Eye Movements and Verbal Report in a Single Case of
Visual Neglect
Valerie Benson1*, Magdalena Ietswaart2, David Milner3
1 Psychology, University of Southampton, Southampton, United Kingdom, 2 Psychology, University of Northumbria, Newcastle, United Kingdom, 3 Psychology, University
of Durham, Durham, United Kingdom

Abstract
In this single case study, visuospatial neglect patient P1 demonstrated a dissociation between an intact ability to make
appropriate reflexive eye movements to targets in the neglected field with latencies of ,400 ms, while failing to report
targets presented at such durations in a separate verbal detection task. In contrast, there was a failure to evoke the usually
robust Remote Distractor Effect in P1, even though distractors in the neglected field were presented at above threshold
durations. Together those data indicate that the tight coupling that is normally shown between attention and eye
movements appears to be disrupted for low-level orienting in P1. A comparable disruption was also found for high-level
cognitive processing tasks, namely reading and scene scanning. The findings are discussed in relation to sampling, attention
and awareness in neglect.
Citation: Benson V, Ietswaart M, Milner D (2012) Eye Movements and Verbal Report in a Single Case of Visual Neglect. PLoS ONE 7(8): e43743. doi:10.1371/
journal.pone.0043743
Editor: Friedemann Paul, Charité University Medicine Berlin, Germany
Received May 22, 2012; Accepted July 24, 2012; Published August 24, 2012
Copyright: ß 2012 Benson et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: The research was supported by a UK MRC Cooperative Group grant (# G0000003) awarded to DM, the third author on this paper. The funders had no
role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
* E-mail: vb1@soton.ac.uk

level visuomotor manipulations. However, awareness for stimuli in
the neglected field can increase with PA techniques, but effects are
modulated by the categorical nature of the stimuli [14], and are
not observed in all cases. Forcing the eyes to scan the neglected
field does not guarantee increased awareness for whatever is under
inspection. There is also some evidence to suggest that although
‘neglect’ patients may be unaware of information on the left, they
may still process such information pre-attentively (e.g. [15]),
however this level of processing is insufficient for the information
to reach awareness, and hence it goes unreported (cf. the burning
house experiment, [16].
To date, evidence from eye movement studies has not
conclusively demonstrated whether neglect reflects a failure to
look at (sample) relevant information, or a failure to show
awareness for (perceptually process) relevant information in the
neglected field. Moreover, it remains unclear as to whether any
disjoints between sampling and awareness (‘looking’ and ‘seeing’)
lie exclusively in the domain of voluntary orienting, or whether the
reflexive orienting system is also impaired. This paper reports data
from a detailed examination of eye movements in P1, a single case
study of hemi-neglect. The aim was to examine awareness (as
tapped through verbal responses) and overt behaviour (eye
movements) to see whether P1 showed any dissociation between
conscious perception for stimuli and saccadic orienting to such
stimuli during lower-level oculomotor, and/or higher-level cognitive processing tasks.

Introduction
Unilateral neglect is a condition in which patients fail to respond
to, orient towards, or report, stimuli located on the side of space
contralesional to brain damage in the absence of sensory motor
deficits [1]. It is observed most frequently and is of longer duration
following damage to the right hemisphere of the brain [2],
resulting most commonly therefore, in the left side of space being
‘neglected’. The examination of eye movements should provide
insights into attentional and processing impairments in neglect
since there is a close relationship between eye movements and
cognitive processing (e.g., [3–5]) for many tasks.
Although hemi-neglect does not result from an inability to scan
the contralesional side of space, early work on eye movements in
this area showed deficits in making contralesional saccades (e.g.
[6–8]). These include multi-stepping hypometric (short) saccades
of long latency into the neglected field, failure to fixate upon visual
information presented in that field, and failure to report
information that may be successfully fixated, in the neglected
hemispace. These and later studies have provided evidence for
hyperattention to the ipsilesional side in neglect (e.g. [9–10]),
although hypoattention to information on the left has also been
argued to underpin neglect [11]. The effects of contralesional
distractors on the time taken to initiate saccades to targets
presented in ipsilesional space [8] has resulted in the suggestion
that an imbalance in the saccadic system can underpins neglect,
and this has received recent support [12].
Exploratory eye movements into the left side of space can be
increased following prism adaptation (PA), but without an increase
in awareness for stimuli in that space [13] suggesting that the
defining perceptual symptoms of neglect are unaffected by low-

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Case History
At the time of testing P1 was a 46-year-old left-handed male
who had suffered a stroke two months prior to recruitment, having

