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Physics
Microwave ovens cook food in an entirely different way than traditional ovens. Instead of using
conduction heat, they use microwaves, which are a form of electro-magnetic radiation. One of the main
advantages of microwave ovens over traditional ovens is speed. For example, it can take over an hour
to cook a potato in an oven, but only about 5 minutes in a microwave.
Why do microwaves work faster than conventional ovens?
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In a traditional oven, the heat that is
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In a traditional oven, heat comes from one
generated initially only reaches the
of two main sources: Gas ovens use
outside part of the potato. In order for the
combustion of natural gas fuel, while
potato to cook fully and be ready to eat,
electric ovens use current to heat metal
the heat has to penetrate all the way to the
coils. The heat that is generated by the gas
center, which takes a long time. But
or the metal coils cooks the potato fully
microwaves, unlike heat, can pass through enough to eat. But microwave ovens,
the potato. The microwaves create friction unlike traditional ovens, convert highin the water inside the potato, which
voltage electric energy to microwave
makes it heat up from the inside.
radiation. The microwaves create friction
in the water inside the potato, which heats
it.
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In a traditional oven, heat initially only
In a traditional oven, heat comes from one
reaches the outside of the potato. In order
of two main sources: Gas ovens use
for the potato to cook fully, the heat has to combustion, while electric ovens use
penetrate into the center, which takes a
current to heat metal coils. The heat from
long time. But microwaves, unlike heat,
the gas or coils cooks the potato. But
can pass through the potato. The
microwave ovens, unlike traditional
microwaves cause the water molecules
ovens, convert electricity to microwave
inside the potato to vibrate. This
radiation. The microwaves cause the
vibration creates friction between the
water molecules inside the potato to
water molecules and other parts of the
vibrate. This vibration creates friction
potato, which heats it up from the inside.
between the water molecules and the
other parts of the potato, which heats it.
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Galaxies are typically categorized by their shapes. There are three main galaxy shapes: elliptical,
spiral, and irregular. Both elliptical and spiral galaxies have masses of stars at their centers, around
which other stars orbit. But some of the irregularly-shaped galaxies look like rings, without any mass
of stars in their centers.
Why do some galaxies have empty space at the center?
Horizontal
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Good
The shape of a galaxy is determined by
Circular
The shape of a galaxy is determined by
the way that it was formed. A ring-shaped
the way in which it was formed. As part
galaxy used to be a spiral galaxy. At some
of the process of galaxy formation, stars
point in time, a smaller galaxy traveled
exert a gravitational pull on each other.
through the center of the spiral galaxy.
When a spiral galaxy forms, the spiral
The central mass of the spiral galaxy was
arms of the galaxy are attracted by the
attracted by the gravity of the smaller
gravity of the galaxy’s central mass.
galaxy traveling through it and was pulled
Sometimes, a spiral galaxy can undergo a
away, leaving a hole in the galaxy’s
change in its shape and became a ring
center.
galaxy.
The shape of a galaxy is determined by
The shape of a galaxy is determined by
how it was formed. A ring-shaped galaxy
how it was formed. In galaxy formation,
used to be a spiral galaxy. At some point,
stars exert a gravitational pull on each
a smaller galaxy traveled through the
other. When a spiral galaxy forms, the
center of the spiral. The stars that were
stars that are in the spiral arms of the
at the center of the spiral galaxy were
galaxy are attracted by the gravitational
attracted by the gravitational pull of
pull of each star in the galaxy’s central
each star in the smaller galaxy and were
mass. Sometimes, a spiral galaxy can
pulled away, leaving a hole in the
undergo a change in its shape and became
galaxy’s center.
a ring galaxy.
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The universe may be expanding. The light spectrums for elements in distant galaxies appear more red
than the equivalent spectrums here on Earth. Because distant galaxies are most likely composed of the
same materials as our galaxy, we would expect the spectrums to also be the same. Therefore, this “red
shift” must occur because the galaxies are moving away from us.
Why do distant galaxies appear red?
Horizontal
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Good
Distant galaxies appear red because, as
Circular
Distant galaxies appear red because the
galaxies move away from us, each
galaxies’ movement away from us
successive wave of light takes longer to
changes how the waves of light come
arrive at the Earth. This decrease in the
from those galaxies to the Earth. This
frequency with which the waves arrive is
modifies the way that we perceive the
equivalent to an increase in the light’s
light wavelengths coming from these
wavelength. Longer-wavelength light
galaxies in a way that makes it look more
looks more red to us.
red to us.
Distant galaxies appear red because as
Distant galaxies appear red because the
galaxies move away from us, each
galaxies’ movement away from us
successive photon of light takes longer to
changes how the photons of light come
arrive at Earth. This decrease in the
from those galaxies to Earth. This
frequency with which the waves arrive is
modifies the way that we perceive
equivalent to an increase in the photons’
photons of light coming from these
wavelength. Longer-wavelength light
galaxies in a way that makes them look
looks more red to us.
more red to us.
