Perception opportunity 1 notes

The Perceptual Process (SLRNPRA)

1. ==Stimulus in the environment==

   1. Distal and Proximal Stimuli \n (Steps 1 and 2)

      1. Distal Stimulus

         1. Environmental stimulus are all objects \n in the environment are available to \n the observer.
         2. Observer selectively attends to \n objects.
         3. Stimulus impinges on receptors \n resulting in internal representation.

2. @@Light is reflected and focused@@

   1. proximal stimulus

      1. focuses on the energy falling on a receptor surface

3. Receptor processes

   1. Sensory receptors are \n cells specialized to \n respond to environmental \n energy
   2. Visual pigment is what \n reacts to light
   3. Transduction occurs, \n which changes \n environmental energy to \n nerve impulses

4. %%Neural processing%%

   1. Neural processing: changes \n that occur as signals are \n transmitted through the maze \n of neurons

   2. Primary receiving area

      1. Occipital lobe
      2. Temporal lobe
      3. Parietal lobe

5. ^^Perception^^

   1. organization, identification, and interpretation of sensory information

6. ^^Recognition^^

   1. the act of recognizing or the condition of being recognized.

7. ^^Action^^

   1. Experience and Action

      1. Electrical signals are transformed into conscious experience.
      2. Person perceives object (such as a tree)
      3. Person recognizes it as a tree (places object in category).

Knowledge: any information the perceiver brings to a situation

Bottom-up processing

Processing based on incoming stimuli from the environment

Also called data-based processing

Top-down processing

Processing based on the perceiver’s previous knowledge (cognitive factors)

Also called knowledge-based processing

**Perception is determined by an interaction between: \n **Top-down processing, which brings the observer’s knowledge into play \n bottom-up processing, which starts with the image on the receptors.

**Studying the Perceptual Process \n **observing perceptual processes at different stages in the system: \n ==PSYCHOPHYSICAL LEVEL OF ANALYSIS== \n Relationship A: the stimulus-perception relationship

ex: A violin and an oboe play the same pitch, 440 hz. Do they sound the same?

@@PHYSIOLOGICAL APPROACH@@ \n Relationship B: the stimulus-physiology relationship

ex: When different pitches are played, different receptors along the Organ of Corti fire \n Relationship C: the physiology-perception relationship

ex: When different receptors fire, you report if a note sounds “high” or “low”

The key to understanding all of this is to:

1. ==know what question you want to ask==
2. @@recognize what is being measured@@

PSYCHOPHYSICAL Ways to Measure Perception \n Gustav Fechner(mid 1800’s physicist) \n Called it “psychophysics” for short \n Published Elements of Psychophysics (1860)

Qualitative Methods \n Describing \n Recognizing \n Quantitative Methods \n Detecting \n Perceiving Magnitude \n Searching

Qualitative Methods of Psychophysical Measurement \n ==Description== \n Indicating characteristics of a stimulus \n First step in studying perception \n Called phenomenological method \n @@Recognition@@ \n Placing a stimulus in a category by identifying it \n Categorization of stimuli \n Used to test patients with brain damage

Quantitative Methods of Classical Psychophysics \n Detection \n ==Absolute threshold==- smallest amount of energy needed to detect a stimulus \n Method of Limits(“Can you hear me now?”) \n Method of Adjustment \n Method of Constant Stimuli

Something to Consider: Is There An Absolute Threshold? \n There are differences in response criteria among \n participants \n Liberal responder- responds yes if there is the \n slightest possibility of experiencing the stimulus \n %%Conservative responder%%- responds yes only if he \n or she is sure that a stimulus was present \n Each person has a different response criterion but \n the sensitivity level for both of them may be the \n same \n Signal detection theoryis used to take individual’s \n response criteria into account.

Difference Threshold (DL) \n The minimal detectable difference between two stimuli \n Measured using the same methods \n Also measured using Weber’s (a physiologist) methods \n Weber was Fechner’s teacher

Difference Threshold (DL) \n Subjects are presented a standard stimuli and then presented a \n comparison stimuli and asked to judge the difference \n When the difference b/n the two is small, the difference is difficult \n to detect \n As the magnitude of the stimulus increases, so does the size of the \n DL

Just Noticeable Difference (JND) \n Psychophysical Methods \n These psychophysical methods have other historical value \n Represented the first time in the history of scientific psychology that mental activity could be measured quantitatively

Quantitative Methods - Modern Psychophysics \n @@Perceiving Magnitude@@ \n Stimuli are above threshold. \n Observer is given a standard stimulus and a value for its intensity. \n Observer compares the standard stimulus to test stimuli by assigning numbers relative to the standard.

Quantitative Methods - Modern Psychophysics \n Magnitude estimation (cont.) \n Response compression \n As intensity increases, the perceived magnitude increases more slowly than the intensity. (ex: brightness) \n Response expansion \n As intensity increases, the perceived magnitude increases more quickly than the intensity. (ex: electric shock)

Other Measurement Methods \n @@Searching for stimuli@@ \n Visual search- observers look for one stimulus in a set of many stimuli \n Reaction time (RT) - time from presentation of stimulus to observer’s response is measured

Why study this? \n Because the physical stimuli and what we perceive don’t always \n match \n That’s the conclusion that Fechner reached on October 22, 1850