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detection rate for single left targets was still under 50%. During
bilateral presentation he reported right targets only at durations of
800 ms and above. P1 therefore presented with a clear neglect,
while the additional effect of extinction was quite small. See
Figure 2 legend, the figure shows P1’s responses on the verbal
detection task. These data were used in the next experiment to
examine whether stimuli presented in P1’s neglected hemifield had
to be presented at durations at which he showed some awareness
for in the verbal detection task, in order to program an eye
movement to those targets.

previously worked as a museum attendant. A CT scan (see Figure 1
legend) taken shortly after hospital admittance showed a large
(4 cm) intracerebral haematoma with haemorrhagic stroke in the
temporoparietal region of the right hemisphere. Screening of P1
was carried out six months post-stroke using a battery of subtests
from the Behavioural Inattention Test [17] including cancellation
tasks, line bisection tasks and scene copying that all showed that P1
neglected information presented in his left hemifield. Figure 1(a)
shows some of P1’s screening data, see Figure 1 legend.
P1 acted as a voluntary unpaid participant in the following
experiments. He had corrected to normal vision and was naı̈ve in
relation to the purpose of the investigation. Ethical approval was
obtained from the Newcastle Upon Tyne Hospitals NHS Trust
and written informed consent was obtained from P1 and control
participants.

Experiment 2: The Remote Distractor Task
The Remote Distractor Effect (RDE) is a robust low-level visual
effect whereby an increase in saccade onset latency (20–40 ms)
occurs when two possible targets are presented simultaneously
(rather than only one), and the task is to saccade to one of these
targets [19]. The RDE has been assumed to be an automatic
reflexive property of the saccadic system [20] and is believed to
result from activation in the fixation cells in the superior colliculus
[19]. Assessment of the RDE in P1 would show whether low-level
interactions in the saccadic system were normal for the presentation of contralesional stimuli. Although some work has been
conducted in this area (e.g. [8]; [21]), surprisingly the studies have
not attempted to manipulate attentional orienting. Using the RDE
paradigm we examined the effects of the prior allocation of
attention to either ipsilesional or contralesional space on saccadic
orienting in P1, and also evaluated whether there was any
dissociation between the saccadic orienting system and conscious
awareness (as indexed by the verbal detection task) for stimuli
presented in P1’s ‘neglected’ hemifield.

Experiment 1: Verbal Detection Task
The aim of the verbal detection task was to test how long stimuli
had to be presented in P1’s visual fields before he became
consciously aware of their presence. Simultaneous presentation of
one stimulus in each hemifield can result in detection of only the
stimulus presented in the right visual field (e.g. [18]) and is known
as extinction.

Method
Materials. Targets and distractors were small black solid
squares, approximately 0.6 degrees in size, set against a grey
background. The centres of targets and distractors were positioned
at 5 degrees to the left or right of the midline of the display. A
display with a black central fixation cross was created for inter trial
presentation to facilitate central fixation at the beginning of each
trial.
Design. A repeated-measures design with independent variables of Target Type (single left, single right and bilateral targets),
and Target Duration (50 ms, 100 ms, 200 ms, 400 ms, 800 ms,
1000 ms, 2000 ms, 3000 ms, 4000 ms and 5000 ms) and dependent variable of response accuracy was employed. P1 completed
one block of 180 trials in which a single target could appear either
on the right (56 trials, 8 per each duration) or the left (56 trials, 8
per each duration) of the screen, or, in the bilateral condition, two
targets appeared, one on each side of the display (56 trials, 8 per
each duration). Random presentation of the target types occurred
during the block along with 12 catch trials where no targets
appeared.
Procedure. P1 was positioned with his eyes in line with the
middle of the screen at a viewing distance of 57 cm. Following
each trial P1 had to verbally report what he had ‘seen’ by
responding, ‘one’, ‘two’ or ‘none’, and was aware that if he
reported ‘two’ this indicated that there was a target present on
each side of the display. Each trial was initiated following P1’s
verbal response to the previous trial.

