Sensation and Perception


  • Sensation is the process by which our senses gather information and send it to the brain
  • A large amount of information is being sensed at any one time such as room temperature, brightness of the lights, someone talking, a distant train, or the smell of perfume
  • With all this information coming into our senses, the majority of our world never gets recognized
  • We only sense those things we are able too since we don't have the sense of smell like a bloodhound or the sense of sight like a hawk; our thresholds are different from these animals and often even from each other

What we don’t see

We don't notice:

  •  Radio waves
  •  X-rays
  • Or the microscopic parasites crawling on our skin
  • We don't sense all the odors around us
  •  Taste every individual spice in our gourmet dinner

Types of Sensations

  • Absolute Threshold (point where something becomes noticeable to our senses)
  • It is the softest sound we can hear or the slightest touch we can feel.
  •  Anything less than this goes unnoticed.
  • The absolute threshold is therefore the point at which a stimuli goes from undetectable to detectable to our senses
  • Difference Threshold (the amount of change needed for us to recognize that a change has occurred)
  • Once a stimulus becomes detectable to us, how do we recognize if this stimulus changes?
  •  When we notice the sound of the radio in the other room, how do we notice when it becomes louder

Absolute Difference

  • Imagine holding a five pound weight and one pound was added.
  • Most of us would notice this difference.
  • But what if we were holding a fifty pound weight?
  • Would we notice if another pound were added?

Signal Detection

  • Signal detection Theory (attempt detect what we want to focus on and ignore or minimize everything else)
    • This is what happens when we focus on one person talking in a crowded room where lots of people are talking.. This focusing in and ignoring the other flood of information is what this theory is stating.

Sensory Adaptation

  • Sensory Adaptation (to stimuli which has become redundant or remains unchanged for an extended period of time)
  • Once we adapt to the ticking of the clock, we stop recognizing it.


  • Again it  refers to the  interpretation of what we take in through our senses
  • The way we perceive our environment is what makes us different from other animals and different from each other
  • Perception helps us make sense of what we see, hear, taste, touch, and smell.


  • In order to interpret what we receive through our senses, Theorists theorized that we attempt to organize this information into certain groups
  • This allows us to interpret the information completely without unneeded repetition
  • When you see one dot, you perceive it as such, but when you see five dots together, you group them together by saying a "row of dots.“
  •  Without this tendency to group our perceptions, that same row would be seen as "dot, dot, dot, dot, dot," taking both longer to process and reducing our perceptive ability

Gestalt Theory

  • Roughly translates to "whole" or "form," and the Gestalt psychologist's sincerely believed that the whole is greater than the sum of its parts
  • The Gestalt principles of grouping include four types: similarity, proximity, continuity, and closure.


  • Similarity refers to our tendency to group things together based upon how similar to each other they are.
  • In the first figure above, we tend to see two rows of Black dots and two rows of Blue dots.
  •  The dots are grouped according to similar color.


  • In the next figure, we tend to perceive three columns of two lines each rather than six different lines.
  •  The lines are grouped together because of how close they are to each other, or their proximity to one another.


  • Continuity refers to our tendency to see patterns and therefore perceive things as belonging together if they form some type of continuous pattern.
  •  In the third figure, although merely a series of dots, it begins to look like an "X" as we perceive the upper left side as continuing all the way to the lower right and the lower left all the way to the upper right. 

Perceptual Consistency


  • Every time an object changed we had to completely reprocess it.
  • The next time you walk toward a building, you would have to re-evaluate the size of the building with each step, because we all know as we get closer, everything gets bigger.
  • The building which once stood only several inches is now somehow more than 50 feet tall.
  • Perceptual constancy (our ability to see things differently without having to reinterpret the object's properties)
  • Definition: A situation or surrounding substance within which something else originates, develops, or is contained

More notes to be given within class to add to these.