Week5 Sensation&Perception Flashcards
What is sensation
The stimulus detection process by which our sense organs respond to and translate environmental stimuli into nerve impulses that are sent to the brain
What is perception
The active process of organising the stimulus input and giving it meaning
Why do we need sensations
They extract information from the environment that we need to function and survive
What is Psychophysics? What are the two focuses?
The scientific study of relations between the physical characteristics of stimuli and sensory capabilities
Two focuses: absolute limits of sensitivity and differences between stimuli
Define absolute threshold and give an example of human
The lowest intensity at which a stimulus can be detected 50% of the time
Vision : candle flame at 30 miles on a clear, dark night
Smell: one drop of perfume diffuse into the entire volume of a large apartment
(Source: Galanter, 1962)
Define Decision Criterion
A standard of how certain they must be that the stimulus is present before they will say they detect it
Define Signal Detection Theory
An account of sensory perception that is concerned with the factors that influence humans judgements about sensory stimuli
Key factors that affect sensory judgments
Fatigue, expectations, and significance of the stimulus
Played and identified?
Played but not identified?
Not played but identified?
Not played and not identified?
Hit
Miss
False alarm
Correct rejection
At a value close to the absolute threshold, participants’ and situations’ characteristics influence the decision criterion
If say yes all the time, what to do?
If say no all the time, what to do?
Yes all the time: increase costs for false alarm to increase detection threshold
No all the time: increase rewards for hits or costs for miss to decrease detection threshold
Subliminal stimulus
A stimulus that is so weak or brief that although it is received by the senses, it cannot be perceived consciously
Define Difference threshold
The smallest difference between two stimuli that people can perceive 50% of the time
(Also referred as just noticeable difference)
What does Weber’s Law say
The difference threshold is directly proportional to the magnitude of the stimulus with which the comparison is being made
An example of a sensory adaptation that occurs in all senses and its importance
Diminishing sensitivity to an unchanging stimulus
It allows our senses to pick up informative changes in the environment that would be important to our survival
What is sensory transduction?
The process whereby the characteristics of a stimulus are converted into nerve impulses
Wavelengths that human vision is sensitive to?
Around 400-700nm
Protections of eyes and how
Eyelid, eyelashes and eyebrows
Eyelid will close automatically if there is a sudden approach of an object
What is pupil and what does it do
An adjustable opening behind the cornea that controls the amount of light that enters the eye
It dilates or constricts using the muscles in the iris
Describe iris
The coloured part surrounding the pupil
What are lens and what do they do
A flexible structure that becomes thinner to focus on distant objects and thicker to focus on nearby objects
It also causes images to be focused on the inner surface of the back of the eye (retina)
Describe accommodation
Focusing the image directly and sharply onto the retina is what determines good all-round vision
Describe Myopia (nearsightedness)
Visual image is focused in front of retina (or too near lens)
Occurs because the eyeball is longer than normal
Describe Hyperopia(farsightedness)
Image is focused behind retina (or too far from lens)
Lens are not thick enough
Retina is
A multilayered light-sensitive tissue at the rear of the fluid-filled eyeball
