Maartje van Loef
UU
Samenvatting cognitie en gedrag
Brain and Cognition, Customized edition 2019. ISBN 978-1-473-
77572-5
Introduction
Cognitive psychology is the branch concerned with scientific study of the mind.
Mind: creates and controls mental functions, such as perception, attention, memory, emotions,
language, deciding, thinking and reasoning. Definition that reflects on role in determining various
mental abilities. Different cognitions.
Definition that reflects on how the mind operates (functioning and survival): a system that creates
representations of the world so that we can act within it to achieve our goals.
1800’s: stated it’s impossible to study the mind.
1868: Donders: wanted to know how long it takes for a person to make a decision. Measured
reaction time: between stimulus and reaction.
- Simple reaction time: push button when light goes on
- Choice reaction time: push left when left light goes on and the other way round.
The time difference from deciding would show the decision making time.
Mental responses cannot be measured directly, must be inferred from observing behaviour.
1879: Wundt: structuralism: our overall experience is determined by combining basic elements of
experience which were called sensations. Wanted to achieve description of components of
experience by using analytic introspection: trained participants described sensations, thoughts
processes and feelings in response to a stimuli. Wundt shifted study of the mind from rationalist
approach to empiricist approach.
1885: Ebbinghaus: used a quantitative method for measuring memory. To determine how much
information was retained after a delay: savings = (original time to learn the list) – (time to re-learn
the list after the delay). Savings curve: plot of percent saving versus time.
1890: william James: observations based not on the results of experiments, but on observations
about the operation of his own mind.
1913: Watson: behaviourism: focus on pure observable behaviour. Closely associated with classical
conditioning. How pairing one stimulus with another affected behaviour.
1938: Skinner: operant conditioning: focused on how behaviour is strengthened by the presentation
of positive reinforcers. Like Watson, not interested in what’s going on in the mind.
Tolman: rat in maze, turned left/right for food. Explanation: cognitive map developed. The use of
‘cognitive’ and the idea that something other than stimulus-response connections might be occurring
in the rats mind, placed Tolman outside the mainstream behaviourism.
Chomsky: language is the product of the way the mind is constructed, rather than a result of
reinforcement. Led psychologists to realize that to understand complex behaviours, it is necessary
not only to measure observable behaviour but also to consider what this behaviour tells us about
how the mind works.
1950’s: cognitive revolution: shift from the behaviourists stimulus- response relationships to an
approach whose main thrust was to understand the operation of the mind.
1940’s: computers came that processed information in stages. Led to information-processing
approach: traces sequences of mental operations involved in cognition. Operation of the mind can be
described as occurring in a number of stages.
Cherry’s dichotic listening experiment: focusing on one story when you hear two.
Broadbents: flow diagram of the mind: way to visualize and analyse the operation of the mind in
terms of a sequence of processing stages.
John McCarthy: artificial intelligence: making a machine behave in ways that would be called
intelligent if a human were so behaving.
Newell and Simon: logic theorist: able to create proofs of mathematical theorems that involved
principles of logic. Human like reasoning.
, Maartje van Loef
UU
Miller: people can hold only about seven items in their mind: many of our cognitive functions have a
limited capacity.
Neisser: 1967: book: cognitive psychology.
2 aspects of research that apply to cognitive psychology in general:
- The role of models in cognitive psychology. Models: representations of structures that help
us visualize the structure or process.
Structural models: representations of a physical structure involved in specific
functions, mimic the appearance of an object. To simplify.
Process models: represent the processes that are involved in cognitive mechanisms.
To simplify complicated processes.
- Benefits for science and society. Cognitive psychologists are called upon to think about ways
to use the knowledge to solve problems in society: improve road safety, healthcare settings.
cognitive strategies in enhancing learning:
- Spacing and interleaving: repeated presentation and reviewing of info facilitates learning and
improves memory. Spacing: distributed over time for more durable retention. Interleaving:
intermixing different topics, will improve performance.
- Retrieval based learning: retrieving info from memory might be beneficial for learning.
Retrieving info from memory increases the chance that the same info will be retrieved in the
near future.
- Note taking and elaboration: taking notes by hand led to superior performance.
Chapter 5 K
Light rays bounce off an object in all directions, but you see only those rays that reflect off the object
and strike your retina.
Müller: law of specific nerve energies: whatever excites a particular nerve establishes a special kind
of energy unique to that nerve. Bvb: brain interprets the action potentials from the auditory nerve as
sounds.
