PSY280 JULY 5.docx

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PSY280 JULY 5, 2012 LECTURE 2: PSYCHOPHYSICS AND PSYCHOBIOLOGY GORIALL STUDY - SAT THE DOOR STUDY - CHANGE BLINDNESS - 45% DIDN’T NOTICE PSYP – RELAtionship between stim and perception how we actually see things – perception input stimulus, example which one sweeter Phys – stimuli and phsy process and perception – anatomy and phy – phys components of perceptions, structure and function of the nervous system, brain regions smaller is neurons, example electrical signals eeg and single cell recordings, look at face and which brain region lights up, phys components Gustav - Founders of pp - Founder bc how perception study of the mind be investigated by evifence based approach - Linked perception with body - Mind was philo - He brought mathematical formulas and evidence - Perception to measurable components Detection - What is measure of detection of stim detection - Smallest detect - Abs thr – 50 perc proabbilty detect it, 50 see or hear vs 50 don’t see or hear - Light smallest amount of light can see - Smallest amount of pressure feel - Or smallest amount of sound pressure can sense - Theoritcxal threshold vs empircale - Hyo is all or nothing, until reach respond no and then yes – staircase function - Perception not all or nothing more of a curved function as more intense the proabbilty increases - Reality 4.5 50 say yes and other say no - Towards the end high or low greater not and detetcting - 50 percent Cont - 4 methods - Constant stim - Limits - Adjustmebt - Staircase - What is threshold needed to detect a sensation or stim Const - Bc giving part a standard set and keep on showing random intervals - Bottom light intessity - Give them predefined light intensity and present 10 times and randomly and have respoind yes or no and compute average - Mult trials where intensity is detected 50 percent of time - Average of 180 abs threshold Limits - Ascending or desc order - As start of low and go higher until no to yes to detecting stimk - Des loud and decrease until switch to yes to no - Crossover point yes or no or yes to no - Multiple trials and identify cross over point which is cvariable - Why within ind not always the same always noise internal or external - Internal gurgling of stomach, neurons always firing - External dropping pen - Much more efficient or superior the constrant stimuli, narrow stimuli much better - Tally up and average Adjustment - Extension limits - Present stim and adjust intensity observer or experimental does - Adjust until barley notices it - Repeat trials lowers or higher pplay around Staircase - Limits - Better detecting absolute threshold and exact boundsaries - Exact as limits, asc or desc, - Example descending, lower and lower till no and then increase a little about Common sense abs threshold - Vision – candle flames 30 miles away - Hearing – ticking watch 20 feet away - Vestibular – tilt less then a minute on clock - Taste – teaspoon of sugar in gallon of water - Smeel – perform drop a perfume 3 rooms - Touch – wing fall 3 inches Discrimation - Between stimuli - Differences threshold two stimuli - Smallest dif between two stimuli - Jnd – smallest differnve - Icing half in and half out two weights judge weight in hand may be little different but not detect - Not stimuli multiple difference but one like weight or volume Contd - Same methods for abs thres - Increasing constant etc - Usuall give standared - 100 grams standard and another to compare like 102 and what is heavier or any other dimenionsion and weight it and change comparision stimulus Contd - Cant use 50 bc then saying cant tell dofference - 50 is subjexirve equality not different, 100 grams and 100.5 no difference - Grap 10 0percent where see eavier and 100 lighter half from 25 to 0 is interval of uncerstainity, 75% - 75 and 25, 102 minus 98 aqnd divide 2 and is value can detect - 101 aftrer 100, not and 102 can and this is discrimation threshold contd - Weight increases so does differcne threshold - So 110 so need more to discrimate between 110 then 100 - Proption however stays the same - Candle 10 candles add 1 see - In room 100 candles and and 10 - Dl increases proportion satsys same - Dl/100 and get constant Webers law - 2 percent increase to get it or 2 percent lower - 1000 grams Contd - How much freids buggae till notice - Luggae 25 pounds, know stand stim and kons - Dl = k times s - Light 8 percent - Taste 8 percent and shock 1 percent - Advantageous to detect Ind diff - No abs threshold everyone have - Have diff among people and within - Theories is signal detection theory - Located appendix tindler and swindon - How ind difference in threshold and factos - Stats theory take into account sensitivity in one sensory system - And response criteria - Respond yes more, another no more - Senstivyt and response criteria two things Sdt - Way done - Argued not make sense give signal and ask always noise internal and external so give signal and catch trials – don’t present any stim just noise - Noise and signal plus noise - Present and then say yes correct - Absent If yes - No absent - Ind difference - Ind more likely respond yes liberal or no cons Contd - Different distribtiuon for noise - And another for noise plus signal - Noise only - And signal noise hits or misses - 2 distribtiuos - Response criterion what intensity to repsoin yes - Response criteria right are fasle alarms - And left are correct rejection Contd - Liberal shift to left - More hits and consequence more false alarms Contd - Conservative - Criteria shift to right - Less lijley respond - Inlike liberal - Shift to right - Fewer hits much more correct rejections - Detect something not there Contd - Difference in ind differnec yes or no bias - Not tell how different - Dee prime – measure of sensitiveity of sensory systems - Look at signal plus noise distribution and noise disturb located - Overalb lot poor sensitivyt csan tdisc - If distribution spaced out can separate - Greater difference greter sensitivity Mag estimation - Stevens look at magnitude - Scale of ones detecte - Above threshold - Standard stimuli and may be given a value such as weight of 5, and then compare how much increase 2 or 3 - Scale estimate - And look at differecees relative to standard - Everyone use different scaling - Ratings across part different but follow similar relationship - The power law Powerl aw - Perceived magnitude - S how intense 100 grams or wats - Constrant how created scale of 5 grams increase 1 - Exponents is rate of change , percie Contd - Compression – light perse bright light increawe for 50 watts only for 25, perceived mag or stim then actual intensity, compresses perceived intensity, expn less then one (slope) - Expansion – opp,
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