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Unit 4: Sensation and Perception

Chapter 4

james etheridge

on 29 October 2018

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Transcript of Unit 4: Sensation and Perception

Sensation: stimulation of sense organs
Sensation and Perception
the study of how physical stimuli are translated into psychological experience
What you see elicits a reaction
Sensation begins with a detectable stimulus
: the concept of the threshold
Absolute threshold
: detected 50% of the time

little little little
The Just noticeable Difference (JND)
, also known as the
Difference Threshold
, is the minimum changing level of stimulation that a person can detect 50-percent of the time.

For example, if you were asked to hold two objects of different weights, the JND would be the minimum weight difference between the two that you could sense half of the time.
Weber’s law
: size of JND proportional to size of initial stimulus

Sensory processes + decision processes=
perception and behavior
Vision Stimulus
Light = electromagnetic radiation
Perception of brightness
Perception of Color
Saturation of color
Clear covering where light enters the eye
Opening that Regulates the amount of light.
Colored muscle
Constricts or dilates depending
on amount of light
The lens focuses the light on to
the back of the Retina
Back of the eye that absorbs light and processes images
Figure 4.9 The retina
Figure 4.8 Nearsightedness and farsightedness
Optic disk:
optic nerve connection/blind spot
Receptor cells:
: black and white/low light vision
: color and daylight vision
Figure 4.9 The retina
Adaptation to light
Becoming more or less sensitive to light as needed.
How vision affects the brain.
The main pathway is divided into different visual channels
Figure 4.15 The what and where pathways from the primary visual cortex
Hubel & Weisel
Feature detectors: Neurons that selectively respond to lines and edges.
Some feature detectors in the Temporal Lobe respond to faces
Short violet
Long Red
How do we see color?
Red, Blue, Green color receptors mix
Opponent processing theory
Trichromatic theory
Young and Helmholz
What about Yellow? For afterimages or colorblindness you need opposite colors that when on turn off their opposing color.
The opposite pairs of colors are:


(mnemonic: think Winter Furlow tree)
(mnemonic: think UCLA)

(mnemonic: think checkers or chess)
The Ear

Much like light sound travels in waves
The vibration of the air molecules becomes sound
=Volume measured in decibels
=how high or low the sound is. the pitch
=purity or complexity of sound
Wavelength is described in frequency which is measured in hz
Collects sound waves, the bigger the dish the better the signal.
The Pinna is part of the outer ear
Figure 4.46 The human ear
The Ossicles
Hammer, Anvil, Stirrup
These bones vibrate from the ear drum against the semicircular canal and cochlea to translate vibration into sound.
Inner ear- fluid filled coiled tunnel hair cells are lined up in the basilar membrane
Figure 4.47 The basilar membrane
1. Sound waves vibrate bones of the middle ear
2. Stirrup hits against the oval window of cochlea Sets the fluid inside in motion
3. Hair cells are stimulated with the movement of the basilar membrane
4. Physical stimulation converted into neural impulses
5. Sent through the thalamus to the auditory cortex (temporal lobes)
The Auditory Pathway
How do we hear?
Hermann von Helmholtz (1863)
Place theory
Rutherford, 1886
Frequency theory
the frequency of the waves in the basilar membrane are interpreted as sound
Georg von Bekesy (1947)-
Traveling wave theory
Two cues critical:
Intensity (loudness) can tell you how close the stimulus is to you.
Timing of sounds arriving at each ear

Head as “shadow” or partial sound barrier
Timing differences as small as 1/100,000 of a second allows you to find the sound.
Figure 4.48 Cues in auditory localization
Soluble chemical substances stimulate receptor cells in taste buds
At the back of the tongue the bitter taste buds keep us from swallowing poisons, causing a gag reflex.
Food that has spoiled will often times be sour.
Sugar and sweet is an indicator of energy necessary for survival.
Salt is necessary for our muscle function and neural function
Physical stimuli carried in the air stimulates the olfactory nerve
Does not go through
the Thalamus
Memories are linked strongly through the sense of smell
Physical stimuli = mechanical, thermal, and chemical energy impinging on the skin.
Mechanical stimuli include tension, pressure or vibration.
Free nerve endings specific to cold or warmth
Free nerve endings that are divided in to fast and slow pain receptors.
Figure 4.53 Pathways for pain signals
Perception: selection, organization, and interpretation of sensory input
Perceiving Forms, Patterns, and Objects
Reversible figures
Perceptual sets
Inattentional blindness
Feature detection theory - bottom-up processing
Form perception - top-down processing
Subjective contours
Gestalt psychologists: the whole is more than the sum of its parts
Reversible figures and perceptual sets demonstrate that the same visual stimulus can result in very different perceptions
Perceiving Forms, Patterns, and Objects
Reversible figures
Perceptual Sets
Innattentional and Change blindness
Feature Detection Theory
Form Perception
a drawing that is compatible with two interpretations that can shift back and forth (see following slides for depiction
is a readiness to perceive a stimulus in a particular way.
involves the failure to see fully visible objects or events in a visual field.
people detect specific elements in stimuli and build them up into recognizable forms…bottom-up processing
Figure 4.22 Feature analysis in form perception
Top down processing, looking at the whole and moving down to the details.
Figure 4.23 Bottom-up versus top-down processing
Subjective Contours
Max Wertheimer
~ principle maintains that the human eye sees objects in their entirety before perceiving their individual parts.
The whole is greater then a sum of it's parts!
a property of perception in which there is a tendency to see parts of a visual field as solid, well-defined objects standing out against a less distinct background. Reversible figure.
We lump like things together to make meaning out of them.
Distal vs. Proximal

To understand what perception does, you must understand the difference between the the proximal (~approximate = close) stimulus and the distal(~ distant) stimulus or object.
Your senses and your positioning vs. what you define what you are seeing as defined by you.
Depth and Distance perception
Binocular Cues
-cues from both of your eyes
Retinal Disparity
-objects within 25 feet project images to slightly different locations on the left and right retinas; thus each eye sees a slightly different view of the object)
-convergence, feeling the eyes converge toward
each other as they focus on a target.
Monocular Cues
-cues from a single eye
Motion Parallax
having images of objects at different distances moving across the retina at different rates.
It's why the moon stays in the sky and the building and the countryside fly by.
The feeling of the lens as it changes shape as the eye focuses.
Perceptual Constancies
You will create a tri-fold Pamphlet that teaches the principles of the Human senses.
Include sight, hearing, taste, smell, touch, etc.
Use this opportunity to learn and demonstrate your knowledge.
Do good work, take pride, have fun!
on Learning Exercise!
The Senses Pamphlet
- knowing the position of the various parts of the body
Kinesthetic receptors
lie in the joints, indicating how much they are bending, or in the muscles, registering tautness or extension.
Other Senses:
Kinesthetic and Vestibular
- responds to gravity and keeps you informed of your body’s location in space.
It provides your sense of
balance or equilibrium

Semicircular canals
~When your head moves, the fluid moves, moving the hair cells, and initiating neural signals that travel to the brain.

occurs when there is a general
decline in sensitivity to
prolonged stimulation.
Sensory Adaptation

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Guy playing a saxophone

Girls Face
We're up on Mexican Lucky
The process of using your brain to organize and interpret sensory input.
Signal-Detection Theory:
Signal-Detection Theory:
Get Ready....
Right half,
close your eyes...
Now, the left half...
as fast as you can, write down what you see....
A Mouse
Old Man w/Glasses
Ames Room
Is this another sense we take for granted?
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