psych 111

• The most important lesson to remember about sensation and perception is that we feel, see, hear, taste, and touch with our brains
• Transduction

  Conversion of one form of energy into another. In sensation, transduction is the transformation of stimulus energies, such as sights, sounds, and smells, into neural impulses that our brain can interpret
• Absolute Threshold

  The minimum amount of stimulation that an organism can detect
• Perception

  The selection, organization, and interpretation of sensory input. The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events
• Top-down processing

  • Information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations
• Psychophysics

  Studies the relationships between the physical energy we can detect and its effects on our psychological experiences
• Individual absolute thresholds vary depending on the strength of the signal and on our experience, expectations, motivation, and alertness
• Threshold

  A dividing point between energy levels that do and do not have a detectable effect
• Sensation & Perception


  • Perception is Subjective
  • Adaptive
  • Experience shapes perception
  • Our brains build the meaning of our sensory information
• Bottom-up processing


  • Analysis that begins with the sensory receptors and works up to the brain’s integration of sensory information
• 3 steps taken by our sensory systems

  1. Receive sensory stimulation, often using specialized receptor cells

  2. Transform that stimulation into neural impulses

  3. Deliver the neural information to our brain
• In everyday life, sensation and perception work together, to blend together, in one continuous process
• Sensation

  The stimulation of the sense organs. The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment
• The absolute threshold is when a stimulus is consistently detected 50% of the time
• Difference Threshold JND

  Just noticeable difference: Minimum difference a person can detect between any 2 stimuli 1/2 the time; increases with stimulus size. JND: the smallest difference in the amount of stimulation that a specific sense can detect
• JND

  The smallest difference in the amount of stimulation that a specific sense can detect
• Weber’s law examples

  • Example 1: 2 lights must vary by an intensity of 8%
  • Example 2: Objects must differ in weight by 2%
• James Vicary claimed snack sales sky-rocketed with a specific 18.1% increase in popcorn sales and 57.7% increase in Coca-Cola sales, calling this "subliminal advertising"
• Subliminal stimuli

  • Stimuli that are too weak to detect 50 percent of the time
• Experiments discount attempts at subliminal advertising and self-improvement
• Subliminal perception

  • The registration of sensory input without conscious awareness
• The detection of stimuli involves both sensory processes & decision processes
• Signal detection theory can be illustrated with the case of identifying enemy aircraft on radar
• Higher mental processes are involved in signal detection theory
• What are the potential costs of making a false alarm and missing in signal detection?
• Resource: Standard magnetic resonance imaging is inadequate for patients with refractory focal epilepsy
• The process whereby sensitivity to prolonged stimulation tends to decline over time
• Difference Threshold JND

  Just noticeable difference: Minimum difference a person can detect between any 2 stimuli 1/2 the time; increases with stimulus size
• In the 1950’s James Vicary claimed that, during a movie, he exposed patrons to fleeting messages (1/3000s) urging them to purchase drinks and popcorn
• Weber’s law

  • For an average person to perceive a difference, 2 stimuli must differ by a constant minimum percentage (not a constant amount); The exact proportion varies, depending on the stimulus
• Research attempting to replicate James Vicary's results were unsuccessful
• Subliminal sensation


  • Sensation that is too fleeting to enable exploitation with subliminal messages
• Subliminal persuasion


  • May produce a fleeting, subtle, but not powerful, enduring effect on behavior
• Both decision & sensory processes are influenced by factors other than stimulus intensity
• Signal detection theory


  • Predicts how and when we will detect a faint stimulus amid background noise
• We set criterion for when a weak signal equals danger
• What level of detection would be most adaptive, or provide the biggest fitness advantage?
• MRIs can be very challenging to read, especially when searching for brain lesions
• Sensory adaptation


  • Influences the registration of sensory stimulus input: prolonged stimulation leads to a gradual decline in sensitivity
• Sensory adaptation

  The process whereby sensitivity to prolonged stimulation tends to decline over time as an organism adapts to current conditions