Topic 4 - Sensation & Perception Flashcards
What are the 3 basic principles of sensation and perception?
- There is no one-to-one correspondence between physical and psychological reality.
- Sensation and perception are active processes.
- Sensation and perception are adaptive - the products of evolutionary adaptations that served our survival and reproduction.
Define sensation.
The process by which sense organs gather information about the environment and transmit it to the brain for processing.
Define perception.
The process by which sense organs gather information about the environment and transmit it to the brain for processing.
What is psychophysics?
The branch of psychology that studies the relationship between attributes of the physical world and our psychological experience of them.
Define transduction.
The process of converting stimulus information into neural impulses.
What are absolute thresholds?
The minimum amount of energy needed for an observer to sense that a stimulus is present.
Define signal detection and the two processes involved.
A sensation is not a passive experience that occurs when the amount of stimulation exceeds a critical threshold; rather, experiencing a sensation means making a judgement about whether a stimulus is present or absent.
Two processes:
- Initial sensory processes
- Decision process (reflecting observers response bias)
What is the difference threshold?
The lowest level of stimulation required to produce a just noticeable difference (jnd) / sense that a change in stimulation has occurred.
Define sensory adaptation.
The tendency of sensory receptors to respond less to stimuli that continue without change.
What is subliminal perception?
The tendency to perceive information outside our conscious awareness.
What is subliminal perception?
The tendency to perceive information outside our conscious awareness.
What are sensory receptors?
Cells in the NS that transform energy in the environment into neural impulses that can be interpreted by the brain.
What are the 5 steps in creating a neural code?
- There is a stimulus in the environment
- Sensory receptors receive energy (stimulus) and transform it into neural impulses.
- Action potentials are generated in sensory neurons adjacent to receptors.
- Brain interprets neural code (reads neural code & translates it into something that is psychologically meaningful)
- Experience of light, sound, taste, touch, smell and motion.
How is intensity of sensation portrayed in neural code?
Usually involves the number of sensory neurons that fire and the frequency.
What factors affect response bias?
Expectations and motivation
What is Weber’s law?
Regardless of the magnitude of two stimuli, the second must differ from the first by a constant proportion for it to be perceived as different.
This proportion can be reflected as a fraction.
What is Fechner’s law?
People only experience a small percentage of actual increases in stimulus intensity and this percentage is predictable.
What is Stevens’ power law?
Fechner’s law didn’t apply to all senses.
Pain is opposite - the greater the pain, the less additional intensity is required for a jnd.
Stevens’ power law can predict subjective experience of pain intensity as readily as brightness.
How is light focused in the eye? (4 steps)
- Light enters through cornea
- Then travels through pupil & iris
- The lens then alters its shape to focus on objects at various distances (accommodation)
- Light is then projected onto the retina that transduces light into visual sensations.
What is the role of the retina?
Translates light energy from illuminated objects into neural impulses (psychologically meaningful info)
How does light transform into sight?
- Rods & cones absorb light & bleach
- This creates a graded potential in neighbouring bipolar cells
- These cells combine info from many rods/cones & produce graded potentials on ganglion cells (which integrate info from many bipolar cells)
- The ganglion cells bundle and form the optic nerve which passes through optic chiasm (where optic nerve splits)
- Combined info from eyes travels along two pathways (> thalamus or superior colliculus)
What are the 2 pathways visual info travels along within each hemisphere?
Pathway 1: Projects to thalamus and then to the primary visual cortex
Pathway 2: Projects to midbrain which helps control eye movements
What are feature detectors?
Neurons in the visual cortex that fire only when stimulation in their receptive field matches a very specific pattern (e.g. horizontal line)