Unformatted text preview:

Prof. Greg Francis1PSY 310: Sensory and Perceptual ProcessesPurdue UniversityIntroductionPSY 310Greg FrancisLecture 02A lot of very smart people were very wrong.Purdue UniversityStudying perception Philosophy Experimental methods Physiology Computation Levels of analysis Perceptual processPurdue UniversityPhilosophy Philosophy used to mean something different than itdoes now Used to mean the study of “anything” All scientists were philosophers As the scientific method became dominant, itrequired specialized skills and training Philosophers became people who only thought aboutthings Long after Newtonian physics was established,human behavior was still the domain of philosophersand religion A lot of very smart people were very wrongPurdue UniversityExperimental psychology Experimental psychology came out of therecognition that scientific methods could beapplied to studying human behavior A revolutionary idea Early studies were on perception Gustav Fechner Elements of Psychophysics (1860) Relate properties of physical stimuli to perceptionPurdue UniversityPsychophysics Measure thresholds Absolute threshold (e.g., energy) Difference threshold Method of limits Method of adjustment Method of constant stimuliPurdue UniversityMethod of limits Is the black line longer than the blue line? Is the black line longer than the green line?3.41Prof. Greg Francis2PSY 310: Sensory and Perceptual ProcessesPurdue UniversityMethod of limits Is the black line longer than the blue line? Is the black line longer than the green line?2.89Purdue UniversityMethod of limits Is the black line longer than the blue line? Is the black line longer than the green line?2.50Purdue UniversityMethod of limits Is the black line longer than the blue line? Is the black line longer than the green line?2.02Purdue UniversityMethod of limits Is the black line longer than the blue line? Is the black line longer than the green line?1.59Purdue UniversityMethod of limits Is the black line longer than the blue line? Is the black line longer than the green line?1.15Purdue UniversityMethod of limits Is the black line longer than the blue line? Is the black line longer than the green line?0.87Prof. Greg Francis3PSY 310: Sensory and Perceptual ProcessesPurdue UniversityMethod of limits Find the perceived equality of the lines Contrast with the physically measured length of thelines What’s a problem with the current design of thisexperiment? How to make it better?Purdue UniversityPercentage correct We often want tomeasure things otherthan thresholds Is the image of the personwith the gun on the left orthe right?Purdue UniversityPercentage correctPurdue UniversityPercentage correctPurdue UniversityPercentage correctPurdue UniversityPercentage correctProf. Greg Francis4PSY 310: Sensory and Perceptual ProcessesPurdue UniversityPercentage correctPurdue UniversityReaction time Another way of getting information about thevisual system is to explore how long it takes toprocess information For example, do the following images contain(non-human) animals? Respond as quickly as possible But try not to make a mistake!Purdue UniversityReaction timesPurdue UniversityReaction timesPurdue UniversityReaction timesPurdue UniversityReaction timesProf. Greg Francis5PSY 310: Sensory and Perceptual ProcessesPurdue UniversityReaction timesPurdue UniversityReaction timesPurdue UniversityReaction time People analyze the properties of pictures thatgive fast or slow reaction times To derive what kinds of image properties allowus to identify animals The same idea works for many other situations Time reveals details about informationprocessingPurdue UniversityNeurophysiology Functional cells in thebrain are neurons Many different types The image shows threepyramidal neurons They have been stained toshow their structure They are nearly 2mm inlength and receive over10,000 inputs from otherneuronsPurdue UniversityNeurophysiology Here is a close up of theneuronsPurdue UniversityNeurophysiology The neurons are not in isolation The image shows hundreds ofneurons and their connections This is a tiny fraction of thenumber of cells actually involvedin a small section of the brain The basic structure is repeatedthroughout the brainProf. Greg Francis6PSY 310: Sensory and Perceptual ProcessesPurdue UniversityWhat do neurons do? The key behavior of a neuron is an actionpotential Spike, firing A rapid change in the electrical differencebetween the inside and the outside of the neuron The action potential carries information The neurons connect together in circuits toprocess and compute informationPurdue UniversityWhat do neurons do? When a neuron has anaction potential, itsends a signal to otherneurons Or muscles The signal influencesthe receiving neuron toeither Have an actionpotential (excitation) Not have an actionpotential (inhibition)Purdue UniversityNeural circuits Thus, neuralprocessing is a matterof circuits of excitationand inhibition In this image, the blueand white colorsindicate inhibitoryfibers that modulatethe excitatory signalsfrom the pyramidalneuronsPurdue UniversityBrain structure Neural circuits are specialized to processcertain types of informationPurdue UniversityBrain structure Neuralcircuits arespecializedto processcertaintypes ofinformationPurdue UniversityBrain structure Neural circuits are specialized to process certaintypes of information Can measure properties of this specialization withbrain scanning technology fMRI Movie: motionProf. Greg Francis7PSY 310: Sensory and Perceptual ProcessesPurdue UniversityThe perceptual processAttended stimulusEnvironmental stimulusActionRecognitionPerceptionProcessingTransductionStimulus onreceptorsPurdue UniversityConclusions Introduced issues in studying perception Philosophy Experimental techniques Physiology It’s much more complicated than this As we’ll see…Purdue UniversityNext time A bit more about brain structures Properties of light Properties of the


View Full Document

Purdue PSY 31000 - Lecture 02

Download Lecture 02
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Lecture 02 and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Lecture 02 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?