Word Identification 551Figure 20.1 Example of the Reicher-Wheeler paradigm. In the condition
on the left, a fixation marker is followed by the target word, which in turn is
followed by a mask and two forced-choice alternatives. In the conditions in
the center and on the right, the sequence of events is the same, except that ei-
ther a single letter or a scrambled version of the word (respectively) is the
target stimulus.Fixation Marker ***
Target Stimulus word d owrd
Mask and ddd
Forced Choice xxxx xxxx xxxx
kkkpreprocessing stage, in which the image is normalized to the
template before the comparison; however, so far no particu-
larly plausible normalization routines have been suggested
because it is not clear how a person could normalize an image
without prior knowledge of what the object is. Another possi-
bility is that many templates exist for each object category;
however, it is not clear whether memory could store all of
these object templates, nor how all of the templates would
have been stored in the first place.
The other class of models are calledfeature models. They
differ in their details, but essential to all of these models
is that objects are defined by a set of visual features. Although
this kind of formulation sounds more reasonable than the
template model to most people, it may not be any better a so-
lution to the general problem because it is not at all clear what
the defining visual features are for most real-world objects. In
fact, most of the more successful artificial intelligence (AI)
pattern recognition devices use some sort of template model.
Their success, however, relies heavily on the fact that they
are typically only required to distinguish among at most a
few dozen objects rather than the many thousands of objects
with which humans must cope.
This rather pessimistic introduction to object identification,
in general, would suggest that we have learned little about how
words are identified; however, that is not the case. Even though
visual words are clearly artificial stimuli that evolution has not
programmed humans to identify, there are several ways in
which the problem of identifying words is simpler than that of
identifying objects in general. The first is that, with a few ex-
ceptions, we do not have to deal with identifying words from
various viewpoints: We almost always read text right side up.
(It is quite difficult to read text from unusual angles.) Second,
if we confine ourselves to recognizing printed words, we do
not encounter that much variation from one exemplar to an-
other. Most type fonts are quite similar, and those that are un-
usual are in fact difficult to read, indicating that they are indeed
poor matches to our mental representations of the letters.
Thus, the problem of understanding how printed words are
identified may not be as difficult as understanding how objects
are identified. One possibility is that we have several thousand
templates for words we know. Or perhaps in alphabetic lan-
guages, all we need are a set of templates for each letter of the
alphabet (more likely, two sets of templates—one for upper-
case letters and one for lowercase letters).
Do We Recognize Words Through
the Component Letters?
The previous discussion hints at one of the basic issues in
visual word recognition: whether readers of English identify
words directly through a visual template of a word, or
whether they go through a process in which each letter is
identified and then the word as a whole is identified through
the letters (we discuss encoding of nonalphabetic languages
shortly). In a clever tachistoscopic paradigm, Reicher (1969)
and Wheeler (1970) presented participants (see Figure 20.1)
with either (a) a four-letter word (e.g., word); (b) a single let-
ter (e.g., d); or (c) a nonword that was a scrambled version of
the word (e.g., orwd). In each case, the stimulus was masked
and, when the mask appeared, two test letters, (e.g., a dand a
k) appeared above and below the location where the critical
letter (din this case) had appeared. The task was to decide
which of the two letters had been in that location. Note that
either of the test letters was consistent with a word—wordor
work—so that participants could not be correct in the task
merely by guessing that the stimulus was a word. The expo-
sure duration was adjusted so that overall performance was
about 75% (halfway between chance and perfect).
Quite surprisingly, the data showed that participants were
about 10% more accurate in identifying the letter when it was
in a word than when it was a single letter in isolation! This
finding certainly rules out the possibility that the letters in
words are encoded exclusively one at a time (presumably in
something like a left-to-right order) in order to enable recog-
nition. This superiority of words over single letters (at least
superficially) may seem to be striking evidence for the asser-
tion that words (short words at least) are encoded through
something like a visual template. However, there is another
possibility: that words are processed through their compo-
nent letters, but the letters are encoded in parallel, and some-
how their organization into words facilitates the encoding
process. In fact, several lines of evidence indicate that this
parallel-letter encoding model is a better explanation of the
data than is the visual template model. First, all the words in
this experiment were all uppercase; it seems unlikely that
people would have visual templates of words in uppercase,
because words rarely appear in that form. Second, perfor-
mance in the scrambled-word condition was about the same
as it was in the single-letter condition. Thus, it appears that