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Lexical quality and eye movements:
Individual differences in the perceptual span
of skilled adult readers
Aaron Veldrea & Sally Andrewsa
a School of Psychology, University of Sydney, Sydney, NSW, Australia
Published online: 25 Aug 2013.
To cite this article: Aaron Veldre & Sally Andrews (2014) Lexical quality and eye movements: Individual
differences in the perceptual span of skilled adult readers, The Quarterly Journal of Experimental
Psychology, 67:4, 703-727, DOI: 10.1080/17470218.2013.826258
To link to this article: http://dx.doi.org/10.1080/17470218.2013.826258
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Lexical quality and eye movements: Individual differences
in the perceptual span of skilled adult readers
Aaron Veldre and Sally Andrews
School of Psychology, University of Sydney, Sydney, NSW, Australia
Two experiments used the gaze-contingent moving-window paradigm to investigate whether reading
comprehension and spelling ability modulate the perceptual span of skilled adult readers during sentence
reading. Highly proficient reading and spelling were both associated with increased use information to the
right of fixation, but did not systematically modulate the extraction of information to the left of fixation.
Individuals who were high in both reading and spelling ability showed the greatest benefit from window
sizes larger than 11 characters, primarily because of increases in forward saccade length. They were also
significantly more disrupted by being denied close parafoveal information than those poor in reading and/
or spelling. These results suggest that, in addition to supporting rapid lexical retrieval of fixated words, the
high quality lexical representations indexed by the combination of high reading and spelling ability
support efficient processing of parafoveal information and effective saccadic targeting.
Keywords: Reading; Eye movements; Individual differences; Lexical quality; Perceptual span.
Skilled reading of text depends upon a dynamic inter-
action of low-level oculomotor and perceptual pro-
cesses with higher level lexical and comprehension
processing. Each of these sets of processes occurs, at
least to some extent, in parallel for both foveal and
parafoveal information. The question of precisely
how foveal and parafoveal information contribute to
skilled comprehension is central to current theories
of eye movement control in reading (see Radach &
Kennedy, 2013; Schotter, Angele, & Rayner, 2012,
for reviews). To contribute to further refinement of
these theories, the two experiments reported here
investigated whether and how individual differences
amongst skilled readers modulate the use of parafo-
veal information during sentence processing.
The reading perceptual span
Critical evidence about the use of parafoveal infor-
mation during sentence reading is provided by
investigations of the perceptual span: the area of
text from which information is extracted during a
single eye fixation. Evidence for the size of the per-
ceptual span comes from the gaze-contingent
moving-window paradigm (McConkie & Rayner,
1975) in which the reader is provided with only a
fixed window of text around their point of fixation,
which moves with their eyes; text outside the
window is masked. The size of the perceptual
span is inferred by determining the size of the
window at which the rate of reading is equivalent
to that achieved with a full line of text.
Previous research has established that, for skilled
readers of English, the perceptual span is approxi-
mately 3–4 character spaces to the left and up to
15 characters to the right of the point of fixation
(see Rayner, 2009, for review). The asymmetry of
the perceptual span is a function of the left-to-
right reading direction of English: In languages
Correspondence should be addressed to Aaron Veldre, School of Psychology, University of Sydney, Sydney, NSW 2006, Australia.
E-mail: [email protected]
#2013 The Experimental Psychology Society 703
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Vol. 67, No. 4, 703–727, http://dx.doi.org/10.1080/17470218.2013.826258
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such as Hebrew, where the normal direction of
reading is right to left, the span is asymmetric to
the left (Pollatsek, Bolozky, Well, & Rayner,
1981), and when English is read right to left, the
span asymmetry reverses (Inhoff, Pollatsek,
Posner, & Rayner, 1989). The perceptual span
for a particular language is also modulated by con-
current processing load and goals. Difficult foveal
processing is associated with a smaller perceptual
span (Henderson & Ferreira, 1990), and the per-
ceptual span extends further to the left before a
regressive eye movement (Apel, Henderson, &
Ferreira, 2012). Such evidence demonstrates that
the size of the perceptual span is, at least in part,
a function of cognitive/linguistic processes.
However, perceptual limitations on visual acuity
mean that the nature of the extracted information is
not uniform across the perceptual span (Rayner,
2009). The high spatial frequency information
required for letter identification is only available
within the foveal region (∼2 degrees; 7–8 characters
around fixation; Häikiö, Bertram, Hyönä, &
Niemi, 2009). The reduced visual acuity of the par-
afoveal region (2–5 degrees around fixation) only
allows extraction of low-level features, such as
word length, word shape, spaces, and beginning
letters (Rayner, 2009).
These differences in the nature of the infor-
mation extracted from foveal and parafoveal
regions lead to differences in the role that each
information source plays in governing decisions
about when and where readers move their eyes. It
is generally assumed that the linguistic information
extracted from foveal vision determines when to
move the eyes, while the low spatial frequency
information about word spacing and letter shape
extracted from the parafovea primarily determines
where to move the eyes (Schotter et al., 2012).
