Movements in Portrait Drawing
shortened version of this study appears in Leonardo, Vol.
34, No. 1, pp. 35 - 40, 2001
Miall, University Laboratory of Physiology,
Parks Road, Oxford OX1 3PT, UK
Tchalenko, Camberwell College of Arts,
Peckham Road, London SE5 8UF, UK
mental processes that allow an artist to transform
visual images - the sight of his model - into a picture
on the canvas are not easily studied. We report
here preliminary work measuring the eye and hand movements
of a single artist, chosen for his detailed and realistic
portraits produced from life. His eye movements
when painting or drawing were very different from
those when not painting, and also very different from
those of novice artists. His eye-hand coordination
pattern also showed differences from that of novices.
This work, alongside work measuring brain activity
in this artist and in novices, has recently been exhibited
at the National Portrait Gallery, London. It
suggests that detailed and quantitative analysis of
a working artist is feasible, and will illuminate
the process of artistic creation.
does a painter transform a vision of the external
world into a picture on the canvas?
Much work has been reported on aspects of
visual processes and on perception of finished
artwork (1), but surprisingly,
cognitive psychologists and art historians
have very little to say about the actual picture
production process (2).
An artist drawing a portrait from life, changes
his or her gaze many hundreds of times from
looking at the subject matter to looking at
the paper or canvas and back again. Less
often, longer periods will be spent just looking
at the sitter or at the emerging picture.
Clearly, this changing gaze is a fundamental
aspect of picture production, and a direct
consequence of the subject-to-picture transformation
taking place in the artist's brain.
There are two possible avenues for investigating
this process. The first involves a detailed
external observation of the artist
at work in order to determine exactly what
is being transformed into what, i.e.
to identify the precise input via the retina
and output via the hand. Ultimately,
of-course, the input is the vision of the
model and the output is the resulting picture,
but we shall see that the details of this
transformation are complex, and as such, revealing
about the process. For this, our main
study, we used an eyetracker, an instrument
that can accurately measure the artist's eye
movements, together with a movement sensor
recording the hand's movements, and close-up
video filming the emerging portrait.
During the preparations for this study, the
opportunity presented itself to use a fMRI
brain scanner to observe the artist's brain
activity while he sketched from photographs
of faces. In theory this would allow
a second avenue for our investigation, an
internal observation of the central
part of the transformation process that we
had set out to record externally with the
eyetracker and movement sensor. In practice,
because of the assumptions that have to be
made when interpreting fMRI data, and the
number of control experiments that need to
be performed, this part of our investigation
remained essentially exploratory. It was aimed
at finding out whether the approach could
be used meaningfully for drawing, and what
questions could be addressed in this way.
Nevertheless, some important interim
results have been obtained (3).
With the help of the eyetracker and brain
scanner, we set out to investigate how one
artist, Humphrey Ocean, produced pictures.
Humphrey paints or draws realistic portraits
from life, which means that both visual input
and manual output are observable to an outsider.
Other artists paint from photographs
or from their imagination, and may do so in
an abstract style, but for our purposes of
establishing a detailed case study from which
we later would be able to diversify, it was
decided to concentrate on the most directly
observable situation. Furthermore, we
already had an appreciable amount of data
on this particular artist.
Study: "Double Portrait"
few years prior to the present study, one of us (JT)
participated in an extensive project, Double-Portrait,
during which Humphrey Ocean was filmed nearly continuously
from the model's point-of-view (4)
while he was painting the camera operator and sound
recordist (Figure 1). The resulting
video material, apart from providing a wealth of observational
information, allowed approximate timings (5)
of the painter's gaze and body movements, and in this
way the key factors governing the picture production
process could be identified.
1: Double Portrait
Click image to enlarge.
first of these factors concerned the number of
times the painter looked at his model to acquire
the visual information. During a small,
20x30 cm, preliminary pencil sketch that was completed
in 12 minutes, he made 157 fixations on the model
(6) at a rate of 13 fixations/minute,
with an average fixation duration of 0.92 seconds.
