CHAPTER 1 - Intro to Perception

Question 1

What are some reasons for studying perception?

Answer 1

• studying perception can help you become more aware of the nature of your own perceptual experiences
• the experiences that you take for granted can be appreciated at a deeper level by considering questions

Question 2

Describe the process of perception as a series of seven steps, beginning with the distal stimulus and culminating in the behavioural responses of perceiving, recognizing, and acting

Answer 2

• Step 1: a person observes an object (distal stimulus)
  
  • it is “distant,” “out there” in the environment
• Step 2: the object reflects light that reaches our visual receptors, and the pressure changes in the air reach our ears (proximal stimulus)
  
  • It is “in proximity” to the receptors
  • the distal stimulus is transformed into the proximal stimulus which represents the object in our eye
• Step 3: receptor processes
  
  • sensory receptors
    
    • visual receptors: respond to light
    • auditory receptors: respond to pressure changes in the air
    • touch receptors: respond to pressure transmitted through the skin
    • smell/taste receptors: respond to chemicals entering the nose and mouth
  • they do two things
    
    1. Transform energy into electrical energy
    2. Shape perception by the way they respond to different properties of the stimulus
       - TRANDUCTION
• Step 4: Neural processing
  
  • Signals sent from sensory receptors travel through a vast interconnected network of neurons that
    
    1. Transmit signals from the receptors to the brain and then within the brain
    2. Change (or process) these signals as they are transmitted
  • Neural processing: the changes in signals that occur as they are transmitted through this maze of neurons
  • Electrical signals created through transduction are often sent to a sense’s primary receiving area in the cerebral cortex of the brain
    
    • Cerebral cortex: 2-mm-thick layer containing the machinery for creating perceptions
    • primary receiving area for vision occupies most of the occipital lobe
    • primary receiving area for hearing is located in part of the temporal lobe
    • Primary receiving area for the skin senses is located in an area in the parietal lobe
  • Frontal lobe receives signals from all of the senses
    
    • Plays an important role in perceptions that involve the coordination of information received through two or more senses
• Step 5: Behavioural response
  
  • electrical signals have been transformed into the conscious experience of perception
• Step 6: Behavioural Response
  
  • Recognition
    
    • Perception = awareness of the object
    • Recognition = placing the object in a category
• Step 7: Behavioural response
  
  • Action: involves motor activities in response to the stimulus

Question 3

what is the role of higher-level or knowledge-based processes in perception? Be sure you understand the difference between bottom-up and top-down processing.

Answer 3

• Bottom-up processing (data-based processing) is processing that is based on the stimuli reaching the receptors
• Top-down processing (knowledge-based processing) refers to processing that is based on knowledge
  
  • Knowledge isn’t always involved in perception, but it is often sometimes without our even being aware of it

Question 4

What does it mean to say that perception can be studied by measuring three relationships? Give an example of how the oblique effect was studied by measuring each relationship

Answer 4

• Stimulus-Behaviour Relationship
  
  • Relates stimuli to behavioural responses (perception, recognition, and action)
  • One way to study: psychophysics
    
    • Measures the relationship between the physical and the psychological
  • Oblique effect: presenting black and white striped stimuli called gratings, and measuring grating acuity, the smallest width of lines that Ps can detect
    
    • Ask Ps to indicate the grating’s orientation and testing with thinner and thinner lines
• Stimulus-Physiology Relationship
  
  • Relationship between stimuli and physiological response (neurons firing)
  • Studied by measuring brain activity
  • Oblique effect example
    
    • measured physiologically by presenting lines with different orientations to ferrets
    • Found that horizontal and vertical orientations caused larger brain responses in visual brain areas than oblique orientations
• Physiology-Behaviour Relationship
  
  • Relates physiological responses and behavioural responses
  • Oblique effect example
    
    • Measuring both the brain response and behavioural sensitivity in the same Ps
    • Behavioural measurements were made by decreasing the intensity difference between light and dark bars of a grating until the P could no longer detect the grating’s orientation
      
      • Ps were more sensitive to horizontal/vertical orientations
    • Physiological measurements were made using a technique called functional magnetic resonance imaging (fMRI)
• Each relationship provides information about different aspects of the perceptual process
• Goal: understand the relationships between these three components

Question 5

What was Fechner’s contribution to psychology?

