Provides Provides an estimat estimate e of the percep perceptual tual quality quality of a stimulus stimulus in numerica numericall terms terms comparisons with other stimuli (i.e. testing aromatic acceptance of a perfume) Allow All ow comp compari arison sons s among among indivi individua duals ls and and even even specie species s Compar Compariso isons ns of diere dierent nt sensor sensory y modali modaliti ties es cross-modal comparison
Can be inear! e"ponential or ogarithmic##$elationship ogarithmic##$elationship determined by# As%ing individual to rate the perceived intensity of a stimulus o o &easuring of the smallest change in stimulus input that cause a 'ust discriminable change in sensation
Ps(c%op%(sics: uantitative description of the relation between the physical energies of the world around us and the sub'ective e"perience of their perception C!assica! Ps(c%op%(sics -
Absolute hreshold* hreshold* he minimum level level of intensity that can be registered registered by the brain as a sensory event +ubthreshold* +timulus intensities below the absolute threshold. ,t will not produce detectable sensation +uprathreshold* region region where sensation ta%es place. $egion where we determine determine how the the slope changes as a function of physical p hysical intensity. intensity. ierence hreshold* the the smallest smallest change change in in stimulus intensity required to produce a discriminable change in sensation. se to determine which function best describe the /stimulus vs. perception0 perception0 relationship
Ps(c%op%(sica! "et%o)s: to obtain absolute and dierence thresholds. Came from 1ustav 2echner. -
ðod of Ad'ustment* human sub'ect is is told to simply ad'ust the physical intensity of a stimulus until it is barely detectable. 3ene4ts 5 fast ðod of imits* +ub'ect is presented presented with a stimulus whose intensity is chosen chosen from from an ascending or descending series. ser ies. 3ene4ts 5 more reliable estimates ðod of Constant +timuli* +timuli* intensity values are are randomly randomly chosen from a preset range and presented to the sub'ect. he sub'ect replies whether or not a sensation occurred and a frequency chart is established
A&so!te T%res%o!) -
+tep 2unctio 2unction* n* Assumes Assumes human human are are ideal ideal detector detector.. A clear clear divisio division n between between subsub- and supra- threshold thus clearly indicating the absolute threshold Psychomet Psychometric ric 2unctio 2unction* n* +-shaped +-shaped (ogive) (ogive) function. function. 6umans 6umans are are not not ideal ideal detecto detectors. rs. +ources +ources of ncertainty ncertainty leading leading to human as not ideal detectors* detectors* 7sp. at low low intensiti intensities es 8 ariability in the intensity of a stimulus 5 no physical device can provide perfect o delivery 9
+ensory system is noisy 5 noise interferes with signal detection to produce instances of misperception o :udgment as to whether a stimulus is perceived 5 'udgement in;uenced by physical! emotional and cognitive factors. hreshold 7stimations* <=> response level. here are no such thing as all or none o
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+i,erence T%res%o!) -
,ncrement hreshold* dierence b?w @<> and <=> brighter response level ecrement hreshold* dierence b?w <=> and <> brighter response level
-e&er La': he greater the intensity level at which we have to ma%e a :B 'udgment! the greater the dierence threfhold needed to attain that :B. ierence threshold is not constant but actually increases in a linear fashion with stimulus intensity * , D E " , * % D FeberGs 2raction D some proportion of the stimulus intensity * he requirement for a :B is that the incremental amount be scaled to the stimulus intensity
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Fec%ner.s La': the change in sensation (+) is constant at all level for a :B! resulting in a log function between sensation magnitude and stimulus intensity * * *
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+ D % " log(,) % is related to the constant in weberGs law but not identical 2echnerGs law asserts that at low intensity levels! the magnitude of our sensations can change quite rapidly with small changes in stimulus intensity. Fe become less sensitive at higher intensities 1ustav 2echner D 2ather of Psychophysics
&agnitude 7stimation* as%ing sub'ects to provide a direct rating on the sensation they e"perienced. Power aw* + D E " , b + D sensation e"periencedH , D physical intensity of the stimulusH % D scaling o constantH bD e"ponent value ierent sensory dimension have dierent e"ponents o +ensory ransducer theory* power law re;ects the operation of sensory systems at their lowest levels 5 at the interface where the physical stimulus becomes converted in to a biological signal.
P(sc%op%(sica! Sca!in/ -
Cross-&odal 7"periments* sub'ects as%ed to compare stimuli from one sensory modality to those of another (i.e. loudness vs. brightness).
+ub'ects were as%ed to ad'ust sound level until it matched the perceived intensity of a stimulus from another sensory domain reating equal sensation functions Prothetic and &etathetic +ensations Prothetic 5 sensory e"periences where sub'ects can ma%e a 'udgment of /how o much0 associated with power law through its addictive properties o &etathetic 5 instead of changing intensities! the quality is entirely changed (i.e. changing wavelength) associated with change in quality substitution of one %ind of neural e"citation by another &ulti-imensional +caling* use to analyIe metathetic percepts such as by pairing which colour is most similar in a triad (method of triads) o
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Sca!in/ o Non*sensor( 0aria&!es: establish measure of sub'ective magnitude in the areas of esthetic preference or social?political options (+ocial psychophysics) -
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iscrimination scaling vs. $atio +caling iscrimination +caling 5 variability in psychological units is constant along a linear o psychological continuum (a%a confusion scaling) $atio +caling 5 equal units of discrimination along the stimulus continuum equal o ratios along the sub'ective continuum. 7%manGs law* detectable changes in sensation were related to sensation in a linear manner. + D % " +
Si/na! +etection T%eor( S+T2 * -
ses statistical concepts that ta%e into account cognitive factors that may in;uence a sub'ectGs decision ma%ing process. &easuring 7ects of +ignal and Boise ,n the e"periments! a /no stimulus0 is given! and the sub'ect as%ed if they perceived o anything. ,n the absence of signal# o A BJ response D correct re'ection A K7+ response D false alarm and is solely due to the noise created by the neurons ,n the Presence of signal# o A BJ response D &iss A K7+ response D 6it Criterion 7ects 1eneral Properties 5 +ub'ects establishe a set point (Criterion 5 L). A K7+ response o can either be a false alarm or 6it. o 7"pectations 5 depending on an inherent e"pectation of stimulus appearance! the sub'ect will be either more or perhaps less inclined to give a positive answer on each trial Probability of hit due to e"pectation is represented by the $JC curve (receiver operating characteristic) pper end D more liberal criterion and vice versa &otivation 5 motivational states induced by dierent pay-o conditions produce di. o criterion shift 6it pay M false alarm pay D more liberal criterion
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6it pay O false alarm pay D more conservative criterion
C%apter 1 #estions: * * *
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Fhich of the following would be the biggest problem in studying perception A. determining whether all the participant see the same blue o Fhy do psychologists ta%e a scienti4c approach to studying sensation and perception A. 6umans are curious! it may provide..All of the Above o he dierence between method of ad'ustment and method of limits is# A. he participants has control over the stimulus intensity in the method of o ad'ustment but not with the method of limits Fhich of the following is BJ mentioned in the te"t as a source of uncertainty A. the participant trying to please the e"perimenter o Fhat is it call if a sub'ect perceive a stimulus that did not e"ist A. 2alse Alarm o