For the final 130x100cm painting which was
completed in about 100 hours over 12 days, we
estimated that over 25,000 fixations had been
made on the model, with a typical rate varying
between 6 to 12 fixations/minute (after allowing
for pauses for mixing paints, adjusting canvas,
etc). Average fixation duration in the painting
case was slightly over 1 second although calculated
only over short episodes of 5 to 6 minutes. Restricting
our study at this stage to the drawing case alone,
the artist was interrupting his work about 12
times a minute to look at the model for about
1 second each time. Why did he not take
longer looks at his subject matter and then spend
longer periods reproducing it onto the canvas?
In trying to understand these timings, a fundamental
rhythm of the painter's movements became apparent.
Each glance to model was the first element
of a four-part cycle lasting a few seconds and
which, in its complete form, consisted of:
1. Looking at a specific detail of the model;
Turning towards the picture;
Drawing or painting the detail;
Looking at the picture.
After this, the cycle was repeated for the next
Steps 1 and 3 were the visual input and the manual
output stages. Step 2 could be thought of as the
main stage during which the brain processed the
eye-hand transformation although, obviously, brain
activity was taking place throughout the cycle.
Step 4 was when the painter evaluated the work
just done before starting a new cycle.
Depending on the type of drawing or painting and
its state of progress, not all these steps were
always present. Thus, from step 1 and 2
the painter could return to 1 without drawing
or painting anything, and after steps 3 and 4
the painter could return to 3 without glancing
again at the model. In very quick drawings,
the 4th step would not take place, or rather,
would take place during the actual drawing or
painting stage. In fact, there always was
some degree of overlap between one step and the
next, creating the fluidity of movement so beautiful
to watch in a painter at work. Finally,
for longer portraits, step 3 could be preceded
by a rehearsing action during which the hand practised
a line many times before committing it to the
paper, with the eye occasionally referring back
to the model. We shall return to this behaviour
the drawing or painting was finished, there were
often long periods of repeated 1-4-1 steps during
which the painter compared the model to the finished
picture. Interestingly, a similar behaviour
was also sometimes observed before starting, when
the painter seemed to "compare" the
model to the blank paper or canvas. Altogether,
however, the full 1-2-3-4 cycle was the norm.
Thus, Double-Portrait enabled us to rough out
the main elements of the picture production process.
However, in order to say more about the
visual input-manual output transformation we needed
to know more precisely what the eye was doing,
i.e. where it was focusing, for how long, and
what action the hand was performing in consequence.
For this we used an 'eyetracker' to record the
movements of the artist's eye during short periods
while he was drawing a portrait from life.
We also recorded his eye movements during selection
of the model from a group of four candidates,
and during a number of shorter portraits and sketches.
Some of the latter were done under strict
laboratory conditions so that we could more carefully
compare the artist's movements with those of untrained
eyetracker (the AlphaBio Eyeputer) is a specialised
video camera system mounted on a headset (Figure
2), and coupled to a computer. The infra-red
sensitive camera records a close-up image of the eye
while an image processing board within the computer
calculates the position of the centre of the pupil.
The headset also includes a second camera (the
'scene camera') filming the scene in front of the
head. Initially, the eyetracker must be calibrated
by asking the artist to steadily look at a set of
fixed targets in a defined grid. After this,
the coordinates of the each point in space that the
artist is viewing can be calculated in real time,
and displayed either as a cursor superimposed on the
scene camera image, or digitally stored on the computer
for detailed analysis.
2: The Eyetracker
Click image to enlarge.
For this project we combined these recordings
with those from a hand movement sensor (Polhemus
Fastrak motion analysis system), so that we could
also follow the movement of the artist's pencil.
This device records the 3D position of a
lightweight marker, attached to the artist's hand
or pencil (7), with the data
also digitally stored on the computer for later
analysis. While these eye and hand movements were
being recorded, the drawing's progress was filmed
continuously with a close-up video camera.
prime consideration throughout the project was
to obtain data about an artist at work, rather
than an artist performing scientific tests.
One of us (JT) had been filming Humphrey over
a number of years in a non-interventionist style,
and had devised with the artist a routine that
allowed him to proceed as normally as possible.
As Humphrey was also well practised in drawing
under difficult conditions, e.g. from moving cars
or aeroplanes, the eyetracker did not constitute
an undue hindrance.
Our observations were made as follows:
Selecting a model
artist, wearing the eyetracker, sat facing an
empty chair, and was presented one by one with
four persons whom he had not seen before.
