Sensation & Perception Unit 4

Intro – sensation & perception Prosopagnosia – inability to recognize faces (even loved ones!) Right brain Shows difference between sensation & perception Sensation – focus on senses (sight, hearing, others) Light waves into brain? Sound waves into brain? AKA: bottom-up processing – think hurt toe goes up to brain Perception – assembles sensory input into meaning AKA: top-down processing – from brain-to-meaning Ex.: imagine you’re blindfolded, given something heavy, hard, rough, rectangular… …a brick Sometimes, we get fooled.

Selective attention We sense a lot! We weed out most. 11,000,000 bits/sec down to… 40 bits/sec Def. – ability to screen out info (to focus). Cocktail party effect – ability to single out one voice amidst many others (like tuning old radio dial) Think conversing in a crowded party – you can weed out other voices to one Accidents: 4X likely for driving/talking 23X for texting/driving

Inattentional blindness Blocking out a bit of sensory input by paying attention to something else. Can be voluntary, called selective inattention Shown in a video… basketball & gorilla suit.

Change blindness Not noticing a change after a brief interruption. Examples…

Change blindness (cont.) Person interrupted while giving directions… doesn’t notice a switcheroo of people.

Choice blindness People are blind to the choices they make. Experiment… People chose “attractive” person. Then… There was a switcheroo. The rejected person was shown, then… They asked, “Why’d you choose him/her?” Only 13% noticed the switch. 84% said “Oh yes, I’d notice.” This is choice blindness blindness—thinking you’re immune to it.

Pop-out This is simple—something is so different, it jumps out at you.

Thresholds Absolute threshold – minimum stimulation to detect a sense 50% of the time Ex.: hearing – below the threshold, you don’t hear it, then…Ahah! Signal detection theory – idea that detection depends on stimulus AND on our experience, expectations, motivation, alertness. Ex.: soldier on guard at night  high alert! Subliminal stimulation – sensation just below our threshold…we sense it but weren’t AWARE of it. Can it affect us? Yes. Experiment – subliminal pics prime us to another response Sad subliminal pic  sadder response; Happy subliminal  happy response

Cont. JND (just noticeable difference) – minimum difference between two stimuli that can be detected 50% of the time Weber’s Law – the PROPORTION difference between two stimuli is more important than the raw AMOUNT difference Ex.: weight – must differ by 2% to be noticed Ex.: sound – tones must differ by 0.3% Sensory adaptation – person’s diminishing sensory adaptation to a stimulus In other words, you get used to something. Think perfume. Strong at first, then you get used to it.

Transduction Def. – changing external physical stimuli into neural messages. This is the magic where light is changed to something the brain can handle. Or… …sound is changed for the brain. Or touch. Or smell. Or taste. Or… …being upside down (vestibular sense). Or moving your body (kinesthetic sense).

Vision Our #1 sense Frequency – refers to the wavelength of light; sets hue/color. Amplitude – refers to the intensity of light; sets intensity/brightness. Draw and label an eye. Most important: retina, rods/cones, fovea, optic chiasm.

Vision (cont.) Feature detectors – specialized brain cells for vision; pick up angles, lines, edges, & movement. (Think animal/soldier at night.) Parallel processing – we can pick up several things at once (angles, lines, etc.) Compare to serial processing – we do one thing at a time & we do NOT multi-task very well. Bottom line – parallel processing seems good for innate/animalistic/survival things (low road); serial processing good for thinking (high road).

Color vision Trichromatic theory – idea that we have 3 color receptors in the retina (like a TV) Opponent-process theory – idea that 3 color receptors act in an either/or manner. Ex.: color fatigue results in opposite color (like the USA flag)

Hearing Ear contains sense of hearing AND balance (vestibular sense) Frequency – cycles per second  pitch, high or low sounds (measured in Hertz) Amplitude – “height” of wave  loudness (measured in decibels) Cochlea – snail-shape, contains hair cilia cells in basilar membrane which pick up certain frequency vibrations. Transduction occurs here; sound becomes neural messages to the brain.

2 pitch theories Place theory – pitch set by the place/position on the basilar membrane with greatest vibration. Frequency theory – pitch is determined by the frequency (not place).

Touch 4 types: pressure, warmth, cold, & pain. Mixing these gives odd results…warm + cold = hot! Rubber hand illusion – shows top-down thinking See video Kinesthesis – bodily feel/knowledge Vestibular sense – balance/motion. Semicircular canals in ear arranged in 3D fashion sense movement.

Pain Pain – body’s warning sign. Gate-control theory – there’s an on/off “gate” switch at spinal cord for pain. Backed up by massage & acupuncture. Endorphins – nature’s pain killer. Phantom limb sensation – amputees report feeling sensation. Tinnitus – ringing in the ears, often result of hearing loss. Focus/distraction affects pain (athlete “plays through it”, virtual reality).

Taste 5 basic tastes…sweet, sour, salty, bitter, and newcomer… …umami (meaty). Taste buds pick up chemicals in food. Expectations matter here! Sensory interaction – 2 or more senses working together. Taste and smell go together. McGurk Effect – sight + sound result in a blended third sound (see vid).

Smell AKA “olfaction” or olfactory sense; 2nd chemical sense. 5 million receptor cells in nose Smells mix uniquely, like letters making words. “Good” smells are often learned. We associate a “good” smell with something good that happened.