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Chapter 4 Powerpoint : Intro and Vision . Detect. Interpreting. Environment. taste. smell. attention. Vestibular Sense. Sensation and Perception. Sensory Information. Senses. sight. touch. Kinesthesis. processing. Organizing. brain. hearing. Warm up.

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Chapter 4 powerpoint intro and vision

Chapter 4 Powerpoint: Intro and Vision

Chapter 4 powerpoint intro and vision







Vestibular Sense

Sensation and Perception

Sensory Information









Warm up

What is sensation? What is perception?


Sensation-- the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.

Perception--the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.

Top down processing
Top-down processing

Information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations.

Bottom- up processing

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

Theories of selective attention

Bottom up Theories

Top Down Theories

Top down theories of attention
Top Down Theories of Attention

  • These theories say that perception starts from the more complex

  • Selective Attention/ Attenuation Theory:

    • We process everything but everything doesn’t reach the highest centers of processing

    • You “pick and choose” what to process the most

    • Ex. Cocktail Party Phenomenon

Bottom up theories of attention
Bottom Up Theories of Attention

  • This theory says that perception starts with sensation

  • Because so much information is coming in, some sensory information is never processed

  • Filter Theory– We can’t process everything

Selective attention
Selective Attention

  • the focusing of conscious awareness on a particular stimulus.

  • You cannot pay attention to everything, only some things


The study of the relationship between physical characteristics of stimuli and our psychological experience of them

  • Light- brightness

  • Sound- volume

  • Pressure- weight

  • Taste- sweetness

Sensation thresholds
Sensation- Thresholds

  • Absolute Threshold

    • minimum stimulation needed to detect a particular stimulus 50% of the time

  • Difference Threshold

    • minimum difference between two stimuli required for detection 50% of the time

    • just noticeable difference (JND)

Selective attention1
Selective Attention

  • List 10 things you saw in the picture…..

Inattentional blindness
Inattentional Blindness

  • failing to see visible objects when our attention is directed elsewhere.

  • Change Blindness (failing to notice changes in the environment)

  • Choice Blindness

  • Choice Blindness Blindness

Sensation thresholds1
Sensation- Thresholds

  • Signal Detection Theory

    • predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise)

    • assumes that there is no single absolute threshold

    • detection depends partly on person’s

      • experience

      • expectations

      • motivation

      • level of fatigue

  • Priming

  • the activation, often unconsciously, of certain associations, thus predisposing one’s perception, memory, or response.

Thresholds signal detection
ThresholdsSignal Detection

  • Signal-detection theory

    • Ratio of “hits” to “false alarms”

Signal detection is not necessarily true



of correct












Intensity of stimulus

Signal Detection is not necessarily true…

  • Subliminal

    • When stimuli are below one’s absolute threshold for conscious awareness

Sensation thresholds2
Sensation- Thresholds

  • Weber’s Law- to perceive as different, two stimuli must differ by a constant minimum percentage

    • light intensity- 8%

    • weight- 2%

    • tone frequency- 0.3%

  • Sensory adaptation- diminished sensitivity as a consequence of constant stimulation

Wrap up

TICKET OUT: What are sensation and perception? How does our perceptual system help us to interpret the world around us? Explain.

Short Video About Sensation and Perception

Warm up1
Warm up

How does the visual system work?


  • Pupil- adjustable opening in the center of the eye

  • Iris- a ring of muscle that forms the colored portion of the eye around the pupil and controls the size of the pupil opening (dilates in response to changing light intensity)

  • Lens- transparent structure behind pupil that changes shape to focus images on the retina

  • Cornea- outer covering of the eye

  • Retina- the light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information.

  • Blind Spot - the point at which the optic nerve leaves the eye, creating a “blind” spot because no receptor cells are located there

  • Fovea- the central focal point in the retina, around which the eye’s cones cluster.

  • Optic Nerve- the nerve that carries neural impulses from the eye to the brain

Chapter 4 powerpoint intro and vision

Distal Stimulus– the object in the outside world

Proximal Stimulus– the object as it is projected on the retina (upside down)

This is how we see
This is how we see

Animation of how this works...

TERMS: Distal stimulus, proximal stimulus, fronto-parallel plane, Distal Object, Percept

Visual information processing feature detection
Visual Information ProcessingFeature Detection

  • Feature detectors

Visual information processing parallel processing
Visual Information ProcessingParallel Processing

  • Parallel processingsimultaneous processing of several aspects of a problem simultaneously

  • Blind sight

What is color
What is color?