The distinction between when and where to
move the eyes is clearly somewhat arbitrary,
because a “where”decision to move the eyes to a
new location can be difficult to distinguish from a
“when”decision to terminate processing of a par-
ticular item. Nevertheless, consistent with neuro-
physiological evidence that separate neural
pathways control the temporal and spatial pro-
gramming of movement (e.g., Findlay & Walker,
1999), most models of eye movement control
assume that “where and when decisions can be con-
sidered separate dimensions of the reading process
with a small degree of overlap”(Schotter et al.,
2012, p. 13). Individual differences in the eye
movement patterns of skilled readers might arise
from either of these processes, or from interactions
between them.
Individual differences amongst skilled adult
readers
Research on eye movements, like other experimen-
tal psycholinguistic literature, has been dominated
by a tacit “uniformity assumption”(Andrews,
2012): that all skilled readers read in the same
way. Although there are a number of detailed com-
putationally implemented theories of reading that
have been systematically validated against empirical
data from eye-tracking paradigms (e.g., Engbert,
Nuthmann, Richter, & Kliegl, 2005; Reichle,
Rayner, & Pollatsek, 2003; Reichle, Warren, &
McConnell, 2009), the benchmark phenomena
used to assess the models consist primarily of
average data obtained from relatively small (n=
20–25) samples of university students. As elabo-
rated below, recent evidence from both single
word and sentence comprehension tasks has chal-
lenged the validity of conclusions based on
average data by demonstrating systematic differ-
ences in both word recognition and sentence pro-
cessing within samples of skilled, university
student readers (see Andrews, 2012, for review).
The extent to which eye movements during
reading are systematically mediated by individual
differences amongst skilled adult readers is also an
area of growing interest.
Jared, Levy, and Rayner (1999) found that more
skilled readers, as measured by the comprehension
subsection of the Nelson–Denny Reading Test,
made significantly shorter fixations than poorer
readers. There was also some evidence of differ-
ences in word identification processes between the
two groups, suggesting that poorer readers relied
more on phonological activation than better
readers. Further evidence of differences in reading
strategy were provided by Ashby, Rayner, and
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VELDRE AND ANDREWS
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Clifton’s (2005) finding that better readers, again
indexed by the Nelson–Denny Reading Test,
showed smaller frequency effects than poorer
readers in neutral sentence contexts and different
patterns of interaction between frequency and
context. While good readers showed additive
effects of frequency and context, poor readers
showed an interaction—stronger context effects
for low-frequency words over both target and post-
target regions of the sentence—suggesting that
they relied more heavily on context for word
identification.
More recent research, using a larger battery of
measures of verbal and cognitive skills to predict
skilled readers’eye movements during sentence
reading, found that word identification and tests
of rapid letter and digit naming (Wolf & Bowers,
1999) were the most robust and pervasive predic-
tors of both early and late eye movement measures
(Kuperman & Van Dyke, 2011). These results con-
verge with Ashby et al.’s (2005) findings in sup-
porting an interactive model of reading skill that
assumes that highly skilled reading relies on
rapid, autonomous lexical retrieval processes that
place minimal reliance on context for word identi-
fication and conserve attentional resources for com-
prehension (Perfetti, 1992; Stanovich, 2000).
The role of lexical quality in skilled reading
The view that optimally efficient reading relies on
autonomous, context-free lexical retrieval is con-
sistent with Perfetti’s (1992, 2007) lexical quality
hypothesis of reading skill, which attributes
highly skilled reading to the development of
“high-quality lexical representations”,defined by
their precision, redundancy, and coherence
(Perfetti, 2007). Orthographic precision refers to
the specificity and completeness of the information
stored in lexical memory about both the identity
and order of the letters defining a particular word,
which ensures that a particular written word
directly activates its lexical representation with
little interference from other similar words. High-
quality representations are also defined by strong
connections between these precise orthographic
forms and the word’s phonology and semantics,
so that presentation of a word triggers consistent,
redundant patterns of activity that yield coherent,
synchronous activation across the orthographic,
phonological, and semantic codes that define a
word’s identity.
According to this view, individual differences in
reading skill amongst adult readers arise from
differences in the average quality of readers’
lexical representations. Highly skilled readers have
fully specified lexical representations of most
words, enabling rapid, automatic word identifi-
cation, which supports effective comprehension
(Andrews, 2008, 2012). However, relying on
passage reading comprehension tests alone to
assess reading skill is not sufficient to identify
lexical quality. Reading comprehension is a necess-
ary but not sufficient predictor of lexical quality
because readers can use contextually based strat-
egies to compensate for their imprecise lexical
knowledge (Andrews, 2012). Spelling ability has
been suggested to provide the most reliable index
of lexical precision because it requires specific
word-form knowledge (Perfetti, 1992).
