Sensation and Perception

Be able to recognize:

1. Difference between “sensation” and “perception.”

2. Absolute thresholds (with examples) and just noticeable

differences.

3. Parts and functions for major components of the visual

processing system.

4. Explanation for near- and far-sightedness.

5. Dark and light adaptation. (text)

6. Hubel and Wiesel's study of processing in the visual cortex.

(text & video)

7. SKIP theories of color vision.

Objectives

Sensation and Perception: The Distinction

• Sensation:

Immediate response in the brain caused by

stimulation of a sensory organ (eye, ear, etc.).

• Perception:

Selection, organization, and interpretation of

sensory input

( adapted from Thomson Higher Education, 2007, 2001)

Sensation

Sensation begins with a detectable stimulus

– Fechner: Concept of “threshold”

– “Absolute threshold” = Detected 50% of the time.

( adapted from Thomson Higher Education, 2001)

Some Human Thresholds

(adapted from Wadsworth/Thomson Learning, 2001)

Visual Sensation

The Eye

( adapted from Thomson Higher Education, 2007)

Cornea Transparent “window” at front of eye

Iris Colored circular muscle that expands and

contracts, controlling amount of light that enters

the eye - Responsible for eye color

Pupil Opening at center of eye through which light

passes

Lens Transparent – focuses light on retina

Blind Spot Area of the retina lacking visual receptors

The Eye

(Cengage, 2019)

The Retina: An Extension of the CNS

• Retina: absorbs light, processes images,

and sends information to the brain

• Receptor cells:

– Cones: Visual receptors for colors and

bright light (daylight)

– Rods: Visual receptors for dim light; only

produce black and white

• Adaptation: becoming more or less sensitive to

light as needed

( adapted from Thomson Higher Education, 2007)

Rods, Cones, & Ganglion Cells

(adapted from Wadsworth/Thomson Learning, 2001)

Nearsightedness

Farsightedness

Dark

Adaption

Visual

Pathways

Hubel & Wiesel: Feature Detectors

Discovering Psychology - Zimbardo

Post-

Occipital

Processing

Reading?