1. VISUAL ATTENTION
Satu Ilta
Anna Kalme
Dan Qin

2. Agenda
1. What is visual attention?
2. Pre-attentive perception
3. Focus
4. Saccades
5. Fixation
6. Tunnel vision
7. Conclusions

3. Experiment
There is only so much the brain can process at a particular time

4. What is visual attention?
• Our brain cannot process everything, so we must attend to something
to be able to act upon visual input
• Four types of seeing with different levels of attention
( from Wolfe j. Visual attention In: De Valois KK, editor. Seeing. 2nd ed. San Diego, CA: Academic Press; 2000. p. 335-386)

5. Example of change blindness
Our visual memory is not as accurate as we might think

6. PRE-ATTENTIVE PERCEPTION

7. Pre-attentive perception
• The unconscious accumulation of information from the
environment.
• All available information is pre-attentively processed. Then,
the brain filters and processes what is important.
E.p We are hardwired to be able to notice color changes in our
environment, and not just consciously, but without thinking.

9. FOCUS

10. Focus
• Retinal cone cells are packed tightly in a small region called fovea.
• The fovea is only about 1% of the retina, but the brain’s visual cortex
devotes about 50% of its area to input from the fovea.
• Information from the visual periphery is compressed (with data loss)
before transmission to the brain, while information from the fovea is not.
• All this causes our vision to have much greater resolution
in the center of our visual field than elsewhere.
On a digital camera’s photo sensor, photo-receptive
The spatial resolution of the human visual field drops greatly from the center to the edges. elements are spread uniformly in a tight matrix, so the
spatial resolution is constant across the entire image
frame. The human visual system is not like that.

11. Test
• Hold your arm straight out and look at your thumb.
• Your thumbnail, viewed at arm’s length, corresponds approximately to the
fovea.
• While you have your eyes focused on the thumbnail, everything else
in your visual field falls outside of your fovea on your retina.
The resolution of our our visual field is high in the center but much lower at the edges.

12. SACCADES

13. Saccades
• Why do we then see our surroundings sharply and clearly all around us?
• We constantly make eye movements – saccades – to focus our fovea.
• These saccadic movements are frequent, between two and five
jerky movements per second.
• During the course of a saccadic eye movement,
we are less sensitive to visual input than we normally are.
Our eyes move rapidly and constantly about three times per second even when
we don’t realize it, focusing our fovea on selected pieces of our environment.

14. Implications 1
• Everything on the screen that is not within 1–2 centimeters of the click
location is in peripheral vision, where resolution is low.
• This why software and Web site users fail to notice error messages.
• Common and well-known methods for fixing this:
• Put it where users are looking
• Mark the error
• Use an error symbol
• Reserve red for errors
• Use sound (e.g. beep)
• Flash or wiggle briefly

15. Implications 2
• We use words focus and periphery in every day speech
• Peripheral vision integrates us with space, Architectural and
while focused vision pushes us out of the space urban settings of
our time tend to
• In editing movie clips (especially) with motion
make us feel like
outsiders,
in comparison
• UFOV = Useful field of vision with the forceful
emotional
engagement of
natural and
historical settings.
UFOV: The area from which one can extract visual
information in a brief glance without head or eye
movement. The limits of this area are reduced by
poor vision, difficulty dividing attention and/or
ignoring distraction, and slower processing ability. End of a clip Start of a new clip

16. FIXATION

17. Fixation
• Fixation or visual fixation is the maintaining of the visual gaze
on a single location.
• Humans (and other animals with a fovea) typically alternate
saccades and visual fixations, the notable exception being in
smooth pursuit, controlled by a different neural substrate
that appear to have developed for hunting prey.
• Contrary to the old view, fixations are not simply the absence
of eye movement; they are made up of much smaller
movements. This is because should your eye be truly still,
you would not actually be able to see as no neurons would
fire.

18. After a few seconds, the image on the retina fades, thus showing
that eye movements are needed to maintain visibility; there are
three types of eye movements that support fixations.
• Micro saccades
a miniature saccade, a movement that corrects ocular drift
and prevents fading. They are small, jerk-like, involuntary eye
movements, similar to miniature versions of voluntary
saccades.
• Ocular drifts
are slow, random eye movements that drift away from the
target of interest, and are said to be a consequence of neural
noise.
• Ocular microtremor
are high frequency tremors of the eye, constant during the
fixation period.

19. Heat maps of individual fixations

20. Fixation implications
Users won't read your text
thoroughly in a word-by-
word manner.
The first two paragraphs
must state the most
important information
Start subheads,
paragraphs, and bullet
points with information-
carrying words that users
will notice when scanning
down the left side of your
content in the final stem of
their F-behavior.

21. Tunnel vision
• Useful field of view = the size of the region from which we
can rapidly take on information
• When cognitive load goes up, the UFOV shrinks
• Tunnel vision occurs especially in highly stressful situations
• Also caused by some
diseases, alcohol
consumption, and adrenaline
peaks
• Can also happen in search
tasks: Focusing on a narrow
area
 Items that contextually belong
together should be placed close
to each other

22. Example of tunnel vision
In this example, UI testing revealed an inability to
spot the year in the first design

23. Conclusions
• Visual attention helps us to choose to which stimuli should we
attend to and act upon
• Cannot attend to everything  leads to perceptional flaws
– In general, we don’t see things we don’t expect to see
– We neither see things in places in which we don’t expect to see them
– Our visual memory isn’t accurate, changes are hard to spot
• Key terms
– Pre-attentive perception: Perceiving before paying attention
– Focus: Vision has a sharp resolution only in the center of our visual field
– Saccades: We constantly make eye movements to see our surroundings
sharply
– Fixation: Maintaining of the visual gaze on a single location
– Tunnel vision: Useful field of view shrinks causing us to omit information
in the peripheral area of our visual field

24. THANKS!