What we’ll sense and perceive…in this chapter:

Sense: especially vision and hearing smell, taste, touch, pain, and

awareness of body position How do the sense organs and

nervous system handle incoming sensory information?

How does the brain turn sensory information into perceptions?

Why is our style of creating perceptions better at perceiving the real world than at decoding tricky optical illusions?

Basic Principles of Sensation and

PerceptionYour brain will interpret, perceive these topics as they enter your sense organs: Sensation vs. Perception, Bottom-

Up vs. Top-Down Processing Transduction and Thresholds Sensory Adaptation Perceptual Set Context Effects on perception Emotion/Motivation effects

DO NOW

What is the difference between sensation and perception?

What is the difference between Bottom-up and Top-down Processing?

Sensation vs. Perception

“The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.”

“The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.”

The brain receives input

from the sensory organs.

The brain makes sense out of the

input from sensory organs.

Sensation Perception

Making sense of the world

What am I seeing?

Is that something I’ve seen before?

Bottom-up processing:

taking sensory information and then assembling and integrating it

Top-down processing:

using models, ideas, and

expectations to interpret sensory

information

Top-down Processing You may start

to see something in this picture if we give your brain some concepts to

apply: “tree”

“sidewalk”“dog”

“Dalmatian”

From Sensory Organs to the Brain

The process of sensation can be seen as three steps:

Reception--the stimulation

of sensory receptor cells by energy (sound, light, heat, etc)

Transduction-- transforming

this cell stimulation into neural impulses

Transmission--delivering this

neural information to the brain to be

processed

Thresholds

The absolute threshold: the minimum level of stimulus intensity needed to detect a stimulus half the time.

Anything below this threshold is considered

“subliminal.”

When Absolute Thresholds are not Absolute

9

Signal detection theory refers to whether or not we detect a stimulus, especially amidst background noise. This depends not just on intensity of the stimulus but on psychological factors such as the person’s experience, expectations, motivations, and alertness.

Subliminal Detection

Although we cannot learn complex knowledge from subliminal stimuli, we can be primed, and this will affect our subsequent choices.

We may look longer at the side of the paper which had just showed a nude image for an instant.

Subliminal:below our threshold for

being able to consciously detect a stimulus

Difference threshold: the minimum difference (in color, pitch, weight, temperature, etc) for a person to be able to detect the difference half the time.

Weber’s law refers to the principle that for two stimuli to be perceived as different, they must differ by a minimum percentage: 2 percent of weight 8 percent of light intensity 0.3 percent of sound wave frequency to notice a

difference in pitch. Any changes noticeable on this slide?

The “Just Noticeable Difference”

To help detect novelty in our surroundings, our senses tune out a constant stimulus, such as: a rock in your shoe the ticking of a clock

If you concentrate on keeping your eyes in one spot, you’ll see the effects, as your eyes adjust to stimuli

Visual sensory adaptation will be tested when discussing opponent-process theory.

Sensory Adaptation

Perceptual SetPerceptual set is what we expect to see, which influences what we do see. Perceptual set is an example of top-down processing .

Loch Ness monsteror a tree branch?

Flying saucersor clouds?

Perceptual set can be “primed.”

Old woman Young woman

Ambiguous

Context Effect on Perception

Spelling test answers:

In which picture does the center dot look larger? Perception of size depends on context.

Did context affect which word you wrote?apple payor payee pairdouble pear

Effect of Emotion, Physical State, and Motivation on Perception

Experiments show that: destinations seem farther

when you’re tired. a target looks farther

when your crossbow is heavier.

a hill looks steeper with a heavy backpack, or after sad music, or when walking alone.

something you desire looks closer.

Vision, and Perceptual Organization and Interpretation

And: ESP, Perception without Sensation

Vision (Sensation): The Eye From light input to mental

images Retina and Receptors Feature Detection Parallel Processing Color Vision

Visual Organization: Form, Depth, and Motion

Perception Size, Shape, and Color

Constancy Visual Interpretation: Restored Vision Perceptual Adaptation

Topics we’ll be looking into:

The Visible

Spectrum

We encounter waves of electromagnetic radiation. Our eyes respond to some of these waves.Our brain turns these energy wave sensations into colors.

Vision: Energy, Sensation, and

Perception

Color/Hue and Brightness

We perceive the wavelength/frequency of the electromagnetic waves as color, or hue.

We perceive the height/amplitude of these waves as intensity, or brightness.

Light from the candle passes through the cornea and the pupil, and gets focused and inverted by the lens. The light then lands on the retina, where it begins the process of transduction into neural impulses to be sent out through the optic nerve.

The lens is not rigid; it can perform accommodation by changing shape to focus on near or far objects.

The Eye

The Retina

The Blind Spot

There is an area of missing information in our field of vision known as the blind spot. This occurs because the eye has no receptor cells at the place where the optic nerve leaves the eye.

To test this, walk slowly up to the screen with one eye closed and the other eye fixed on the dot, and one of the phones will disappear.

Photoreceptors: Rods and Cones When light reaches the back of the retina, it triggers

chemical changes in two types of receptor cells: Rods help us see the black and white actions in our

peripheral view and in the dark. Cones help us see sharp colorful details in bright light.

Visual Information Processing

The images we “see” are not made of light; they are made of neural signals which can be produced even by pressure on the eyeball.

The rods and cones send messages to ganglion and bipolar cells and on to the optic nerve.Once neural signals enter the optic nerve, they are sent through the thalamus to the visual cortex.