  • Color is the psychological attribute given to our response to different wavelengths of visual light

  • It is psychological because it is perceived

  • Humans can only perceive colors on the visual spectrum. Perception has to do with light getting reflected off an object and onto the different types of cones in the eye

The stimulus input light energy
The Stimulus Input: Light Energy

Transductionconversion of one form of energy to another

In sensation, transforming of stimulus energies into neural impulses

Wavelengththe distance from the

peak of one wave to the peak of the next


Dimension of color determined by wavelength

of light


Amount of energy in a wave determined

by amplitude

Retina s reaction to light receptors
Retina’s Reaction to Light- Receptors

  • Rods

    • peripheral retina

    • detect black, white and gray

    • twilight or low light

  • Cones

    • near center of retina

    • fine detail and color vision

    • daylight or well-lit conditions

Rods and cones
Rods and Cones

Rods are sensitive only to black and white and are sensitive to light and dark.

Cones come in three types, each sensitive to a different color: red, green, and blue. Cones are concentrated in the center of the retina, while rods form the periphery of the retina.

The eye the retina
The EyeThe Retina

  • Rods and Cones



How cones perceive colors
How Cones Perceive colors

There are 3 different types of cones that respond to different types of wavelengths.

•Short-wavelength cone receptors β

•Middle-wavelength cone receptors γ

•Long-wavelength cone receptors. ρ

Different “colors” of light stimulate the different cone cells in different combinations, thus accounting for the different colors we see.

This is called the Trichromatic Theory of Color Vision

Color vision
Color Vision

  • Young-Helmholtz trichromatic (three color) theory

    • Red – Green - Blue

    • Monochromatic vision

    • (only can perceive 1 of 3) vision

    • Dichromatic vision (2 of 3)

    • People who can’t read the

      number in the box could

      be color blind

Color vision1
Color Vision

  • Opponent-process theory

    • Three sets of colors

      • Red-green

      • Blue-yellow

      • Black-white

    • Afterimage

Color blindness
Color Blindness

  • The inability to differentiate certain colors

  • More common in men because on x chromosome (women need 2 genes to inherit but men only have 1 x chromosome)

  • There are three types:

    • Red/ green (95%)

    • Blue/ yellow

    • All colors

Color Blindness Simulator

Chapter 4 powerpoint intro and vision


On worksheet fill in definition and one example.

How does the eye work like a camera?

Chapter 4 powerpoint intro and vision

Visual Information Processing

  • There are 4 different “cues” to perception. They are:

    • - Shape Constancy

    • Size Constancy

    • Color Constancy

    • Monocular and Binocular Depth Cues

How do they work???


  • Accommodation- the process by which the eye’s lens changes shape to help focus near or far objects on the retina

  • Acuity- the sharpness of vision

  • Nearsightedness- condition in which nearby objects are seen more clearly than distant objects because distant objects in front of retina

  • Farsightedness- condition in which faraway objects are seen more clearly than near objects because the image of near objects is focused behind retina


  • Normal Nearsighted Farsighted

    Vision (myopic) Vision (hyperopic)


What is an illusion?

What is an illusion
What is an illusion?

  • Also known as Visual Illusions

  • involves visual deception.

  • When looking at an illusion our visual system can perceive misleading visual effects

  • There is no one good reason

  • Because Perceptual Constancies (size, shape, color, etc.) are just merely cues we can misinterpret what we look at

  • Also our visual system groups items (gestalts) and this can cause misperception


  • Spinning wheel illusion (after image)

  • Magic coins illusion (after image)

  • Wundt-Jastrow illusion

  • (effect of context/contrast on perception)

Ponzo illusion
Ponzo Illusion

Ambiguous figures
Ambiguous Figures

  • In some illusions there is not enough information in the image to make a decision as to the “best” interpretation

  • Shows us the importance of “interpretation”

  • How we see it depends on how we perceptually organize.

  • Also depends on the context in which we just saw it and individual bias, etc.

Reversible figures
Reversible figures

  • Follow the same principle

Impossible figures
Impossible Figures

  • Follow the same principle of not enough information so we interpret it

  • Usually a 2-D figure which interpreted by the visual system as representing a projection of a three-dimensional object that is not geometrically possible

M c escher
M.C. Escher



Researchers have traditionally used what is known as lateral inhibition to explain why people see these gray areas. This phenomena demonstrates a very important principle of perception: we don't always see what's really there. Our perceptions depend upon how our visual system responds to environmental stimuli and how our brain then interprets this information. New theories suggest there might be a better explanation.

Muller lyer illusion
Muller-Lyer Illusion

Zollner illusion
Zollner Illusion

Chapter 4 powerpoint intro and vision

Ponzo Illusion

Chapter 4 powerpoint intro and vision

How does it work?

  • The Ames room forms an identical image of a normal cubic room on your retina even though it is not cubic.