The duration and location of his initial fixations
during the first few seconds were recorded in
order to establish what he was looking for in
a prospective model.
artist then wished to make brief sketches of his
candidate models to help him in his selection.
He drew in ink in a small sketchpad held
in his left hand, each sketch lasting 1-2 minutes.
Because of the difference in viewing distance
between eye and model versus eye and sketchpad,
these eyetracker results were used only to study
fixation timings on the model.
3. The main portrait
Having chosen his model, the eyetracker
system was set up on the following day to allow
recording of the artist's right eye, as he sat
with a near-vertical drawing pad positioned on
an easel about 45cm in front and to the left of
his head. The model sat just to the right
of the drawing pad, at the same distance, so minimising
parallax errors in the video recordings made from
the scene camera. The eyetracker was calibrated
and used for about 10-15 minutes each hour, and
the artist then worked normally without the eyetracker
for the next 30-40 minutes, while the model and
artist rested for the remaining 10-15 minutes
per hour. Thus 5 recordings were made, spanning
the entire process of the portrait drawing.
Humphrey's drawings were all life-size.
For the third and fifth session, we placed a motion
tracking monitor on the back of the artist's hand,
such that the position of the pencil could be
calculated with an accuracy (8)
of about 10mm, but with a resolution of about
1 mm. This provided a record of the spatial
location of major hand movements and also a record
of the timing of all hand movement.
The following day, 3 short portraits were performed,
two of a different subject and the third a self-portrait
made using a mirror. These drawings were
aimed to take about 10 minutes each, so that the
eyetracker could be worn throughout the entire
process. In fact, the second drawing took
just under 12 minutes, while the self-portrait
was completed in 22 minutes.
For each, a motion tracker was attached to the
shaft of the artist's pencil, allowing him to
use the pencil comfortably, but increasing the
spatial accuracy of the recording of the pencil
tip to about 2mm, again with a resolution of 1mm.
Comparison with untrained subjects
Some weeks after the detailed study, a series
of very brief sketches were made by the same artist,
and by three untrained subjects. Each subject
sketched from a black and white photocopy of a
face (9), and was restricted
to 1 minute per sketch. Again, both eye gaze and
pencil positions were recorded.
Selecting a model
As each candidate in turn entered the
scene camera's field of view, and sat down, Humphrey
had already fixated on the person's left eye.
He then proceeded with a number of rapid fixations,
each lasting an average of 0.4 seconds, until
his eye came to rest temporarily with a longer
fixation of about 1 second (Figure
3: The four candidates
Click image to enlarge.
the last candidate, Nick (subsequently selected
as the model for the main portrait), these first
fixations were essentially confined to the person's
eyes (10). In this case,
as in most of Humphrey's portrait work, empathy
with the subject was the artist's overriding consideration.
It suggests that his eye movements during the
first 2 to 4 seconds were governed by a first
time encounter with a new face rather than by
any professional consideration. This high
rate of fixations, about 140 per minute, was also
seen when Humphrey viewed portraits produced by
others, and when viewing his own completed works.
It is typical of the eye movement rate reported
by others (11).
rate and duration over the four sketches were
remarkably consistent (Table 1). Overall average
fixation duration on the model was 1 second, and
the rate just under 22 fixations/minute.
duration of drawing (minutes)
of fixations on model
fixation duration (seconds)
1. Humphrey Ocean's eye fixations on the four candidate
models during brief pen sketches.
The main portrait.
data collected by the eyetracker can also be usefully
viewed as a time series which emphasises the temporal
pattern of eye movement (Figure
4). In the figures that follow, we have used
the spatial location of the eye's gaze to colour
code the time series, with the convention of lines
shown in blue denoting the eye looking at the
model, and in black, at the paper. Blinks, which
hide the eye's pupil from the eyetracker camera,
appear as vertical lines.
Click image to enlarge.
