The Interpretation of Sensory Information
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The Interpretation of Sensory Information

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The Interpretation of Sensory Information

The Interpretation of Sensory Information
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The Interpretation of Sensory Information The Interpretation of Sensory Information Presentation Transcript

  • The Interpretation ofSensory Information
  • PsychophysicsPsychophysics - is the study of therelationships between sensory experiences andthe physical stimuli that cause them.Sensation – “window”Perception – interpretation of what comes intoour “window”
  • Sensation x Perception
  • The World and Our Perceptions of It“A picture is worth a thousand words.” – NapoleonBonaparte"One look is worth a thousand words.“A complex idea can be conveyed with just a singlestill image.One of the main goals of visualization is making itpossible to absorb large amounts of data quickly.
  • The World and Our Perceptions of It
  • Perception of Minimal StimuliSensory Thresholds and Signal DetectionSome of the earliest psychological researchers tried todetermine the weakest sounds, lights, and touches thatpeople could detect.Absolute Sensory Threshold – is intensity at which agiven individual detects a stimulus 50% of the time.= lowest level at which a stimulus can be detectedSenses Minimum StimuliVision A candle flame seen at 30 miles on a dark, clear nightHearing The tick of a clock at 20 feet under quiet conditionsTaste One teaspoon of sugar in 2 gallons of waterSmell One drop of perfume diffused into six roomsTouch The wing of a fly falling on your cheek from a distance of 1 cm
  • Perception of Minimal StimuliSensory Thresholds and Signal DetectionNoise – is a background stimulation that interferes with theperception of other stimuli, as defined by psychophysicists.Terminal Threshold – is the maximum intensity ofstimulation that the individual perceives in a normal way.Just Noticeable Difference or Difference Threshold – isthe smallest difference that people could detect betweenone stimulus and another. (introduced by Ernst Weber)
  • Perception of Minimal StimuliSensory Thresholds and Signal DetectionWhen people try to detect weak stimuli, they can be correctin two ways:Stimulus actuallypresentStimulus actuallyabsentReport stimuluspresentHit False alarmReport stimulusabsentMiss Correct rejection
  • Perception of Minimal StimuliSensory Thresholds and Signal DetectionSignal-Detection Theory – is the study of people’stendencies to make hits, correct rejection, misses, andfalse alarms.• The people’s responses depend on their willingnessto risk misses or false alarms.Experiment 1 -- Instructions:Suppose you are the participant and you are told that:a.) you will receive a 10-cent reward for correctlyreporting that a light is present. You will be penalized 1cent for reporting that a light is present when it is not.
  • Perception of Minimal StimuliSensory Thresholds and Signal Detectionb.) you will receive a 1-cent reward for correctlyreporting that a light is present. You will bepenalized 10 cents and subjected to an electricshock for reporting that a light is present when it isnot.
  • Perception of Minimal StimuliSensory Thresholds and Signal DetectionImplication:The people’s answers depend on the instructions and theirstrategies, not just their senses.
  • Perception of Minimal StimuliSensory Thresholds and Signal DetectionExperiment 2:Participants were asked to read words that flashedbriefly on a screen.a.) Ordinary words (such as river or peach)b.) Emotionally loaded words (profanity)
  • Perception of Minimal StimuliSensory Thresholds and Signal DetectionResults:a.) The participants were able to perform well.b.) The participants said that they were not sure withwhat they saw.
  • Perception of Minimal StimuliSensory Thresholds and Signal DetectionIn other settings…The legal system is also a signal-detection situation.The jury can be right in two ways and wrong in twoways:Defendant is “guilty” Defendant is “innocent”Jury votes “guilty” Hit False alarmJury votes “not guilty” Miss Correct rejection
  • Perception of Minimal StimuliSubliminal PerceptionSubliminal Perception – is the idea that stimulisometimes influence our behavior even when they arepresented so faintly or briefly that we do not perceive themconsciously.Choosing how to perceive themhas been aninteresting topic forchildren of all ages and theknowledge of theirexistence keeps people up to all hours of theNight
  • Perception of Minimal StimuliSubliminal PerceptionChoosing how to perceive themhas been aninteresting topic forchildren of all ages and theknowledge of theirexistence keeps people up to all hours of theNight
  • Perception of Minimal StimuliSubliminal PerceptionWhat Subliminal Perception Cannot DoClaim: Subliminal messages could control people’sbuying habits.“EAT POPCORN” – in the middle of a film*Customers who were not aware of the message couldnot resist so they would flock to the concession stand tobuy popcorn.Claim: Certain rock-’n’-roll recordings contain satanicmessages that were recorded backward.*Researchers found out that people listening tobackward message cannot determine what it wouldsound like forward, and the messages do not influencebehavior.
  • Perception of Minimal StimuliSubliminal PerceptionClaim: “Subliminal audiotapes” with faint, inaudiblemessages can help you improve your memory, quitsmoking, lose weight, raise your self-esteem, and soforth.*The improvement depended on people’s expectations,not the tapes.
  • Perception of Minimal StimuliSubliminal PerceptionWhat Subliminal Perception Can DoClaim: Subliminal messages do produce effects,although most are brief and subtle.*Happy --- Neutral --- Angry*Fear x Scary movie --- Disgust x Strange food*Handgrip response --> stronger handgrip (with reward)
  • Perception and the Recognition of PatternsBrightness contrast – is the increase or decrease in anobject’s apparent brightness by comparison to objects aroundit.
  • Perception and the Recognition of PatternsFace recognitionWe recognize people by hair as well as facial features.
  • Perception and the Recognition of PatternsThe Feature-Detector ApproachFeature Detectors – are specialized neurons in the visualcortex which respond to the presence of simple features.Do Feature Detectors Explain Perception?Feature detectors cannot completely explain how weperceive letters, much less faces. Perception of apattern requires more than just simple feature detectors