Chapter 2 - Sensation and Perception

Question 1

Types of Receptors (7)

Answer 1

1. Photoreceptors: respond to electromagnetic waves in the visible spectrum
2. Hair cells: respnd to movement of fluid in the inner ear structures (hearing)
3. Nociceptors: respond to painful or harmful stimuli (somatosensation)
4. Thermoreceptors: respond to changes in temperature (thermosensation)
5. Osmoreceptors: respond to the osmolarity of the blood (water homeostasis)
6. Olfactory Receptors: respond to volatile compounds (smell)
7. Taste Receptors: respond to dissolved compounds (taste)

Question 2

Threshold

Answer 2

• The minimum amount of a stimulus that renders a difference in perception

Question 3

Absolute Threshold

Answer 3

• The minimum of stimulus energy that is needed to activate a sensory system. It is therefore a threshold in sensation, not in perception.
• In other words, the minimum intensity at which a stimulus will be transduced (converted into action potentials)

Question 4

Difference Threshold

Answer 4

• Refers to the minimum difference in magnitude between two stimuli before one can perceive this difference
• Also called just-noticeable difference (jnd)

Question 5

Weber’s Law

Answer 5

• There is a constant ration between the change in stimulus magnitude needed to produce a jnd and the magnitude of the original stimulus

Question 6

Signal Detection Theory

Answer 6

• Focuses on the changes in our perception of the same stimuli depending on both internal (psychological) and external (environmental) context.

Question 7

Response Bias

Answer 7

• Refers to the tendency of subjects to systematically respond to a stimulus in a particular way due to nonsensory factors.

Question 8

Signal Detection Experiment

Answer 8

• Catch Trials = trials in which the signal is presented
• Noise Trials = the signal is not presented
• After each trial, the subject is asked to indicate whether or not a signal was given
• Hits = subject correctly perceives the signal
• Misses = subject fails to perceive signal
• False Alarms = subject seems to perceive a signal when none was given
• Correct Negatives = subject correctly identifies that no signal was given

Question 9

Adaptation

Answer 9

• Refers to a decrease in response to a stimulus over time

Question 10

Cones

Answer 10

• Used for color vision and to sense fine details
• Most effective in bright light
• Fovea contains only cones. Therefore, visual acuity is best at the fovea.

Question 11

Rods

Answer 11

• More functional in reduced illumination
• Only allow sensation of light and dark because they all contain a single pigment called rhodopsin
• Low sensitivity to details and are not involved in color vision, but permit night vision
• More rods and cones in the human eye
• Concentration of rods increases further away from the fovea

Question 12

Parallel Processing

Answer 12

• The ability to simultaneously analyze and combine information regarding color, shape, and motion of an object and to integrate this information to create a cohesive image of the world
• Also calls on memory systems to compare a visual stimulus to past experiences to help determine the object’s identity.

Question 13

Parvocellular Cells

Answer 13

• Detects shape
• Allow us to see very fine detail (high spatial resolution)
• Only work with stationary or slow-moving objects because they have very low temporal resolution

Question 14

Magnocellular Cells

Answer 14

• Detects motion
• Very high temporal resolution
• Low spatial resolution
• So… provides a blurry but moving image of an object

Question 15

Visual pathway from where light enters the cornea to the visual projection areas in the brain?

Answer 15

cornea ==> pupil ==> lens ==> vitreous ==> retina ==> optic nerve ==> optic chiasm ==> optic tract ==> lateral geniculate nucleus (LGN) of thalamus ==> visual cortex (occipital lobe)

Question 16

Place Theory

Answer 16

• States that the location of a hair cell on the basilar membrane determines the perception of pitch when that hair cell is vibrated
• High-pitched sounds cause vibrations at the base of the cochlea, whereas low-pitched sounds cause vibrations at the apex of the cochlea

Question 17

5 Basic Tastes

Answer 17

1. Sweet
2. Sour
3. Salty
4. Bitter
5. Umami (savory)

Question 18

4 Main Modalities of Somatosensation

Answer 18

1. Pressure
2. Vibration
3. Pain
4. Temperature

Question 19

Two-Point Threshold

Answer 19

• Refers to the minimum distance necessary between two points of stimulation on the skin such that the points will be felt as two distinct stimuli.
• The size of the two-point threshold depends on the density of nerves in the particular area of skin being tested.

Question 20

Gate Theory of Pain

Answer 20

• Proposes that there is a special “gating” mechanism that can turn pain signals on or off, affecting whether or not we perceive pain
• In this theory, the spinal cord is able to preferentially forward the signals from other touch modalities to the brain, thus reducing the sensation of pain.
• Ex: Rubbing an injury seems to reduce the pain of the injury.

Question 21

Bottom-Up Processing

Answer 21

• Data-driven
• Refers to object recognition by parallel processing and feature detection
• Essentially, the brain takes the individual sensory stimuli and combines them together to create a cohesive image before determining what the object is.

Question 22

Top-Down Processing

Answer 22

• Conceptually driven
• Driven by memories and expectations that allow the brain to recognize the whole object and then recognize the components based on these expectations.
• Allows us to quickly recognize objects without needing to analyze their specific parts

Question 23

Gestalt Principles (6)

Answer 23

1. Proximity: Components close to one another tend to be perceived as a unit.
2. Similarity: Components that are similar (color, shape, size) tend to be grouped together.
3. Good Continuation: Components that appear to follow in the same pathway tend to be grouped together.
4. Subjective Contours: Edges or shapes that are not actually present can be implied by the surrounding object.
5. Closure: When a space is enclosed by a group of lines, it is perceived as a complete or closed line.
6. Pragnanz: Perceptual organization will always be as regular, simple, and symmetric as possible.