Humphrey's eye movements adopted a regular rhythm
from the beginning of Nick's portrait (Figure
5). For the first 35 seconds (Figure
5a), he scanned the blank paper occasionally referring
back to the model, suggesting that a visualisation
process was operating. He then started with
Nick's right eye (12), immediately
falling into a pattern of regular fixations on
the models face, each lasting about 0.6-1.0 seconds,
at a rate of about 12 per minute. During
the five hours it took to make Nick's portrait,
a total of about one hour was spent looking at
the model, capturing each detail in epochs lasting
about one second, the eye going directly to its
intended target to "lock" onto it in
a single stable fixation. One of the first
continuous lines Humphrey drew (at 55 seconds)
was a 4.5 cm contour of the model's eyebrow (marked
5,6,7 in Figure 5b). While drawing this line,
he stopped the pencil twice to glance back at
the model, suggesting that his eye was capturing
about 1.5 cm of detail per fixation. The
drawing of the right eye proceeded for about 1
hour with the accumulation of such small marks.
Click image to enlarge.
subtle variations of this basic pattern were observed
over the five-hour period. In Figure
6, we show 3 two minute segments of the process,
the upper panel being the start of the session,
the central panel occurring 1 hour later as he
drew the hair, and the bottom panel taken during
the 3rd hour as he drew the lips. Notice
the long fixations on the model at the start (the
first minute); the very rapid sequences as he
was drawing the hair and the regular and spaced
sequence as he was drawing the lips. These
differences suggest that there may be a consistent
relationship between the complexity of the visual
object being viewed and the viewing pattern.
In particular, when considering the spatial location
of the sweep of the hair, rapid comparison of
the model and the paper was made. When adding
detail to the already partly drawn lips, a regular
cyclic process of visual capture and then drawing
took place. The eye frequently returned
to the same location on the model (13),
at a rate that would indicate visual memory being
refreshed on average every 5 seconds.
the end of the session, an increasing number of
fixations on the model were being replaced by
fixations on the partly completed drawing.
Click image to enlarge.
made a detailed analysis of the hand movements during
one period when Humphrey was drawing the model's lips
(Figure 7). As for the eye
movement data, the motion of the pencil is presented
as a time series to emphasis its temporal profile.
We observed two interleaved movement cycles. The
first, with a period of about 20 seconds, when Humphrey
raised his hand from his lap to position the pencil
close to the paper, and drew and/or practised, and
then lowered his hand again to his lap. The
second, with a period of about 5 seconds, when he
fixated one detail on the model for 1 second, and
then fixated one or more positions on the paper as
he drew that detail. The precise timing of these
movements requires more exploration, but we would
point out one key feature: as Humphrey raised his
arm to begin a new drawing epoch, his eyes would fixate
the model at the moment the pencil approached the
paper (Figure 7, panel 1). This is likely to
be a strategy to provide the most recent visual input
before making an accurate hand movement. It
is part of the overlap between the different steps
of the painting cycle first seen in Double-Portrait.
Click image to enlarge.
Another observation highlighting the complexity
of the drawing process is shown in Figure 7, panel
2. When Humphrey started on the lips, the
model's left eye had already been completed, but
something was obviously not to the artist's satisfaction.
He therefore momentarily interrupted the drawing
of the lips to return to the eye. There
he traced the drawn eye in a smooth cyclic pattern,
at a rate of three cycles per second, with the
pencil tip held just over the paper's surface.
These fine movements of the pencil tip were followed
precisely by Humphrey's eyes, in a smooth movement
(14). Remarkably, however,
no mark was ever made on the paper, and he eventually
returned to continue the drawing of the lips.
The drawing of the lips was also frequently accompanied
by such practice strokes (Figure
8). The pencil would move several times
just above the paper's surface, gradually defining
the line before it was eventually drawn.
Occasionally, the eyes would look away with a
rapid fixation to the corresponding detail on
the model, or even to another part of the drawing,
before returning to follow the pencil tip. We
suggest that the purpose of this behaviour is
to aid in the control of the pencil. Practice
movements are seen in many tasks and sports requiring
skilled movement, and probably allow the brain
to refresh a short term 'motor memory' of how
the body moves (15). In
other instances, the practice also resulted in
very faint pencil marks being made on the paper,
suggesting that they also aided in deciding on
the exact form the final pencil line should take
(16). The differences
between these two movement types, practice and
drawing, were so slight (probably less than 1mm
from the paper surface) that our tracking technique
could not separate them and close-up video was
required for their study.
Click image to enlarge.
previous sections have shown that our methods
allow detailed analysis of the movement of
the eye during drawing and that there were
clear patterns of behaviour of arm and eye
movement that were maintained, with subtle
changes, throughout the five hour period.
