Sensation & Perception
Sensation: Detection of stimuli
Perception: Interpretation, identification,
and organization of sensory information
Sensation: Detection of stimuli
The Senses
Vision
Hearing
Touch
Taste
Smell
Balance
Kinaethesia
Proprioception
Light
Sound waves
Pressure, temperature
Chemicals
Chemicals
Gravity
Movement
Limb position
Sensation
 Bottom-Up Processing
 analysis that begins with the sense receptors and
works up to the brain’s integration of sensory
information
 reflects physical stimuli veridically (accurately)
• Absolute threshold - The minimum amount
of energy our senses can consciously detect
50% of the time.
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Vision – candle flame at 30 miles
Hearing – ticking watch at 20 feet
Taste – 1 tsp sugar in 1 gal water
Smell – 1 drop perfume through 3 rooms
Touch – bee wing falling on face at 1 cm
Sensation - Thresholds
 Difference Threshold
 Also called “just noticeable difference” or JND
 the smallest difference between two stimuli that is
detectable 50 percent of the time
 Smallest detectable difference between two stimuli
Adaptation & Habituation
 Sensory adaptation - tendency of sensory
receptors to fatigue and stop responding to an
unchanging stimulus.
 This is a physical, bottom-up process
Habituation
 Habituation - tendency of the brain to stop
noticing constant, unchanging information.
 Example – your clothing, fan noise, perfume!
 Psychophysics
 study of the relationship between physical
characteristics of stimuli and our
psychological experience of them
 Light- brightness
 Sound- volume
 Pressure- weight
 Taste- sweetness
Perception
1. Perceptual cues are used
2. Perception is active, constructive
3. Perceptual interpretations can be
wrong (illusions)
4. Perception is affected by experience
Perception
 Top-Down Processing
 information processing guided by higher-level
mental processes
 when we construct perceptions by drawing on our
experience and expectations
 Often imposes a meaning that does not exist in the
physical stimulus (not veridical)
Top Down Processing
• Aoccdrnig to a rscheearch at Cmabrigde
Uinervtisy, it deosn't mttaer in waht oredr the
ltteers in a wrod are, the olny iprmoetnt tihng
is taht the frist and lsat ltteer be at the rghit
pclae. The rset can be a total mses and you
can sitll raed it wouthit porbelm. Tihs is
bcuseae the huamn mnid deos not raed ervey
lteter by istlef, but the wrod as a wlohe.
• Amzanig huh?
Perceptual Organization
• Top- down process (individualized by
experience)
• how your brain makes sense of the world,
which includes “hiding” from you certain
changes in stimuli so that the stimuli continue
to appear constant to you
Gestalt Principles of Perception
Perception of Depth
• Images on the retina are 2-D
• How do we perceive 3-D (depth)?
• CUE approach – we learn the connection
between cues and depth through experience,
yielding 3-D perceptions
Binocular Cues
• Binocular cues - cues for perceiving depth
based on both eyes.
1.retinal disparity
 images from the two eyes differ
 closer the object, the larger the disparity
2. convergence
 neuromuscular cue
 two eyes move inward (converge) more as objects
get nearer
Monocular Cues
• Monocular cues (pictorial depth cues) –
cues for perceiving depth based on one eye
only.
1.
2.
3.
4.
5.
Linear perspective
Relative size
Interposition (overlap)
Texture gradient
Motion parallax
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