Unit 4 - Sensation & Perception
Psyc 101 – Eva Zysk
Sensation & Perception
- Sensation the stimulation of the sense organs
Sight (vision), sound (audition), smell (olfaction), taste (gustation), touch (somatosensation)
Temperature, kinaesthesia, proprioception, pain, balance
- Perception the selection, organization, identification, and interpretation of sensory input, in order to
form a mental representation.
- Blue vs white dress
Black Dress yellow light
White dress blue shadow
- Transduction: a process in which the sensors in the body convert physical signals from the environments
into encoded neural signals sent to the CNS
Transduction Conduction Transmission
- Sensory adaption
Sensitivity to prolonged stimulation tends to decline over time as an organism adapts to current
conditions
Adaptation is a useful process for most organisms
Our sensory systems respond more strongly to changes in stimulation than to constant
stimulation
A changing stimulation warrants a response
Psychophysics
- Psychophysics: methods that measure the strength of a stimulus and
the observer’s sensitivity to that stimulus
- Absolute threshold: the lowest level of a stimulus needed to detect a
change 50% of the time.
Absolute threshold – candle flame 50 km away on a dark
night
- Just noticeable difference: the smallest change in intensity of a
stimulus that one can detect.
Just noticeable difference is relative
If the surroundings are bright, a larger JND is needed in
order to detect change than when its dark.
- Weber’s law: the change in a stimulus that will be just noticeable is a
constant ratio of the original stimulus.
To do with the proportion
Weber’s Law: E.g. 10% of original stimulus
o 100g vs 110g = 10g
o 500g vs 550g = 50g
Information Processing
- Bottom up: begins with perception of raw stimuli and ends with our synthesizing them into a meaningful
concept
- Top down: begins with beliefs and expectations which are imposed onto raw stimuli
, Prior experience priming
How do we interpret the sensation?
The role of prior experience, attention, memory, personality, culture.
Eyeball
- Two functions of the eyeball:
1. Channels light to the neural tissue called the retina
2. House that tissue
Eye Part Function
Sclera The white part of the eyeball
Cornea Clear outer tissue that protects the eye. Cannot regenerate
Iris Coloured ring of muscle surrounding pupil
Pupil Helps regulate the amount of light passing into the eyes
Lens Bends and focuses the light
Retina Light sensitive tissue layer
- Neural tissue lining inside back surface of the eye
- Absorbs light
- Processes images
- Sends information to the brain
Optic Nerve Transmits visual info from retina to brain
Blind Spot Area where there are no rods or cones and the optic nerve leaves.
Waves
- Wavelength (colour)
- Amplitude (brightness)
- Number of wavelengths – purity (saturation)
Sensation & Perception - VISION
- Accommodation: the lens adjusts and changes its curvature to alter the visual focus
- Myopia: near-sightedness
- Hyperopia: far-sightedness
The Retina
- Rods: visual receptors that play a key role in night vision and
peripheral vision. More sensitive than cones
- Cons: visual (i.e. “photo”) receptors that play a key role in
daylight vision and colour vision
Psyc 101 – Eva Zysk
Sensation & Perception
- Sensation the stimulation of the sense organs
Sight (vision), sound (audition), smell (olfaction), taste (gustation), touch (somatosensation)
Temperature, kinaesthesia, proprioception, pain, balance
- Perception the selection, organization, identification, and interpretation of sensory input, in order to
form a mental representation.
- Blue vs white dress
Black Dress yellow light
White dress blue shadow
- Transduction: a process in which the sensors in the body convert physical signals from the environments
into encoded neural signals sent to the CNS
Transduction Conduction Transmission
- Sensory adaption
Sensitivity to prolonged stimulation tends to decline over time as an organism adapts to current
conditions
Adaptation is a useful process for most organisms
Our sensory systems respond more strongly to changes in stimulation than to constant
stimulation
A changing stimulation warrants a response
Psychophysics
- Psychophysics: methods that measure the strength of a stimulus and
the observer’s sensitivity to that stimulus
- Absolute threshold: the lowest level of a stimulus needed to detect a
change 50% of the time.
Absolute threshold – candle flame 50 km away on a dark
night
- Just noticeable difference: the smallest change in intensity of a
stimulus that one can detect.
Just noticeable difference is relative
If the surroundings are bright, a larger JND is needed in
order to detect change than when its dark.
- Weber’s law: the change in a stimulus that will be just noticeable is a
constant ratio of the original stimulus.
To do with the proportion
Weber’s Law: E.g. 10% of original stimulus
o 100g vs 110g = 10g
o 500g vs 550g = 50g
Information Processing
- Bottom up: begins with perception of raw stimuli and ends with our synthesizing them into a meaningful
concept
- Top down: begins with beliefs and expectations which are imposed onto raw stimuli
, Prior experience priming
How do we interpret the sensation?
The role of prior experience, attention, memory, personality, culture.
Eyeball
- Two functions of the eyeball:
1. Channels light to the neural tissue called the retina
2. House that tissue
Eye Part Function
Sclera The white part of the eyeball
Cornea Clear outer tissue that protects the eye. Cannot regenerate
Iris Coloured ring of muscle surrounding pupil
Pupil Helps regulate the amount of light passing into the eyes
Lens Bends and focuses the light
Retina Light sensitive tissue layer
- Neural tissue lining inside back surface of the eye
- Absorbs light
- Processes images
- Sends information to the brain
Optic Nerve Transmits visual info from retina to brain
Blind Spot Area where there are no rods or cones and the optic nerve leaves.
Waves
- Wavelength (colour)
- Amplitude (brightness)
- Number of wavelengths – purity (saturation)
Sensation & Perception - VISION
- Accommodation: the lens adjusts and changes its curvature to alter the visual focus
- Myopia: near-sightedness
- Hyperopia: far-sightedness
The Retina
- Rods: visual receptors that play a key role in night vision and
peripheral vision. More sensitive than cones
- Cons: visual (i.e. “photo”) receptors that play a key role in
daylight vision and colour vision