However, during discussion with the artist,
it became clear that the intermittent test
sessions imposed an unnatural break to his
normal routine. We therefore agreed
that he would produce a portrait within a
shorter period (although without forcing a
specific finishing time), allowing us to monitor
eye and hand movement throughout, without
recalibration of the headset, and without
any pause in his work. Figure
9 shows the complete record of eye and
hand movement during an 11.5-minute drawing
referred to as Luke 2. Here one can
see the very rhythmical sequence of eye movements
between the paper and the model, while the
upper record shows a similar pattern of hand
movement to that seen in Figure
7. The only significant difference
here is that the rest periods of the hand
were less frequent, his hand dropping about
once per minute. This may have reflected
the increased time pressure compared to the
previous, longer portrait. In the eye
movement trace, the steady pattern of fixations
on the model is again clear, with an average
rate of 13 per minute, although for brief
periods, e.g. at 5.3 minutes and 8 minutes,
the rate increases. As before, it seems
likely that this very rapid comparison of
model and drawing was made in order to assess
the correct spatial arrangement, as each case
was followed by the drawing of a new facial
feature (the right eye at 5.3 minutes, the
lips at 8 minutes). The slower and steadier
sequences were seen when drawing the finer
details of each feature.
Click image to enlarge.
Figure 10 shows the completed
drawing, and the corresponding spatial record
of the pencil tip movement. There must of course
be a close correspondence between these two, but
the differences reflect both the large scale motion
of the pencil to and from the paper, indicated
by the red segments of the line, while the differences
between the black lines and the final drawing
reflect the practice movements of the hand that
were not committed to paper.
Click image to enlarge.
Comparison with untrained subjects
we present the preliminary comparisons that we
have made between the behaviour of the artist,
Humphrey Ocean, and three novices. Here
we imposed a time limit of 1 minute per sketch,
and also requested the subjects to copy photographed
faces, although neither of these is typical of
Humphrey's style. Figure
11 presents histograms of the distribution
of eye fixation durations on the 'model' (the
photograph). The artist's fixation duration
0.6-1.0 second was typical of durations recorded
previously. The novices' durations were
about half as long. Furthermore, the artist's
fixations were always single, whereas the novices'
were generally multiple. So the artist locked
his gaze onto a single position, apparently taking
in a single detail, while the novices fixated
2 or more positions, sometimes spatially quite
separate. The briefer and less consistent
fixation durations of the novices were more typical
of everyday eye movements, and more typical of
Humphrey's fixation pattern when not drawing or
Click image to enlarge.
seems possible that there will be a graded pattern
of eye movement that correlates with drawing skill.
The most fluid and accurate drawing of our three
novices was made with the more consistent, longer
duration eye fixations of the model, the least accurate
made with the least consistent eye movement pattern.
However, we will require more tests to confirm
principal finding from the eyetracker study of Humphrey
Ocean at work was that his eye movements while drawing
a portrait were different from his normal eye movements.
While drawing, he made a sequence of regular
single fixations on selected details of the model's
face. Each fixation lasted about 1 second and
was repeated at a rate of about 12 fixations/minute.
In Table 2 we can see that these timings characterised
this artist's normal working rhythm, although for
the very short sketches he would refer back to the
model twice as often. Interestingly, even in
this latter case, the fixation duration that governed
the visual input of information remained quite constant
at 1 second or just under.
- main portrait (pencil)
2 - secondary portraits (pencil)
(st. dev. 0.47)
photo sketches (pencil)
2: Humphrey Ocean's average fixation timings while
drawing a portrait.
contrast, while selecting his model, looking around
the room or viewing paintings, Humphrey's eye
movements followed a pattern of rapid fixations,
each lasting about 0.3-0.4 seconds and repeated
at a rate of about 140 fixations/minute. We refer
to this pattern as his "normal" eye
movements. The untrained subjects we tested, when
asked to draw, did not show this change in eye
movement behaviour from their normal pattern.
