Lecture 2 - Sensation and perception

Question 1

What is perception?

Answer 1

• Process of acquiring knowledge regarding environmental objects or events via the senses.

Question 2

What is the perceptual process?

Answer 2

• Perceptual process = two stages: sensation - energy form physical stimuli simulates sensory receptors then this is converted to neural impulses which are sent to the brain, perception - interpreting these input signals for conscious awareness and action.
• Distal stimuli -> Proximal stimuli -> Sensation (conversion to neural signals which are sent to the brain) -> Perception (signal processing and interpretation).

Question 3

What is perception for?

Answer 3

• Aristotle (384-322 BC): animals must have perception if they are to live.
• It has evolved for survival and reproductive purposes of organisms.
• Our senses help us to seek out desirable objects/situations and to avoid dangerous ones.

Question 4

What is somatosensory perception?

Answer 4

Touch

Question 5

What is olfactory perception?

Answer 5

Smell

Question 6

What is auditory perception?

Answer 6

Hearing

Question 7

What is visual perception?

Answer 7

Seeing

Question 8

What is Gustatory perception?

Answer 8

Taste

Question 9

What is proprioception?

Answer 9

Sense of body position and movement.

Question 10

What is nociception?

Answer 10

Pain

Question 11

What is thermoception?

Answer 11

Temperature

Question 12

What are some examples of different species’ abilities to sense energies humans cannot?

Answer 12

• Caribou - sense light into the UV spectrum meaning they can detect camouflaged predators.
• Elephants - sensitive to very low frequency sounds and vibrations so they can communicate over large distances.
• Snakes - can detect infrared radiation so they can generate a ‘thermal imageʼ of prey.

Question 13

Is perception veridical (accurate)?

Answer 13

• Senses would not have evolved if they did not provide reasonably accurate information.
• May not be a ‘clear windowʼ onto reality.

Question 14

What are illusions?

Answer 14

• Situations where perception differs from reality.
• Can provide insight into the processes of sensation and perception.

Question 15

What are ambiguous figures?

Answer 15

• Images that can give rise to two or more distinct perceptions.
• Our perception is rarely ambiguous but alternates over time.
• Also referred to as bistable images.
• Sometimes produce different perceptions between different people that are stable over time (e.g black and blue vs white and gold dress).

Question 16

What are some examples of ambiguous figures?

Answer 16

• The ‘Necker cube’
• Duck/rabbit illusion

Question 17

What are ambiguous sounds? Give an example.

Answer 17

• Can give rise to multiple bistable and stable perceptions.
• For example Laurel or Yannie?

Question 18

What are impossible objects?

Answer 18

• Sensory input can be interpreted by the brain as representing objects/scenarios that are physically impossible.

Question 20

What are some examples of impossible objects?

Answer 20

• Penrose triangle.
• Schuster’s conundrum (devil’s fork).
• Endless stairs.

Question 21

What sources of information affect how we perceive things?

Answer 21

Current sensory input and existing knowledge regarding environment.

Question 22

What is a top-down process?

Answer 22

Use of knowledge about structure of the world to influence perception (ʼconceptually drivenʼ process).

Question 23

What is a bottom-up process?

Answer 23

Takes information from the senses and make judgments about the world based on this (ʼdata-drivenʼ processes).

Question 24

What are some key ideas of constructivist theories of perception?

Answer 24

• Emphasise top-down processing.
• Helmholtz (1821-1894) - inadequate information provided by the senses is augmented by unconscious inference.
• Gregory (1923-2010) - elaborated the theory of perception as inference: best interpretation of the available data.
• Many illusions are better described as rational inferences rather than ‘perceptual errors’ in this approach.

Question 25

What are some key ideas of direct theories of perception?

Answer 25

• Emphasise bottom-up processing.
• James Gibson (1904-1974) -argues the constructivist approach underestimates the richness of the sensory evidence we receive.
• There are various cues in the natural world which provide information about the structure of the environment.
• The perceiver is not a passive observer but interacts with the environment - interaction is key to picking up useful information.