AP PSYCH 3.1 Principles of Sensation

Gestalt Psychology

• Notable people are Wertheimer, Kohler, Koffka, and Perls
• This theory is the origin of cognitive psychology
• Rose in the early 1900s
• Based upon the idea that “the whole is greater than the sum of its parts”
• Gestalt translation: “placed” or “put together” or “pattern”
• What are the sum parts of our perceptions as our mind puts sensations into patterns?
• Describes principles that describe these patterns of human perceptions

Figure and Ground

Pragnanz

• The word pragnanz is a German term meaning “good figure”
• The law of good figure or the law of simplicity
• This law proposes that objects in the environment are perceived in the simplest way possible
• All Gestalt principles are based on how we simplify our world in similar ways
• Figure and ground is the organization of the visual field into objects (figures) that stand out from their surroundings (ground)

Grouping

• We group things in our visual field in a number of ways
• We do this in proximity, similarity, continuity, connectedness, closure
• These things may not actually be grouped in any way, but our perception organizes them in this way

Depth Perception

• The ability to perceive distance of objects in one’s visual field
  • We perceive in three dimensions: length, width, and depth
• There are two different kinds of cues we rely on to help us perceive distance or depth

Binocular cues

• Requires both eyes
• Convergence
  • Neuromuscular cue
  • Two eyes move inward for nearby objects
  • Two eyes straighten for further objects
• Retinal disparity
  • Images from each eye differ, coming together to make one perception
  • The closer the object, the larger the disparity
  • The further the object, the smaller the disparity

Monocular cues

• Requires only one eye
• Relative size
• Interposition
• Light and shadow
• Relative height
• Texture gradient
• Linear perspective

Sensory Transduction

• Stimulus goes into sensory receptors, which turn the stimulus into neural impulses our nervous system can understand, a sensation

Absolute Threshold

• The smallest amount of energy that will produce a sensation ‘most,’ or 50% of the time
• At what point, what what intensity does stimulus have to be, for us to detect it?
• Thresholds are usually very low, we are very sensitive to sensations
  • We don’t want them to be too low, however, because if we’re detecting everything, we can’t focus
• Children typically have lower thresholds than adults
  • Sensitivity lowers with age, like the natural degradation of hearing with age

Sensory Adaptation

• Diminished sensory awareness due to constant stimulation above the threshold
• Thanks to sensory adaptation, we are tuned to change
• After playing loud music for a long time, you won’t notice how loud it is after a while

Difference Threshold

• The smallest amount of change in a stimulus that will produce a change in sensation
  • Also called the just-noticeable difference
• Weber’s Law (or Weber-Fechner Law)
  • Physical proportion of change necessary before we “sense” the change
  • The ratio of actual change in the stimulus compared to the perceived change
• Like when getting a haircut, how much hair has to be cut off for you to notice the slightly different weight/feeling on your head?

Signal Detection Theory

• At what point are we able to detect a sensory signal?
  • In other words, how much stimulation is necessary to meet our absolute threshold for awareness?
• This idea was originally used in radar detection in the military
• Used in the medical field
• Used, now, in psychology
  • How do we strategize based on our own measure of detection