Sensation & Perception
Sensation = process by which sense organs gather info from the world and transmit it to
the brain for initial processing
Perception = process by which the brain selects, organizes, and interprets sensations
Dual, 2-stage process
2 perceptions from a single sensation
Stage 1 - Bottom-up processing
Automatic (aka data-driven processing)
Stage 2 - Top-down processing
active/constructive (aka conceptually-driven processing)
From the Physical to the Mental
Emphasizing incoming sensory information is insufficient to explain perception
considerations of context and of the perceiver's expectations and prior learning must also
there is no one-to-one correspondence between physical and psychological reality
Sensing the environment
Senses share common features:
o Sensory neurons
Anatomical coding (Doctrine of specific nerve energies (Johaness Muller,
How Sensory Modalities lead to Different Perceptions:
Stimulus- Olfactory Nerve- Smell Stimulus- Optic Nerve- Sight
Stimulus- Auditory Nerve- Sound
Mixing of sensations/perceptions
letter/digit color synaesthesia most common
Chromesthesia - color hearing
occurs with musical sounds in particular
bright colors - high pitch
dark colors - low pitch
basis is uncertain, possibly genetic
Brain codes for intensity and quality of sensory stimulation
Absolute threshold- Measuring the acuity of our senses
The smallest intensity of a stimulus that must be present for it to be detected.
Signal detection theory
Signal to noise ratio
5. Tuning out irrelevant information
Neurons stop firing when the stimuli is constant.
Sensory systems are more sensitive to changes in the environment than to steady
Reinforces an important and fundamental lesson for us:
We do not perceive the world as it is, but rather, as it is useful for us to perceive it!
Sensory Deprivation- can lead to hallucinations or could be relaxing (depending on
context and mindset going into it).
Sensory Overload- leads to selective attention
Selective Attention o Cocktail party effect --> you can focus on one person at a party and you will
perk up at the mention of your name because you were unconsciously paying
o Can lead to "unintentional blindness".
o Change blindness--> door passed between and guys switched.
Vision is about 80% of what we perceive from the world (ex. We look away from needles).
Light completes its journey; where transduction occurs
Photoreceptors- Rods and Cones- they transduce light into nerve impulses.
Blind Spot = no photoreceptors
The Challenge for vision researchers is t