Course: PSYC*1000 (DE)
Professor: Harvey Marmurek
Schedule: Summer, 2012
Textbook: Psychology – Tenth Edition in Modules authored by David G. Myers
Textbook ISBN: 9781464102615
Module 17: Basic Principles of Sensation and Perception
• Heather Sellers – face blindness; perception; upside is that she won’t harbour ill feelings when seeing that
o Underside of brain’s right hemisphere that helps us recognize a familiar face in only about 1/7 of a
What are sensation and perception? What do we mean by bottom-up processing and top-down
• Heather Seller’s curious mix of “perfect vision” and face blindness illustrates the distinction between
sensation and perception
o Sensation – looks at a friend and her sensation is normal
o Perception – processes by which brain organizes and interprets sensory input (almost normal in
o May recognize people from their hair, walk, etc., but not their face
What three steps are basic to all our sensory systems?
• Every second of every day, our sensory systems perform an amazing feat: They convert one form of energy
into another (vision processes light energy, hearing processes sound waves. All our senses (a) receive
sensory stimulation, often using specialized receptor cells; (b) transform the stimulation into neural impulses
(c) deliver the neural information to our brain
• In each case, there are three steps to consider – receiving, transforming, and delivering the information to
What is the rough distinction between sensation and perception?
Sensation is the bottom-up process by which the physical sensory system receives and represents stimuli.
Perception is the top-down mental process of organizing and interpreting sensory input.
What are the absolute and difference thresholds, and do stimuli below the absolute threshold have any
influence on us?
• Absolute Thresholds (minimum stimulation needed to detect a particular stimulus 50% of the time)
o Gustav Fechner (1801-1887), German scientist and philosopher studied awareness of faint stimuli
o Signal detection theory predicts when we will detect weak signals – vary as circumstances change
*why do people react differently to the same stimuli; why reactions vary as circumstances change
o Subliminal – below one’s absolute threshold for conscious awareness
o Prime – activating certain associations
o Masking stimulus – interrupts brain’s processing before conscious perception
o Dual-track mind at work: much of our information processing occurs automatically, out of sight, off
the radar screen of our conscious mind.
• Difference Thresholds (minimum difference between stimuli required for detection 50% of the time)
o Really, it’s just a noticeable difference; hearing something out of tune; child’s voice in a crowd
• Subliminal persuasion – subliminally presented stimuli can subtly influence people, experiments discount
attempts at subliminal advertising and self-improvement
o Anthony Greenwald experimented – commercial subliminal messages – self-esteem and memory
What three factors will make it more likely that you correctly detect a text message?
(1) you are expecting a text message; (2) it is important that you see the text message and (3) you are alert
Using sound as your example, illustrate the distinctions among these concepts: absolute threshold, subliminal
stimulation, and difference threshold. Absolute threshold is the minimum stimulation needed to detect a particular sound (such as an approaching
bike on the sidewalk behind us) 50% of the time.
Subliminal stimulation happens when, without our awareness, our sensory system processes that sound
(when it is below our absolute threshold).
A difference threshold is the minimum difference for us to distinguish between two sounds.