Sensation and Perception Flashcards
Sensation
When sense organs gather information about the environment, then transmit the info the brain for initial processing
- (from out side world to inside)
Perception
process when the brain select, organise and interpret sensations
Basic principles for sensation and perception
- no one to one relationship between physical reality and psychological reality
- they are active processes
- they are adaptive
Common Features to all sensory systems
- has sensory receptors (detect energy/light waves + transduction)
- require a min. amount of energy to activate the system (threshold)
- requires constant decision making
“turning down the volume” for efficient processing - sensing require changes in stimulation to notice
Absolute Threshold
- sensory systems require a min. amount of energy for activation
- vary from person to person and from situation to situation
- this is because of noise, external (actual noise), internal (random firing of neurons- psychological factors, stress, motivation etc
Signal detection theory
- sensation is not passive,no absolute threshold, threshold=judging if stimulus is present/absent → two processes:
1. Initial sensory process: observers sensitivity to stimulus
2. Decision process: the observers response bias (hit, false alarm, miss, correct rejection)
Just Noticeable Difference and Weber’s Law
- lowest level of stimulation to sense a change has occurred (not fixed/constant)
- Webers’ Law: differ by a constant proportion from the first to be perceived as different → ratio of change for JND - WF is constant
Sensory receptors
- from energy → neural impulses that can be interpreted by the brain
- Transduction= converting physical energy or stimulus info into neural impulses/translating info from environment into neural signals
Basic processes that occur in the eyes
- Light is focused on the retina by the cornea and pupil and lens
- Retina transduces this visual image into a code that the brain can read
Rods and Cones
Rods: sensitive to light (night-vision), no colour, periphery of retina
Cones: not sensitive to ligh (need strong light), detailed vision, centre of retina (Fovea: central part of reina, sharp, clear vision), respond to wavelength (colour) and adapt quick to dark
Two pathways
From optic nerve → two pathways → midbrain or thalamus → Visual Cortex
- What pathway: what object is, shapes, color, identifying object, temporal lobe
- Where pathway: parietal lobe, process location of object and you + hand movement (locating object in space)
Young-Helmholtz (trichromatic theory)
- eye has three types of sensory receptors: red, green and blue
- colour is explained by differential activation of the three
- explains colour blindness
- processes in the retina
Top down/Bottom up process
Top-down= knowledge, memory, expectations → features that meet expectations about stimulus → form perception
Bottom-up= sensory input→ analyse (colour, shapes etc)→ form perception
Influences on perception= expectations (context, schemas, experiences, learning, motives)
Form perception: 1. Gestalt Laws of Perceptual Organisation and 2. recognition by component
- basic rules that brain automatically use to organise and make sense of sensory input (rules of thumb, but sometimes misleading because they are based on experience)
- Law of similarity, proximity, good continuation, closure, familiarity, common fate
- basic rules that brain automatically use to organise and make sense of sensory input (rules of thumb, but sometimes misleading because they are based on experience)
- More recent, break it down into component parts, much like words
Depth Perception:
Three dimensions, through binocular and monocular visual cues.
Monocular cues: (from one eye)- can still see distance! using:
interpositioning, linear perspective, texture gradient, aerial perspective(less clear, more blue), familiar size(smaller=further away)
