Supplementary Materials

In Experiment 1, network type (independent vs. conjunctive) was manipulated within-subject and so each subject learned two independent causal links and one conjunctive one. It was manipulated between-subjects in Experiment 2 and so each subject learned either four independent causal links or two conjunctive ones.

Table S1

Materials for Romanian Rogos.

Features / Independent
Causal Relationships / Conjunctive
Causal Relationships
High amounts of carbon monoxide
Damaged fan belt
Long-lived generator
Butane-laden fuel
Loose fuel filter gaskets
Hot engine temperature / High amounts of carbon monoxide in the exhaust causes a long-lived generator. The carbon monoxide increases the pressure of the exhaust that enters the turbocharger, resulting in the turbocharger drawing less electricity from the generator, extending its life.
A damaged fan belt causes a long-lived generator. When the damaged fan belt slips, the generator turns at lower RPMs, which means that it lasts longer.
Butane-laden fuel causes hot engine temperature. The butane in the fuel burns at a hotter temperature than normal gasoline.
A loose fuel filter gasket causes hot engine temperature. Loose gaskets allow more air to be mixed in with the fuel, meaning that the gas is more fully burned, resulting in the engine running hotter than normal. / High amounts of carbon monoxide and a damaged fan belt together cause a long-lived generator. Because it slips, a damaged fan belt would normally allow a generator to turn at lower RPMs, meaning it would last longer. But when this happens the engine compensates for the generator’s reduced electrical output by running faster so as to return the generator’s RPMs (via the fan belt) to its normal level. However, because high amounts of carbon monoxide, which increases the pressure of the exhaust that enters the turbocharger, allows an engine to run more efficiently, the engine needs less electricity to run and so doesn’t compensate for the slower generator. Thus, when a damaged fan belt and high amounts of carbon monoxide are both present, a long-lived generator is the result.
Butane-laden fuel and loose fuel filter gaskets together cause a hot engine temperature. Loose fuel filter gaskets allow a small amount of fuel to seep into the engine bearings. This normally has no effect. However, if there is butane in the fuel, it undergoes a chemical reaction that creates heat as a byproduct. Thus, when a car has both butane-laden fuel and a loose filter gasket, the engine runs at a hot temperature.

Table S2

Materials for Kehoe Ants.

Features / Independent
Causal Relationships / Conjunctive
Causal Relationships
Blood high in iron sulfate
A hyperactive immune system
Thick blood
Fast nest building
Slow digestion
Long expected life span / Blood high in iron sulfate causes thick blood. Iron sulfate provides the extra iron that the ant uses to produce extra red blood cells. The extra red blood cells thicken the blood.
A hyperactive immune system causes thick blood. A hyperactive immune system produces a large number of white blood cells, which results in the blood being thicker.
Fast nest building causes a long expected life span. Ants are vulnerable to predators while they're building their nest, so building it quickly increases their life expectancy.
A slow digestive system causes a long expected life span. The slow rate of digestion results in fewer free radicals in the blood stream. Fewer free radicals means less damage to the ant's DNA. Because genes that regulate the ant's metabolic processes are thus preserved longer, the expected life span increases. / Iron sulfate in the blood and a hyperactive immune system together cause thick blood. When iron sulfate is absorbed into bone marrow, it stimulates the production of red blood cells, resulting in the blood becoming thicker. However, absorption of iron sulfate only occurs when the immune system is already busy producing an excess number of white blood cells (that is, when it is hyperactive). Thus, if iron sulfate and a hyperactive immune system are both present, thick blood results.
Fast nest building and a slow digestive system together cause a long expected life span. Ants build nests to provide protection from predators. Nevertheless, fast nest building by itself does not lead to the nest being completed earlier because the greater energy consumption it requires means that the ants must more often stop nest building to look for food. However, because ants with a slow digestive system process nutrients more completely, they do not need to look for food as often and thus do not need to interrupt nest building. Thus, if fast nest building and slow digestive system are both present, a long expected life span results.

Table S3

Materials for Meteoric Sodium Carbonate.

