Exam 2 - Sensation and Perception Flashcards
Ch. 4 material
Sensation
The simple stimulation of a sense organ
Perception
occurs in CNS organizes, identifies, and interprets sensation to form mental representation
Transduction
Process in which body converts physical signals (sensations) into neural activities via the CNS (transition state from sensation to perception)
Transduction w/ sight
light reflected of surfaces provide eyes with info about the shape, colour, and position of objects
Transduction w/ sound
vibrations causes changes in air pressure that travel through space (in the form of a wave) that is registered by the eardrum
Transduction w/ touch
Pressure of a surface against the skin signals shape, texture, vibration, pattern & temperature
Transduction w/ Taste and Smell
Molecules dispersed in the air or dissolved in saliva real ID of substances that we may or may not want to eat.
Psychophysics
methods that measure strength of stimulus and the observer’s sensitivity to that stimulus by reporting whether they felt the stimulus or not
Dr. Gustav Fechner
1801-1887
Inventor of psychopysics
Absolute threshold
The minimal intensity needed to just barely detect a stimulus 50% of the time
Transition between detecting and not detecting sound is gradual rather than abrupt
Absolute threshold of vision
candle flame 50 km away on clear, dark night
Absolute threshold of hearing
clock tick 6 meters away when everything is quiet
Absolute threshold of touch
fly’s wing falling on cheek from 1 cm away
Absolute threshold of smell
single drop of perfume diffused through area equivalent to 6 rooms
Absolute threshold of taste
5 mg of sugar dissolved in 7.5 L of water
Just noticeable difference (JND)
minimal change in a stimulus that can just barely be detected *not a fixed quantity
Weber’s Law
The just noticeable difference of a stimulus is a constant proportion despite variation in intensity
Signal Detection theory
The detection of a stimulus depends both the intensity of the stimulus and the physical/psychological state of the individual
Used to measure the way we make decisions under conditions of uncertainty
Touch (Somatosenses)
Sensory receptors in our muscles, tendons, joints, and varieity of receptors in our skin allow us to percieve the world through touch
How do we sense touch?
transduction of skin sensations to neural signals
Note that some areas of the body discriminate fine spatial detail more effectively than others (think of the homoncolus)
Connection of touch to psychology?
Touch is more than just the perception of the sensation; it is also influenced by who or what we percieve to be touching us (this influences our reaction)
(recall the ticklish example)
Pain
“An unplasent sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage”
Why is pain important?
Essential for survival, as it tells you what is wrong
Changes your behaviour
serves as contrast to pleasurable stimuli
Absence of pain (ex. Congenital insensitivity to pain) is not good, as one cannot tell if you injured yourself
Relationship between pain and psychology?
Pain is influenced by psychological and social processes
Often of great concern to people, as it usually means you should see a doctor
Visual Acuity
The ability to see fine detail
Snellen Chart
Chart used to measure visual acuity
Sensing light
Visual system transduces visible light into neural signals in brain
Properties of Light Wave
Pupil
Circular hole where light enters the eye
Iris
Doughnut-shaped coloured area that contains muscles that control the pupil
Sclera
The white, outer surface of eye
Cornea
Curved, transparent layer covering iris & pupil
Function: Bends incoming light to focus the incoming visual image at the back of the eye
Lens
Also bends light, but is adjustable in curvature (controlled by cilliary body; extra info) and allows fine-tuning of curvature
Accomodation
