Introduction to Perception

Question 1

What are the steps in the perceptual process?

Answer 1

1. stimulus in the environment (distal stimuli)
2. stimulus hits the receptors (proximal stimuli)
3. receptor processes
4. neural processing
   5,6,7. perception, recognition, action

Question 2

What is the perceptual process?

Answer 2

• seven steps, plus knowledge inside the person’s brain, describe the process of perception
• these steps occur between the time a person looks at the stimulus in the environment, perceives the stimulus, recognizes it, and takes action toward it

Question 3

What is distal stimuli?

Answer 3

• environmental stimuli are all objects in the environment that are available to the observer
• observer selectively attends to objects
• stimulus impinges on receptors resulting in internal representation
• stimuli from the environment reach the sensory receptors
• information about object is carried by light

Question 4

What are proximal stimuli?

Answer 4

• the representation of the distal stimulus on the receptors
• stimulus is in proximity to the receptors
• light is transformed when it is reflected from object, when it travels through the atmosphere and when it is focused on the eye’s optical system
• image on retina

Question 5

What is transformation?

Answer 5

• When the stimuli and responses created by stimuli are transformed, or changed, between the environmental stimuli and perception
• first transformation occurs when light hits the object and is then reflected from the object to the person’s eyes
• as this reflected light enters the eye, it is transformed again as it is focused by the eye’s optical system onto the retina

Question 6

What is representation?

Answer 6

• everything a person perceives is based not on direct contact with stimuli but on representations of stimuli that are formed on the receptors and the resulting activity in the person’s nervous system

Question 7

What are receptor processes?

Answer 7

• Sensory receptors are cells specialized to respond to environmental energy
• each sensory system’s receptors specialized to respond to a specific type of energy
• Transduction occurs, which changes environmental energy to nerve impulses
• The end result is an electrical representation of the object
• when the sensory receptors receive the information from the environment: they transform environmental energy into electrical energy and they shape perception by the way they respond to different properties of the stimuli

Question 8

What is transduction?

Answer 8

• the transformation of environmental energy to electrical energy
• allowing the information that is out there to be transformed into a form that can be understood by the brain
• sensory receptors are like a bridge between the external sensory world and internal (neural) representation of that world

Question 9

What is neural processing?

Answer 9

• changes that occur as signals are transmitted through the maze of neurons
• sensory receptors travel through a vast interconnected network of neurons and transmit signals from the receptors to the brain and then within the brain and change or process these signals as they are transmitted
• some signals become reduced or are prevented from getting through and others are amplified so they can arrive at the brain with added strength
• the changes in these signals that occur as they are transmitted through this maze of neurons is neural processing
• the electrical signals created through transduction are sent to a sense’s primary receiving area (lobe)
• once signals reach the primary receiving areas, they are then transmitted to many other structures in the brain

Question 10

What is the cerebral cortex?

Answer 10

• 2 mm
• creating perceptions, language, memory, emotions, and thinking

Question 11

What are behavioural responses?

Answer 11

• perception, recognition and action
• electrical signals have been transformed into the conscious experience of perception which leads to recognition
• Person perceives object
• Person recognizes it
• Person reacts to it

Question 12

What is visual form agnosia?

Answer 12

• an inability to recognize objects

Question 13

What is knowledge?

Answer 13

• any information the perceiver brings to a situation
• prior experience or expectations
• can affect steps in the perceptual process
• ex: rat man demo

Question 14

What is bottom up processing?

Answer 14

• Processing based on incoming stimuli from the environment, reaching the receptors
• data-based processing

Question 15

What is top down processing?

Answer 15

• Processing based on the perceiver’s previous knowledge (cognitive factors)
• knowledge-based processing
• very involved in perception
• as stimuli become more complex, the role of top down processing increases
• our knowledge of how things usually appear in the environment, baed on our past experiences, can play an important role in determining what we perceive

Question 16

How can we split the perceptual process into three major components?

Answer 16

1. stimulus (distal and proximal)
2. physiology (receptors and neural processing)
3. behaviour (perception, recognition, action)

Question 16

What is the stimulus-behaviour (perception) relationship?

Answer 16

• relates stimuli to behavioural responses
• study using psychophysics (measures relationship between physical and psychological)
• oblique test using grating acuity, (smallest width of line that can be detected - indicate correct orientation)
• the results show that acuity is best for gratings oriented vertically or horizontally
• the stimulus is oriented gratings, and the behavioural response is detecting the grating’s orientation

Question 16

What is the oblique effect?

Answer 16

• people see vertical or horizontal lines better than lines obliquely

Question 17

How can we study the perceptual process?

Answer 17

• by observing perceptual processes at different stages in the system
• the stimulus-behaviour (perception) relationship
• the stimulus-physiology relationship
• the physiology-behaviour (perception) relationship

Question 18

What is the stimulus-physiology relationship?

