Lecture 2 - Sensation and perception Flashcards
What is perception?
- Process of acquiring knowledge regarding environmental objects or events via the senses.
What is the perceptual process?
- 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).
What is perception for?
- 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.
What is somatosensory perception?
Touch
What is olfactory perception?
Smell
What is auditory perception?
Hearing
What is visual perception?
Seeing
What is Gustatory perception?
Taste
What is proprioception?
Sense of body position and movement.
What is nociception?
Pain
What is thermoception?
Temperature
What are some examples of different species’ abilities to sense energies humans cannot?
- 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.
Is perception veridical (accurate)?
- Senses would not have evolved if they did not provide reasonably accurate information.
- May not be a ‘clear windowʼ onto reality.
What are illusions?
- Situations where perception differs from reality.
- Can provide insight into the processes of sensation and perception.
What are ambiguous figures?
- 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).
What are some examples of ambiguous figures?
- The ‘Necker cube’
- Duck/rabbit illusion
What are ambiguous sounds? Give an example.
- Can give rise to multiple bistable and stable perceptions.
- For example Laurel or Yannie?
What are impossible objects?
- Sensory input can be interpreted by the brain as representing objects/scenarios that are physically impossible.
What are some examples of impossible objects?
- Penrose triangle.
- Schuster’s conundrum (devil’s fork).
- Endless stairs.
What sources of information affect how we perceive things?
Current sensory input and existing knowledge regarding environment.
What is a top-down process?
Use of knowledge about structure of the world to influence perception (ʼconceptually drivenʼ process).
What is a bottom-up process?
Takes information from the senses and make judgments about the world based on this (ʼdata-drivenʼ processes).
What are some key ideas of constructivist theories of perception?
- 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.
What are some key ideas of direct theories of perception?
- 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.