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When you ride in a car with a helium balloon, you will observe a curious phenomenon. Although
people and other objects in the car will move backwards when the car accelerates and forward when it
brakes, the balloon will move in the opposite direction. It will drift forwards as a car accelerates and
backwards as it brakes.
Why does a helium balloon move with a car rather than against it?
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Good
A helium balloon floats because it
Circular
A helium balloon floats because it
contains helium gas. Denser air below the
contains helium gas, which is also used as
helium balloon exerts pressure that pushes a coolant in rocket engines. When a car
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the balloon upwards. When a car
accelerates, the air in the car is affected by
accelerates, the air in the car is pushed
the acceleration and there is higher
backwards. This creates higher pressure at
pressure at the rear of the car than at the
the rear of the car than at the front. The
front. These changes in pressure don’t
increased pressure at the back of the car
affect solid objects in the car, which slide
pushes the balloon forwards.
backwards.
A helium balloon floats because it
A helium balloon floats because it
contains helium gas. Denser air below the
contains helium gas, which is also used as
balloon exerts pressure that pushes the
a coolant in rocket engines. When a car
balloon upwards. When a car accelerates,
accelerates, the air molecules in the car
air molecules in the car are pushed
are affected by the acceleration and there
backwards. There are now more
are more molecules at the rear of the car
molecules at the rear of the car than the
than at the front. These changes in the
front. The increased number of
number of molecules don’t affect solid
molecules at the back of the car push the
objects in the car.
balloon forwards.
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Chemistry
Wine is an alcoholic beverage made by pressing grapes and fermenting their juice. Wine is thus made
up partially of alcohol, partially of water, and partially of dissolved grape solids. Some bottles of wine
also contain small crystals, known as “wine diamonds,” which often can be seen sparkling on the
bottom of the cork. Wine diamonds are more common when the wine is cold.
Why do wine diamonds form in cold wine?
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Wine contains some ions that come from
Circular
Wine contains some ions that come from
the grape solids. Because warmer liquids
the grape solids. Because some liquids
contain more energy, the water molecules
contain more energy, the water molecules
in room-temperature wine move around
in the wine mix with alcohol and the ions.
and surround the ions. The ions therefore
The properties of the ions typically allow
cannot get close enough to each other to
for them to come together. After the wine
come together and form a solid. The
is bottled, wine diamond crystals attach to
movement of water molecules decreases
the cork, or sometimes they collect at the
at lower temperatures, allowing the ions
bottom of the bottle.
to form solid crystals.
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Wine contains ions that have opposite
Wine contains ions that have opposite
charges. Because warmer liquids contain
charges. Because some liquids contain
molecules with greater kinetic energy,
molecules with greater kinetic energy,
water molecules in room-temperature
water molecules in wine mix with alcohol
wine move around and surround the ions.
and the ions. The ions’ opposite charges
The ions cannot get close enough for
typically allow for their attraction to
their attraction to each other to pull
each other to pull them together. After
them together into a solid. The water
wine is bottled, wine diamond crystals
molecules’ movement decreases at lower
attach to the cork or collect at the bottom
temperatures, allowing the ions to form
of the bottle.
solid crystals.
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Usually, chewing food doesn’t have any effect other than to break the food down into smaller pieces.
But crunching a piece of hard candy between your teeth may additionally release a spark of light for a
brief moment. This effect is known as “triboluminescence.” It will happen with just about any type of
hard candy, but it is particularly noticeable with wintergreen flavored mints.
Why is the triboluminescence effect stronger with wintergreen mints?
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When you bite down on the candy, you
Circular
When you bite down on the candy, you
break the crystalline structure of the
break the physical structure of the candy
sugars in the candy, releasing energy into
inside your mouth, releasing energy into
the air. This energy is released as both
the air. This happens when the hard candy
visible light and non-visible light. This
is broken up by your teeth. This effect is
effect is more apparent to the eye with
more apparent to the eye with wintergreen
wintergreen mints because wintergreen oil mints. Wintergreen oil, which flavors the
absorbs the non-visible light that is
candy, strengthens the effect and leads to
released and converts it to a more visible
a brighter spark being released.
form.
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Biting the candy breaks the crystalline
When you bite down on the candy, you
structure of the sugars, releasing
release electrons. The electrons collide
electrons. The electrons collide with and with and transfer energy to molecules
transfer energy to molecules in the air.
in the air. This happens when the hard
This energy is released as both visible and
candy is broken up by your teeth. This
non-visible light. This effect is more
effect is more apparent to the eye with
apparent to the eye with wintergreen
wintergreen mints. Wintergreen oil, which
mints because wintergreen oil absorbs the
flavors the candy, strengthens the effect
non-visible light that is released and
and leads to a brighter spark being
converts it to a more visible form.
released.