Answer 18

• relationship between stimuli and physiological responses
• studied by measuring brain activity
• horizontal and vertical orientations caused larger brain responses in visual brain areas than oblique orientations

Question 19

What is the physiology-behaviour (perception) relationship?

Answer 19

• relates physiological responses and behavioural responses
• Horizontal and vertical orientations result in better acuity (behavioural response) and more brain activation (physiological response) than oblique orientations
• When behavioural and physiological responses to stimuli are similar like this, researchers often infer the relationship between physiology and behaviour
• can measure the physiology–behaviour relationship directly
• measuring both the brain response and behavioural sensitivity in the same participants
• more sensitive to the horizontal and vertical orientations
• fMRI
• measurements showed larger brain responses to vertical and horizontal gratings than to oblique gratings

Question 20

What is optical imaging?

Answer 20

• Electrical activity of neurons is related to local metabolic activity and blood flow
• Correlates of brain activity:
• Blood volume changes
• Blood oxygenation changes
• Light scattering changes caused by ion
  and water movementH

Question 21

How can we measure perception?

Answer 21

• absolute threshold
• difference threshold

Question 22

What is the absolute threshold?

Answer 22

• the smallest stimulus level that can just be detected
• the smallest amount of energy needed to detect a stimulus
• thresholds measure the limits of sensory systems; they are measures of minimums—the smallest

Question 23

What are methods for measuring the threshold (classical psychophysical methods)?

Answer 23

• method of limits
• method of constant stimuli
• method of adjustment

Question 24

What is the method of limits?

Answer 24

• stimuli of different intensities presented in ascending or descending order
• observer responds to whether she perceived the stimulus ‘
• cross over point (change from yes to no or vice versa) is the threshold
• The threshold is then determined by calculating the average of all of the crossover point

Question 25

What is the method of constant stimuli?

Answer 25

• the stimulus intensities are presented in random order
• the threshold is usually defined as the intensity that results in detection on 50 percent of trials
• most accurate method
• but it is time consuming

Question 26

What is the method of adjustment?

Answer 26

• the participant—rather than the experimenter—adjusts the stimulus intensity continuously until he or she can just barely detect the stimulus
• This just barely audible intensity is taken as the threshold
• the threshold is determined by taking the average setting
• fastest

Question 27

What is the difference threshold?

Answer 27

• measure the threshold between two stimuli
• the smallest difference between two stimuli that enables us to tell the difference between them

Question 28

What is the technique used to answer the question: What Is the Perceptual Magnitude of a Stimulus?

Answer 28

Magnitude Estimation

Question 29

What is magnitude estimation?

Answer 29

• The experimenter first presents a “standard” stimulus to the participant and assigns it a value of, say, 10
• participant then hears sounds of different intensities
• assign a number to each of these sounds that is proportional to the loudness of the original sound
• participant assigns a loudness value to each sound intensity
• This number for “loudness” is the perceived magnitude of the stimulus

Question 30

What is the technique used to answer the question: What Is the Identity of the Stimulus?

Answer 30

Recognition Testing

Question 31

What is the recognition test?

Answer 31

• testing the ability of people with brain damage
• asking them to name objects or pictures of objects
• Recognition is also used to assess the perceptual abilities of people without brain damage

Question 32

What is the technique used to answer the question: How Quickly Can I React to It?

Answer 32

Reaction Time

Question 33

What is reaction time?

Answer 33

• The speed with which we react to something can be determined by measuring reaction time
• the time between presentation of a stimulus and the person’s reaction to it
• participant responded more quickly when the target was flashed where he or she was directing attention

Question 33

What is the technique used to answer the question: How Can I Describe What Is Out There?

Answer 33

Phenomenological Report

Question 34

What is a phenomenological report?

Answer 34

• Describing what is out there
• Phenomenological reports are 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

Question 35

What is the technique used to answer the question: How Can I Interact With It?

Answer 35

Physical Tasks and Judgments

Question 36

What are physical tasks and judgements?

Answer 36

• This last question is concerned not with perception but with actions that follow perception

Question 37

Why is the difference between physical and perceptual important?

Answer 37

• One of the most crucial distinctions in the study of perception is the distinction between physical and perceptual
• Perception of the light is measured not by determining the intensity but by determining perceived brightness using a method such as magnitude estimation
• there is not a one-to-one relationship between the physical intensity of the light and our perceptual response to the light
• what physical measuring instruments record and what we perceive are two different things

Question 38

What is the electromagnetic spectrum?

Answer 38

• a band of energy ranging from gamma rays at the short-wave end of the spectrum o AM radio and AC circuits at the long-wave end
• we see just the small band of energy called visible light, sandwiched be- tween the ultraviolet and infrared energy bands