stimulus detection process by which our sense organs respond to and translate environmental stimuli into nerve impulses which are sent to the brain
perception
making sense of what our senses tell us
sensation systems
designed to extract from the environment the information we need to function and survive
psychophysics
area that studies relations between the physical characteristics of stimuli and sensory capabilities
absolute threshold
lowest intensity at which a stimulus can be detected 50% of the time
decision criterion
a standard of how certain they must be that a stimulus is present before they say they detect it
signal detection theory
factors that influence sensory judgement e.g. fatigue, expectation and significance of stimulus
subliminal stimuli
weak or brief stimuli that is received by senses but cannot be perceived consciously
difference threshold
smallest difference between two stimuli that people can perceive 50% of the time- just noticeable difference
Weber's law
difference threshold is directly proportional to the magnitude of the stimulus with which the comparison is being made
sensory adaptation
diminishing sensitivity to an unchanging stimulus- occurs in all senses, allows our senses to pick up informative changes in the environment that could be important to survival
sensory transduction
process whereby characteristics of a stimulus are converted into nerve impulses
vision
stimulus is electromagnetic energy (light waves)
sensitive to different wave lengths (400-700)
different wavelengths of visible light have different colours
pupil
behind cornea- controls how much light can enter eye
lens
flexible structure- thinner to focus on distant objects, thicker on closer objects
causes images to be focused on inner surface of the eye (retina)
myopia
near sighted- visual image focused in front of retina, eyeball is longer than normal
hyperopia
farsightedness- image is focused behind retina, lens doesn't thicken enough
photoreceptors
retina, rods, cones, fovea
retina
multi-layered light sensitive tissue at the rear of fluid filled eyeball- contains to types of receptor cells
rods
black and white brightness receptors- function best in dim light
cones
colour receptors- function best in bright illumination
fovea
small area in centre of retina-no rods but densely packed cones- responsible for more detailed vision
rods and cones have synaptic connections with bipolar cells
connected to ganglion cells
axons are collected into a bundle, forms optic nerve
absence of receptors where optic nerve exits the eye creates a blind spot
visual process
lens reverses image
photoreceptors and neurons send input to the brain, reconstructs it in right direction
many rods are connected to one bipolar/ganglion cell as each photoreceptor can only respond to lights in its vicinity
visual transduction
protein molecules allow rods and cones to translate light waves into nerve impulses
produces a chemical reaction that changed rate of neurotransmitter release
greater the change, stronger the signal passed to bipolar and ganglion cells
dark adaptation
progressive improvement in brightness sensitivity that occurs over time under conditions of low illumination
analysis and reconstruction
from retina- optic nerve sends message to thalamus
input is routed to the primary visual cortex in the occipital lobe
feature detectors
cells within primary visual cortex that fire selectively in response to visual stimuli that have specificcharacteristics