Lecture 9 & 10
Overt attention:
- Refers to the conscious act of directing one's visual attention to a particular location
in the visual field. This involves moving one's eyes to focus on the desired object or
location. For example, if you are looking for your keys, you might use overt attention
to scan the room with your eyes until you locate them on the table.
- Useful when searching for a specific object or when navigating through a complex
environment
Covert attention
- Refers to the unconscious or automatic shifting of attention without moving the eyes.
It is the ability to selectively enhance the processing of information at a particular
location in the visual field, without moving the eyes or head. For example, if you are
reading a book, you might use covert attention to focus on a particular word or
phrase without moving your eyes.
- Processes multiple stimuli in parallel and filtering out irrelevant information
The cocktail party effect
- Covert attention
- One may pretend to listen to someone in front of you, while actually focusing on
what is said in another conversation
o Or, while listening to the person in front of you, your attention may be
suddenly captured by someone saying your name in another conversation:
attentional capture
Different types of attention
- Top-down attention (voluntary attention):
o Refers to the process by which prior knowledge, expectations, and goals
influence our attentional focus and perception.
o Top-down attentional processing is driven by higher-level cognitive
processes such as memory, reasoning, and context
o Example: if you are in a noisy room trying to have a conversation with
someone, your top-down attention will help you focus on the person's voice
by filtering out the background noise. This filtering process is based on your
prior knowledge and expectation that the person's voice is the most
important thing to attend to in this situation.
o An important mechanism that allows us to selectively attend to relevant
information and filter out distractions based on our higher-level cognitive
processes and goals
o Experiment:
- Bottom-up attention (capture):
o Refers to the process by which external stimuli automatically capture our
attention, regardless of our goals or intentions.
, o Bottom-up attentional processing is driven by the sensory features of stimuli
themselves, rather than our prior knowledge or expectations.
o Example: if a loud noise suddenly interrupts your conversation with
someone, your attention will be immediately captured by the noise. This is
because the loud noise is a salient, unexpected stimulus that automatically
draws your attention to it, even if you were not intentionally looking or
listening for it.
o An important mechanism that allows us to respond quickly and effectively to
salient and unexpected stimuli in our environment, even when we are not
actively seeking them out
o Experiment:
- Object based attention
o A type of attentional processing where attention is directed to a specific
object in our visual field, rather than to a particular location.
o When we attend to an object, we automatically process its features, such as
its shape, colour, and texture, and prioritize processing of this object and its
related features over other objects in the visual field.
o Example: if you are searching for your keys on a cluttered desk, you will
automatically focus your attention on the object (the keys) rather than on the
location (the desk). Object-based attention enables us to quickly and
efficiently locate and identify objects in our environment by allowing us to
selectively process relevant object features while ignoring irrelevant ones.
o An important mechanism that allows us to selectively process relevant
information in our environment, and helps us make sense of complex
sensory inputs
o Experiments:
, - Feature based attention
o A type of attentional processing in which attention is directed towards
specific features of an object, such as colour, shape, or orientation, rather
than the object as a whole.
o When we attend to a feature, we prioritize the processing of that feature over
other features of the same object, or other objects in the visual field.
o Example: if you are searching for a red pencil among a group of pencils of
different colours, you will automatically focus your attention on the feature of
colour, specifically the colour red, and prioritize processing of the red pencil
over other pencils of different colours.
o A mechanism that allows us to selectively process relevant information in
our environment, and helps us to filter out irrelevant information. It is an
important aspect of our visual and auditory perception, and plays a crucial
role in our ability to make sense of complex sensory inputs.
o Experiment:
What is the effect of attention on processing?
- Top down attention:
o Effect is an enhanced response to stimuli that appear at the
attended location. The Posner cueing task increases the amplitude
of visual evoked potentials recorded from the human scalp (P1
component).
o This enhanced response is specific for the attended location (so it
is not a general or overall increase in neural responsiveness). The
P1 attention effect is topographically distributed over the visual
cortex in accordance with the location of the visual field where
attention is directed at, see picture on the right →
- Attentional capture:
o Effect is an increased response for
stimuli at the cued (or rather captured)
location. Inhibition of return results in a
decreased response at the cued location,
in accordance with the now decreased
attention at that site
, o These effect of capture (and inhibition of return) again show spatial
specificity, in that they occur only at the cortical locations where the
attention is directed to (drawn away from)
o In monkey area V4, there is an increased response when attention is directed
towards the preferred stimulus (Desimone). Spatial attention causes
increased signals.
- Feature based attention:
o Attention to a feature (direction of motion) enhances responses to that
feature all over the visual field (Treue et al., 1999): Feature based attention
causes increased signals of attended features.
o Feature based attention (colour) in area V4. Fixation dot reveals which colour
to attend (and later discriminate). Record activity from task-irrelevant
stimuli.
- Object based attention:
o increases signals of the attended object:
▪ Attending to faces enhances activity in the fusiform-face-area, while
attention to houses enhances activity in the parahippocampal place
area →