Method
Eye movement recording. For the following experiments
eye movements were monitored using an Eyelink 1 video-based eye
tracker with spatial gaze resolution of ,0.5 degree. P1’s chin was
positioned in a chin cup to facilitate stable fixation and minimise
gross head or body movements during testing. Eye position was
sampled every 4 ms. Viewing was binocular, but only the
movements of the right eye were used for analyses. Stimulus files
were displayed on a 19-inch monitor at a viewing distance of
57 cm. Calibration was carried out by asking P1 to sequentially
fixate points on the display that covered the appropriate
dimensions for each relevant task. To calibrate in the neglected
field P1 followed the experimenter’s finger to each point and
remained fixating it until asked to move his eyes to the next one.
Materials. The same stimulus displays employed in the
Verbal Detection task were used for the RDE experiment.
Design. A repeated measures design was employed with
independent variables of Target Type (single left, single right and
bilateral targets), and Instruction for bilateral target presentation
(go left, go right, go to either, whenever two targets were presented
simultaneously). Dependent variables were saccade onset latencies
(the time taken to initiate a saccade from the onset of the trial
display) and directional errors (eye movements directed to the
target in the opposite direction to the task instruction). P1
completed three blocks of 180 trials in which a single target could
appear either on the right (60 trials), on the left (60 trials) of the
screen, or, in the bilateral condition, the target appeared with a
peripheral distractor positioned mirror symmetrically in the
opposite hemifield to the target (60 trials). Random presentation
of the target types occurred for all blocks.
Procedure. P1 was instructed to move his eyes to the target
as quickly and accurately as possible whenever a single target was

Results and Discussion
P1 responded ‘none’ on 100% of the catch trials, showing that
he was not simply guessing when making his responses. On target
present trials, at presentation durations of 1 s P1 detected 100% of
single right targets, 77% of single left targets, and 44% of bilateral
targets (reported both left and right). At durations of 3 s P1
detected 100% of single left targets and 90% of bilateral targets. At
durations of 400 ms and below, P1 detected 100% of single right
targets, no single left targets, and no bilateral targets. The verbal
detection task confirmed that P1 was unaware of single left targets
when these were presented for less than 400 ms. At 800 ms his
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Figure 1. (a) shows some of P1’s screening data for the line bisection, cancellation and scene copying tasks. (b) A CT scan of P1
showing the haematoma with bleeding, and the dark area anterior to it, which is the haemorrhagic stroke.
doi:10.1371/journal.pone.0043743.g001

occurred (9%), saccades started before 100 ms (11%), the eye
was off-centre (9%) at the onset of stimulus display.
Error data. Directional errors (19%) were excluded from the
analysis of eye movement onset latency. See Figure 3 legend. The
figure shows the proportion of saccades directed to the right or
the left for each of the three bi-lateral target instructions, and the
proportions of left and right saccades for all conditions, and
illustrates the error data. When P1 was instructed to go left on
bilateral target presentation he was unable to do this and instead
moved his eyes to the distractor on the right on 89% trials.
Additionally, in the condition where he was free to go to either
possible target, P1 moved his eyes to the right target on 88% of
trials. These data show that the attentional bias to the right visual
field shown by P1 appears not to be under voluntary control and
are similar to Van der Stigchel and Nijboer [12] who used a
variant of the RDE paradigm to examine oculomotor capture in
neglect. The error data support the theory that neglect involves
hyperattention to the ipsilesional field (e.g. [10]) rather than
hypoattention to the contralesional field [11].
Saccade latency analyses. Saccade latency was compared
in a two factor ANOVA with Target Type (single left, single right,

presented. In the case of two possible targets appearing P1 was
instructed as to which target to move his eyes to prior to each
block of trials. Each trial began with a central fixation cross for a
variable d of either 500 ms, 1000 ms or 1500 ms and simultaneous with the offset of this a target was presented for 1s, either in
isolation or with a distractor in the opposite hemifield, followed by
a blank screen for 1 s. We knew (from the verbal detection task)
that at this presentation duration P1 had some awareness for
targets presented in his neglected hemifield (70%) and for bilateral
targets (44%). A practice block (20 trials) preceded experimental
blocks with breaks taken on a request basis. In block A, P1 was
instructed to look to either target when two targets were presented;
in block B, P1 was instructed to look to the right target when two
targets appeared; and in block C, P1 was instructed to look to the
left target when two targets were presented.