Answer 5

• Introduced a number of ways to measure threshold
  
  • Provided a new way to study the mind
• His insight: the mind and body should not be thought of as totally separate from one another but as two sides of a single reality
• The mind can be studied by measuring the relationship between changes in physical stimulation and a person’s experience
• 3 methods for measuring the threshold (AKA classical psychological methods)
  
  • method of limits
  • method of constant stimuli
  • method of adjustment

Question 6

Describe the differences between the method of limits, the method of constant stimuli, and the method of adjustment

Answer 6

• Method of limits
  
  • stimuli presented in either ascending order or descending order
  • First series of trials: P indicates by a “yes” response that they hear the tone
  • Experimenter presents another tone –> P responds
  • Continues until P responds with “no”
  • This change from “yes” to “no” is the crossover point and the threshold for this series is taken as a mean
  • Next series of trials begins below the P’s threshold, so that the response is “no” in the first trial, and continue till it’s “yes”
  • Because the crossover points may vary slightly, this procedure is repeated a number of times
  • The threshold is then determined by calculating the average of all the crossover points
• Method of constant stimuli
  
  • Different stimuli intensities are presented one at a time
  • Stimulus intensities are presented in random order
  • The threshold is usually defined as the intensity that results in detection on 50% of trials
• Method of adjustment
  
  • P adjusts the stimulus intensity continuously until they can just barely detect the stimulus
  • This barely audible intensity is taken as the threshold
  • The procedure is repeated numerous times, and the threshold is determined by taking the average setting
• the choice among these methods is usually determined by the degree of accuracy needed and the amount of time available

Question 7

Describe the five questions that can be asked about the world out there and the measurement techniques that are used to answer them

Answer 7

• Q1: What is the perceptual magnitude of a stimulus?
  
  • Technique: magnitude estimation
    
    • Determining the relationship between physical stimuli and the perception of their magnitude
    • Experimenter presents a “standard” stimulus to the P and assigns it a value
    • P then hears sounds of different intensities and is asked to assign a number to each of these sounds that is proportional to the loudness of the original sound
    • This number for “loudness” is the perceived magnitude of the stimulus
• Q2: What is the identity of the stimulus?
  
  • Technique: Recognition testing
    
    • Categorizing: recognition, is measured in many different types of perceptual experiments
    • One application: testing the ability of people with brain damage (asking them to name objects or pictures of objects)
    • Also used to access the perceptual abilities of people without brain damage
    • Not only visual: can also be used for hearing, touch, taste, and smell
• Q3: How quickly can I react to it?
  
  • Technique: Reaction Time
    
    • Measuring the time between presentation of a stimulus and the person’s reaction to it
• Q4: How can I describe what is out there?
  
  • Technique: Phenomenological Report
    
    • Describing what is out there is called phenomenological report
    • Important because they define the perceptual phenomena we want to explain, and once a phenomenon is identified, we can then study it using other methods
• Q5: How can I interact with it?
  
  • Technique: Physical tasks and judgments
    
    • Ps carry out tasks that involve both perception and action
    • Physical tasks have also been studied by having people make judgments about tasks before they actually carry them out

Question 8

Why is it important to distinguish between physical and perceptual?

Answer 8

• Example 1:
  
  • Person A: light from one light bulb with a physical intensity of 10
  • Person B: light from two light bulbs, with a total intensity of 20
    
    • All of this is physical
  • Perception of the light is measured not by determining the intensity but by determining perceived brightness using a method
• Example 2:
  
  • Electromagnetic spectrum
    
    • a band of energy ranging from gamma rays at the short-wave end of the spectrum to AM radio and AC circuits at the long-wave end
    • We only see just the small band of energy called visible light (between ultraviolet and infrared energy bands)
    • What physical measuring instruments records and what we perceive are two different things
• Perception is psychology, not physics, and perceptual responses are not necessarily the same as the responses of physical measuring devices