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Smog is a type of air pollution that makes breathing difficult and reduces how far one can see into the
distance. In the 1990s, the city of Los Angeles had an especially bad problem with smog. Although
smog was present nearly every day of the year, it appeared to be much denser and darker when the
weather was hot.
Why does smog look denser when the weather is hot?
Horizontal
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Good
Smog contains two types of gas, one of
Circular
Smog contains two types of gas, a dark
which is dark brown (NO2) and the other
brown one (NO2) and a colorless one
of which is colorless (N2O4). The reaction
(N2O4). The reaction that makes the dark
that makes the dark brown gas needs
brown gas involves both oxygen and
energy to happen. Higher temperatures
nitrogen. Higher temperatures provide
provide greater thermal energy. So more
greater thermal energy. The amounts of
of the brown gas and less of the colorless
the two gases that are present in the smog
gas is formed on hot days, making the air
vary from day to day, though some
look darker.
amount of each gas is always present.
Smog contains two gases, a dark brown
Smog contains two types of gas, a dark
one (NO2) and a colorless one (N2O4).
brown one (NO2) and a colorless one
The reaction that makes the dark brown
(N2O4). The reaction that makes the dark
gas requires energy. Higher temperatures
brown gas involves oxygen and nitrogen.
provide greater thermal energy, which is
Higher temperatures provide greater
associated with faster movement of gas
thermal energy, which is associated with
molecules. So the equilibrium between
faster movement of gas molecules. The
the two gases is shifted on hot days.
equilibrium between the two gases
More brown gas is formed, making the air
shifts from day to day, though some of
look darker.
each gas is present.
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Graphite and diamond are both made primarily of carbon. However, despite their nearly identical
makeup, their properties are very different. Graphite is soft, dark gray or black, and is used as an
industrial lubricant to make machine parts more slippery. Diamond is extremely hard, colorless, and
can be used in blades and abrasives for cutting or grinding other materials.
Why does carbon sometimes form soft graphite rather than hard diamond?
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Good
Graphite is made of layers of carbon that
Circular
Graphite is made of layers of carbon that
are arranged in 2-dimensional sheets,
are arranged in 2-dimensional sheets
which can easily slide sideways across
which can easily slide sideways across
each other. But the carbon that makes up
each other. But the carbon that makes up
diamond is arranged in a rigid 3-
diamond is arranged in a rigid 3-
dimensional structure that can’t easily
dimensional structure that can’t easily
slide in any direction. Forming this rigid
slide around. Even though these
structure requires extreme pressure. If the
properties are very different, both
carbon is not under enough pressure, it is
substances are made from the same
as likely to form graphite as diamond.
material. Carbon can be formed into either
soft graphite or hard diamond.
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Graphite is made up of layers of carbon
Graphite is made up of layers of carbon
atoms arranged in 2-dimensional lattices
atoms arranged in 2-dimensional lattices
with only weak interactions between
with only weak interactions between
layers, which can slide sideways across
layers, which can easily slide sideways
each other. The carbon atoms in
across each other. The carbon atoms in
diamonds are strongly bonded in a rigid
diamonds are strongly bonded in a rigid
3-dimensional lattice that can’t easily
3-dimensional lattice. Even though these
slide. Forming this rigid structure requires
properties are very different, both
extreme pressure. If the carbon is not
substances are made from the same
under enough pressure, it is as likely to
material. Carbon can be formed into either
form graphite as diamond.
soft graphite or hard diamond.
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Biology
Cancer occurs when a buildup of cells in one part of the body forms a tumor that spreads to other
tissues. Although some tumors are benign, malignant tumors can lead to a breakdown of normal bodily
functions. Cancer cells can also break away from the original tumor and spread throughout the body,
making treatment difficult.
Why do tumors form?
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Under normal circumstances, some cells
Circular
Under normal circumstances, some cells
in the body multiply when they are
in the body multiply when they are
needed and die when they are no longer
needed to carry out normal bodily
needed. Many cancerous cells have a
functions. Many cancerous cells have a
mutation in their cellular material. They
mutation in their cellular material.
do not appropriately regulate cell division, Because cancer can develop from any
and therefore they divide faster than the
type of cell, cancerous cells can form
other cells in the body. This leads to an
tumors in different bodily organs. When
excess of cancerous cells which are
cancerous cells build up, they interfere
clustered together in a tumor.
with the organ’s ability to maintain the
health of the body.
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Under normal circumstances, some cells
Under normal circumstances, some cells
in the body multiply when they are
in the body multiply when they are
needed and die when they are no longer
needed to carry out normal bodily
needed. Many cancerous cells have an
functions. Many cancerous cells have an
error in the P53 gene. They do not
error in the P53 gene. Because cancer
appropriately regulate cell division, and
can develop from any type of cell,
therefore they divide faster than the other
cancerous cells can form tumors in
cells in the body. This leads to an excess
different bodily organs. When cancerous
of cancerous cells which are clustered
cells build up, they interfere with the
together in a tumor.
organ’s ability to maintain the health of
the body.
