PSYC100 Lecture Notes - Lecture 7: Pareidolia, Optical Flow, Parallax
PSYCH100 - FOUNDATIONS OF PSYCHOLOGY
Wk. 7 – Sensation vs Perception
Sensation
Registering information through senses
Perception
Interpreting (making sense of) sensation
Selection, organisation and interpreting
Extremely complex process, but done with very little effort
Approaches to Perception
Computable Approach
Attempt to imitate perception with computer programming to work out what
computations are made in the nervous systems
Computers have trouble matching humans in speed and accuracy
Constructivist Approach
Reality constructed from fragments of sensory information
Perception influenced by experience
Ecological Approach
External stimuli in environment hold many clues that allow us to perceive our
surroundings
Thresholds (and subliminal messages)
How strong must a stimulus be in order to trigger a conscious perceptual experience?
Early research
Gustav Freschner
Absolute threshold
No absolute cut off
Smallest amount of stimulus energy that can be detected 50% of the time
Half way between always detected and never detected.
Sense Absolute Threshold
Vision Candle flame at 48kms on clear night
Hearing Tick of a watch at 6m
Taste 1 teaspoon of sugar in 7.5L of water
Smell One drop of perfume in a six room apartment
Touch Wing of a fly falling on check from 1cm
Signal Detection Theory
find more resources at oneclass.com
find more resources at oneclass.com
Model to explain likelihood of an individual detecting a near-threshold
stimulus
Individual differences
Personal sensitivity
Ability to detect stimulus from background of competing
stimuli
Affected by noise (irrelevant stimuli) and stimulus strength
Response Bias
Internal rule used to decide whether to report a signal
Affected by expectations and motivation
E.g. airport security screeners
Just Noticeable Difference (JND)
Smallest difference detectable
Webers law: size of JND proportional to size of initial stimulus
The smaller the initial stimulus the less change needed to detect a difference
The larger the initial stimulus the greater the change needed to detect a
difference.
Visual Perception
Where does one object stop and another begin?
Perceptual organisation
What stimuli go together to form an object
Gestalt Psychology
Gestalt psychologists – early research in perception.
The sum is worth more than the parts
Perception is more than just sensation
Cognition is an important process
Figure-Ground Principle
Figure = what we are attending to
Ground = what is in the background that we are not attending to
Grouping
Proximity
Objects close together are grouped together
Similarity
Objects similar in size, shape, or colour are grouped together
Continuity
Elements that follow the same direction are grouped together
See lines that connect 1 to 2 and 3 and 4 in C
Rather than a combination of the odd forms
Closure
Fill in gaps to form a complete image
Texture
Features with the same texture are grouped together
Common Fate
Objects moving at the same pace and same direction grouped together
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Extremely complex process, but done with very little effort. Attempt to imitate perception with computer programming to work out what computations are made in the nervous systems. Computers have trouble matching humans in speed and accuracy. Reality constructed from fragments of sensory information. External stimuli in environment hold many clues that allow us to perceive our surroundings. Smallest amount of stimulus energy that can be detected 50% of the time. Half way between always detected and never detected. 1 teaspoon of sugar in 7. 5l of water. One drop of perfume in a six room apartment. Wing of a fly falling on check from 1cm. Model to explain likelihood of an individual detecting a near-threshold stimulus. Ability to detect stimulus from background of competing. Affected by noise (irrelevant stimuli) and stimulus strength. Internal rule used to decide whether to report a signal. Webers law: size of jnd proportional to size of initial stimulus.
