1、1Chapter4 Sensation and PerceptionSensation & perceptionSensation: an activation of our senses.Perception: the process of understanding these sensations.Transduction a process through which signals are transformed into neural impulses. Signalsneuro impulsesthalamusdifferent cortices of the brain(the
2、 sense of smell is the one exception to this rule.)Sensory adaptationdecreasing responsiveness to stimuli due to constant stimulationSensory habituation/Perceptual adaptationour perception of sensations is partially due to how focused we are on them.Cocktail-party phenomenonWhile talking to a friend
3、, your attention will involuntarily switch across the room when someone says your name.Energy senses Vision（electromagnetic waves）, hearing (vibration in air) and touch.They gather energy in form of light, sound waves, and pressure.Chemical sensestaste and smell.Body position sensesVestibular and ki
4、nesthetic help with body position and balance.Vision General process:Step1: Gathering lightStep2: Within the eyeStep 3: TransductionStep 4: In the brainStep1: Gathering light1. The color we perceived depends on intensity 强度 and light wavelength 光波长.a) Intensity describes how much energy the light co
5、ntains, how bright the object appears.b) Light wavelength determines the particular hue we see.c) Light wave length: Ultraviolent waves 紫外线/X-rays elbow)3. Pain:If touch or temperature receptors are stimulated sharply, pain receptors will also fire. Pain is a useful response because it warns us of p
6、otential dangers.4. Gate-control theory: When a higher priority message is sent, the gate swings open for it and swings shut for a low priority message. Endorphins (pain-killing chemicals) swing the gate shut.Taste/Gustation1. Papillae: bumps you can see on your tongue where taste buds 味蕾 are locate
7、d. 2. Some taste buds respond more intensely to a specific taste and more weakly to others.3. People differ in their ability to taste food.(whether taste buds packed densely)4. 5 types of tastes: sweet, salty, sour, bitter and umami.5. Flavor: a combination of taste and smell.Smell/ olfaction1. Gene
8、ral process:Moleculesmucous membrane on nostrilreceptor cellsolfactory bulbamygdalahippocampusThe molecules settle in a mucous membrane at the top of each nostril and are absorbed by receptor cells located there.The receptor cells are linkedto the olfactory bulb, which gathers the messages from the
9、olfactory receptor cells and sends this information to the amygdala and then to the hippocampus. 2. This direct connection to the limbic system（for emotion and memories）6may explain why smell is such a powerful trigger for memories. (other senses go through the thalamus first before being sent to th
10、e appropriate cortices)Vestibular sensetells how our body is oriented in space (overall orientation).Three semicircular canals in the inner ear give the brain feedback about body orientation.Kinesthetic sensegives us feedback about the position and orientation of specic body parts (specific orientat
11、ion). Receptors in our muscles and joints send information to our brain about our limbs.PerceptionAbsolutethresholdthe smallest amount of stimulus we can detect. The technical denition of absolute threshold is the minimal amount of stimulus we can detect 50 percent of the time.Subliminal messagesSti
12、muli below the absolute threshold.Difference threshold/just-noticeable differencethe smallest amount of change needed is a stimulus before we detect a changeWebers law the change needed is proportional to the original intensity of the stimulus.In other words, the ratio of the increment threshold to
13、the background intensity is a constant. But the constants differ between the senses.Signal detection theory1. investigates the effects of the distractions and interference we experience while perceiving the world. 2. Response criteria/ receiver operating characteristics:how motivated we are to detec
14、t certain stimuli and what we expect to perceive.3. By using factors like response criteria, signal detection theory tries to explain and predict the different perceptual mistakes we make:False positive: when we think we perceive a stimulus that is not there.无中生有False negative: when we do not percei
15、ve a stimulus that is present. 视而不见In some situations, one type of error is much more serious than the other, and this importance can alter perception. In the surgeon example, a false negative (not seeing a tumor that is present) is more serious mistake than a false positive (suspecting that a tumor
16、 is there)Top-down processingoccurs when we use background knowledge to ll in gaps in what you perceive.=脑补Schemata: mental representations of how we expect the world to be.7Perceptual set: a predisposition to perceiving something in a certain way.Backmasking: supposed hidden messages musicians reco
17、rded backward in their musicBottom-up processing/feature analysisto use only the features of the object itself to build a complete perception. We use both top-down & bottom-up Top-down is faster but more prone to error Bottom-up is slower but is more accurateFigure-ground relationshipto determine wh
18、at part is the ground and what part is the gureGestalt rules Gestalt psychologists：whole part1. Proximity: Objects that are close together are more likely to be perceived as belonging in the same group.2. Similarity: Objects that are similar in appearances are more likely to be perceived as belongin
19、g in the same group.3. Continuity: Objects that form a continuous form are more likely to be perceivedas belonging in the same group.84. Closure: Objects that make up a recognizable image are more likely to be perceived as belonging in the same group even if the image contains gaps that the mind nee
20、ds to ll in.Constancy Our ability to maintain a constant perception of an object despite these changes is called constancy.1. Size constancy: Objects closer to our eyes will produce bigger images on our retinas, but we take distance into account in our estimation of size. We keep a constant size in
21、mind for an object and know that it does not grow or shrink in size as it moves closer or farther away.2. Shape constancy: Objects viewed from different angles will produce different shapes on our retinas, but we know the shape of an object remains constant.3. Brightness constancy: We perceive objec
22、ts as being a constant color even as the light reecting off the object changes.Perceived motionIn a number of situations, our brains perceive objects to be moving when, in fact, they are not.1. Stroboscopic effect: used in movies or ip books. Images in a series of still pictures presented at a certa
23、in speed will appear to be moving.2. Phi phenomenon: A series of lightbulbs turning on and off at a particular rate will appear to be one moving light.3. Auto-kinetic effect: If a spot of light is projected steadily onto the same place on a wall of an otherwise dark room and people are asked to star
24、e at it, people will report seeing it move.Depth cues 1. Visual cliff experimentan experiment to demonstrate that human infants can perceive depth.2. Monocular cues1) Linear perpective: one of the most common cues. Artists use it when they start by9drawing two lines that converge somewhere toward th
25、e top of your paper.2) Relative size cue: to draw objects closer to the viewer larger than objects off in the distance.3) Interposition cue: objects that block the view to other objects must be closer to usdue to this cue.4) Texture gradient: to draw objects closer in detail.5) Shadowing: you can im
26、ply where the light source is by shading part of your picture and thus imply depth and position of objects.3. Binocular cues 1) Binocular disparity/retinal disparity Each of our eyes sees any object from a slightly different angle. The brain gets both images. It knows that if the object is far away,
27、 the images will be similar, but the closer the object is, the more disparity there will be between the images coming from each eye.2) ConvergenceAs an object gets closer to our face, our eyes must move toward each other to keep focused on the object. The more eyes converge, the closer the object mu
28、st beEffects of Culture on PerceptionMost perceptual rules apply in all culture, but some of the perceptual rules are learned and vary between cultures.Study it byCross-cultural research Extrasensory perception (ESP)1. ESP：Perceive a sensation “outside” the senses of vision/hearing/smell/taste/touch/vestibular balance system 2. Are better explained by deception, magic tricks or coincidence.3. Skeptical 持怀疑态度的10