Results and Discussion
Eye movement onset latency was detected automatically using a
velocity criterion of 30deg/s and each record was inspected
individually. Trials were removed (29% total) if signal loss

Figure 2. Shows the proportion of correct responses for the different types of target (single right or left or bi-lateral) against the
time each of these were presented for.
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Figure 3. Shows the proportions of saccades directed to left and right for the different conditions. Panel (a) shows the proportion of
saccades to left and right for each bi-lateral target instruction and panel (b) shows the proportion of saccades to left and right for all conditions.
doi:10.1371/journal.pone.0043743.g003

between Instruction and Target Type (F (4,315) = 1.40, p..24).
Table 1 shows the mean eye movement latencies and the standard
deviations for each condition. P1 showed a pattern of overall
slower saccades to single left targets, which has also been recently
demonstrated in another patient [12], and slower saccade
execution in the condition where he was instructed to saccade to
the left target when two targets were presented simultaneously.
RDE comparisons. To check whether P1 showed evidence
of implicit processing for stimuli presented in his contralateral
hemifield we compared the latency for the single target trials to the

bilateral) and Instruction for the bilateral presentation (go left, go
right, go to either) as independent variables. A main effect was
observed for Instruction (F (2,315) = 10.70, p,.0001), which
showed that latencies were longer for the look-left condition
(272 ms) compared to the look-right condition (220 ms) and the
uninstructed condition (208 ms). A main effect was also observed
for Target Type (F (2,315) = 59.10, p,.0001), which showed that
latencies were longer for the single left targets (313 ms) compared
to those for single right targets (187 ms) and saccades generated for
bilateral target presentation (200 ms). There was no interaction

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presented at durations of 400 ms, however, in the RDE task eye
movement recordings demonstrated that he was able to make
saccades to single left targets on approximately 70% of those trials,
and that the average latency for those saccades was 313 ms. This
means that P1 is capable of moving his eyes to targets for which he
shows no awareness for in the verbal detection task. Thus, we
think our findings suggest that the relationship between awareness
and saccadic orienting is disrupted for both the ipsilateral, and the
contralateral fields in P1 for low-level orienting tasks. Furthermore
in higher-level cognitive processing tasks, described below we were
also able to contrast awareness and eye-movement patterns within
the same tasks.

Table 1. The mean onset latencies and standard deviations
(in parentheses) for each condition for the RDE Experiment.

Mean saccade latencies for correct responses (ms)
Instruction for bilateral targets

Target Type

Go to
either

Go left

Single
Single Left Right

208 (86.95)

272 (125.48) 220 (90.04) 313 (114.24) 187 (66.41)

Go right

Bilateral
200 (75.41)

doi:10.1371/journal.pone.0043743.t001

latency for trials where a distractor was presented with a target, for
all conditions (see Figure 4 for the means). In the condition where
P1 was free to move to either target in bilateral presentation,
comparisons were made separately for bilateral trials where he
looked toward the right target and where he looked toward the left
target.
In the No Instruction condition single target-right latencies were
not significantly different from latencies to the right target in
bilateral presentation (F (1, 79) = 1.27, p = .264), and single targetleft latencies were not significantly different from latencies to the
left target in bilateral presentation (F (1,25),1). In the Instructed
right condition, there was no significant difference between
latencies for single right targets, and latencies for right targets
when a distractor was present in the left hemifield (F
(1,86) = 1.196, p = .277). Finally, in the Instructed left condition,
there was no significant difference between latencies for single left
targets, and latencies to left targets when a remote distractor was
present in the right hemifield (F (1,38),1), though the error data
showed that there were only a small number of trials where P1 was
able to do this making this comparison unreliable. Together, these
analyses suggest that independent of instruction type and saccade
direction, P1 showed no evidence of implicit processing of
distractors presented simultaneously with a saccade target.
P1 did not show the characteristic RDE effect when distractors
were presented in his contralesional hemifield, a finding consistent
with previous reports (e.g. [8]). The lack of a RDE in hemi-neglect
has been proposed to reflect the absence of competition between
fixation-neuron activity in the two superior colliculi that normally
occurs when two rather than one possible targets are presented
simultaneously [12]. Since the SC receives extensive direct
projections from the cerebral cortex on the same side of the brain
[22–23], large cortical lesions could be expected to deprive the
ipsilateral SC of substantial downstream facilitation effects. It is
important to note here that in the verbal detection task P1
reported awareness for bilateral targets presented in his left field
for durations of 1s on 44% of trials. Therefore, the failure to
observe a RDE in P1 occurred even though he would have been
consciously aware of the distractor in his neglected field on almost
half of the trials suggesting the possibility of a dissociation between
awareness for bilateral targets and P1’s saccadic orienting system.
The earlier work on the RDE in neglect has assumed unawareness
for distractors in the neglected field, hence explanations for the
lack of an RDE were thought to reflect an imbalance in the
saccadic system [8], but here we have shown a failure to elicit an
RDE in the presence of awareness for distractors. We think that
our findings do not reflect a simple imbalance in the saccadic
orienting system per se; rather, we think that the hyperattention to
the right shown by P1 (from our error data in this task) is also
responsible for the lack of an RDE.
In the verbal detection task P1 failed to report the presence of
single left targets in his contralesional hemifield when these were
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Experiment 3: Scanning of a Complex Visual
Scene
Patterns of saccades and fixations can reflect not only which
features of a display drive the eye movements for a given task [5]
but also how task instruction can modulate saccadic scanning for
the same stimulus. For example, the early work of Yarbus [24]
provided a compelling demonstration of how eye movements can
reflect the on-line cognitive processing during complex scene
inspection in healthy individuals. We used a modified version of
the Yarbus study [24] to investigate whether P1 showed evidence
of an ability to modulate his voluntary saccadic orienting in line
with different inspection instructions during complex scene
viewing.