In between fixations on his model, Humphrey would
look at his drawing with shorter, more rapid fixations,
or, alternatively, with smooth movements which
followed the pencil tip across the paper. Such
co-ordination between eye and hand was most dramatically
illustrated by the practice sequences when the
pencil stroke was preceded by a rehearsing action
just off the paper's surface.
changing his gaze from picture to model, or model
to picture, Humphrey's fixations unhesitatingly
found, and "locked" onto, the minute
detail he was targeting. This behaviour was in
sharp contrast to that of the non-artists subjects
then does a skilled painter transform a vision
of the external world into a picture on the canvas?
The following five remarks help situate
our observations of Humphrey Ocean in the more
general context of his way of working.
12: Portrait of Nick
Click image to enlarge.
1. The capture of visual information detail by
detail, rather than in a more holistic manner,
is reflected in the way the drawing or painting
is built up. This proceeds systematically,
by small geometric areas, gradually building up
to the picture's main elements: right eye, left
eye, nose, lips, etc. Each detail and each element
is of intrinsic importance. In the artist's
own words: "The shape you are putting
down is always abstract. (
) That next rhomboid
is the side of the nose - or it is an abstract
shape. Each bit of the picture has to be able
to exist in its own right. Even if there was none
of the rest of the painting, if you put that bit
down, it would work."
2. The artist's actions are essentially driven
by the picture's progress - they are goal oriented
rather than, as in his first encounter with his
candidate models, stimulus controlled. Thus
his next glance at the model is for the purposes
of advancing whatever he is drawing at the time.
Such behaviour is quite different from the normal
way of perceiving a face or a painting. Perception
and cognition studies made in other areas, such
as face recognition or the viewing of art, will
not necessarily be relevant to the production
3. The artist's eye and eye-hand skills are definable
in terms of physiological parameters: fixation
stability, fixation duration, targeting efficiency,
etc. As they are not found in untrained
subjects, one may assume, at this stage at least,
that they are acquired through training and practice,
i.e. they are not innate. Furthermore, with
Humphrey, they are put to the service of precision.
"If it (the line) lands a millimetre to
the right or a millimetre to the left, it changes
the weight, in some way, of the shape that it
is describing. So when that line lands, you just
want it to land in the right position, whatever
4. Nevertheless, the eye and eye-hand skills alone
cannot define the picture production process.
Other artists working from life in Humphrey's
style have similar skills and goals, yet, if asked
to draw the same model, would produce entirely
different portraits. The reason for this
is not how they draw, but what they draw.
There are very few lines in a portrait that represent
actual lines on the face: a few wrinkles and perhaps
a few contours. The rest are subtle demarcations
between areas of different light intensities,
texture differences and colour changes.
Take for example the many lines drawn at the inner
corner of Nick's right eye (Figure
12). Not only are their precise locations
on the model's face subjective to each viewer,
but for the artist, they also depend on what he
wants to do with them. At the end of Double-Portrait
Humphrey remarked about my hands that he had just
painted: "I'm sure of what I am seeing,
I'm not quite sure what I am going to do about
it. So I make a decision. The final
result is made up of a great many decisions."
The artist's skills allow him to draw with
precision whatever line he chooses; the choice
of line is determined by other factors.
5. The last observation centres on this choice:
"At any given moment I will start from
what I can see from where I am. I try to
achieve a likeness. But what I want is a
likeness to the reaction I have to something I
can see". Undoubtedly Humphrey's
reaction is dominated by the visual input to his
retina. When he is doing a portrait, his
vision concentrates nearly exclusively on the
model and the canvas. It is this vision
that we have investigated with the eyetracker.
But with Humphrey, as with other painters,
sound and smell are also very important, as are
thoughts, preoccupations, memories of other portraits,
even what he had for lunch, that tooth-ache, and,
of-course, his artistic ambition at that precise
moment in time.
are due to the Wellcome Trust for support of Dr
Miall's research and for a Sci-Art grant to the
- a head mounted device used to record eye
movement, by providing a close-up video image
of the pupil of one eye.
motion analysis system. A device comprising a
very weak electromagnetic transmitter mounted
on a table top, and a small lightweight receiver
mounted on the moving object, capable of recording
the position and angle of a moving object within
a sphere of about 90 cm radius.
- the eye moves most commonly in brief jumps,
saccades, each lasting about 100ms. In between,
the eye steadily views a single gaze position
(or if the target is moving, a single object).
- functional magnetic resonance imaging.
