define perception
also psychophysics
- the relationship between physical stimuli and their subjective or psychological correlates
- there is no other way for information to enter the brain - senses and your perception of them is the only way
- determines what we believe is real and mediates everything we have ever learned
what are the senses?
Sight (visual)
Hearing (auditory)
Smell (olfactory)
Taste (gustatory)
Touch (tactile / haptic)
Balance (equilibrioception)
Body awareness (proprioception)
Heat (thermoception)
Classification system of the senses
Vision
Audition
The chemical senses (gustation, olfaction)
The body senses
- somatosensation (haptics + proprioception)
- equilibrioception
Neuropsychology
- Apperceptive / associative agnosia: study of people with lesions in their brain - testing them on various tasks and finding patterns of what they can’t do
- phantom limbs/pain
- rubber hand illusion
- alien hand syndrome
Clinical psychology
Eating disorders: body dysmorphia - people systematically misperceive their own body shape
Inability to recognise facial emotion in psychopaths, depressives, autistics, schizophrenics
Forensic psychology
Eye witness testimony - many errors
Illusions of spatial vision
Hermann grit: seeing grey patches
Craik-O’brien/Cornsweet illusion (simultaneous contrast)
illusions of depth
thatcher illusion
illusions of motion
Sensation vs perception
artificial distinction
more sensible to think of the whole sequence of events from conversion of the external energy by the receptors (transduction) to understanding what is seen/heard/felt as the process of perception
psychophysics
the scientific study of the subjective experience of perception
i.e. perceiving not the real world but your subjective impression of it
Sensory systems
Vision - occipital
Hearing - temporal lobe
Touch (somatosensation)
- layers of skin have many different receptors
- these receptors convey information about touch, temperature and ‘pain’
- when the skin is deformed, it causes changes in the neurons which send their electrical signals towards your brain
- receptors convert pressure into neural signals (touch), conver heat energy into neural signals (temperature) but none for ‘pain’ because that’s psychological
somatosensory cortex
at the top of the brain (behind the motor cortex)
organised in a way that matches up to the motor cortex
larger regions in the cortex devoted to areas that are experiencing lots of touch / stimulus
taste (gustation)
mostly in your tongue
collected in clumps called taste buds located on small projections on the tongue called papillae
respond to chemicals dissolved in saliva
different tastes:
- salt, sweet, sour, bitter, umami
traditionally thought of tongue maps, but this is wrong
smell *olfaction
- only dissolved chemicals in the mucus in the nose can activate the smell receptors
- certain smell receptors respond to particular chemicals
- at least 7 primary smell receptors
- odours activate receptors in the olfactory epithelium (top of nasal cavity)
- these receptors synapse directly onto the olfactory bulb
- bypasses the thalamus - going straight to the cortex
balance (equilibrioception)
- vestibular system provides us with information about accelerations, orientation
- in the inner ear on each side (next to the cochlea) - two components = semicircular canals, utricle and saccule
- semicircular canals: provide information about angular (rotational) accerlerations in 3 dimensions (pitch, yaw, roll)
- utricle and saccule: provide info about linear accelerations (including gravity) –> the hair cells project into a thick fluid which remains stationary as our head moves, causing hair cells to bend
Body sense (proprioception)
- receptors in our muscles and joints
- completely unaware of this input
- seamlessly integrated with vestibular input
what is sound
the stimulus for hearing is sound
- pressure wave in air
- these vary in amplitude (up and down - intensity of the sound) and frequency (pitch)
structure of the ear
- inner ear does most of the hearing
- pinna –> auditory canal –> tympanic membrane vibrates–> the ossicles (malleus, incus, stapes) move the basilar membrane up and down inside the cochlea –> causes hair cells to fire electrical signals which get sent through the auditory nerve to the thalamus
- amount of basilar membrane movement codes amplitude (perceived as loudness)
- place of maximum movement codes frequency (pitch)
low vs high freq sounds
low freq: maximum basilar membrane displacement at the end FURTHEST from the stapes
high freq: closest to the stapes
auditory localisation
- interaural time difference (reaching right ear before left ear)
- interaural intensity differences (louder in the right than the left)
-modifications to the sound wave caused by the pinnae which enables monaural localisation - the ‘cone of confusion’
cone of confusion
changes to the sound wave made by the pinnae help us decide between the possibilities in the cone of confusion, as well as head movements
types of hearing loss
conductive deafness: caused by an impediment ot the transmission of the soudn wave to the basilar membrane
sensorineural deafness caused by damage to some part of the neural apparatus of hearing
parts of hte eye
- lens is useful for focusing light from various distances (accomodation)
- retina has many nerve cells
- optic nerve is where all of the signals and electric impulses exit your eyeball
visual pathways
- optic nerve to the thalamus (lateral geniculate nucleus)
- signals are relayed on by optic radiations and terminate in the primary visual cortex in the occipital area
- information from the right side of space is processed in the left hemisphere and vice versa - as a result of the optic chiasm