Method
Materials and procedure. The Repin picture was downloaded from (http://www.abcgallery.com), and presented to P1
seven times, each presentation lasting 20 seconds. The same
inspection instructions as those used in the Yarbus study were
given to P1 on a trial by trial basis, and, in addition, the picture
was flipped in the horizontal plane such that the ‘unexpected
visitor’ appeared on the left for half of the trials, and on the right of
the picture for the other half of the presentations. P1 was informed
of this manipulation and was shown the picture in both
orientations prior to testing. Two additional inspections of the
Repin picture were also completed. In trial 8 the instruction was to
count the number of people in the picture. In trial 9 a previous
instruction was repeated, but the orientation of the picture was
switched such that the ‘unexpected visitor’ was on the opposite
side to the original presentation. Following each inspection P1
gave a verbal response and a transcript of these, along with order
of inspection instruction, and a record of the location of a critical
figure in each scene presentation is shown in table format in the
appendices (see Appendix S1). This information is also given for a
control participant (C1) with right brain damage and no neglect.
At the time of testing C1, a 61-year-old male had suffered a first
stroke three months previously. A CT scan revealed damage to the
right fronto-parietal region. Initial screening showed minor
evidence of neglect for drawings which recovered and which was
absent at testing for the Repin study.

Results and Discussion
Proportion of fixations and dwell time. Vertical calibration problems made it impossible to analyse the exact distribution
of fixations to specific objects in the scene on all trials. Therefore
sampling biases in P1 were examined by dividing the Repin
picture into four equal sections, far left (Region 1), left (Region 2),
right (Region 3) and far right (Region 4), where left and right refer
to the side of space from the midline of the picture, and comparing
the mean number of saccades made to, and the mean total time
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Figure 4. Shows the mean latency for eye movements executed in each of the bi-lateral target instruction conditions, for single
right and left saccades, and for saccades that were made when two possible targets were presented.
doi:10.1371/journal.pone.0043743.g004

of the saccades and fixations made during each trial display
showed that regardless of orientation, C1 fixated the ‘unexpected visitor’ in less than 2 seconds, whereas P1 fixated the
‘unexpected visitor’ within 2 seconds when he appeared on the
right of the display (first presentation) but took over 8 seconds
to fixate him when he appeared on the left, see Figure 5 legend.
Thus, despite consciously knowing the location of the critical
information based on previous alternating picture orientations P1
is unable to move to that information in the scene immediately.
Furthermore, for the inspection instruction ‘count the number of
people in the picture’ P1 reported that there were 12 people,
where in fact there were only 7. During this inspection P1 failed to
fixate the two children positioned on the far left, and so one,
tentative, explanation is that he multiplied the number of people
that he did fixate by two, and then added the two children that he
had ‘seen’ when they were presented in a previous orientation on
the far right of the picture. Movie clips of trials 7, 8 and 9 are in
Appendix S3 for P1.
This study has shown that P1 cannot easily modulate his
voluntary saccadic orienting in line with different inspection
instructions during complex scene viewing, and furthermore, the
data also reveal that for this high level cognitive task there is also a
dissociation between what P1 looks at (sampling) and what he sees
(awareness).