A technique to measure small changes in blood
oxygen levels, that allows estimation of brain
activity because of a close coupling between increased
neural activity and increased blood flow to that
area of the brain.
position - the position on the visual scene
viewed during a fixation. In these experiments,
we consider gaze position to include a single
visual detail, although we cannot access by measuring
eye movements alone how much peripheral visual
input is also captured.
- the smallest observable movement of the eye;
this is smaller than the spatial accuracy, as
only the relative movement of the gaze position,
and not its true position, is measured.
- the rapid motion of the eye from one position
to another, usually lasting between 50 and 150
milliseconds, and typically occurring 2-3 times
accuracy - the accuracy with which gaze position
can be calculated, with respect to the actual
Reviews of existing literature may be found in P.J.
Locher (1996) "The contribution of eye-movement research to an understanding
of the nature of pictorial balance perception: a review of the literature"
Journal of the International Association of Empirical Studies
14(2): 143-163; C.F. Nodine, P.J. Locher and E.A. Krupinski (1993)
"The role of formal art training on perception and aesthetic judgment
of art compositions" Leonardo 26(3): 219-227; R.L. Solso
(1994) "Cognition and the Visual Arts" MIT Press, p. 294. Back
Recent contributions include J. Fish and
S. Scrivener (1990) "Amplifying the mind’s eye," Leonardo
23 (1): 117-126; V.J. Konecni (1991) "Portraiture: an experimental
study of the creative process," Leonardo 24 (3): 325-328;
C. Frith and J. Law (1995) "Cognitive and physiological processes
underlying drawing skills," Leonardo 28 (3): 203-205; D.J.
Cohen and S. Bennett (1997) "Why can’t most people draw what they
see?" Journal of Experimental Psychology, Human Perception and
Performance 23 (3): 609-621. Back
See R.L. Solso, "Cerebral
activities in an expert versus a novice artist: an
fMRI study" Leonardo (Spring 2001). Back
See J. Tchalenko (1991)
"The making of Double-Portrait," Dulwich Picture Gallery,
To an accuracy of 1/25th second,
although the start and end of each eye movement were
difficult to determine with precision. Back
Strictly speaking, we could
only be sure at this stage that the artist was
looking at his model, an action that we termed
"glance". However, subsequent eyetracker
work with Humphrey showed that, virtually without
exception, each of his glances was made up of
a single fixation, and we can therefore anticipate
here by using the term fixation. Back
With Humphrey, pencil, hand
and often also his arm move as a single unit.
Thus, the spatial location of the pencil tip can be
determined from a marker placed on the back of his
hand, as there is little movement between pencil and
for explanation. Back
Ekman P. (1972) Emotion
in the human face: guidelines for research and an
integration of findings. Pergamon Press, New York,
Yarbus AL (1967) Eye movements
and vision. Plenum Press, NY. Back
See Yarbus (1967); Carpenter
RHS (1988) Movements of the eyes. Pion Press, London;
Henderson JM and Hollingworth A (1999) "High-level
scene perception"Ann. Review Psychol. 50: 243-271.
Humphrey nearly always starts
a portrait with an eye, working outwards to the rest
of the face. Back
The eye’s fixation point
could be estimated to about 2 degrees, under these
conditions. The fovea, the region of highest
spatial acuity on the retina, is about 0.5 degrees
in diameter. Hence we cannot be certain that
the eye was actually fixating the exact detail twice,
but this seems likely, given drawing of the same part
frequently followed each fixation. Back
The human eye makes 5 main
types of eye movement. We mainly considered
the rapid shifts of gaze known as saccades (Dodge
R, 1903, Am. J. Physiol. 8: 307-329) which are typical
of voluntary eye movement across a scene. However,
the eye can also smoothly track a slowly moving target,
to maintain the target image steady on the retina.
In the cases observed here, we believe that the smooth
tracking may be a combination of smooth pursuit of
the moving pencil and smooth eye movement compensating
for small head oscillations (less than 0.6 degrees
maximum) synchronous with the hand movements. Back
Human Motor Behavior. edited by JAS Keslo
(1982) Lawrence Erlbaum Assoc. Hillsdale, NJ, London; Schmidt RA
(1991) Motor learning & performance: From principles to practice.
Human Kinetics Books, Champaign, IL. Back
was that he would draw the line only once he could
"see" it. Back