Set #3 (Lectures 7 & 8)
GOOD LUCK ON YOUR MIDTERMS!
January 26 , 2010
CHAPTER FOUR: ATTENTION (Continued)
We looked at what attention selects, and figured that it could select space or objects. We will talk
about object-based attention later on when we talk about tasks. Then we talked briefly about two
types of attention: covert orientating that is not accompanied by observable eye movements, so
basically where you are attending is dissociated from where you are looking. Overt orienting on the
other hand is accompanied by observable eye movements. Where you are attending is where you
are actually looking. We also talked about how covert and overt orienting are linked.
When we go study covert orienting, it is tricky because you have to restrict the subject. There are a
number of ways of doing that. You can monitor their fixation with an eye-tracking device; when
you make an eye movement it makes a noise, an air trial. You have to keep asking your participants
to fixate at the center, and whatever you present them has to be sufficient that they can see it
without moving their eyes. When we talk about the cuing task, we will see how that is
Overt orienting, we actually measure eye movements. We dont want to restrict eye movements, we
want to measure them. Usually eye trackers are used to do that (there is a picture of a head-mounted
on in out book; there are a lot of infrared (IR) trackers that are remote; you dont have to wear any
headgear and it records where your eyes are). The measures of eye movements can tell us how fast
the movement has been initiated to a special location or object, how long they were looking at it and
transitions: what they looked at first, or second, which is interesting for perception studies.
Example of tracking (one of the professors studies):
We had this IR tracker, and we wanted to see where babies attend when they are shown complex
social scenes. This is a nine-month-old baby looking at these images. You will see that some of them have these colorful static objects, and some of them have social interactions. You will see that
the size of the circle is how long the baby is looking at a particular part of the picture and then you
also see transitions.
The problem with tracking babies is that they tend to move their head a lot, so when you see it go
off the screen, what they do is that they will move their head instead of moving their eyes. One of
the findings from this study was that eight month old babies look at exactly the same picture where
adults look; they compute social information in the same way. They are attending to faces and
hands. In this dynamic picture, they are figuring out where people are attending by looking at eyes,
then hands, then cards. In these types of studies, we can see how long the fixation took and we can
divide this image into regions, ex. objects and backgrounds, and count the number of fixations in
one region. This gives us an estimate of where attention was, by measuring eye movements. That is
what eye movement techniques are for.
Our book talks about one of the applications from this eye movement technique is reading
applications. How do we read? We have this intuitive understanding that we read by following the
text, but when we measure peoples eyes movements when they read, we make regressions, we go
back to previous words. Its not an easy progression of right to left while reading. This is in terns of
type. There are two types of control, how attention can be controlled:
1) Automatic/reflexive/exogenous orienting. This occurs when the stimulus and the
environment automatically capture your attention. If someone is taking a picture and the
flash occurs in your peripheral vision, you will pay attention to it. Or, if someone is throwing
something around the classroom, it would automatically attract your attention to this
location. That is called automatic orienting. Some bottom-up theories attention say that
automatic orienting is really how our attention works. These basic features in our environment really guide our attention. Things like colour and luminance in the picture
capture our attention and guide it to producing perception.
2) Volitional/endogenous orienting. Orienting from within. This is our willful attention, when
we decide to allocate your attention to this lecture versus Facebook. You decide where you
allocate your attention and where you maintain it. It is an effortful process.
These two types interact. Volitional orienting can be interrupted by automatic orienting. Automatic
orienting is all about survival. Things that move attract our attention because it could be a lion
approaching, or some sort of other predatory animal that can eat you. It interrupts volitional
When we look at these two types: covert and overt in terms of type of control, we come up with a
two by two matrix.
Control Reflexive Reflexive
These four types of attention are how we think about spatial attention these days. There seem to be
different mechanisms in the brain that controls each of these types of attention. When we measure
overt orienting we need to use eye movement techniques. When we measure reflexive orienting, we
elicit an eye movement using an external stimulus. We measure how fast someone will look at a
flash of light or something that suddenly start moving.
When we study reflexive covert orienting, we measure participants response time while keeping
their eyes fixed.
Same thing with volitional. When we measure volitional, we ask people to direct their eye
movements to a position where a target is likely to occur.