320 ch. 2

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320 ch. 2
2010-09-30 23:39:43


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  1. psychophysics
    study of the relationship between properties of physical stimuli and psychological reactions to those properties
  2. absolute threshold
    • abrupt change from not being able to detect a stimulus to just being able to do so
    • aka absolute limen
  3. Fechner's 3 different methods used to determine absolute thresholds
    • method of limits
    • method of adjustment
    • method of constant stimuli
  4. method of limits
    observer presented with several alternating ascending and descending series
  5. descending series of trials
    begin with a stimuli that is clearly noticeable and then present increasingly weaker stimuli until the observer reports that they can't detect it
  6. ascending series of trials
    start with a stimulus clearly below threshold and the present increasingly stronger stimuli until observer reports that they can detect it
  7. errors of habituation
    • believe that stimulus is likely to be the same as last time, so just keep giving same answer
    • tend to keep saying no on ascending series and keep saying yes on descending series
  8. errors of anticipation
    • stimulus is likely to be different from last time so change answer and "jump the gun"
    • on ascending series, claim that they can detect stimulus when they can't
    • on descending series, claim they can't detect stimulus anymore when they can
  9. method of adjustment
    • observer adjusts the intensity of the stimulus instead of the experimenter
    • observer makes continuous adjustments rather than discrete
  10. method of constant stimuli
    • stimuli presented in random order
    • experimenter usually selects between 5-9 stimuli, with the weakest stimulus clearly below threshold and the strongest stimulus is clearly above threshold- these values must be chosen after pretesting with a quick method like method of adjustment
    • constant stimuli- constant set of stimuli chosen before testing and present these stimuli a constant number of times during testing
  11. sensitivity
    • people with high sensitivity are capable of detecting minor changes in those around them or have a low threshold for detecting change
    • insensitive people have very high threshold
    • sensitivity is inversely related to thresholds
  12. signal detection theory
    • argues that the thresholds obtained by classical psychophysical methods are composites of 2 separate processes
    • 1. observer's sensitivity to the stimulus
    • 2. observer's decision-making strategy or criterion
    • can separate sensitivty from criterios by examining observer's responses to trials with a signal and trials with only noise
    • top-down processing- physical stimulus alone isn't sufficient to determine perception- mental factors also critical
  13. signal
    weak physical stimulus is present
  14. noise
    no physical stimulus is present, only background noise
  15. criterion
    willingness to say that you detect a stimulus
  16. signal+noise trials
    • some of the trials will have no tone presented, only normal background noise present
    • remaining trials will have a very weak tone presented, added to the background noise
  17. correct rejection
    observer responds no on all noise-only trials indicating no stimulus is present
  18. false alarm
    observer incorrectly responds yes to a noise-only trial
  19. hit
    when observer responds yes when a stimulus is actually present
  20. miss
    observer will occasionally respond no when stimulus is present
  21. d-prime
    • index of sensitivity
    • distance between peaks of 2 distributions
  22. payoff
    • important determinant of the criterion
    • rewards and punishments associated with a particular response
  23. ROC curve
    • receiver operating characteristic curve
    • shows relationship between the probability of a hit and the probability of a false alarm
  24. 2AFC
    • two-alternative forced choice procedure
    • trial with 2 presentations- one with a target stimulus and one without
    • observer's task is to indicate which of the 2 presentations is the target
    • effects of expectations and criteria are minimized
  25. discrimination studies
    • variation of psychophysical methods- determines smallest amount a stimulus must change to be perceived as different
    • present a standard stimulus & comparison stimulus
  26. difference threshold
    • measures observers' discrimination ability
    • smallest change in a stimulus that is required to produce a noticeable difference 50% of the time
    • amount of change in a physical stimulus required to produce a jnd in the psychological sensation
  27. point of subjective equality
    value of the comparison stimulus that the observer considers equal to the value of the standard stimulus
  28. method of limits for measuring discrimination
    standard stimulus remains the same and comparison stimulus is presented in alternating ascending and descending series
  29. method of adjustment for measuring discrimination
    ex. determine point of subjective equality by asking observer to adjust the comparison stimulus until it seems to match the standard stimulus
  30. method of constant stimuli for measuring discrimination
    experimenter presents comparison stimuli in random order and may ask observer to judge whether each comparison stimulus is > or < the standard stimulus
  31. Weber's law
  32. weber fraction
    • k or constant number
    • smaller fractions indicate better discrimination abilities because less change is needed to produce a jnd
  33. Fechner's law
    S=k log I
  34. logarithm
    exponent that 10 must be raised to equal that number
  35. Stevens's power law
  36. magnitude estimation
    observers are asked to give numbers to match (estimate) their impression of psychological magnitude
  37. cross-modality matching procedure
    observers asked to judge one stimulus modality (loudness of sound) by using another modality (brightness of light)
  38. action potential
    • happens when neurons are stimulated
    • change from a neg to a pos state and then return to neg state
  39. single-cell recording
    extremely small microelectrode is used to measure activity of a single neuron
  40. EEG
    • electroencephalography
    • to study massed activity of many neurons by attaching electrodes to the scalp
    • waves often with a distinctive pattern
  41. 2 approaches to brain mapping
    PET and MRI
  42. PET
    • positron emission tomography
    • injecting a radioactive chemical into the bloodstream
  43. MRI