Distinguish between sensation and perception

Psychophysics: absolute threshold and difference threshold

Identify each major sensory system, their receptors, and type of sensory information each receives

Perception: selection, organization and interpretation


A process by which our sensory receptors and nervous system receive and represent stimulus energy

Process of receiving, converting, and transmitting information from the outside world

       (input of sensory information)

Perceptual Features: Basic stimulus patterns

Sensory Coding: Converting important features of the world into neural messages understood by the brain

Sensory Localization: Type of sensations you experience depends on which area of the brain is activated 




       Smell (olfaction)

       Taste (gustation)

       Vestibular sense (balance)

       Kinethesis (body movement)

       Touch (pressure, pain, temperature)


       Visual receptor cells located on retina: rods for night vision and cones for color vision

       The eye captures light and focuses it on the visual receptors, which convert light energy to neural impulses sent to the brain


       Audition (hearing) occurs via sound waves, which result from rapid changes in air pressure caused by vibrating objects

       Receptors located in the inner ear (cochlea) tiny hair cells that convert sound energy to neural impulses sent along to brain


Olfaction (smell) receptors are located at top of nasal cavity

Gustation - (taste) receptors are taste buds on tongue.  Four basic tastes: sweet, salty, sour and bitter


       Vestibular sense (sense of balance) results from receptors in inner ear

       Kinethesis - (body posture, orientation, and body movement) results from receptors in muscles, joint and tendons

       Skin senses detect touch (pressure, temperature and pain)


Sensory reduction - filtering and analyzing of sensations before messages are sent to the brain

Transduction - process of converting receptor energy into neural impulses the brain can understand

Adaptation - decreased sensory response to continuous stimuli


       Study of the relationship between the physical properties of stimuli and a person’s experience of them

       Absolute threshold - minimum amount of energy we can detect

       Difference threshold - (jnd) the smallest change in a stimulus we can detect


 Our sensory and perceptual processes work together to help us sort out complex processes


    Bottom-Up Processing

    • Analysis that begins with the sense receptors and works up to the brain’s integration of sensory information

Top-Down Processing

    • Information processing guided by higher-level mental processes
    • As when we construct perceptions drawing on our experience and expectations
  • Absolute Threshold 
    • minimum stimulation needed to detect a particular stimulus 50% of the time
  • Difference Threshold
    • minimum difference between two stimuli required for detection 50% of the time
    • just noticeable difference (JND)
  • Signal Detection Theory
    • predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise)
    • assumes that there is no single absolute threshold
    • detection depends partly on person’s
      • experience
      • expectations
      • motivation
      • level of fatigue


    • predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise)
    • assumes that there is no single absolute threshold

Detection depends partly on person’s

      • experience
      • expectations
      • motivation
      • level of fatigue


Stimuli and Receptors create experience which may be used to sense the external world.

Sensation is experience based


 a process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.

    “…a constructive process by which we go beyond the stimuli that are presented to us and attempt to construct a meaningful situation”.

  It is our reaction to the incoming stimulus


Prior experience leads you to expect to see certian things.

Certian is misspelled but you filled in the gap!

       Top-down:  perception is guided by  higher-level knowledge, experience, expectations, and motivations

       Bottom-up: perception that consists of recognizing and processing information about the individual components of the stimuli

Key Concepts:

  1. Selection
  2. Organization
  3. Interpretation
  4. Subliminal perception and ESP


Affected by:

        Selective attention (novelty,  familiarity,

       Feature detectors (brain)

       Habituation (getting used to)




Our minds likes simplicity/shortcuts to  understand the world

       Figure-Ground Organization: Inborn part of a stimulus stands out as a figure (object) against a less prominent background (ground)

Gestalt Principle

       Rules that summarize how we tend to organize bits and pieces of information into meaningful wholes

Organization is affected by:

       Figure ground (separation of background)

       Nearness: Stimuli that are near each other tend to be grouped together

       Similarity: Stimuli that are similar in size, shape, color, or form tend to be grouped together

       Closure/proximity: Tendency to complete a figure so that it has a consistent overall form

       Contiguity: Nearness in time and space; perception that one thing has caused another

       Common Region:  Stimuli that are found within a common area tend to be seen as a group

Constancy influences the organization of stimuli:

       Size constancy

       Shape constancy

       Color constancy

       Brightness constancy


Four factors are important for interpretation:

       Perceptual adaptation

       Perceptual set

       Individual motivation

       Frame of reference

       Brightness constancy

Subliminal interpretation:

       Stimuli that occur below the threshold of our conscious awareness but have a weak, if any effect on behavior

Depth Perception

Ability to see three-dimensional space and to accurately judge distances

What do you need to perceive distance and depth?

       Depth Cues: Features of environment, and messages, that supply information about distance and space

       Binocular Depth Cue: Depth cue that can be sensed with two eyes

Height Perception

       Context is important in judging the height!

       The mind decides the height of the object by comparing the object with features of the environment

Distance Perception.

Cues for depth:

      Linear Perspective: Based on apparent convergence of parallel lines in environment

      Overlap (Interposition): When one object partially blocks another

      Texture Gradients: Texture changes can contribute to depth perception; coarse texture implies closeness, fine texture implies distance

      Relative Motion (Motion Parallax): Nearby objects move a lot as your head moves; distant objects move slightly

Perception of Motion

       How do you know that you are moving (forward or backwards)?

       How do you approximate the speed?

       Background is important (the concept of figure/background applies)


    Misleading or distorted perceptions of stimuli that actually exists (error in perception)

   Hallucination: When people perceive objects or events that have no external basis in reality


       Bottom-Up Processing: Analyzing information starting at the bottom (small units) and going upward to form a complete perception

       Top-Down Processing: Preexisting knowledge that is used to rapidly organize features into a meaningful whole

       Perceptual Set: Readiness to perceive in a particular manner, induced by small expectations



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