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The Hawaiian bobtail squid lives in a symbiotic relationship with a species of bacteria known as Vibrio
fischeri. The bacteria benefit from the relationship because they live inside the squid and receive
necessary nutrients from it. The squid also benefits from the relationship: The bacteria protect the
squid by helping to hide it from predators while it hunts at night.
Why are the bacteria able to protect the squid from predators?
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This type of bacteria live inside a special
Circular
This type of bacteria live inside a special
organ inside the squid. When the
organ inside the squid. When the
concentration of the bacteria reaches a
concentration of the bacteria reaches a
certain threshold, it triggers a process that
certain threshold, it triggers a process that
emits light. The light mimics the effect of
emits light. The light is typically blue or
the moonlight filtering into the water from green in color. Squid are active primarily
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above, making the squid essentially
at night when they are hunting, and the
invisible to predators below it while it is
light helps to protect the squid from
active at night.
predators.
This type of bacteria live inside a special
This type of bacteria live inside a special
organ inside the squid and secrete a
organ inside the squid and secrete a
chemical. When the concentration of this
chemical. When the concentration of this
chemical reaches a certain threshold, it
chemical reaches a certain threshold, it
triggers a chemical reaction that emits
triggers a chemical reaction that emits
light. The light mimics the effect of the
blue or green light. Squid are active
moonlight filtering into the water from
primarily at night when they are hunting,
above, making the squid essentially
and the light helps to protect the squid
invisible to predators below it.
from predators.
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The waves in the wake of a ship on the ocean at night will often appear to glow. The glow is not
reflected light from the moon or the lights of the ship. Rather, it is produced by organisms in the ocean.
The process by which some organisms produce their own light is known as “bioluminescence.”
Why do these bioluminescent organisms produce light?
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Good
Dinoflagellates are single-celled algae.
Circular
Dinoflagellates are single-celled algae.
They exist in high concentrations, and
They exist in high concentrations, and
they are the most common source of
they are the most common source of
bioluminescence in the ocean. These
bioluminescence in the ocean. These
algae use bioluminescence as a defense
algae use bioluminescence as a biological
mechanism. The mechanism that produces mechanism. The light-producing
the light is triggered by a mechanical
mechanism is triggered by some events,
disturbance, such as a passing ship. The
such as a passing ship. When the algae
algae emit light to ward off small fish that
begin producing light, it causes the
might eat them.
glowing phenomenon in the wake of the
ship.
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Dinoflagellates are single-celled algae.
Dinoflagellates are single-celled algae.
They exist in high concentrations, and
They exist in high concentrations, and
they are the most common source of
they are the most common source of
bioluminescence in the ocean. These
bioluminescence in the ocean. These
algae use bioluminescence as a defense
algae use bioluminescence as a biological
mechanism that is triggered by
mechanism. The light-producing
mechanical disturbance, such as a passing
mechanism is triggered by passing ships.
ship. It initiates a chemical reaction
It initiates a chemical reaction whereby
whereby the algae emits light to ward off
the algae emits light. When the algae
small fish that might eat them.
produce light, it causes the glowing
phenomenon in the waves.
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Male anole lizards bob their heads up and down rhythmically as part of a mating ritual to attract
females. They typically increase their rate of head-bobbing when they see a female lizard of their
species. However, their rate of head-bobbing also increases when they see another male lizard of the
same species, even if no female lizards are present.
Why do male lizards bob their heads when other males are nearby?
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This happens because the male lizards are
Circular
This happens because the male lizards are
extremely territorial, and head-bobbing is
seeking mates, and head-bobbing is a
a distinctive behavior typical of this
distinctive behavior typical of this species
particular species of lizard. During mating of lizard. During mating season when they
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season when they are in competition with
are trying to attract females, males use a
each other for females, males use various
variety of behaviors that are characteristic
dominance displays to defend their
of anole lizards. They perceive the
territory. They perceive other males as a
presence of other males and engage in
threat and engage in increased head-
increased head-bobbing, which is
bobbing, which is a sign of aggression.
commonly seen during mating season.
This happens because the male lizards are
This happens because the male lizards are
extremely territorial. During mating
seeking mates. During mating season
season when they are in competition with
when they are trying to attract females,
each other for females, males use various
males use a variety of behaviors that are
dominance displays to defend their
characteristic of lizards. They perceive the
territory. They perceive other males as a
presence of other males and engage in
threat and engage in increased head-
increased head-bobbing, which is
bobbing, which is a sign of aggression.
commonly seen during mating season.
