Lecture 4 Flashcards
(39 cards)
What does it take to notice a choice option? And when does this fail?
Just giving something a bright colour or making it shiny is not enough in certain circumstances.
- E.g., a parrot wearing a red santa hat doesn’t stand out on a picture filled with red parrots wearing bright colours.
If everything is screaming for your attention, nothing actually catches your attention.
- E.g., times square
What do we need to perceive?
We need our senses: touch, sight, taste, smell and sound.
You can argue that there are more senses, for example perception, where are you in space and the sensation on your lips.
Sensation
The processing of the information that comes from our sensory system.
Senses just sense.
Perception
The organisation, identification, and interpretation of sensory information in order to represent and understand the environment.
This is the brain process.
What is our main sense?
Our visual sense
Are perception and sensation interchangeable terms?
No
Principles of perception
- Constancy (standvastigheid)
- Grouping
- Contrast effect
Constancy principle
The tendency to perceive an object you are familiar with as having a constant shape, size, and brightness despite the stimuli changes that occur.
- Related to the status quo bias; we like things the way they are.
- E.g., a door looks like the same door from different angles.
The principle of things being constant works in two ways (the sensory information is the same):
- If the input is different we still perceive it as one object (this happens most of the time).
- It creates an illusion. This is because we know how certain things work (e.g., shadows) and we overcorrect.
Grouping
From gestalt psychology
The tendency to perceive patterns in and between objects based on certain rules (regular, orderly, simple etc). We like to group things together.
- In heuristics this is called a cluster illusion.
Proximity, similarity and enclosure.
Proximity
Grouping
We tend to see things that are in close proximity of each other as a bigger whole.
Similarity
Grouping
We tend to see things that are similar as one thing
- E.g., in the example you tend to see four rows and not four columns.
Enclosure
Grouping
Focuses specifically on the use of borders or containing shapes. It focuses on how we perceive objects enclosed in a common area.
Elements enclosed within a boundary tend to be perceived as a figure against the surrounding ground.
Contrast effect
Object are not perceived alone.
In the context of other objects and their features the perception changes.
Salience
The level at which an object stands out from other objects based on one or more features.
Visibility
The state of on object being able to be perceived per se.
Are salience and visibility interchangeable terms?
No.
What do models of attention concern themselves with?
Salience
How can saliency differ?
Saliency can be big and small.
When you are searching for a particular object or a person, the saliency is very small.
If you are searching for a particular person with a santa suit on in a street filled with people wearing santa suits that person’s salience is very small.
Visual search research
If you get a single visual search task, it doesn’t matter how many distractors there are, the green letter T stands out, it’s quite salient.
But as soon as the features of the distractors are played with, e.g., by adding green X’s, it becomes a harder task to find the green letter T. This is because the green T doesn’t stand out as clearly, it is less salient.
This is where the focus of attention comes in.
Models of attention
- Feature Integration Theory
- Guided Search Theory
What do models of attention deal with?
They deal with salience.
They answer questions like:
- How does salience arise when it’s small?
- How do specific combinations of features of an object get made salient and get selected for further processing?
Anne Treisman’s Feature Integration Theory
At some point attention grabs into perception. Typically you first perceive separate features (e.g., colour, orientation).
If a feature in the visual field is already salient enough, then there is no attentional switching needed. But if the unique thing that you’re searching for is in a combination map (a feature integration map), then you need your attentional process.
Attention = A top-down active search light moving over a ‘combined features’ map.
Wolfe’s Guided Search Theory
Similar to the theory of Anne Treisman, but more parallel.
The image you get in your visual field is split up into multiple components. He also talks about a combination feature map,. He says that every feature gives some activation on the location in the vision field, and at some point there is a net activation, which is the highest level of saliency if you had to pick out certain objects. In some cases, there is not a clear peak, he argues that in those cases attention sets the gaze for different features differently (either colour or orientation etc.). He argues that the attention is somewhere on a lower level.
Attention = An amplifier of important feature maps that lead to a clear salient combination over others.
What do Treisman and Wolfe have in common?
In both cases they describe the attentional process as something where your brain decides to search for something. This is a top-down process, whereas something that pops up automatically is harder to perceive.