spent in each region, , see Figure 5 legend. Overall, the far left
region of the Repin picture was sampled less often and for less time
in P1 compared to the other regions, and compared to C1.
Scanpaths. Plots of P1’s scan paths during each inspection
(see Appendix S1) showed that he was able to scan and fixate both
sides of the picture, although there were occasions where he failed
to fixate relevant items/people in the scene. However, comparing
proportions of fixations and time spent in either half, or in smaller
sections of the picture says little about how the picture was
sampled over time.
Temporal analyses. A temporal analyses showed that
although P1 was able to scan and fixate the left half of the
scene, this was never done in an immediate way. For example,
during a free viewing inspection of the scene, P1 scanned the
right half of the picture for over 10 seconds before he began
inspecting the ‘unexpected visitor’ who was positioned on the
left of the scene in that trial. By contrast, C1 fixated this critical
figure in the same position and under the same inspection
instruction in less than 2 seconds. For another of the
instructions the display was presented in one orientation, and
later, it was presented again in the opposite orientation. For
these two presentations P1 and C1 were asked to ‘‘estimate how
long they thought the ‘unexpected visitor’ had been absent for’’.
A qualitative difference between P1 and C1 in the pattern of
saccades was observed for each viewing, and a temporal analysis

Figure 5. Shows the distribution of fixations and proportion of time, for the two participants, across the different regions of the
Repin picture. Panel (a) shows the amount of time and the number of fixations made to the four different regions of the Repin picture over the first
eight inspection instructions, for P1, and for a control participant C1. Panel (b) shows the amount of time and the number of fixations made to the
four different regions of the Repin picture for the final trial where one of the inspection instructions was repeated.
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towards the beginning of the sentence (e.g., a clause or phrase
beginning) that could potentially be the first word of each
sentence. Indeed, P1 was never able to locate the word at the
beginning of each sentence with his first fixation (P1 0%)
compared to the control (C2 100%), and on average across the
sentences, his first fixation landed on the fourth word (s.d. = 1.5) of
the sentence.
We also examined characteristics of P1’s fixation durations and
reading times in relation to the control participant. P1 had
significantly longer total reading times (mean 4.5s) for the sentence
than C2 (mean 3.2s) (t (1, 38) = 6.80; p,.001), however, his
average fixation duration during reading (mean 242 ms) did not
differ from that of C2 (mean 244), (t,1). Durations of fixations
during reading are largely determined by the ease with which a
word can be identified [3–4]. Thus, the average fixation duration
data suggest that P1 was perfectly able to lexically identify each of
the individual words of a sentence when he fixated them.
Together, the eye movement data suggest that the primary source
of difficulty was reading the text from left to right sequentially, i.e.
processing the words in their appropriate order, making it unlikely
that processing difficulty was linguistic in nature.
Word skipping usually occurs for short high frequency words
within the language, however, given that P1 often made many
regressive saccades as he searched for a leftward point in the
sentence from which to start reading, his skipping behaviour does
not resemble that observed in a typical reader. On average, P1
skipped 4.8 words in the sentence, as contrasted with 1.2 words
skipped by C2 (t (1, 38) = 9.35; p,.001). In other words, P1 failed
to directly fixate approximately a third of the words within a
sentence, contributing to his comparatively low comprehension
scores. We also computed the number of words P1 revisited, along
with the number of re-fixations he made on words overall (either
after a fixation on the same word, or after a fixation on a different
word). P1 made many more revisits to words (mean 4.8) than C2
(mean 1.3), (t (1, 38) = 9.90; p,.001), and many more re-fixations
on words (mean 9.7) than C2 (mean 1.6), (t (1, 38) = 12.40;
p,.001). Once again, the increased revisits and re-fixations that
P1 made as he read the sentence are entirely consistent with the
conclusion that he experienced significant disruption to cognitive
processing as he read the sentences. A similar tendency to re-visit
items is commonly seen in visuospatial search tasks in neglect
patients [28]. Table 2 shows the means and standard deviations for
the reading measures for both participants.
In normal populations readers systematically make a series of
left-to-right saccades from a starting fixation on the leftmost word
in the sentence until they fixate the final word in the sentence.
Although leftward saccades do occur, these are usually associated
with words or phrases that cause linguistic processing difficulty and
the overall pattern of saccades and fixations is influenced by a
variety of visual and linguistic variables (e.g. [4]). P1’s abnormal
pattern of saccadic orienting during reading shows that he is not
able to move his eyes using the optimal strategy; instead, in an
attempt to comprehend what he is reading, he makes repetitive
regressive saccades. Movie clips of P1 and C2 recorded while
reading one of the sentences where P1 answered the comprehension question incorrectly are provided in Appendix S3.
When P1 was asked to read a further twenty sentences out loud,
his accuracy was 50%. In the incorrectly read sentences P1 made
left word omissions (10%), mispronounced the left portions of one
of the words (5%), added words to the sentences (30%), and failed
to complete the sentences (10%). There were also long gaps, either
before beginning to read the sentences, or sometimes during the
reading of them. Together the reading data suggests that P1 is
unable to sequentially fixate the words in a sentence, and instead