Aggressive behavior is known to be
Aggressive behavior is known to be
associated with elevated levels of
associated with elevated levels of
testosterone and other aggression-
testosterone and other aggression-
enabling hormones.
enabling hormones.
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Neuroscience
Neuroscience research uses numerous techniques to observe the human brain. In order to gather
important data about brain activity, such as a cognitive defect caused by a stroke, different brain
scanning techniques can be employed. Functional magnetic resonance imaging (fMRI) is a crucial tool
in the study of neuroscience. It allows for the measurement of patterns of activation by monitoring
blood flow in an active brain.
Why does fMRI use blood flow as an indicator of brain activity?
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Good
Circular
fMRI uses a magnetic field to measure the fMRI uses a magnetic field to measure
transport of oxygen through the brain.
relative activity in different areas of the
Blood carrying high levels of oxygen
brain. Blood carrying high levels of
reacts differently to the magnetic field
oxygen reacts differently to the magnetic
than blood carrying low levels of oxygen.
field than blood carrying low levels of
Highly active brain areas will receive a
oxygen. Highly active brain areas are
higher amount of oxygen-rich blood to
detected using the magnetic field
replenish the active cells. fMRI machines
generated by the fMRI machine. fMRI
detect this flow of oxygen-rich blood to
machines detect the flow of blood through
the active areas, providing data about
the brain, providing data about activity in
neural activity.
each brain region.
fMRI uses a magnetic field to measure the fMRI uses a magnetic field to measure
transport of oxygen through the brain.
relative activity in different areas of the
Hemoglobin in blood that is carrying
brain. Hemoglobin in blood that is
oxygen has a different magnetic
carrying oxygen has a different
resonance than hemoglobin without
magnetic resonance than hemoglobin
oxygen. Highly active brain areas will
without oxygen. Highly active brain
receive a higher amount of oxygen-rich
areas can be detected using the magnetic
blood to replenish the active cells. fMRI
field generated by the fMRI machine.
machines can detect this flow of oxygen-
fMRI machines detect the flow of blood
rich blood to the active areas, providing
through the brain, providing data about
data about neural activity.
activity in each brain region.
Some pharmaceutical drugs are designed to treat depression by affecting levels of serotonin, a
chemical used by neurons in the brain for communication. When released from one neuron, serotonin
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binds with receptors on another and activates it. Lower levels of serotonin in the brain leads to less
activation of these neurons. One class of antidepressants work by increasing the brain’s serotonin
activity.
Why are serotonin-based treatments effective at combatting depression?
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Good
Shortly after release, serotonin is
Circular
There are many types of antidepressant
reabsorbed by the first neuron in a process medications that target different
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known as reuptake. Antidepressants such
chemicals in the brain. Antidepressants
as Prozac inhibit the reuptake process by
such as Prozac are known as ‘selective
blocking the mechanism that transports
serotonin reuptake inhibitors’ or SSRIs.
serotonin back into the neuron. Serotonin
They inhibit the reuptake of serotonin by
therefore stays in the synapse longer,
blocking the mechanism that transports
allowing for more activation of the
serotonin back into the neuron. Many
postsynaptic neuron. This increase in
different anti-depressants work by
serotonin activity can relieve depressive
targeting serotonin re-uptake, but Prozac
symptoms for some patients.
and Zoloft are two of the most common.
After release, serotonin is reabsorbed by
Many types of antidepressant medications
the first neuron in a process called
target different chemicals in the brain.
reuptake. Antidepressants such as Prozac
Antidepressants such as Prozac are known
inhibit reuptake by blocking the action of
as ‘selective serotonin reuptake inhibitors’
SERT, the protein responsible for
or SSRIs. They inhibit the reuptake of
transporting serotonin back into the
serotonin by blocking the action of
neuron. Serotonin therefore stays in the
SERT, the protein responsible for
synapse longer, allowing for more
transporting serotonin back into the
activation of the postsynaptic neuron.
neuron. Many anti-depressants work by
This increase in serotonin activity can
targeting serotonin re-uptake, but Prozac
relieve depressive symptoms for some
and Zoloft are two of the most common.
patients.
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Exposure to artificial light may be disruptive to sleep. This is especially true for blue light from high
efficiency light bulbs and electronic devices. People who wear blue-light blocking glasses for 3 hours
before going to bed have higher sleep quality and better mood than people who don’t.
Why does blue light disrupt sleep cycles?
Horizontal
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Good
Sleep cycles are governed by a part of the
Circular
Sleep cycles are governed by a part of the
brain called the suprachiasmatic nucleus
brain called the suprachiasmatic nucleus
(SCN). The SCN receives input from the
(SCN). The SCN receives input from the
eyes and is sensitive to light. It also
eyes and is sensitive to light. It also
produces a hormone important for
produces a hormone important for normal
regulating sleep patterns. When it reaches
functioning. When it reaches the eye, blue
the eye, blue light triggers the suppression
light interferes with the body’s normal
of the SCN’s production of this hormone.
rhythms and disrupts sleep patterns. Poor
Lower levels of the hormone interfere
sleep quality is related to a wide variety of
with the ability to regulate sleep.
other health problems.