Lightpupil (opening in iris): focused by the lens (adjustable) and the cornea (not adjustable),
projected onto the retina: rear surface of the eye, lined with visual receptors. The image is inversed:
light from above strikes the bottom of the retina.
Messages from the receptors from the back of the eye go to bipolar cells (located closer to the center
of the eye). send their messages to ganglion cells (located still closer to the center of the eye).
Their axons travel to the brain. Amacrine cells get info from bipolar cells and send it to other bipolar,
amacrine and ganglion cells. They refine the input to ganglion cells, enabling certain ones to respond
mainly to particular shapes, directions, movements.
The ganglion cell axons join to form the optic nerve, exits through back of the eye. The point at which
it leaves: blind spot: it has no receptors. You don’t notice your blind spot because:
- Brain fills in the gap
- Anything in the blind spot of one eye is visible with the other eye.
Fovea: central portion of retina, specialized for acute detailed vision. Blood vessels and ganglion cell
axons are nearly absent. Tight packing of receptorsperception of detail. Each receptor in the fovea
connects to a single bipolar cell connected to single ganglion cellaxon to brain.
Midget ganglion cells: ganglion cells in the fovea: each is small and responds to a single cone. Midget
ganglion cells provide 70% of input to brain: vision is dominated by what you see near fovea.
Periphery of retina: receptors converge onto bipolar and ganglion cellsbrain cant detect exact
location of a peripheral light sourcesummations enables perception fainter lights. Foveal vision has
better acuity, peripheral vision has better sensitivity to dim light.
Vertebrate retina contains 2 types of receptors:
- Rods: abundant in the periphery, respond to faint light, not useful in daylight.
- Cones: abundant in/near fovea, less active in dim light, more useful in bright light, essential
for colour vision.
So, good colour vision in fovea but not in periphery.
, Maartje van Loef
UU
Although rods outnumber cones by about 20 to 1, cones provide about 90% of the brains input.
People vary in the number of axons in their optic nerve and the size of the visual cortex (genetics).
Rods and cones contain photopigments: chemicals that release energy when struck by lightconsist
of 11-cis-retinalbound to opsins (proteins)modify photopigments sensitivity to different
wavelengths of lightlight converts 11-cis-retinal into all-trans-retinal: releasing energyactivates
second messengers.
Trichromatic theory/Young-Helmoltz theory: we perceive colour through the relative rates of
response by 3 kinds of cones, each one max sensitive to a different set of wavelengths. We
discriminate among wavelengths by the ratio of activity across the 3 types of cones.
All 3 types of cones equally active: we see white or grey.
Long and medium wavelength cones are more abundant than short wavelength cones: easier to see
tiny red, yellow or green dots than blue dots.
Visual field: part of the world that you see, before you can identify the colour.
Negative colour afterimage: a replacement of the colour you had been staring at with the opposite
colour.
Ewald Hering: opponent-process theory: we perceive colour in terms of opposites: the brain has a
mechanism that perceives colour on a continuum from red to green, another from yellow to blue and
another from white to black. After you stare at 1 colour in 1 location long enough, you fatigue that
response and swing to the opposite.
Trichromatic theory + opponent-process theory cant explain colour consistency: the ability to
recognize colours despite changes in lighting.
To account for colour and brightness consistency: Edwin Land: retinex theory: the cortex compares
info from various parts of the retina to determine the brightness and colour for each area.
Dale Purves: whenever we see anything we make an inference. Visual perception requires reasoning
and inference, not just retinal stimulation.
Colour vision deficiency: cause: people with certain genes fail to develop 1 type of cone, or develop
an abnormal type of cone.
Women have 2 X chromosomes. Some have one long wavelength receptor with serine and one with
alanine able to make finer distinctions between colours. Because men have only 1 X: women’s
performance on colour vision tests is more variable than men’s is.
Rods and cones of retina make synapses with horizontal cells + bipolar cells. Horizontal cells make
inhibitory contact onto bipolar cells, which in turn make synapses onto amacrine cells and ganglion
cells: axons form the optic nerve: leaves retinato lower surface of brain. The 2 optic nerves meet at
the optic chiasm: half of the axons from each eye cross to the opposite side of the brain.
Most ganglion cell axons go to the lateral geniculate nucleus part of the thalamus: sends axons to
other parts of the thalamus and the visual cortex. Axons from the cortex to the thalamus modify
thalamic activity.
Lateral inhibition: retina’s way of sharpening contrasts to emphasize the borders of objects.
Receptors send messages to excite nearby bipolar cells and also send messages to horizontal cells
that slightly inhibit those bipolar cells and the neighbours to their sides. Result: heighten contrast
between an illuminated area and its darker surround.
