Perception part 2 (lec. 5) Flashcards
Perceptions are subjective
Perceptions are affected by emotion and
motivation. Desirable objects will appear closer/larger than less desirable objects. For example, a water bottle appears closer than crackers when thirsty, hills look steeper when you are tired, etc.
The sense of touch
Mechanreceptors -> Spine -> Somatosensory cortex. In cortex: homonculus (spatially organized map of the body for sensory and motor), but current evidence suggests an update of motor homunculus to include regions that
control integrative, whole-body actions.
Olfaction
Chemicals moving through the air pass through olfactory epithelium to olfactory bulb. Direct connections to memory and emotion brain regions (not through the thalamus like other senses). Smell has a stronger link to memory and emotion than any of the other senses. This explains why the smell of cut grass can trigger a memory better than an image of grass. New research shows that sense of smell is also related to brain and early symptom of dementia.
Taste system
- Works with olfaction (this explains why things do not taste as good when our nose is stuffed)
- Taste buds on tongue, palate, pharynx, and upper esophagus measure chemicals that
have been ingested - They then relay message to thalamus and then the primary gustatory cortex, and other areas like PFC and reward areas of the brain.
- Flavour (taste) is also affected by other senses, including vision: reddish colours associated with sweet tastes, and greenish colours associated with bitter tastes.
Constructivist Theory of
Perception
A top-down theory of perception:
* Perception is influenced by stored knowledge and context, mental models
* We make unconscious inferences to interpret and to predict sensory data
* Illusions support this theory
Gestalt psychology
- Bistable figures suggest that we can experience spontaneous subjective change in perception. They direct us to understand what factors (constraints) are driving this effect or how we organize perception
- Gestalt Psychology: There are fundamental organizational principles to deal with ambiguity in our environment. These principles are based on knowledge and experience (top-down processes) and shared among people.
The Gestalt organizational principles
- The principle of experience: figure ground segmentation
Visual grouping principles: - Principle of proximity
- Principle of closed forms
- Principle of good contour
- Principle of similarity
Principle of experience
- Image segmentation (figure-ground) depends on sensory input, detect edges or shadows (bottom-up)
- Experience and knowledge also drives figure-ground segmentation. Regions perceived as the figure are the ones that are more familiar and more easily named to the observer (top-down)
Principle of proximity
Objects or features that are close to one another in a scene will be judged as belonging together
Principle of closed forms
We see a shape in terms of closed forms, and we like to see items that enclosed as whole (ex. Panda logo from WWF)
Principle of good contour
We perceive objects as continuous in cases where it is expected that they continue
Principle of similarity
We organize objects or features of a scene based on similarity
Direct models theory
- Against the idea that ‘top-down’ processes are needed for perception
- A passive bottom-up approach to perception
- Sensory information is rich enough for perception
- Requires an an ecological approach to understand perception – study it in the real world (JJ Gibson)
- The ambient optical array (AOA) that reaches the retina has enough information to direct perception and movement
- There are cues (computational tricks) in the AOA (not in the mind) that are used to guide perception and action (bottom-up cues)
Examples of cues in the AOA
- Topographical breakages: Discontinuity helps see edges and define objects
- Scatter reflection: How widely light scatters off an object’s surface provides cues about the nature of the surface (smoother: less scattered)
- Texture gradients: Near objects are farther apart and far objects are closer together. Incremental changes in texture can provide information about your movement and distance.