Sleep cycles are governed by a part of the
Sleep cycles are governed by a part of the
brain called the suprachiasmatic nucleus
brain called the suprachiasmatic nucleus
(SCN). The SCN receives input from the
(SCN). The SCN receives input from the
eyes and is sensitive to light. It produces
eyes and is sensitive to light. It produces
melatonin, a hormone important for
melatonin, a hormone important for
regulating sleep patterns. When absorbed normal functioning. When absorbed by a
by a photopigment in the eye, blue light
photopigment in the eye, blue light
triggers the suppression of the SCN’s
interferes with the body’s rhythms and
production of this hormone. Lower levels
disrupts sleep patterns. Poor sleep quality
of the hormone interfere with sleep
relates to a variety of other health
regulation.
problems.
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Morphine is an effective pain medication because it mimics the body’s natural pain relief mechanism.
In response to a painful stimulus, the body releases endorphins. Endorphins bind to neurons in the
brain, causing dopamine to be released. Increased dopamine in the brain reduces the feeling of pain.
Morphine can also bind to endorphin receptors and cause the release of dopamine. Although morphine
is very effective, it is also highly addictive.
Why is morphine addictive?
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Good
Morphine is addictive because prolonged
Circular
Prolonged used of morphine leads to
use decreases the sensitivity of the
changes in the endorphin receptors in the
endorphin receptors in the brain. Thus, the brain. Users will generally experience
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body’s own endorphins become less
cravings for more of the drug. When a
effective, and the user experiences painful
person stops taking it, they often
withdrawal symptoms. Because the
experience painful withdrawal symptoms.
receptors become less sensitive to the
Such symptoms can last for up to 72
drug, over time the user requires larger
hours and include aching muscles,
doses to achieve the same effects.
anxiety, and insomnia.
Morphine is addictive because prolonged
Prolonged used of morphine changes the
use changes the protein structure of the
protein structure of the endorphin
endorphin receptors, decreasing their
receptors in the brain. Users will
sensitivity. Thus, the body’s own
generally experience cravings for more of
endorphins become less effective, and the
the drug. When a person stops taking it,
user experiences painful withdrawal
they often experience painful withdrawal
symptoms. Because the receptors become
symptoms. Such symptoms can last for up
less sensitive to the drug, over time the
to 72 hours and include aching muscles,
user requires larger doses to achieve the
anxiety, and insomnia.
same effects.
Bolded words indicate reductive content
Psychology
Sometimes people don’t notice something that’s right in front of them. When people view rapidly
presented images and are told to press a button every time they see a house, they are generally good at
this. However, if two houses are presented close together, people often fail to press the button for the
second house. This failure to detect the second house is called “attentional blink.”
Why does the attentional blink effect happen?
Horizontal
Good
The attentional blink effect occurs
Circular
The attentional blink effect occurs
because of how people’s perceptual and
because of how people’s perceptual and
decision-making abilities function in
decision-making abilities function in
response to the stimuli. People are limited
response to stimuli like this. People are
in how many things they can pay attention limited in how well they can perform on
to at any given point in time. They
this type of task. The second house
generally miss seeing the second house
appears later in the sequence than the first
because they are still processing the first
house, and the failure to notice it when it
and do not have enough attentional
appears causes the attentional blink.
resources left.
Reductive
The attentional blink effect occurs
The attentional blink effect occurs
because of how areas in the frontal lobe, because of how areas in the frontal lobe,
previously shown to mediate attention,
previously shown to mediate attention,
function in response to stimuli. People are
function in response to stimuli. People are
limited in how much they can pay
limited in how well they can perform on
attention to at any given time. They miss
this type of task. The second house
seeing the second house because they are
appears later in the sequence than the first
still processing the first and do not have
house, and the failure to notice it causes
enough attentional resources left.
the attentional blink.
Bolded words indicate reductive content
People generally have difficulty in telling two faces apart if they come from a race other than their
own. For example, in the United States, white people are typically better at recognizing white faces
than black faces. The finding that it is more difficult in general to recognize faces of races different
from one’s own is known as “the other-race effect.”
Why does the other-race effect occur?
Horizontal
Reductive
Good
The other-race effect is caused by a
Circular
The other-race effect is caused by a
difference in the way that people respond
difference in the way that people respond
to faces within a particular group. In
to the faces within a group. In
communities where the majority of the
communities where the majority of the
people are white, white faces are seen
people are white, white faces are more
more frequently than are those of other
easily recognized by the community
races. This greater experience with white
members than are those of other races.
faces tunes the perceptual system to
This greater accuracy with white faces is
recognize greater detail across those
due to the fact that the perceptual system
faces, making it easier to tell them apart.
is responsible for perceiving faces.
