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
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 . . .
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
Sooooo . . . The grass really IS greener on the other side of the fence!!!
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.”)