasons. Some errors occur that are inaudible. This
has been shown by Mowrey and MacKay (1990), who mea-
sured activity in muscles of the vocal tract as speakers pro-
duced tongue twisters (e.g., Bob flew by Bligh Bay). In some
utterances, Mowrey and MacKay observed tongue muscle
activity for /l/ during production of Bayeven though the word
sounded error free to listeners. The findings show that errors
occur that transcribers will miss. Mowrey and MacKay also
suggest that their data show that subphonemic errors occur, in
particular, in activation of single muscles. This conclusion is
not yet warranted by their data, because other, unmonitored