Experiment 4: Text Reading
Neglect dyslexia describes errors made in reading where either
whole words or the left part of words are misread or omitted [25]
and hemi-neglect can result in this condition. Anecdotally, P1 has
reported that he is an avid reader of novels, but given that he
neglects information on the left, how is he able to accomplish this
task? We investigated whether P1 exhibited a normal pattern of
saccades for reading, and if not, whether he could nonetheless
comprehend what he read. Only one paper has examined eye
movements and text reading in neglect [26], and our experiment
provides the first eye-movement study of single sentence reading in
neglect to investigate whether scanning of the text corresponds
with comprehension.

Method
Materials and procedure. We presented P1 with 20
sentences, none of which exceeded a single line in length, one at
a time, positioned in the centre of a computer screen. P1 had to
read each sentence silently whilst his eye movements were
recorded, and following each sentence a comprehension question
was asked. The information needed to answer the question was
positioned on the far left of the screen (at the beginning of the
sentence) for half the sentences, and on the far right of the display
(at the end of the sentence) for the other ten sentences. See
Appendix S2 for the sentences presented paired with the relevant
comprehension question, and the transcribed response for P1.

Results and Discussion
P1 made no comprehension errors when the relevant information appeared towards the end of the sentence, but was correct on
only 50% of occasions when the relevant information was
presented in his neglected field. Based on the semantic content
of P1’s incorrect answers, it appears that he made inferences
related to those portions of the sentence he had actually read. For
example, the following sentence ‘The large tiger lay in the sun and
ignored the tourists taking photos’ was followed by the question
‘What ignored the tourists’? and P1 responded ‘people lying in the
sun’.
In the analyses of the eye movement data, as is standard in
reading studies (e.g., [4]), fixations lasting less than 80 ms and
greater than 800 ms were removed. Below we provide a broad
description of several eye movement measures where P1 differs
significantly from an age matched healthy control participant (C2).
Paired t-tests showed that the mean number of saccades from left
to right during sentence reading was greater for C2 (mean 10.7)
compared to P1 (mean 8.15); (t (1, 38) = 5.00; p,.001), whereas
the mean number of saccades from right to left during reading was
greater for P1 (mean 5.20) compared to C2 (mean 1.25), (t (1,
38) = 10.20; p,.001). Furthermore, the range in words (1–15) over
which P1 made right-to-left fixation shifts was reduced (mean
9.85), relative to C2 (mean 13.30); (t (1, 38) = 28.36; p,.001).
Clearly, P1’s saccadic movements during reading were markedly
different to those of the control participant, who showed a normal
reading pattern [27]. This finding might initially seem somewhat
counterintuitive, in that P1 made more leftward saccades, into his
neglected field, than the control participant. However, the fact that
P1 made so many leftward movements can explain why he did not
exhibit the typical sequence of left to right saccades during
reading. P1 made significantly more regressive movements back
through the sentence (mean 4.75), compared to C2 (mean 1.25); (t
(1, 38) = 9.89; p,.001) and these regressions appear to have been
made for two reasons; first, in order to re-inspect text that he had
already fixated, and, secondly, to allow him to identify a point
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Eye Movements and Neglect

accurately report information that has been looked at. Finally P1’s
eye movements for reading single sentences also show disordered
scanning coupled with an inability to correctly report visually
sampled information in his neglected field. Together the findings
indicate that in P1 there is a dissociation between the eye
movement sampling system and conscious processing of information that has been sampled, lending support to the notion that in
neglect the defining characteristic is not simply an imbalance in
the saccadic orienting system, as shown by the RDE study, but also
an inability to perceive information that has been sampled, as
shown by the scene inspection and reading studies.
Our findings from the P1 experiments do not fully support
Heilman’s [1] original definition of neglect, as the ‘‘failure to
respond to, orient towards, or report, stimuli located on the side of
space contralesional to brain damage in the absence of sensory
motor deficits’’. In particular, the failure to report a stimulus in the
neglected field is not necessarily coupled with a failure to fixate
that stimulus. Our data fit with recent findings showing that
rehabilitation techniques that ‘force’ low-level oculomotor shifts of
attention into the neglected field, e.g. prism adaptation [29] which
may affect dorsal rather than ventral pathways [30], fail to result in
any real improvement in perceptual awareness in neglect. As we
have shown with P1, a shift in gaze does not necessarily equate to a
perceptual shift.
In the introduction we proposed that the evidence from eye
movement studies had not conclusively demonstrated whether
neglect reflects a failure to look at (sample) relevant information, or
a failure to show awareness for (process) relevant information in
the neglected field. What appears to be disrupted in P1 is the tight
coupling that is normally shown between attention and eye
movements. For example, one can move attention to a new
location without moving the eyes (e.g. [31]), but it has been argued
that in normal populations moving the eyes to a new location is
usually accompanied or preceded by a shift in attention (e.g. [32])
to that location, when engaged in a task. This is not the case for
P1, and this impaired relationship between attention and eye
movements could account for P1’s ability to ‘look’ at information
without ‘seeing’ it. Future work with larger samples should aim to
test, experimentally, whether the lack of awareness for stimuli in
the neglected field results from disruption between the eye
movement orienting system and the attentional orienting system.
These two systems may be subserved by the same neural circuitry
(e.g. [33]) in normal populations, and they normally work together
in the visual selection process.

