Sensation & perception Flashcards
what is perrception?
process of acquiring knowledge about environmental objects or events via the senses
perceptual process is often..
broken down into 2 stages:
sensation: process of transforming physical stimuli to electrical signals
perception: process of interpreting these signals for conscious awareness and for action
sensation
process of transforming physical stimuli to electrical signals
- energy from physical stimuli in the environment stimulates sensory receptors
- converted to neural impulses, which are sent to brain
perception
process of interpreting these signals for conscious awareness and for action
perceptual process using tennis examples
stimuli; distal and proximal
- > sensation: conversion to neural signals which are sent to the brain
- > perception: signal processing and interpretation
difference between 2 different types of stimuli
Distal stimuli = objects in the world e.g. ball hitting racket
Proximal stimuli = refers to energy e.g. light from sun reflecting off opponent (vision) and sound waves
what is perception for?
has evolved to aid survival and reproduction
- help us seek out desirable objects and avoid dangerous ones
- some species sense energies that humans cannot e.g. reindeer directly perceive UV so break camo
different sense
- Somatosensory perception (touch)
- visual perception
- gustatory perception (taste)
- auditory perception
- olfactory perception (smell)
- Proprioception (body position and movement)
- Nociception (pain)
- Themoception (temperature)
is perception veridical?
yes as senses would not evolve if they did not provide accurate information of the world
- however, perception is not a clear window as we don’t directly perceive stimuli we have to go through perceptual process
define illusions
situations in which perception differs from reality
- in some illusions our perception of objects is systematically distorted
examples of illusions :(
- the lilac chase
- the hermann grid illusions
Ambiguous figures
A type of illusion which are images that can give rise to 2 or more distinct perceptions
- Our perceptions are rarely ambiguous as our brains always deliver a perception thats not amibguous
- also referred to as bistable images
examples of ambiguous figures
- old/young lady
- dress
- duck rabbit
Ambiguous sounds
can also give rise to multiple bistable and stable perceptions
- Auditory stream segregation
impossible objects
= things that we perceive and know that can’t exist in the physical world
- sometimes sensory input is interpreted by the brain as representing objects or scenarios that are physically impossible e.g. penrose triangle, endless stairs, shepard scale illusion
Top down process
= pre existing knowlegde
- use knowledge about the strutuce of the world to influence perception
- AKA conceptually driven processes
bottom up process
= info from senses
- take information from senses and make judgements about the nature of the world solely based on this info
- AKA data driven processes
top down and bottom up processes
both important as perception is frequently modified by knowledge but knowledge can always override perception
- some theories focus on one component more than the other
constructivist theories of perception
Emphasise top down processing (knowledge)
- Helmholtz (1821-1894) argued brain is trying to make the best guess
- popularised by gregory (1923-2010) -‘perception.. best interpretation of the available data’
According to this approach many illusions are better described as rational references rather than perceptual errors
e. g. ponzo illusion
- hollow mask illusion
direct theories of perception
Emphasise bottom up processing (senses)
- James Gibson (1904-1974) argued constructivist approach underestimated richness of sensory evidence
- The perceiver is not a passive observer but interacts with the environment which is key to picking up useful info
modern approach - information processing paradigm
Stimuli (sensory input) ->
physiology (neural representations & processes) convert physical stimulus in neural code and process it ->
perception and action (output) judgements and actions
3 key scientific approaches
- psychophysics
- neurophysciology
- psychophysiology & brain imaging/ stimulation
psychophysics
measure relationship between stimulus and perception (no physiology)
- manipulate stimulus and see how peoples perceptions change
neurophysciology
measure relationship between a stimulus and the physiological response (no perception)
- manipulate stimulus and see what happens to responses of neurons in brain
psychophysiology & brain imaging/ stimulation
measure relationship between physiological responses and perception (no stimuli)
- Try and relate whats happening in the brain through functional imaging to what people are perceiving and doing