Light strikes rods/conesdecreased spontaneous outputreceptors make inhibitory synapses onto
the bipolar cellslight on rods/cones decreases inhibitory outputexcitation of bipolar cells.
Lateral inhibition: the reduction of activity in one neuron by activity in neighbouring neurons.
Heightens contrast. Important for many functions in the nervous system.
Each cell in the visual system of the brain has a receptive field: an area in visual space that excites or
inhibits it.
A rod or cone has a tiny receptive field in space to which it is sensitive (the point in space from which
light strikes the cell). One or more receptors connect to a bipolar cell, with a receptive field that is
the sum of the receptive fields of all those rods or cones connected to it. Several bipolar cells report
to a ganglion cell, which therefore has a still larger receptive field.
, Maartje van Loef
UU
Ganglion cells:
- Parvocellular neurons: small cell bodies and small receptive fields (in/near fovea). Suited to
detect visual details. Also respond to colour (located at fovea, so many cones)
- Magnocellular neurons: larger cell bodies and receptive fields (evenly throughout retina, incl
periphery). Respond to movement and large overall patterns, not to colour or fine details.
- Koniocellular neurons: small cell bodies, but occur throughout retina. Several functions.
Info from lateral geniculate nucleus (LGN)primary visual cortex in occipital cortex (area V1 or
striate cortex).
V1: necessary for conscious vision, visual imagery.
Blindsight: damage to area V1: ability to respond in limited ways to visual info without perceiving it
consciously. 2 explanations:
- Small islands of healthy tissue within a damaged visual cortex: no conscious perception, but
limited visual functions.
- Thalamus sends visual input to temporal cortex.
Conscious flash suppression: viewer is conscious of rapidly changing stimuli, not the steady picture in
front of them. Proof of experience of blindsight with an intact brain.
Hubel and Wiesel: recorded activity from cells in cats’ occipital cortex while they shined light patterns
on the retina: cell had a bar shaped receptive field instead of circular receptive field like cells in retina
and lateral geniculate. Distinguished several types of cells in the visual cortex:
- Simple cell: receptive field with fixed excitatory and inhibitory zones. More of the receptive
fields respond to horizontal or vertical orientations rather than to diagonals.
- Complex cells: in area V1 and V22, don’t respond to exact location of stimulus. Responds to a
pattern of light in a particular orientation. Most respond strongly to a stimulus moving in a
particular direction. Responds equally throughout a large area.
- End stopped cell/hypercomplex cell: resemble complex cells but: has a strong inhibitory area
at one end of its bar shaped receptive field.
Cells with similar properties group together in the visual cortex in columns perpendicular to the
surface. Cells within a given column respond best to lines of a single orientation.
Feature detectors: neurons whose responses indicate the presence of a particular feature.
Top down processes: other brain areas interpret the visual stimulus and send messages back to
reorganize the activity in the primary visual cortex.
Many cortical neurons respond best to a particular spatial frequency rather than other frequencies.
Thus a series of spatial frequency detectors, some sensitive to horizontal patterns or vertical
patterns, could represent any possible display.
Newborn mammals: normal properties of the visual system develop normally. Waves of spontaneous
activity sweep over the developing retina, synchronizing the activity of neighbouring receptors and
enabling appropriate combinations of receptors to establish connections with cells in the brain.
Visual experience after birth modifies and fine-tunes many of the connections.
Deprived experience in one eye: synapses in the visual cortex gradually become unresponsive to
input from the deprived eye. More strongly in young animals.
Deprived experience in both eyes: no axon outcompetes any other: cortex remains responsive to
visual input for the first weeks, longer: cortical responses lose well-defined receptive fields, visual
cortex starts responding to auditory and touch stimuli instead.
Sensitive period: when experiences have a particularly strong and enduring influence. Depends on
inhibitory neurons. Cortical plasticity is greatest in early life but never ends.
Stereoscopic depth perception: visual cortex compares inputs from 2 eyes. Requires brain to detect
retinal disparity: discrepancy between what left eye and right eye sees. Experience fine-tunes
binocular vision.
Strabismus: lazy eye: eyes do not point to same direction. Patch on active eye: forcing attention to
lazy eye. Or three dimensional action video games: require attention to both eyes.
Astigmatism: a blurring of vision for lines in one direction, caused by an asymmetric curvature of the
eyes. 70% of infants, normal growth reduces the prevalence of astigmatism to about 10% in 4 y/o.