Table 2. The means and standard deviations for the reading
measures for P1 and the control participant C2.

Variable

Participant Mean

Std. Deviation

Number of fixations

P1

(2.09)

C2

13.4

(2.66)

Total time (ms)

P1

4500.

(447.21)

C2

3245.

(699.34)

Mean fixation duration (ms)

P1

242

(20.51)

C2

244

(37.28)

P1

4.75

(1.59)

C2

1.15

(0.67)

P1

8.15

(1.95)

C2

10.7

(1.17)

P1

5.2

(1.67)

C2

1.25

(0.44)

P1

4.75

(1.02)

C2

1.25

(1.21)

Number of words skipped

Rightward saccades

Leftward saccades

Number of words refixated

Number of refixations

Fixation range

18.6

P1

9.7

(2.45)

C2

1.55

(1.64)

P1

9.85

(1.69)

C2

13.3

(0.73)

doi:10.1371/journal.pone.0043743.t002

he appears to rely on holding individual words in memory
temporarily before mentally arranging them into something that
approximates a meaningful sentential interpretation, which he
then ‘reads out. In line with the two studies reported above, the
consistent finding from P1 is of a disjoint between what he is
looking at and what he actually perceives.

General Discussion
An important question concerning neglect relates to whether an
inability to ‘see’ something results from a failure to ‘look’ at that
something, which would indicate a deficit in saccadic orienting, or
whether information is ‘looked’ at but still not actually ‘seen’,
which would indicate a deficit at a higher level of perceptual
processing. We have tried to address these issues in this paper by
examining eye movements and verbal responses for both low-level
oculomotor control tasks and higher-level visuo-cognitive processing tasks.
It appears in the case of P1 that his low level reflexive orienting
system is intact, at least as shown by his ability in the RDE
paradigm to orient to single targets presented in his neglected field,
albeit with a slower latency than he is able to orient to targets in his
good hemifield. However he does not show the characteristic
RDE, and appears often not to ‘see’ the targets that he has looked
at as shown by his responses in the verbal detection task,
demonstrating a dissociation between awareness for stimuli and an
ability to orient to those stimuli reflexively in this very simple task.
The scene inspection findings reflect an inability in P1 to
voluntarily ‘look’ to information presented in his neglected field,
which he can overcome if he is made aware that crucial
information is presented there, but his default strategy is to
initially orient to information in his right visual field. Moreover, in
this higher -level task the sequence of eye movements should be
cognitively driven, and this is not the case for P1, who is unable to

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Supporting Information
Appendix S1 Shows a transcript of the verbal responses
for both participants along with order of inspection
instruction, a record of the location of a critical figure in
each presentation and the participant’s eye movements
overlaid for each inspection.
(DOCX)
Appendix S2 Shows the sentences presented, paired
with the relevant comprehension question, and the
transcribed response for P1.
(DOCX)
Appendix S3 Includes some movie clips for some trials
from the scene inspection and reading studies.
(DOCX)

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Acknowledgments

Author Contributions

The authors are grateful to both patients reported in this paper for their
generous cooperation, and to Dr Robert D McIntosh for his early input
and his later critical comments on a draft of the paper. A very brief
summary of some of this work was reported as part of a book chapter on
eye movements in special populations [34].

Conceived and designed the experiments: VB DM. Performed the
experiments: VB MI. Analyzed the data: VB MI. Contributed reagents/
materials/analysis tools: VB DM MI. Wrote the paper: VB DM MI.
Obtained the funding: DM.

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