Although reading and spelling ability are quite
highly correlated in large samples of typical
readers (e.g., Malmquist, 1958), many competent
readers are poor spellers, even within university
populations (Andrews, 2012). Frith (1980) attribu-
ted this profile to use of a contextually guided
reading strategy that relies on “partial visual cues”
rather than “bottom-up”analysis of the full ortho-
graphic form of words required to develop high-
quality lexical representations.
Recent evidence from studies employing the
masked priming paradigm has shown that spelling
predicts unique variance in orthographic priming.
Andrews and Hersch (2010) showed that the
absence of masked priming from one-letter-differ-
ent neighbours for target words from dense lexical
neighbourhoods that is typically reported for
skilled readers (e.g., Forster, Davis, Schoknecht,
& Carter, 1987) is due to averaging the results of
good and poor spellers: Good spellers showed inhi-
bition from a higher frequency orthographic neigh-
bour prime (e.g., note NODE), whilst poor spellers
showed facilitation. These results suggest that the
precise lexical representations indexed by measures
of spelling ability support fast activation of the
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LEXICAL QUALITY AND EYE MOVEMENTS
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representations of briefly presented primes, which
rapidly inhibit orthographically similar represen-
tations, including that for the target word.
Andrews and Lo (2012) extended these findings
by showing that individuals with high spelling
ability relative to their level of reading comprehen-
sion and vocabulary showed stronger inhibitory
priming from transposed letter (TL) prime–target
pairs, which differ only in letter order (e.g., colt
CLOT), suggesting that they are particularly sensi-
tive to competition between the representations of
words that share all of their constituent letters. By
contrast, individuals with poor spelling relative to
their reading and vocabulary levels showed facilita-
tory priming from both neighbours and TL words,
suggesting that they are relatively insensitive to
letter order and benefit from sublexical overlap
between primes and targets. However, they do
not appear to activate the prime representations
quickly enough to trigger lateral inhibition of
similar words (Perry, Lupker, & Davis, 2008).
This evidence that masked orthographic
priming effects are modulated by spelling ability
implies that the speed of lexical retrieval is not
solely determined by the linguistic properties of
words, but depends on the precision of the
reader’s representations of these words. The broad
goal of the present research is to investigate
whether and how these differences in lexical
quality influence the information that readers
extract during sentence reading. As well as support-
ing rapid, autonomous retrieval of fixated words
(Ashby et al., 2005), precise lexical representations
might facilitate the extraction and use of parafoveal
information to “guide eye movements …to the
optimal viewing position for full-form word recog-
nition”(Kuperman & Van Dyke, 2011, p. 56). To
provide direct evidence about readers’extraction
and use of parafoveal information during reading,
we used the moving-window paradigm
(McConkie & Rayner, 1975), described earlier, to
investigate individual differences in the perceptual
span amongst skilled readers.
Individual differences in perceptual span
Developmental investigations of the perceptual
span have found that young children have smaller
perceptual spans than older children (Häikiö
et al., 2009) and adults (Rayner, 1986).
Underwood and Zola (1986) found no difference
in the size of the perceptual span between good
and poor fifth-grade readers. However, rather
than using the moving-window paradigm, they
estimated span by replacing particular letters in par-
afoveal vision.
There is a growing body of research investi-
gating the size of the perceptual span amongst
skilled adult readers. Kuperman and Van Dyke
(2011) interpreted their finding of differential
word length effects on gaze duration for poor rela-
tive to good readers as being consistent with skill-
based differences in the size of perceptual span.
More direct evidence using the moving-window
paradigm was provided by Rayner, Slattery, and
Bélanger (2010) who split their sample of skilled
adult readers on reading speed, assessed when no
moving window was present. They found that the
reading rate of slow readers reached asymptote
with a two-word-rightward window whereas the
reading rate of fast readers did not reach asymptote
with a three-word window. Similarly, Ashby, Yang,
Evans, and Rayner (2012) found a larger disruption
in silent reading rate with one-word than three-
word windows for fast than for slow readers.
However, whilst speed is certainly a component
of reading ability, fast readers are not necessarily
effective readers (Perfetti, 2007). Differences in
reading speed may also arise because some fast
readers adopt a lower comprehension threshold
and read in a careless fashion. Consistent with
this possibility, Hyönä, Lorch, and Kaakinen’s
(2002) investigation of individual differences in
reading strategy found that the fastest readers did
not produce better summaries of a text than
readers classified as “topic structure processors”,
who read the text significantly more slowly and
with more regressive saccades. The minimal com-
prehension requirements of the relatively simple
comprehension questions used in most eye-move-
ment experiments potentially encourage a fast,
careless reading style in sentence-reading tasks
(Wotschack & Kliegl, 2013).
Two recent studies provide evidence that
reading strategy may influence the perceptual
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