WEEK 2 BRAIN AND COGNITION- visual perception
Is the physical world the same thing as our visual experience- no BERKELEY + EINSTEIN
‘your physical skull is beyond the experienced dome of the sky’- VELMANS 2009
VISUAL ILLUSIONS- show the rules that the brain uses to construct visual experience eg KANISZA
TRIANGLE – the visual brain is constructing things that aren’t three [see Bertamini’s psych 309]
The brain only sees in 2D and so it interprets the retinal image and creates a representation= the
interpretation – its always looking for a 3D representation
Sensations inform perception- our visual and sensory experiences can be described as ‘percepts’ –
sensations are more basic elements which are elaborated into precepts by visual parts of the brain.
Top down and Bottom up contributions*
General properties of sensory systems
Vision is just one sensory modality (e.g. sound, taste) … the visual system responds to light, auditory
systems responds to vibrations, olfactory systems responds to chemicals in nose and gustatory
systems to chemicals in the mouth, tactile receptors respond to mechanical deformation of skin. WE
DON’T JUST HAVE 5 SYSTEMS- we have nociception responding to skin damage and vestibular
system responding to gravity and acceleration of the head.
EXTEROCEPTION AND INTEROCEPTION.
Exteroception provides brain with signals about energies in the outside world, interoception
provides the brain with signals of what’s going on inside the bodyProprioception is the main example
of interoception – it provides signals about the contraction of muscles and the angles of our joints
(allows you to know your current posture in a totally dark room). The brain is also bombarded with
interoceptive signals about heart rate, breathing, gut dilation, blood sugar concentrations and so
on… Emotional states are intimately linked to interoception (James, 1890).
Sensory systems are ‘bounded’- very limited window on the physical world with narrow boundaries.
WHY… TRANSDUCTION- The conversion of physical energy into action potentials
The psychophysics approach- a part of psychology that plots lawful relationships between physical
world and subjective experience.
What is the minimum strength of stimulus we can detect? [through the narrow window] eg what is
too quiet to hear and what can we just about hear. We like to determine JNDs (just noticeable
differences) eg applied pressure = pedestal stimulus and slightly harder pressure= test stimulus
JND increases with stimulus intensity- WEBERS LAW--- ‘Imagine you are poor and have one
pound, and you get another pound. That would change your life quite a lot. Imagine you are rich and
have million pounds, and you get another pound. That would hardly change your life at all.’
Scaling- Steven’s power law is a more refined version of Weber Fechner type scaling. The
relationship between physical stimulus and sensation often non-linear.
Is the physical world the same thing as our visual experience- no BERKELEY + EINSTEIN
‘your physical skull is beyond the experienced dome of the sky’- VELMANS 2009
VISUAL ILLUSIONS- show the rules that the brain uses to construct visual experience eg KANISZA
TRIANGLE – the visual brain is constructing things that aren’t three [see Bertamini’s psych 309]
The brain only sees in 2D and so it interprets the retinal image and creates a representation= the
interpretation – its always looking for a 3D representation
Sensations inform perception- our visual and sensory experiences can be described as ‘percepts’ –
sensations are more basic elements which are elaborated into precepts by visual parts of the brain.
Top down and Bottom up contributions*
General properties of sensory systems
Vision is just one sensory modality (e.g. sound, taste) … the visual system responds to light, auditory
systems responds to vibrations, olfactory systems responds to chemicals in nose and gustatory
systems to chemicals in the mouth, tactile receptors respond to mechanical deformation of skin. WE
DON’T JUST HAVE 5 SYSTEMS- we have nociception responding to skin damage and vestibular
system responding to gravity and acceleration of the head.
EXTEROCEPTION AND INTEROCEPTION.
Exteroception provides brain with signals about energies in the outside world, interoception
provides the brain with signals of what’s going on inside the bodyProprioception is the main example
of interoception – it provides signals about the contraction of muscles and the angles of our joints
(allows you to know your current posture in a totally dark room). The brain is also bombarded with
interoceptive signals about heart rate, breathing, gut dilation, blood sugar concentrations and so
on… Emotional states are intimately linked to interoception (James, 1890).
Sensory systems are ‘bounded’- very limited window on the physical world with narrow boundaries.
WHY… TRANSDUCTION- The conversion of physical energy into action potentials
The psychophysics approach- a part of psychology that plots lawful relationships between physical
world and subjective experience.
What is the minimum strength of stimulus we can detect? [through the narrow window] eg what is
too quiet to hear and what can we just about hear. We like to determine JNDs (just noticeable
differences) eg applied pressure = pedestal stimulus and slightly harder pressure= test stimulus
JND increases with stimulus intensity- WEBERS LAW--- ‘Imagine you are poor and have one
pound, and you get another pound. That would change your life quite a lot. Imagine you are rich and
have million pounds, and you get another pound. That would hardly change your life at all.’
Scaling- Steven’s power law is a more refined version of Weber Fechner type scaling. The
relationship between physical stimulus and sensation often non-linear.
