Chapter 4, pt.1

Question 1

What is sensation?

Answer 1

Sensation is the stimulation of a sensory receptor — the basic registration of light, sound, pressure, odor, or taste as parts of the body interact with the physical world.

Question 2

What is perception?

Answer 2

Perception is the brain’s organization, identification, and interpretation of sensory input to form a mental representation.

Question 3

What is transduction?

Answer 3

It’s the process where sensors in the body convert physical signals from the environment into encoded neural signals sent to the CNS.

Question 4

What type of energy does each sensory receptor respond to?

Answer 4

Vision → light

Hearing → vibrations

Touch → mechanical pressure

Taste & smell → molecules

Question 5

What is meant by “the illusion of perception”?

Answer 5

We perceive a rich, detailed world even though we sense only a small subset of sensory signals — each species lives in its own sensory bubble (Umwelt).

Question 6

Define Umwelt.

Answer 6

“Surrounding world” — the perceptual world specific to an organism based on its sensory capabilities.

Question 7

What is sensory adaptation?

Answer 7

The gradual decline in sensitivity to a constant stimulus; sensory receptors respond more strongly to changes than to constants.

Question 8

What is psychophysics?

Answer 8

The study of how physical stimuli relate to the sensations and perceptions they produce — linking measurable stimulus properties to subjective experience.

Question 9

Define absolute threshold.

Answer 9

The minimal intensity of a stimulus that can be detected at least 50% of the time.

Question 10

What factors influence absolute threshold?

Answer 10

Type of stimulus, individual differences, and environmental conditions.

Question 11

What does absolute threshold measure?

Answer 11

Sensitivity — how responsive we are to faint stimuli.

Question 12

Define difference threshold.

Answer 12

The smallest detectable change in a stimulus (just noticeable difference)

Question 13

What does difference threshold measure?

Answer 13

Acuity — how well we can distinguish between similar stimuli.

Question 14

State Weber’s Law.

Answer 14

The change in a stimulus that is just noticeable is a constant proportion despite variation in intensities.
- For larger or stronger stimuli, a greater change is required to notice a difference, while for smaller or weaker stimuli, a smaller change is sufficient to be detectable.

Question 15

What does Signal Detection Theory (SDT) study?

Answer 15

How people distinguish between the presence and absence of stimuli amid background noise.

Question 16

What factors influence signal detection?

Answer 16

Attention, expectations, and motivation.

Question 17

What is a decision criterion in SDT?

Answer 17

The threshold or standard used to decide if a stimulus is present or absent.

Question 18

What part of the spectrum is visible light?

Answer 18

The portion of the electromagnetic spectrum detectable by the human eye.

Question 19

What property of light determines hue?

Answer 19

Wavelength (length of the wave).

Question 20

What property of light determines brightness?

Answer 20

Amplitude or intensity.

Question 21

What property of light determines saturation?

Answer 21

Purity — the degree to which a light source is mixed with other wavelengths.

Question 22

What is accommodation in vision?

Answer 22

The process by which the eye maintains a clear image on the retina by adjusting the lens shape.

Question 23

What causes nearsightedness (myopia)?

Answer 23

The eyeball is too long; light focuses in front of the retina, making distant objects blurry. Corrected with a concave lens.

Question 24

What causes farsightedness (hyperopia)?

Answer 24

The eyeball is too short; light focuses behind the retina, making nearby objects blurry. Corrected with a convex lens.

Question 25

What is the retina?

Answer 25

The light-sensitive tissue lining the back of the eye.

Question 26

What are the two types of photoreceptors in the retina?

Answer 26

Cones — color and detail; concentrated in the fovea. Rods — active in low light; peripheral vision.

Question 27

What are bipolar cells?

Answer 27

Cells that transmit signals from photoreceptors to ganglion cells.

Question 28

Structure of the retina

Answer 28

Innermost layer: Photoreceptor cells (rods and cones) Middle layer: Bipolar cells conveying neural messages from rods and cones to the ganglion cell layer. Outermost layer: Retinal ganglion cells (RGC) that organize the signals and send them to the brain

Question 29

What are retinal ganglion cells (RGCs)?

Answer 29

Neurons that organize visual signals and send them to the brain via the optic nerve.

Question 30

What is the optic nerve?

Answer 30

A bundle of RGC axons that carries visual information from the retina to the brain.

Question 31

Where does the optic nerve send visual signals in the brain?

Answer 31

To the lateral geniculate nucleus (LGN) of the thalamus, then to the primary visual cortex (V1) in the occipital lobe.

Question 32

What is contralateral control in vision?

Answer 32

Information from the right visual field goes to the left hemisphere and vice versa.

Question 33

Define hue, brightness, and saturation.

Answer 33

Hue: Color (determined by wavelength) Brightness: Light intensity Saturation: Color purity or richness

Question 34

What is the trichromatic color representation hypothesis?

Answer 34

Color perception is based on activity patterns across three cone types — red (Long), green (Medium), and blue (Short).

Question 35

What is the opponent-process theory of color vision?

Answer 35

Colors are processed in opposing pairs — red/green, blue/yellow, and light/dark — where one color inhibits the other.

Question 36

Explain color afterimages using the opponent-process theory.

Answer 36

Staring at green fatigues M cones switching to white activates all cones equally, but fatigued M cones respond weakly, causing a red afterimage.

Question 37

Which pairs of cones work in opposition to create complementary color afterimages?

Answer 37

Long (red) vs. Medium (green) Short (blue) vs. Medium (green)

Question 38

What is color vision deficiency?

Answer 38

Genetic disorder where one or more cone types function abnormally or are missing (color blindness). Usually X-linked, more common in men.

Question 39

Describe deuteranomaly.

Answer 39

Mild color blindness due to abnormal green-sensitive (M) cones.

Question 40

Describe protanopia.

Answer 40

Absence or malfunction of red-sensitive (L) cones.

Question 41

Describe tritanopia.

Answer 41

Absence or malfunction of blue-sensitive (S) cones.

Question 42

What is the difference between dichromats and tetrachromats?

Answer 42

Dichromats (e.g., dogs): 2 cones → see shades of blue, yellow, gray. Tetrachromats (e.g., birds, insects, fish): 4 cones → broader color vision range.

Question 43

Where is the fovea and what is its function?

Answer 43

The central area of the retina with only cones — the area of clearest vision.

Question 44

What causes the blind spot?

Answer 44

The point where the optic nerve exits the retina; no photoreceptors are present.