Detection of external stimuli Response to the stimuli Transmission of the response to the brain

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2 Sensation Detection of external stimuli Response to the stimuli Transmission of the response to the brain Perception Processing, organizing and interpreting sensory signals Internal representation of the stimulus

3 Stimulus Sensation Sensory receptors in the eye detect the stimulus

4 Sensory Coding Stimulus is transduced (translated into chemical & electrical signals that are sent to the brain) Perception The brain processes the neural signals and constructs a representation of the green light a signal to go

5 The 5 Senses

6 Stimuli Molecules on the tongue Receptors Cells in taste buds on the tongue Pathways to the brain Portions of facial, glossopharyngeal, and vagus nerves

7 Stimuli Molecules on mucus membranes in the nose Receptors Sensitive ends of olfactory neurons Pathways Olfactory nerves

8 Stimuli Pressure on the skin Receptor Sensitive ends of touch neurons in skin Pathway Cranial nerves for touch above the neck, spinal nerves for touch elsewhere

9 Stimuli Sound waves Receptors Pressure-sensitive hair cells in the cochlea of the inner ear Pathways Auditory nerve

10 Stimuli Light waves Receptor Light sensitive rods and cones in the retina of the eye Pathway Optic nerve

11 Sensory organs constantly acquire information from the environment

12 The minimum intensity of stimulation that must occur before you experience a sensation Approximate Absolute Sensory Threshold Taste 1 tsp. of sugar in 2 gallons of water Smell 1 droplet of perfume in a standard size room Touch a fly s wing falling on your cheek Hearing the tick of a clock at 20ft in quiet conditions Vision a candle flame seen at 30 miles on a dark, clear night

13 The just noticeable difference between 2 stimuli Minimum amount of change required for a person to detect a difference Example: If you re reading a book and watching TV, a commercial comes on that is louder than the show you look up and notice something has changed The DT is the minimum change in volume required to detect a difference

15 Detecting a stimulus requires making a judgment about its presence or absence Example A hearing test Person wears headphones and is told to raise their hand when they hear the tone in that ear

16 A decrease in sensitivity to a constant level of stimulation Example You are studying and your neighbor starts mowing their lawn After a few minutes the noise seems to blend in or fade into the background

18 The 2 nd sense to vision Sound waves pattern of changes in air pressure Amplitude loudness Frequency pitch

19 Sound waves arrive at the outer ear Travel down the auditory canal to the eardrum Then to the middle ear Sound waves make the eardrum vibrate Vibrations transfer to 3 tiny bones Hammer Anvil Stirrup Then to the auditory nerve

21 Most important source of knowledge Does a place look safe or dangerous? Does a person look friendly or hostile?

22 Light first passes through the cornea (transparent outer layer) Cornea focuses incoming light, which enters the lens Forms an image on the retina (thin inner surface of the back of the eyeball) THE RETINA IS THE ONLY VISIBLE PART OF THE BRAIN OUTSIDE THE SKULL! Pupil dark circle at the center Contracts gets smaller Dilates gets larger

23 Iris eye color Behind the iris, muscles change the shape of the lens Lens focuses images through accomodation

24 Rods Respond to extremely low levels of light Used primarily in night vision Cones Respond in bright levels of light Used for seeing color and detail

25 Determined by wavelength An object appears to be a particular color because of the wavelength it reflects Color is always a product of our visual system; there is no color in the physical world!

26 ROYGBIV

27 3 different types of cones that are sensitive to different wavelengths 1. Short (blue-violet) 2. Medium (yellow-green) 3. Long (red-orange)

28 Some colors seem to be opposites Stare at a red image see a green afterimage Stare at a green image see a red afterimage Stare at a blue image see a yellow afterimage Stare at a yellow image see a blue afterimage

29 Hue Distinctive characteristics of a color Ex. blue, light blue, navy blue, turquoise Saturation Color s purity, vividness Ex. lime green, fluorescent yellow Brightness Perceived intensity Two of the same exact colors can be perceived differently in different light

31 Brain regulates the experience of pain Producing it Suppressing it Depends on biological, psychological, and cultural factors

32 For a person to experience pain: Pain receptors must be activated A neural gate in the spinal cord must allow the signals through to the brain Eventually, the gate closes and no more pain signals reach the brain

33 Illusions are tools used by psychologists to determine how the brain understands information

34 Organized whole

Binocular Both eyes Monocular Each eye separately

outward with changes in distance (2 eyes) 3.

40 Binocular Both eyes Monocular Each eye separately 1. Accommodation change in the shape of the lens that varies with distance (1 eye) 2. Convergence the way the eyes rotate inward and outward with changes in distance (2 eyes) 3. Binocular disparity difference between the images provided by each eye

41 3 Principles 1. The figure is more thinglike and more memorable than the ground 2. The figure is seen as being in front of the ground 3. The ground is seen as unformed material and seems to extend behind the figure

42 Occulsion A near object blocks an object that is farther away Relative Size Far-off objects project a smaller retinal image than close objects Linear perspective Parallel lines appear to converge in the distance Texture gradient Shows depth or looks dense Position relative to the horizon Objects below the horizon that appear higher in the visual field are perceived as being farther away

43 Different kinds of movement: A figure moving against a stationary background Objects at rest against a moving background Objects moving at different speeds in relation to each other Observer s own movements in relation to his/her surroundings Induced movement perception of movement of an object that is not moving

45 Which line appears longer?

46 Which of the two horizontal lines on the track appear longer?

47 The cubes seem to shift and another side seems closer to you. Then it shifts back again

48 Designed by E.G. Boring Ambiguous figure Young girl/old woman

49 Albert Ames Appears to be a normal room Actually shaped so the left corner is almost twice as far from the viewer as the right corner The viewer perceives the nearer person as being much larger than the other, although both are exactly the same height

Sensation and Perception. What We Will Cover in This Section. Sensation

Sensation and Perception. What We Will Cover in This Section. Sensation Sensation and Perception Dr. Dennis C. Sweeney 2/18/2009 Sensation.ppt 1 What We Will Cover in This Section Overview Psychophysics Sensations Hearing Vision Touch Taste Smell Kinesthetic Perception 2/18/2009