Name that tune. Song title? Performer(s)?
Sensation and Perception Start of two weeks on “The Knower” 1/25/10
Objectives After this class you will be able to (it is my hope!): • Describe some eye and ear physiology • Explain how the visual system works (somewhat) • Identify visual cues to depth • Explain how perceptual and cognitive psychology influence HCI designs • Have an early appreciation for psychological models
Designing Stuff • In Week 1, I asked the question “What would a system look like if we were designing it for dogs?” • Wouldn’t be a lot of text. • Wouldn’t require a lot of dexterity. • Might code information in smells and tastes. • But we’re designing systems for humans (usually!). So it will behoove us to know something about how human beings take in and process information. • So, this is the first of four lectures on “The Knower.” • Ultimately our goal will be to design information systems to fit people instead of the other way around.
Human Information Processing • How do human beings take in and process information? • Sensory psychology – how humans transform physical energy (e.g., light and sound waves) into sensory signals to and in the brain. • Perceptual psychology – how humans interpret these sensory signals as perceptions. • Cognitive psychology – how humans think about these perceptions, and previous experiences, and their own mental creations, and . . . • Psycholinguistics – The psychology of language -- what goes on between the time I have a thought and you have the same (or similar!) thought, whether I say it or write it.
Turning Energy into Sensations • Vision • The energy is light waves. • Waves of different frequencies. Different frequencies get perceived as different colors. • The nerve cells are “rods” and “cones” in the retina in the back of the eye. • Audition • The energy is sound waves. • Waves of different frequencies. Different frequencies get perceived as different pitches. • The nerve cells are hair cells on the basilar membrane
Ear Physiology
Basilar membrane
Eye Physiology
Eye Muscles
Visual Field
Retinal Physiology
Distribution of Rods and Cones
Visible Spectrum
Visual Sensitivity
Neural Pathways
Theories of Pattern Recognition • Template Matching Theory • We compare a visual stimulus with a set of templates, or specific patterns that we have stored in memory. • Feature Analysis Theory • More flexible – a visual stimulus is composed of a small number of characteristics or “distinctive features.” • E.g., an “A” has a diagonal line, another diagonal line, a horizontal line . . .
Aftereffect
Ambiguous Figure
Sensation/Perception • POINT: Perceptions are made up of more than just a collection of sensations! • OTHER things influence our perceptions, e.g., • Our experiences • Our biases • The context • Our current emotional state • Etc. • So, what does that have to say about designing human-computer interfaces???
Bottom-up vs. Top-down Processing • Bottom-up • Emphasizes the stimulus, and the sensory receptors • Top-down • Any theory of recognition must include something OTHER than the stimulus – the ambiguous figure proves this • Also, check this out – the word superiority effect: we can identify a single letter more accurately and rapidly in the context of a word than in isolation, or in a string of unrelated letters
Perceptual Psy – Color Vision • Color perception – 3 types of cones (RGB) A B
Perceptual Psy -- Depth • Different visual cues to depth • Oculomotor vs. Visual • Oculomotor – Lens accommodation and extraocular muscle convergence are “read” by the brain • Visual: Binocular vs. Monocular • Binocular – Stereopsis (retinal disparity) • Monocular (next screen) • Static • Motion parallax
More Depth Cues • Monocular • Static • Interposition • Size • Perspective • Linear perspective • Texture gradient • Aerial perspective • Shading • Motion parallax
Monocular Cues -- Interposition
Monocular Cues -- Size
Object Constancy
Monocular Cues – Linear Perspective
Monocular Cues – Texture Gradient
Sooooo . . . The grass really IS greener on the other side of the fence!!!
Monocular Cues – Aerial Perspective
Monocular Cues -- Shading
Monocular Cues – Motion Parallax
Resources • www.britanica.com • Matlin, M. W. (2009). Cognition. Hoboken, NJ: John Wiley and Sons, Inc. • Blake, R., & Sekuler, R. (1980). Perception. McGraw-Hill. • A discussion of sensation vs. perception: http://www.learninginfo.org/sensation-perception.htm • Good size constancy demo: http://psych.hanover.edu/KRANTZ/SizeConstancy/index.html • A decent, half-hour video: http://video.google.com/videoplay?docid=-8724039763795336038#
Today’s song was “Soft Parade” by The Doors. • Why do you suppose we chose to play it before THIS class? • (It was from The Doors’ album “Perception.”)
