psychology

PSY-101: Principles of Psychology

Chapter 4: Sensation and Perception

SENSING THE WORLD AROUND US Sensation

● Activation of the sense organs by a source of physical energy

Perception ● Sorting out, interpretation, analysis, and

integration of stimuli carried out by the sense organs and brain

IS PERCEPTION RELIABLE?

SENSATION VS. PERCEPTION

● The physical sensation of the two squares is identical ○ The light entering your eye from each are the same

● Our brains perceive them being different shades based upon expectations ○ We expect a “checker pattern” and assume the “white”

square is lighter because a shadow is cast over it

TURNING DOWN OUR NEURAL RESPONSES

Sensory Adaptation ● An adjustment in sensory capacity after

prolonged exposure to unchanging stimuli ● Allows us to “tune out” unchanging (and

potentially unimportant) stimuli

THE VISUAL SYSTEM You should be able to describe the basic anatomy of the visual system:

● Cornea ● Iris ● Pupil ● Lens ● Retina ● Fovea ● Optic Nerve

THE CELLS OF THE RETINA Rods

● Concentrated in the periphery ● Work well in low-light conditions

Cones ● Concentrated in the fovea ● Work well in bright light and allow us to detect

color

HOW WE SEE 1. Light waves enter the eye through the pupil 2. Lens focuses the light on the retina 3. Rods and cones “fire” in response to the light 4. These neural impulses travel through the optic

nerve to the brain for processing

COLOR VISION

OPPONENT-PROCESS THEORY ● There’s no color in the image when it changes over

○ Your brain adds color as an afterimage ● Your rods and cones get fatigued from overstimulation

○ When the image changes, we can only perceive the opponent process of those respective cells ■ Red → Green ■ Blue → Yellow ■ Black → White

THE AUDITORY SYSTEM

HOW WE HEAR 1. Sound waves cause the eardrum to vibrate 2. Vibrations move ossicles (i.e., middle ear bones) 3. Movement of ossicles moves fluid in the cochlea 4. Movement of the fluid in the cochlea moves hair

cells on basilar membrane 5. Movement of the hair cells creates neural impulses

that are sent to the brain for processing

THE OTHER SENSES Taste and Smell

● Molecules (e.g., of food) bond to receptors on the tongue (taste buds) and in the nose (olfactory cells)

● When molecules attach to these receptors, neural impulses are created and sent to the brain for processing

THE OTHER SENSES Touch, Temperature, and Pain

● Cells throughout the skin (and other bodily tissues) respond to pressure, vibrations, and stretch

● When cells fire in response to stimuli, neural impulses are created that are sent to the brain for processing

MANAGING PAIN “Flood the pain gate”

● Create extra sensory information from area surrounding the source of pain ○ e.g., heavily massage whole foot after bumping toe

“Close the pain gate” ● Refocus attention on something other than the pain

○ e.g., tickle a child and be silly after they bump their toe

GESTALT PRINCIPLES ● Help us explain how we organize visual sensory

information ● Our perceptions are subjective

○ Influenced by bias, past experiences, and expectations

○ They’re our brain’s “best guesses” ○ Can be incredibly inaccurate

THE TAKEAWAY... ● The way you perceive the world is just that. The way

“YOU” perceive the world ● No one person is living an objective reality

HELP ME BUILD A BETTER CLASS!

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The material for these slides was adapted from:

Introduction to Psychology An open-access text written and edited

by multiple individuals and organizations

Greg Mullin, 2022 - Licensed CC BY - SA