Do Now

1. Do Now How would evolutionary psychologists explain obesity/bad eating habits in many societies today? Again, using evolutionary psychology, how would you explain why a person would run into a burning house to save his/her child? Would they do this for the child of a stranger?

2. Sensation and Perception • Sensation – the stimulation of sense organs (eyes, ears, mouth, nose, and skin). The process of interpreting these senses is called bottom-up processing. • Perception – the interpretation of sensory input (sight, hearing, taste, smell, and feeling). These are constructed using experience and expectations, a process called top-down processing.

3. It has been said that our five senses take in about 11,000,000 bits of information a second! So how do we sort these out to only focus on the important ones? • Selective attention – this is the ability to only focus your conscious awareness on what is needed or wanted. • coctail party effect – the ability to focus on only one voice among many in a crowd • Selective inattention, or inattentional blindness, is when you fail to notice a change in the environment because of intense focus on something else. • Change blindness • Change deafness • Choice blindness – when you defend a choice you didn’t make after being told that you made it!

4. Gustav Fechner and psychophysics • Psychometrics is the study of how physical stimulus are translated into psychological experience. Gustav Fechner (predecessor of Wilhelm Wundt) studied the threshold of stimulus. Threshold is the dividing point between detecting stimulus and not detecting it.

5. Absolute Threshold is the minimum stimulus intensity that an organism can detect. Examples: • Candle flame 30 miles away on a clear, dark night. • Tick of a watch in quiet conditions at 20ft away • One teaspoon of sugar in two gallons of water • The wing of a fly falling on your cheek from a distance of 1 centimeter.

6. Difference Threshold • Difference threshold is the minimum difference between two stimuli that as subject can detect 50% of the time. The difference between this and absolute threshold is that absolute threshold is the just noticeable differencefrom nothing, and JND is the difference after the initial stimulus has occurred.

7. Weber’s Law • This law states that the JND between two stimuli is a constant minimum proportion of the stimulus. Example: If the difference of 10% in weight is noticeable, then Weber’s law predicts that a person could discriminate between 10- and 11-pound weights.

8. Modern Psychophysics • Signal-detection theory claims that detection of stimulus involves decision making as well as sensory processes, which are influenced by more than just stimulus intensity. These are: • Experience • Expectations • Motivation • Alertness

9. Subliminal Perception Can stimuli below the threshold of awareness still influence behavior? Subliminal perception is the registration of sensory input (like a flashing screen with an image on it) without conscious awareness. Can you give an example of how subliminal messaging has been used?

10. Sensory Adaptation • Sensory adaptation is the gradual decline of sensitivity to prolonged stimulation. Example: • Jumping into cold water • Smelly feet • Clothes in the morning • Sun in the morning (Chilean miners) This is good because it allows us to focus on what is important, and not on all the uninformative stimuli.

11. Sense of Sight “seeing is believing” Good ideas are “bright” ideas A good explanation is “illuminating” Sight is usually “seen” as the most important of our senses, because, as the first quote says, “seeing is believing”.

12. Light Two major characteristics of light waves affect our perception of it. • Amplitude – (height) of wavelength, affects perception of brightness. - This is associated with intensity of light (or sound) • Wavelength – (distance between peaks) affects our perception of hue, or color.

13. Structures of the Eye • Cornea (first layer) • Iris (your eye color) • Pupil (black circle/center of your eye) • Lens (just like a camera lens) • Retina (brains envoy in the eye) • Optic Disk (messenger line to brain)

14. Diagram of the Eye

15. Eye Oddities • Nearsightedness – cannot see things at a distance clearly because the light rays being reflected from an object are converging in front of the retina. • Farsightedness – close objects are blurry because the lights rays do not converge before hitting the retina. • Blind Spot – caused when the focus of an image falls on the optic disk (hole in the retina where optic nerves fibers exit the eye)

16. The Retina There are two types of receptors cells: • Cones – play a key role in daylight, detail, and color vision. The fovea is the retina’s point of central focus, and contains all cones. Images focused on this area are clearest. • Rods – play key role in night and peripheral vision.

17. Brains role in vision Without the brain, we would not see. The eye simply receives and sends stimuli to the brain, where it is then given meaning. Parallel Processing refers to the process in which the brain interprets different stimuli at the same time.

18. Processing in the visual cortex Studies have show that the neuron cells in the visual cortex don’t respond much to simple visual stimuli, but to complex stimuli. • Feature detectors are neurons that respond selectively to very specific visual features, such as movement, angle, and shape.

19. Theories of Color Vision Young-Helmholtz trichromatic theory Our cones work in teams of three, in which each rod specialized in reading the colors of red, blue, and green. Opponent-process theory Belief that opposing retinal processes enable color vision.