Chapter 4 -- Sensation and Perception

Question 1

What is perception?

Answer 1

The selection, organization,
and interpretation of sensory input

Question 2

What is sensation?

Answer 2

The stimulation of sense organs – receiving energy from the environment, and transforming it into action potentials.

Question 3

What is transduction?

Answer 3

The process by which specialized receptor cells convert energy from an external stimulus to relay info to the brain

Question 4

What is bottom-up processing?

Answer 4

Sensory receptors register information about the external environment and send it up to the brain for interpretation. (ex: feeling the tune of a new song)

Question 5

What is top-down processing?

Answer 5

Cognitive processing in the brain allows us to apply that framework to incoming info from the world. (ex: Having a perceptual experience of a song you’ve heard before)

Question 6

What are the three main categories of sensation?

Answer 6

Photoreception (detection of light)

Mechanoreception (detection of pressure, vibration and movement)

Chemoreception (detection of chemical stimuli)

Question 7

What is an absolute threshold?

Answer 7

The minimum amount of stimulus energy that a person can detect

Question 8

What is a difference threshold or a “just noticeable difference”?

Answer 8

The degree of difference that must exist between two stimuli before the difference is detected.

Question 9

What is Weber’s law?

Answer 9

The principle that two stimuli must differ by a constant minimum percentage (rather than a constant amount) to be perceived as different.

Candle example: Adding 1 candle to a bundle of 20 is noticeable (5% increase); adding 1 to 120 candles is unnoticeable (<1% increase)

Question 10

What is the detection of information below the level of conscious awareness.

Answer 10

Subliminal perception

Question 11

Is subliminal perception possible according to studies?

Answer 11

Studies show that the brain responds to info presented below the conscious threshold but it is often only a weak effect, and sometimes it can shape our behaviour.

Question 12

What is signal detection theory and what does it help us understand?

Answer 12

Signal detection theory is an approach to perception that focuses on decision making about stimuli under conditions of uncertainty. It helps us examine processes that reveal our ways of judgement when it comes to whether we perceive stimulus or not, and the mistakes (misses/false alarms) we may make and why.

Question 13

What are the four outcomes in signal detection?

Answer 13

Hit (correct) – SIGNAL EXISTS
Miss (mistake) – SIGNAL EXISTS
False alarm (mistake) – NO SIGNAL
Correct rejection (correct) – NO SIGNAL

Question 14

What are the two components of signal detection theory?

Answer 14

Information acquisition (gathering relevant indicators)

Criterion (standards used to make a decision)

Question 15

What is attention vs selective attention?

Answer 15

Attention is the process of focusing awareness on a narrow aspect of the environment while selective attention is focusing on a specific aspect of experience while ignoring others.

Question 16

What is a perceptual set?

Answer 16

Readiness to perceive something in a particular way. Reflect top-down perception.

Question 17

What is sensory adaptation?

Answer 17

The sensory system changes responsiveness to the average level of stimulation.

Question 18

Why is vision functional?

Answer 18

It allows for the detection of movement (predator/prey) and colour (ripe/spoiled) which is crucial for survival.

Question 19

What are the two types of photoreceptors?

Answer 19

Cones (sensitive to fine detail and colour)
Rods (sensitive to movement)

Question 20

How does the transduction of light work?

Answer 20

Light travels through the retina to impinge on photoreceptors at the back of the eye

Light bleaches a pigment contained within the photoreceptors

Bleaching leads to a graded receptor potential that eventually produces an action potential in the ganglion cell

Question 21

How does the brain process visual information?

Answer 21

1. The optic nerve leaves the eye, carrying information about light toward the brain.
2. Stimuli from left/right visual fields stimulate rods and cones in the OPPOSITE half of the retina in both eyes.
3. At the optic chiasm, the optic nerve fibres separate, and half of the nerve fibres cross over the midline of the brain.
4. The visual information originating in the right halves of the two retinas (from objects in the left visual field) is transmitted to the right side of the occipital lobe in the cerebral cortex,

and the visual information coming from the left halves of the retinas (from objects in the right visual field) is transmitted to the left side of the occipital lobe.

5. The visual stimuli is then processed in the visual cortex of the brain.

Question 22

What is a feature detector?

Answer 22

Neurons in the brain’s visual system that respond to particular features of a stimulus.

Question 23

What did David Hubel and Toren Wiesel discover about humans from their research on feature detectors?

Answer 23

Humans “learn” to perceive through experience.

Question 24

What is parallel processing?

Answer 24

The simultaneous distribution of information across different neural pathways that allows information to be processes quickly.

