Chapter 4: Sensation vs. Perception PDF

Preview

Summary

Summary of Chapter 4...

Description

CHAPTER 4 – SENSATION VS. PERCEPTION Sensation o Sensory cells in our sense organs receive stimuli o Sensory cells translate stimuli into neural impulses

Perception o Brain assigning meaning to neural impulses coming from sensory organs

How do we convert external stimuli into information we can use? 1. Bottom-Up Processing – from parts to whole a. Combines many small bits of sensory input to form meaningful information 2. Top-Down Processing – from whole to parts a. Begins with cognitive processing using prior knowledge, expectations b. Moves down to individual stimuli  



Example: Reading Beginners: Bottom-up processing o First, recognize letter shapes, sounds, and individual words Experts: Top-down processing o Yuor aiblity to raed using top-dwon prcessoing makes it psosbile Example: Art Young and old people get the same sensory info, but perceive different things

Major Senses Sensory Processing 1. Transduction (Signal goes in) a. Converting sensory stimuli into neural impulses 2. Coding (Signal is interpreted) a. Neural impulses travel different routes to different brain regions; same stimuli lead to distinct sensations

  

Vision Stimulus: light waves Receptors: light-sensitive rods (black and white) and cones (colour) in the retina (eye) Brain area: visual cortex in the occipital lobe 1. Cornea: protection, focus rays 2. Pupil: opening adjusted by iris (light, emotion)

3. 4. 5. 6.

  

Crystalline lens: muscles focus image on retina Retina: rods/cones Fovea: pit filled with cones; sharp vision Optic nerve: relays the information to the visual cortex (occipital lob) – blind spot Vision problems Myopia - nearsightedness o Images focused in front of the retina Hyperopia – farsightedness o Images focused behind the retina Presbyopia – inflexible lenses o Can’t see things held up close o Common in old(er) age Light and Dark Adaptation





Dark Adaptation o From light to dark o Rods are bleached (non-functional) in bright light o Regain sight quickly, but sight improves 20-30 min Light Adaptation o From dark to light o Cones o 7-10 min to improve

Colour Vision Trichromatic Theory o Three kind of cones: red, green, blue o Other colours are just a mix  Opponent Process Theory o Three colour systems o Colour receptors respond in on/off fashion  Red vs. Green  Blue vs. Yellow  Black vs. White o People can’t see reddish-green light  Trichomats o See red, green, bue  Genetic deficiencies for o Red-Green o Blue-Yellow  Monochromats o Black-White only 

Audition (Hearing) 

Stimulus: sound waves

 

Receptors: pressure-sensitive hair cells in cochlea (ear) Brain area: auditory cortex in temporal lobe 1. Pinna: captures and funnels sound 2. Tympanic membrane (ear drum): vibrations move ossicles 3. Ossicles: vibrations slosh the cochlear fluid 4. Cochlea: fluid moves hair cells (receptors)

Pitch Perception – Higher pitch = higher frequency sound wave 1. Place Theory a. Different sound waves stimulate different places on the cochlea’s basilar membrane (different hair cells) 2. Frequency Theory a. Higher pitches cause auditory receptors to fire more frequently 3. Volley Principle a. Clusters of receptors take tunes (volley) firing [Pitch = frequency of volleying between clusters] BioPsychoSocial Implications of Pitch  Deeper voices tend to earn more respect  





  

Volume (Soft vs. Loud) Wave height o Distance between peaks and valleys Measured in decibels o Higher decibels damage hearing Hearing Loss Conduction o Mechanical problems with sounds waves getting to cochlea  Hearing aids (amplify incoming sound waves)  Surgery Sensorineural o Damage to hair cells or auditory nerve  Causes  Diseases  Aging  Exposure to loud noise  Treat with  Cochlear implant but only if auditory nerve is intact

Olfaction (Smell) Stimulus: molecules dissolved on nose mucous membrane (on the back of the nasal cavity) Receptors: neurons in the olfactory epithelium (nose) Brain area: temporal lobe, limbic system

    

Gustation (Taste) Stimulus: molecules dissolved on tongue Receptors: taste buds on tongue surface Brain areas: limbic system, somatosensory cortex, frontal lobe Chemical Senses: Smell and Taste Difficult to separate o Receptors located close together, interact Smell and taste receptors are regenerated every few days

