SENSES: VISION. Chapter 5: Sensation AP Psychology Fall 2014

Transcription

1 SENSES: VISION Chapter 5: Sensation AP Psychology Fall 2014

2 Sensation versus Perception Top-Down Processing (Perception) Cerebral cortex/ Association Areas Expectations Experiences Memories Schemas Anticipation Perception Bottom-Up Processing (Sensation) Sensory detection (incoming sensory information) Sensory receptors Neural signals

3 SENSATION: Theories & Concepts

4 Sensory Threshold Theory #1: Absolute Threshold Minimum stimulation to detect stimulus 50% of time Different for each individual Theory #2: Signal Detection Ability to detect stimulus depends on: Motivation, fatigue, expectations Our minds prepare us to see or hear certain stimuli over others

5 Adjusting to new stimulus (temperature of water, level of darkness in a room, etc.) Sensory Threshold Difference Threshold: Detecting a change in stimulus that can already be detected Weber s Law: exact proportion Light: 8% Weight: 2% Tone:.3% Sensory Adaptation (We get used to it and don t notice it anymore!) Diminishing sensitivity to constant stimulus (we no longer notice the feeling of our clothes on our skin)

6 Subliminal Stimuli Stimuli below one s conscious ability to detect it Our minds still see the stimuli Subliminal messages cannot make us behave differently than we normally would Subliminal messages can affect our mood, which can be associated with a particular product (in advertising) and we may feel positively when we see that product on the store shelves.

7 An example of the impact of subliminal messages Derren Brown Experiment

8

9 VISION: LIGHT ENERGY

10 Electromagnetic Spectrum We can only see a very small section of electromagnetic energy Our eyes are designed to only be receptive only to a very small range of wavelengths.

11 Properties of Waves wavelength: the distance from one wave peak to the next (color) Intensity: the amount of energy in light waves (color brightness); determined by Amplitude: height of the wave

12 VISION: TRANSDUCTION (the process of changing energy from one source to another)

13 Transduction Process Step 1 Step 2 Light enters eye (enough that we can perceive it) Cornea: protects eye; bends light Step 3 Pupil: regulated by iris (a muscle); determines amount of light that enters eye

14 Transduction Process Pupil: regulated by iris; determines amount of light that enters eye Step 3 Lens: focuses rays into image on back of the retinal wall (accommodation) Step 4 Retina: rods and cones located here (where energy waves are turned into electrical impulses Step 5

15 Transduction Process Retina: rods and cones located here Step 5 Rods: Black and white receptors; more sensitive to light Step 5a Cones: Color receptors Step 5b Fovea: point of central focus; cones only for sharp vision Step 5c

16 Transduction Process Step 6 Bipolar Cells: neural impulse created Step 7 Ganglion Cells: converge to form Step 8 Optic Nerve: blind spot

17 FIND YOUR BLIND SPOT!

18 Transduction Process Optic Nerve: blind spot Step 8 Thalamus Step 9 Visual Cortex (Occipital Lobe): This is where the pixels are put back together to create images. Step 10

19 COLOR VISION: A 2-Step Process

20 Color Vision: Step 1 Young-Helmholtz trichromatic (3-color theory): Cones Retina has 3 types of color receptors: blue, green, red This means that we have specific cones that are receptive to the wavelengths for red, green and blue

21 Color Vision: Step 1 Young-Helmholtz trichromatic (3-color theory): Retina has 3 types of color receptors: red, green, blue This means that we have specific cones that are receptive to the wavelengths for red, green and blue We see other colors besides those 3 because the our receptors are stimulated to various degrees and add wave lengths together as in the additive color process The longer the wave length (as colors are added together), the lighter the color becomes (until it appears white)

22 Color Vision: Step 2 Hering s opponent-process theory: Neurons Neurons that transmit electrical impulses from the retina to the thalamus and the visual cortex are turned on or activated while other neurons aren t. Some of these neurons are turned on or activated by: Red and green cones while other neurons are turned on or activated by: Blue and yellow Black and white

23 Color Vision: Step 2 Hering s opponent-process theory Neurons that transmit visual information are set up on an opponent system: Red and green are opposites on the color wheel. Blue and orange are opposites on the color wheel. Black and white are opposites. Our neurons are set up the same way: a red-green neuron can only fire either red or green.

24 Color Vision: Step 2 Hering s opponent-process theory This theory explains why we experience the afterimage effect: staring at red for a period of time activates the neurons responsible for transmitting red-green visual information to the visual cortex. Those neurons tire out after awhile! So when the eye shifts its focus from a red wavelength to a blank background, the afterimage will appear green. This happens because the red-green neuron has worn out its sensitivity to red, so we perceive its opponent color instead.

25 Color Vision: Step 2 Hering s opponent-process theory

26 Color Vision: Step 2 Hering s opponent-process theory

27 Color Vision: Step 2 Hering s opponent-process theory

28 Color Vision: Step 2 Hering s opponent-process theory

29 Feature Detection Putting the visual information together into meaningful images involves several components of our visual cortex working together simultaneously Specific neural nets within our visual cortex are responsible for identifying specific features (Feature Detection) Strong neural fibers running from visual cortex to hippocampus

30 Parallel Processing Specific neural nets within our visual cortex are responsible for specific tasks involved in vision (Parallel Processing): Color Motion Form Depth

31 THE END

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