Chapter 4: Sensation & Perception

Question 1

What is a genotype & a phenotype?

What are dominant & recessive traits?

Answer 1

Genotype:
-Set of genes transmitted from our parents to us.

Phenotype:

• Set of observable traits.
• Shaped by environmental influences. (parenting etc.)

Dominant traits:
-Mask other genes’ effects.

Recessive traits:
-Expressed only in absence of dominant trait.

Question 2

Charles Darwin’s theory:

Answer 2

• Hypothesized that populations of organisms change over time by selective breeding among individuals within population who possess an adaptive advantage.
• Some organisms possess adaptations that make them better suited to their environment.
• Adaptations are physical & behavioural, like aggressive behaviour.

Question 3

What are behavioural genetics?

Answer 3

• Scientists us behavioural genetics to examine influence of nature & nurture psychological traits. (intelligence for e.g.)
• Permit us to look at roles of both genes & environment in behaviour.
• Allow us to estimate heritability of traits & diseases.
• %

Question 4

What are heritability misconceptions?

Answer 4

1. Applies to single individual rather than to differences among individual.
   Fact: Applies only to groups of people.
2. Tells us whether a trait can be changed.
   Fact: Says little or nothing about how malleable a trait it.
3. Fixed number.
   Fact: Can differ dramatically across different time periods & populations.

Question 5

How do scientists estimate heritability? (3 designs)

Answer 5

• They use three behavioural genetic designs.
  1. Family studies
  2. Twin studies
  3. Adoption studies

Question 6

What are family studies? Advantages & disadvantages:

Answer 6

-Examine extent to which a characteristic runs tog. in intact families.
-Estimates risk of disorder among relatives.
-Don’t allow us to disentangle effects of nature & nurture.
(environmental from genetic influences).

Question 7

What are twin studies? Advantages & disadvantages:

Answer 7

• Examine differences between identical & fraternal twins in traits.
• If identical twins are more alike than fraternal (on psychological characteristic), we can infer that this characteristic is genetically influenced. (assuming environments are same in both sets of twins).

Question 8

What are adoption studies? Advantages & disadvantages:

Answer 8

• Examine extent to which children adopted into new homes resemble their adoptive as opposed to biological parents.
• if they resembled characteristics from biological parents, its genetically influenced.
• Cofound: selective placement.

Question 9

What is sensation?

Answer 9

Sensation:
-Detection of physical energy by our sense organs (eyes, ears, skin, nose, tongue), which relay info. to brain.

-Picks up signals in enviro.

Question 10

What is perception?

Answer 10

Perception:
-Brain’s interpretation of these sensory inputs.

-Allows up to assemble signals into something meaningful.

Question 11

What is filling-in?

Answer 11

• Perceptual process which occurs without awareness.
• Adaptive.
• Can fool us.

Question 12

What is tranduction?

Answer 12

• Process by which n.s. converts an external stimulus, into electrical signals within neuron.
• Specific type of sense receptor, transduces a specific stimulus.
• Specialized cells at back of eye transduce light; cells in cochlea transduce sounds; endings attached to axons transduce pressure; receptor cells lining inside of nose transduce odourants; taste buds transduce chemicals containing flavour.

Question 13

What is sensory adaptation? What would happen if we didn’t engage in sensory adaption?

Answer 13

• Activation is greatest when we first detect a stimulus. After that, our response declines in strength -sensory adaptation.
• The adaptation takes place at level of sense receptor.
• This receptor reacts strongly at first, then tamps down its level of responding.

If we didn’t engage in sensory adaptation, we’d be attending to just about everything around us, all of the time.

Question 14

Does human error decrease or increase as stimuli become weaker in magnitude?

Answer 14

-It increases.

Question 15

What is absolute threshold?

Answer 15

Psychophysicists study the absolute threshold of stimulus:

• The lowest level of a stimulus we can detect on 50 % of trials when no other stimuli of that type are present.
• Absolute threshold demonstrates how sensitive out sensory systems is.

Question 16

What is the just noticeable difference? (JND) What is Webers Law?

Answer 16

(JND):

• Smallest change in intensity of a stimulus that we can detect.
• Relevant to our ability to distinguish a stronger stimulus from a weaker stimulus.

Weber’s Law:
-States that there’s a constant proportional relationship between JND & original intensity.

-Stronger the stimulus, the bigger the change needed for a change in stimulus intensity to be noticeable.

Question 17

What is the Signal Detection Theory?

Answer 17

• Found a way to account for peoples’ response biases.
• People can report that they heard a sound when it was present (true positive).
• Deny hearing a sound when it was present (false negative).
• Report hearing a sound when it wasn’t there (false positive).
• Deny hearing a sound when it wasn’t there (true negative)

Question 18

What is the doctrine of specific nerve energies? What are phosphenes? Why & where do they occur?

Answer 18

• States that even though there are many distinct stimulus energies (light, sound, touch), sensation we experience is determined by the nature of sense receptor, not the stimulus.
• (E.g. phosphenes: )
• Phosphenes:
• Vivid sensations of light caused by pressure on your eye’s receptor cells.
• Occur in cerebral cortex.- different areas devoted to diff. senses.
• Once a visual sense receptor send their signals to cortex, brain interprets their input as visual, regardless of how our receptors were stimulated in first place.

Question 19

What is the McGurk Effect?

Answer 19

-Demonstrates that we integrate visual & auditory info. when processing spoken language, & our brains automatically calculate most probable sound given the info. from two sources.
(“ba,” “da,” “ga.”)
-3rd sound is brain’s best guess at integrating two conflicting sources of info.

Question 20

What is the rubber hand illusion? What is the eerie illusion?

What does this cross model reveal?

Answer 20

• Shows how our senses of touch & sight interact to create a false perceptual experience.
• This illusion causes a person to experience an eerie illusion. -rubber hand seems to be her own hand.
• Cross model effects may reflect cross talk among different brain regions.
• However, in some cases a single brain region may serve double duty, helping to process multiple senses.

Question 21

What is synesthesia?

Answer 21

• Darwin & S.F. Galton discovered.
• Condition in which people experience cross-model sensation, like hearing sounds when they see colours called colour-hearing, or even tasting or smelling colours.
• Most common form is grapheme-colour synesthesia, in which a 6 may always seem red, & a 5 green.

Question 22

What is selective attention? What are the major regions that control it?

Answer 22

• Allows us to select one channel & turn off the others, or at least turn down their volume.
• Major brain regions for controlling selective attention are reticular activating system (RAS), & forebrain.
• Activates regions of cerebral cortex.

Question 23

How do magicians fool us?

Answer 23

-They trick people by misdirecting attention and awareness.

Question 24

What is the filter theory of attention? What is dichotic listening?

Answer 24

• Broadbent’s theory enables us to pay attention to important stimuli & ignore others (filter).
• Used dichotic listening: People hear 2 diff. messages, 1 delivered to left ear & other to right ear.

-However, Info we supposedly filtered out of our attention is still being processed at some level- even when we are not aware of it.

Question 25

What is the cocktail party effect?

Answer 25

-Explains how we can become aware of stimuli outside our immediate attention when it is relevant to us.

Question 26

What is important about inattentional blindness?

What is change blindness?

Answer 26

-We need to pay close attention to pick out even dramatic changes in environment.

-Failure to detect obvious changes in one’s environment.
(particularly in pilots.)

Question 27

What is the Binding Problem?

Answer 27

• Great mystery of psychology:
• Brains manage to combine diverse pieces of information into a unified whole.
• Perception & attention work together.