Sensation and PerceptionChapter 3

Psychophysics

• This is how we experience our physical world.

• Classroom demo judging weight of pill bottles.

• Which one do you think weighs the most?• The more compact weight “felt” heavier to

your brain when in reality it weighed the same as the large container.

Sensation

• The process by which our sensory systems (eyes, ears, and other sensory organs) and nervous system receive stimuli/info from the environment

• A person’s awareness of the world through their senses.

Sensation usesBottom-Up Processing

• Information processing that focuses on the raw material entering through the eyes, ears, and other organs of sensation

Perception

• The process of selecting, organizing and interpreting sensory information

• How you make sense of your sensory information.

Perception usesTop-Down Processing

• Information processing that focuses on expectations and experiences in interpreting incoming sensory information

Read the following

• Aoccdrnig to rscheearch at Cmabrigde Uinervtisy, it deosn’t mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a total mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.

Bottom-Up vs. Top-Down ProcessingFollow the directions carefully!

• Go to http://jeffmilner.com/backmasking.htm. Pick a song from the list and listen to it normally (play forward).

• Now listen to it in reverse. DO NOT CLICK ON “SHOW REVERSE LYRICS”

• Now listen to it in reverse again, this time “Show the Reverse Lyrics”• Can you hear the “secret” message?• Why couldn’t you hear it the first time you listened in reverse?

– You had no expectations. Just heard sounds. This is Bottom-Up processing!

• Why could you make out the “hidden message” when you could see the reverse lyrics?– When told what to listen for the task becomes Top-Down

processing! You are using your expectations!

Do subliminal messages work?• Subliminal messages make two assumptions:1. We can unconsciously sense the subliminal (below

threshold) message. - TRUE2. Without our awareness, the stimuli have suggestive

powers. - FALSE• Subliminal messages can affect how we “feel” about

something for a short period of time but CANNOT persuade us to actually go out and do something.

• Remember, weak stimuli have weak responses and strong stimuli have strong responses.

• Extra credit to anyone who can make a coherent song that when played backwards says, “I love psychology!”

I Love Psych!!!

Did it work?

• Do you really love psychology now?

• It was worth a try!

Principles of Sensation

• Transduction— process where physical energy is converted into neural signals

• How we convert stimuli from the environment into action potential that the brain can understand.

The Major Senses• There are 6 major senses

– vision

– hearing

– touch

– taste

– pain

– smell

• The list can be extended with balance, joint senses and others

• Vision has been studied most extensively