Question 25

What is binding in the sense of vision?

Answer 25

Bringing together and integrating what is processed by different neural pathways or cells to paint a whole picture of what we see.

Question 26

What is the trichromatic theory?

Answer 26

• Thomas Young’s theory
• Colour perception is produced by 3 types of cone receptors in the retina that are sensitive to different and overlapping ranges of wavelengths.

Question 27

What is the opponent-process theory?

Answer 27

• Ewald Hering’s theory
• Cells in the visual system respond to complementary pairs of red-green and blue-yellow colours.
• A given cell might be excited by red and inhibited by green, whereas another cell might be excited by yellow and inhibited by blue.

Question 28

How are both the trichromatic theory and the opponent-process theory correct?

Answer 28

Red, blue and green cones in the retina are connected to retinal ganglion cells, therefore the three-colour code is immediately translated into the opponent-process code which is sent to the optic nerve and brain.

Question 29

What is Getsalt psychology?

Answer 29

People naturally organize their perceptions according to certain patterns.

Question 30

What are the 3 Getsalt principles and what do they do?

Answer 30

Closure: we fill in disconnected figures to see them as complete

Proximity: Objects near each other are seen as a unit.

Similarity: similar objects tend to be seen as a unit

They identify how we innately connect stimuli together.

Question 31

What is the place theory?

Answer 31

• The inner ear registers the frequency of sound
• Each frequency produces vibrations at a particular spot on the basilar membrane.

Question 32

Why is the place theory acceptable and flawed?

Answer 32

It explains high-frequency sounds and says they stimulate a precise area on the basilar membrane.

It does not identify an exact location on the membrane that is associated with hearing low-frequencies.

Question 33

What is Frequency Theory?

Answer 33

• The inner ear registers the frequency of sound
• The perception of a sound’s frequency depends on how often the auditory nerve fires.

Question 34

Why is the frequency theory limited and what principle did researches come up with?

Answer 34

The frequency theory was limited because it does not apply to frequencies that would require a neuron to fire more rapidly. One neuron fires at a max rate of 1000 times per second

The volley principle states that a cluster of nerve cells can fire neural impulses in rapid succession or alternating turns, producing a volley of impulses.

Question 35

How does the brain process sounds via the auditory nerve?

Answer 35

The auditory nerve receives information about sound from the hair cells of the inner ear and carries these neural impulses to the brain’s auditory areas.

Question 36

How do we know where sounds are coming from?

Answer 36

Timing and intensity help us localize the source of sounds. From equal distances, the pinna distorts sounds based on where they come in space and our brain cells can detect the difference.

Question 37

What is the perpetual dimension of amplitude (intensity) of a sound?

Answer 37

Loudness

Question 38

What is the perpetual dimension of frequency of a sound?

Answer 38

Pitch

Question 39

What is the perpetual dimension of complex sounds (voices, music, intersecting frequencies)?

Answer 39

Timbre: tone saturation

Question 40

How do we feel touch and how are signals sent to our brain?

Answer 40

We detect mechanical energy (pressure against skin). Touch receptors produce action potentials that go to the spinal chord, brain stem, then the opposite sides, to the thalamus which projects to the parietal lobes.

Question 41

How do we feel temperature?

Answer 41

Thermoreceptors, sensory nerve endings under the skin that respond to changes in temperature at or near the skin and provide input to keep the body’s temperature at 37 degrees Celsius.

Question 42

How do we feel pain?

Answer 42

Pain receptors detect when a stimulus is too intense that it could cause danger to our bodies. They are unevenly distributed throughout the body.

Neuroscientists believe that the experience of pain is signalled by endorphins. Motivation and expectation could impact the perception of pain.

Question 43

How do we taste?

Answer 43

We detect chemicals dissolved in our saliva. Papillae increase the surface area of our tongue to make more room for taste buds which transmit stimuli to the brain for analysis.

Question 44

How do we smell?

Answer 44

The olfactory epithelium lining of the roof of the nasal cavity, contains a sheet of receptor cells for smell. The neural pathway goes to the olfactory areas in the temporal lobes then various brain regions, especially the limbic system responsible for emotion and memory.

Question 45

What are kinesthetic senses and vestibular senses?

Answer 45

Kinesthetic senses provide information about movement, posture, and orientation. Vestibular sense provides information about balance and movement.

Question 46

How does vestibular sense make its way to the brain?

Answer 46

Via the auditory nerve. Semicircular canals and vestibular sacs transmit info about movement and head position. Messages go to the medulla or directly to the cerebellum.