STUDY PATHWAYS  10 000 distinct smells o Including specific people o Pheromones: chemical signs that trigger responses in others of the same species  Agression, mating  False expectations (ex. 90$ bottle of wine) o Five senses of taste: Sweet, Sour, Bitter, Salty, Umami

  

  

Body Senses Vestibular (balance) o How our head is oriented with respect to gravity Kinesthesis o Location, orientation, movement of individual body parts Skin Sense o Pain and temperature o Fine touch and pressure

Touch Stimulus: mechanical pressure to skin Receptors: mechanoreceptor Brain areas: somatosensory cortex in parietal lobe Psychophysics The study of the nature of stuff and how we perceive it

 

Concepts Absolute threshold o Minimum amount of stimulation needed to consciously detect a stimulus 50% of the time Difference threshold – Just Noticeable Difference (JND) o Smallest physical difference between two stimuli that is consciously detectable 50% of the time Subliminal Stimuli

 









Detection of stimuli below the absolute threshold for conscious awareness We can detect subliminal stimuli but it may not be enough for us to code it and be conscious of it Subliminal Messaging in Advertising  Tachiscope o Flashes images too fast for conscious recognition but slow enough to be registered by the brain  Results in priming o Readying the brain to access related information o Music and food study Sensory Adaptation When a stimuli is constant for a prolonged period of time: o Our receptors get tired o Fire less often o We get less signal from the same stimulus This helps us ignore stimuli that we’ve already attended to (e.g. contrition noise outside) o But also dangerous (e.g. gas smell) The Beauty of Distraction Distraction lessens pain o Shifting your attention away from the pain  Even under anesthesia: 20% less postsurgical pain Gate control theory of pain Pain messages must get past a “gatekeeper” in the spinal cord o Gate is shut by neural messages, large spinal cord fibers, endorphins o Gate is opened with tissue damage signals from small spinal cord fibers and substance P

Phantom Limb Syndrome  Brain can generate pain and other sensations o People with missing limb still feel its pain ~ 80% of amputees o Top-Down processing Sight and sound are transduced from electromagnetic waves 1. Wavelength: distance between peaks 2. Amplitude: the height of the wave 3. Range: mixture of waves



Hallucinations and Delusions Hallucinations: false sensory experiences that occur without external stimuli



o e.g hearing voices, drug-induced visual distortions Delusions: false beliefs o may accompany drug use of psychotic episodes Selection More sensory input that we can attend to

Selective attention  Process of focusing awareness on specific stimulus while filtering out others o Attend to important stimuli and ignore others Feature detectors  Specialized neurons that only respond to specific characteristics of visual stimuli o Shape o Angle o Movement (peripheral vision) o Faces 9we have specific receptors) Habituation*  Brain is most responsive to the changing info  Brain ignores/stops responding to unchanging information o Infant stimulus discrimination o Compliments from new friends/partners Habituation [intentional] Adaptation [involuntary] Sensory receptors fatigue/stop firing Learned tendency to stop responding to unchanging stimuli Humans attend to stimuli that are…  Intense  Novel  Moving  Contrasting  Repetitive *We habituate slower to content that is interesting, complex, emotional Organization Assembling perceptions in a meaningful way 1. Form perception: Gestalt psychologists: Focus on how the brain organizes bits of information into meaningful wholes [figures vs. ground]  Principles of Form Perception o Proximity o Continuity (pattern) o Closure o Similarity 2. Depth perception: Ability to perceive 3D space, distance [learned and based in binocular and monocular cues]

Binocular Cues Retinal disparity o Different location of images on each retina indicate object distance from face  Far objects – image close to nose  Close objects – image close to ear  Convergence o Amount of strain in eye muscles by turning eyes inward [as things get closer] is a cue to interpret distance  Finger to nose Monocular Cues  Linear perspective o Parallel lines converge when face away  Interposition o Overlapping objects – Closer  Relative Size o Larger objects – Closer  Texture gradient o More texture – Closer  Light/Shadow o Brighter objects – Closer  Relative Height o Lower objects – closer  Motion Parallax o Close – Fast o Far - Slow 3. Constancies Perception  Size constancy o Regardless of distance from us/image on retina, we perceive an individual object as keeping a fixed size  Colour/Brightness Constancy o Colour/brightness remain the same despite changing light conditions  Shape Constancy o Perceived shape stays the same, despite changing angle of view 

Interpretation 

Final stage of perception o Influenced by:  Sensory adaptation  Perpetual set: readiness to perceive in a particular manner  Frame of reference: context...