1. Sensation and Perception By Sarah Fredericks Period 1

2. What are sensation and perception? Sensation- relationship between physical stimulation and its psychological effects Perception- how we recognize, interpret, and organize our sensations

3. Thresholds Detection- the act of sensing a stimulus Absolute threshold- the level of stimulation that is right on our perceptual borderline. We cannot detect lower levels of stimuli, but we can detect higher levels. Just Noticeable Difference-the minimum amount of distance between two stimuli that can be detected as distinct Measuring detection thresholds- signal detection theory- the signal (stimulus) is either present or it is not Weber’s Law- the observation that JND is a proportion of stimulus intensity. The greater the magnitude of the stimulus the larger the differences must be to be noticed.

4. Receptor Process Receptor cells- designed to detect specific types of energy Receptive field- the area from which our receptor cells receive input Transduction- takes place at the level of the receptor cells, and then the neural message is passed to the nervous system Contralateral shift- level of the thalamus. Most of the sensory input from one side of the body travels to the opposite side of the brain No matter what the form of input at the level of receptor, it must be converted, transduced

5. Sensory Mechanisms Sensory coding- the process by which receptors convey such a range of information to the brain Wavelengths of light and frequency of sound are hue and pitch Amplitude brightness for light and loudness of sound Single cell recording- technique by which the firing rate and pattern of a single receptor cell can be measured in response to varying sensory input Visual sensation- occurs when the eye receives light input from the outside world Distal stimulus- the object as it exits in the environment Proximal stimulus- the image of that object on the retina. Is inverted so the brain can interpret the image

6. Ear

7. How the ear functions Auditory input- in the form of sound waves enters the ear by passing the outer ear and into the ear canal Outer ear collects and magnifies sound waves Vibration enters the tympanic membrane, hit the ossicles, and vibrates them Last of the three ossicles, stapes, vibrate against the oval window (beginning of the inner ear) Further vibrate the cochlea, which contain receptor cells located structures, basilar membrane and organ of corti Inner ear- responsible for balance and has vestibular sacs-receptors sensitive to tilting

8. Sensory Adaptation Detect changes in stimuli intensity and quality Adaptation- unconscious, temporary change in response to environmental stimuli Habituation- process by which we become accustomed to a stimulus, and notice it less and less over time Dishabituation- occurs when a change in the stimulus, even a small change, causes us to notice it again

9. Attention Attention- processing through cognition of a select portion of the massive amount of information incoming from the senses and contained in memory Selective attention- attend to one thing while ignoring another Divided attention- trying to focus n more than one task at a time, is most difficult when attending to two or more stimuli that activate the same sense. Declines with age

10. Eye

11. How the eye functions Light passes through the cornea (protective layer) Under the cornea, Lens (bends in order to focus an image of the outside world on the retina). This focusing- accommodation Retina at the back of the eye and is covered with receptor cells, rods and cones Rods- sensitive in low light Cones- bright light and color vision Cones clustered in the fovea- greatest visual acuity Information travels to the visual association areas for processing Young Helmholtz theory- the cones in the retina are activated by light waves associated with blue, red, and green. Opponent process theory- black/white, blue/yellow, red/green operates in theses color sets. If one color is activated the other isn ’ t

12. Perception Perceptual processes- how our mind interprets these stimuli Bottom-up processing- achieves recognition of an object by breaking it down into its component parts Top-down processing- relies on prior experience with an object Theory of constructive perception- states that we create perceptual constructs out of their pieces or elements with the involvement of higher cognitive functions. If we are missing part of something we are still able to figure out the whole Direct perception- takes the view that our sensations and sensory context are all we need for perception. Prior knowledge or learning is not necessary. Depth perception- perceive depth, size, shape, and motion. Is facilitated by various perceptual cues -Monocular depth cues- are those that we need only one eye to see -Binocular depth cues- rely on both eyes viewing an image

13. Continued Relative size- refers to the fact that images that are farther from us project a smaller image on the retina than do those that are closer to us. Texture gradient- textures, or patterns of distribution of objects, appear to grow more dense as distance increases Interposition- which occurs when a near object partially blocks the view of an object behind it Linear perspective- a monocular cue based on the perception that parallel lines seem to draw a closer together as the lines recede in to the distance Vanishing point- as your looking at two rails and they are moving away from you they draw closer together Aerial perspective- another perceptual cue, which is based on the observation that atmospheric moisture and dust tend to obscure objects in the distance more than they do nearby objects. Things look more distant than they actually are

14. Finally Gestalt approach- top-down theory. Most perceptual stimuli can be broken down into figure-ground relationships. Proximity- the tendency to see objects near to each other as forming groups Similarity- the tendency to prefer to group like objects together Symmetry- the tendency to perceive preferentially forms that make up mirror images Continuity- the tendency to perceive preferentially fluid or continuous forms, rather than jagged or irregular ones Closure- the tendency preferentially to close up object that are not complete Law of Pragnanz- minimum tendency, meaning that we tend to see objects in their simplest forms Features- different orientations Feature detectors- neurons that respond to specific features