The other-race effect is caused by the
The other-race effect is caused by the
way the fusiform face area in the brain
way the fusiform face area in the brain
responds to faces within a group. In
responds to faces within a particular
communities where the majority of the
group. In communities where the majority
people are white, white faces are seen
of the people are white, white faces are
more frequently than are those of other
more easily recognized by community
races. This greater experience with white
members than are those of other races.
faces tunes the fusiform face area to
This greater accuracy with white faces is
recognize greater detail across those
due to the fact that the fusiform face area
faces, making it easier to tell them apart.
is responsible for perceiving faces.
Bolded words indicate reductive content
People’s word-association abilities change depending on how long it takes them to say the first word
that comes to their mind. Words that are said very quickly after hearing the target word are likely to
sound similar to the target. However, words that are said after a short delay are more likely to have a
similar meaning to the target.
Why does timing affect the type of words people associate with a target?
Horizontal
Reductive
Good
The effect of timing on word associations
Circular
The effect of timing on word associations
is due to the cognitive system that allows
is due to the cognitive system that allows
people to use language. This system
people to use language. This system
categorizes words first according to their
associates two different types of words
sounds and later according to their
with the target word at different times.
meanings. Therefore, the more time one
Therefore, the more time one takes to say
takes to say an associated word, the more
an associated word, the more likely it is
likely it is that that word will have a
that that word will have a similar meaning
similar meaning to the target word.
to the target word.
The effect of timing on word associations
The effect of timing on word associations
is due to Broca’s area, a part of the
is due to Broca’s area, a part of the
brain’s language system. This brain
brain’s language system. This brain
area categorizes words first according to
area associates two different types of
their sounds and later according to their
words with the target word at different
meanings. Therefore, the more time one
times. Therefore, the more time one takes
takes to say an associated word, the more
to say an associated word, the more likely
likely it is that that word will have a
it is that that word will have a similar
similar meaning to the target word.
meaning to the target word.
Bolded words indicate reductive content
Babies are capable of doing simple arithmetic. For example, babies see a doll placed on a stage that is
then hidden behind a screen. Then, they see a hand place another doll behind the screen. They look
longer if the screen is dropped to reveal only one doll instead of two. This looking time difference
between one and two dolls shows that babies can calculate 1 + 1 = 2.
Why does this looking time difference show that babies can do arithmetic?
Horizontal
Good
Babies’ understanding of numbers and
Circular
Babies’ understanding of numbers and
mathematics starts to emerge early in their mathematics starts to emerge early in their
lives. This understanding of numbers
lives. This understanding of numbers
governs the babies’ expectations about
governs the amount of time babies look at
how many dolls there should be on the
the stage. This time is indicative of how
stage. The babies know that there should
long they attend to the display, and it can
be two dolls on the stage, and their
be used to calculate babies’ tendency to
surprise at seeing only one leads to their
look at the single doll when it appears.
looking longer.
Reductive
The part of babies’ brains known to be
The part of babies’ brains known to be
involved in math is the parietal lobe.
involved in math is the parietal lobe.
This brain area governs the babies’
This brain area governs how long babies
expectations about how many dolls there
look at the stage. This time is indicative of
should be on the stage. The babies know
how long they attend to the display, and it
that there should be two dolls on the
can be used to calculate babies’ tendency
stage, and their surprise at seeing only one to look at the single doll when it appears.
leads to their looking longer.
Bolded words indicate reductive content
Social Science
Men and women generally have equal intellectual abilities when it comes to learning about science and
learning about the humanities. But in secondary school, boys tend to get higher grades in science and
math classes, while girls tend to get higher grades in language and literature classes.
Why do boys and girls perform at different levels in different subjects?
Horizontal
Good
Different cultural norms govern the
Circular
Different cultural norms govern the
expectations that are put on boys and
expectations that are put on students.
girls. Because boys and girls are each
Because boys and girls are each expected
expected to succeed in different subjects,
to attend all of their classes, this creates
this creates different incentive structures
different incentive structures for students’
for students’ efforts in different subjects.
performance in their classes. Even though
Even though there are no intrinsic
there are no intrinsic differences between
differences between boys’ and girls’
boys’ and girls’ abilities, boys outperform
abilities, this differential encouragement
girls in some subjects while girls
leads to different grade distributions for
outperform boys in others.
the two genders.
Reductive
Teachers and parents put different
Teachers and parents put different
expectations on boys and girls. Because
expectations on students. Because
teachers and parents expect boys and
teachers and parents expect boys and
girls to succeed in different subjects, each
girls to attend all their classes, each
individual student puts more effort into
individual student puts more effort into
the subject where he or she is expected to
their performance in the classes they are
succeed. Although there are no intrinsic
taking. Even though there are no intrinsic
differences between boys’ and girls’
differences between boys’ and girls’
abilities, this differential encouragement
abilities, boys outperform girls in some
leads to different grade distributions for
subjects while girls outperform boys in
the two genders.
other subjects.
