Sensation and Perception

Sensation: your window to the world Perception: interpreting what comes in your window.

(you are sensing and perceiving right now by reading this!)

Sensation

detecting physical energy from the environment and encoding it as neural signals

(associated with bottom-up processing)

Perception

selecting, organizing, and interpreting our sensations as meaningful objects and events

(associated with top-down processing)

Sensation and Perception WORK TOGETHER!!!

• Examples: – Hearing – you “sense” the noises the

vocal tract makes when a person speaks, you “perceive” the meaning of what those noises represent

– Health Problem – you “sense”sudden pain in your heart,

you “perceive” by recognizing you are suffering a heart attack

ATTENTION!

• I am going to show you a picture… what’s the FIRST thing you notice?

• Half of the class needs to cover their ears while I make an announcement before displaying the picture…

Bottom-Up Processing

• Also called feature analysis.

• Analysis that begins with the sensory receptors and works up to the brain’s integration of sensory information

Top-Down Processing

• Guided by higher-level mental processes, such as experience, motivation, and expectations

• If you see many old men in glasses, you are more apt to process a picture of an old man (even when you may be in error).

BOTTOM-UP PROCESSING:

**detecting lines, angles, and

colors that form the horses,

riders, and surroundings

TOP-DOWN PROCESSING:

**consider the painting’s title,

notice the apprehensive

expressions, and attend to

aspects that give meaning

The Impossible Tune

• Listen to the clip…

• After I play it, take 30 seconds and THINK about an explanation…

• Remember, we’re talking about SENSATION and PERCEPTION!!! How might they explain?

Perceptual Interpretation

Perceptual Adaptation

(vision) ability to adjust to an artificially displaced visual field

prism glassesdemonstration

Invertedimage Video

Psychophysics and Transduction

• Psychophysics: the study of how physical energy relates to our psychological experience

• Transduction: conversion of one form of energy into another

• Information goes from the senses to the thalamus, then to the various areas in the brain.

Remember Ethan in Sky High. He changes his body to slime. Solid form to liquid form. Change from one form of energy to another.

Absolute Threshold

the minimum stimulation needed to detect a particular

stimulus 50 percent of the time

•A single candle flame 30

miles away

•A drop of perfume in a

six-room apartment

•a ticking of a watch from

20 feet away

•The pressure of a wing

of a bee falling on our cheek

Difference Threshold(Just Notable Difference)

the minimum difference a person can detect between

any two stimuli half the time

Weber’s Law: difference thresholds differ by a

constant percentage rather than amount**exact proportion varies by stimulus: weight must differ by 2%; light intensity by 8%

Signal Detection Theory

• predicts when we will detect weak stimuli amid background noise

• Things like motivation, experience, expectations, or physical state can effect what we sense

A mom might sleep through a thunderstorm, but if one of her sons even whimpers, she is up!!!

Subliminal Messages

• Stimuli below our absolute threshold.

• We unconsciously sense it

• Do Subliminal Messages work?

• To an extent… they can prime your later behavior to a very small degree

Play “Help” backwards "Now he uses marijuana.“

Sensory Adaptation• diminished sensitivity

as a consequence of constant stimulation

• Purpose is to help us focus on changes in our environment

– Water is cold at first but then you get used to it!

– Hear the “buzz” of a powered TV at first, but then goes away

– Why doesn’t our vision go away??

Do you feel your underwear all day?