why study perception
- understand how to best move about and interact with our environment
- evolution, higher chance of survival
analog representation of the world from a digital signal
- assumption from the brain to perceive missing information
- experience/ expectation instead of perception
importance of knowing how stimuli are encoded and perceived
- help create technology designed to restore those with sensory loss
- brain computer interfaces, brain signals = stimuli = perception
- computer vision, self driving vehicles
bottom up information
- shape
- color
- motion
top down information
- theory
- knowledge
- context
cognitive penetration
- cognitive factors shaping perception ie everything seeming brighter and hard tasks being easier when you are in a good mood, placebo
- debated whether perception is different or the description is affected
vestibular sense
- where we are orientated in the world
proprioception
- where our limbs are positioned
sensation and perception
- physical stimulus
- stimuli reach the sensory organ, bind to receptors
- sensory cells translate stimulus into a code to be interpreted by the brain (transduction, involving action potential)
- interact with experience, different perceptions from the same stimuli
method of limits
- stimuli presented sequentially either increasing or decreasing
method of constant stimuli
- stimuli of varying levels presented randomly, above and below threshold
method of adjustment
- participants adjust stimuli to find their own threshold value
absolute threshold
- how much pressure or how bright or loud a stimulus must be to perceive it
difference threshold
- how much a stimuli needs to be changed to notice a difference
point of subjective equivilance
- point at which two stimuli are judged to be perceptually identical
what theory to use to account for possible bias during self report method
signal detection theory
- our ability to be accurate
- greater sensitivity, greater chance of being accurate
hit
correct rejection
false alarm
miss
more correct responses, curved upward to the left
electrical stimulation
neuroimaging EEG
electroencephalogram
- up to 128 electrodes placed on the scalp
- measuring electrical potential generated by the brain
- continuous signal
- hard to tell where in the brain the activity is coming from, can’t move
neuroimaging MEG
magnetoencephalogram
- measures magnetic field distortions caused by the electrical activity in the brain
- less portable and more expensive but better at determining where in the brain
neuroimaging MRI/ fMRI
functional magnetic resonance imaging
- very detailed images of brain processes
- expensive, non portable
- scary, claustrophobic
- not suitable for some populations ie pacemakers
hubel and wiesel
- using animal models to record electrical outputs of individual neurons
- lowered an electrode so it was adjacent to neurons in the primary visual cortext in a cat
- work helped describe orientation columns in the visual cortex
- neurons are tuned to specific stimulus features
neuropsychological studies
- patients with focal damage in a small region of the brain, strange patterns of perceptual behaviour
- documenting their behaviour and damage site, infer the role of the damaged area in perception
lesion studies
- in animals creating specific lesion models and testing for perception
- permenant damage to neural tissue or reversible approaches such as cortical cooling
cortical cooling - certain brain areas turned off by cooling them off so action potentials can’t be generated, recovered by warming
transmagnetic stimulation (TMS)
- group of technologies
- stimulate the brain via electric current
- magnetic field generator (coil) on the head of participants
- coil induces an electrical current in the particular brain region beneath the coil, induces changes in how the region functions which can be perceptual or behavioural
- temporary experimental analyses
- on the optical nerve can result in temporary blindness