Bolded words indicate reductive content
There are many different political systems in the world. Even among democracies, there are different
ways that governments are organized. This is especially true when it comes to the number of active
political parties. Some democratic countries have three or six or even ten major political parties with a
role in the government, but the United States only has two.
Why has the United States maintained a two-party system?
Horizontal
Good
The two major US political parties are
Circular
The two major US political parties are
very well established, and both are
very well established, and both are
opposed to competing against smaller
sufficiently strong to collect enough votes
parties. This leads to the assumption that
to win an election. This leads to the
no one other than a major party candidate
assumption that the two major parties are
will generate enough votes to win
very well entrenched in the political
elections. Votes cast for third-party
system. Votes cast in elections are seen as
candidates are seen as ineffective, making
ineffective, so the US continues to
it hard for these candidates to establish
maintain a two-party system.
themselves.
Reductive
The two major US political parties are
The two major US political parties are
very well established, and both are
very well established, and both are
opposed to competing against smaller
sufficiently strong to win an election. This
parties. This leads voters to assume that
leads voters to assume that the two major
only a major party candidate will generate
parties are very well entrenched in the
enough votes to win elections. Voters feel political system. Voters feel that the
that their votes for third-party candidates
votes they cast in elections are ineffective,
are ineffective, making it hard for these
so the US continues to maintain a two-
candidates to establish themselves.
party system.
Bolded words indicate reductive content
People who are experts in a certain field know a great deal about that field. Such people should be able
to make good decisions about issues concerning that field. But when these abilities are put to the test, it
is often the case that groups of ordinary, independent people make better decisions about certain issues
than individual experts. This is known as “the wisdom of crowds.”
Why do groups make better decisions than individuals?
Horizontal
Good
The aggregated information brought
Circular
The aggregated information brought
together by a group is a more
together by a group can lead to more
representative sample of the total
appropriate decisions being made, so a
information available, so a group will
group will decide how to think and act
know much more in total about a topic
about a topic better than any individual
than any individual expert can. Putting
expert can. Working together in a group
this information together takes everyone’s
can benefit everyone, and can therefore
knowledge into account, and can therefore lead to a better decision.
lead to a better decision.
Reductive
Every person knows a unique set of
Every person knows a unique set of
facts which together create a more
facts which together can lead to more
representative sample of the total
appropriate decisions being made, so the
information, so the members of a group
members of a group will decide how to
will know much more in total than any
think and act better than any individual
individual expert can. Putting this
expert can. Working together in a group
information together takes everyone’s
can benefit everyone, and can lead to a
knowledge into account, and can lead to a
better decision.
better decision.
Bolded words indicate reductive content
Neighborhoods with visible petty crime, such as vandalism and graffiti, tend to also have higher levels
of major crime, such as robbery and murder. When steps are taken to prevent petty crimes, the rate of
major crimes goes down as well, even if nothing is done to specifically prevent major crimes. This has
been called the “broken windows” theory of crime.
Why does cleaning up vandalism and graffiti reduce rates of major crime?
Horizontal
Reductive
Good
When a neighborhood is not kept clean,
Circular
When a neighborhood is not being kept
this is taken as an indication of low police
clean, this is taken as an indication of low
presence in the area. Therefore, this
police interest in preventing vandalism.
neighborhood comes to be seen as
Therefore, this neighborhood comes to be
somewhere major crimes can be
seen as a place where graffiti and
committed without risk of being caught.
vandalism are common occurrences.
However, maintaining the neighborhood
However, maintaining the neighborhood
by cleaning up graffiti and replacing
by cleaning up graffiti and replacing
broken windows leads to the perception of
broken windows leads to the perception of
an increased police presence. This
an increased police presence directed at
perception works as a deterrent against all
preventing vandalism. This perception
criminal activity, including major crimes.
works as a deterrent against petty crimes.
When a neighborhood is not kept clean,
When a neighborhood is not being kept
criminals take this as an indication that
clean, criminals take this as an indication
police officers are not present in the area.
that police officers are not trying to
Therefore, criminals see this
prevent vandalism. Therefore, criminals
neighborhood as somewhere that major
see this neighborhood as a place where
crimes can be committed without risk of
graffiti and vandalism are common.
being caught. However, maintaining the
However, maintaining the neighborhood
neighborhood by cleaning up graffiti and
by cleaning up graffiti and replacing
replacing broken windows leads people to
broken windows leads people to think
think that police officers are paying
that police officers are paying increased
increased attention. Criminals are
attention directed at preventing
therefore deterred from committing
vandalism. Criminals are therefore
crimes, including major crimes.
deterred from committing petty crimes.