Features / Independent
Causal Relationships / Conjunctive
Causal Relationships
Radioactive
Forms a pyramid structure
Positively charged
Highly reactive
Forms a crystal lattice
Low melting point / Radioactivity causes the molecule to have a positive charge. The theta particles that get emitted due to the molecule being radioactive are negatively charged, and so leave the molecule with a positive charge.
The pyramid structure causes the molecule to have a positive charge. Atoms are packed close together in the pyramid structure, and so are able to share electrons. Because they can be shared, the molecule has fewer negatively-charged electrons, and hence the molecule has an overall positive charge.
Being highly reactive causes a low melting point. Reactions with foreign molecules release energy. This energy breaks down the molecular bonds necessary for a material to exist in a solid state.
Having a crystal lattice causes a low melting point. The crystalline structure (which is responsible for the substance's solid state) is easily disrupted by the increases in molecular vibrations that accompany rises in temperature. / Radioactivity and a pyramid structure together cause a positive charge. Radioactive molecules can react with each other, causing a net positive charge through loss of electrons. However, for the reactions to take place, the molecule must be positioned at optimal bonding angles. Such bonding angles can only be achieved can only be achieved when the molecule has a pyramid structure. Thus, if a molecule is both radioactive and has a pyramid structure, a positive charge results.
Being highly reactive and having a crystal lattice together cause a low melting point. Lattice structures enable a substance to remain in a solid state. Crystal lattices are structured so that they disintegrate when only a small number of molecules are removed from the lattice. Highly reactive molecules are likely to leave the lattice because they easily form bonds with other molecules. Thus, if a molecule is both highly reactive and forms a crystal lattice, it becomes liquid at a lower temperature.

Table S4

Materials for Myastars.

Features / Independent
Causal Relationships / Conjunctive
Causal Relationships
Ionized helium
Very hot temperature
High density
Has a binary companion
Unstable gravitational field
A disk shape / Ionized helium causes the star to have high density. Ionized helium is stripped of electrons, and helium nuclei without surrounding electrons can be packed together more tightly.
A hot temperature causes the star to have high density. Because they have a positive charge, helium atoms normally repel one another. The unusually high temperature provides the energy necessary to overcome that force, allowing the helium to be more dense.
A binary companion causes the star to have a disk shape. The gravity between a star and its binary companion causes a mutual pull between the star and its partner that distorts the star's shape into a disk along the axis of rotation.
An unstable gravitational field causes the star to have a disk shape. Because of the inconsistent gravitational forces, the star's angular momentum eventually causes it to "bulge" at the equator as it rotates around the north-south axis, and thus the star takes on a disk shape. / A binary companion and an unstable gravitational field together cause the star to have a disk shape. When the force of gravity is sufficiently unstable, a star can take on a permanently non-spherical shape. However, a lone star does not interact with enough objects in order for it to be distorted. Therefore, when a star is part of a stellar binary, the star's partner can provide enough force to alter the shape of the star.
Ionized helium and a high temperature together cause the star to have high density. Ionized helium makes high density possible because the nuclei can be packed together more tightly, but only if there aren't other elements that come between the nuclei. However, an especially high temperature vaporizes the other elements. Thus, if a star has both ionized helium and a high temperature, it will be very dense.

Table S5

Materials for Neptune Personal Computers.

Features / Independent
Causal Relationships / Conjunctive
Causal Relationships
A magnetic power supply
A fast clock speed
Hot computer temperature
A bright screen image
Wireless video output
A short battery life / Magnetic power supplies cause a hot computer temperature. The magnetic field causes the copper atoms in electrical circuits to orient themselves perpendicularly to the flow of electricity. This increases the circuits' electrical resistance, which results in more heat being generated.
A fast clock speed causes a hot computer temperature. A faster clock speed allows the computer to perform more mathematical operations each second. The larger number of operations generates more heat.
A bright screen image causes a short battery life. The brighter screen causes the battery to drain more quickly. The constant charging and recharging of the battery shortens its life.
Wireless video output causes a short battery life. The high capacity wireless signal needed to transmit video signals polarizes the lithium ions in the battery, shortening its life. / A magnetic power supply and a fast clock speed together cause a hot computer temperature. Because they perform more mathematical operations each second, computers with a faster clock speed draw more electricity. Magnetic power supplies produce that additional electricity by oscillating their magnetic field, a technique that enhances the flow of current but also heats the copper in electrical circuits. Thus, if a computer has both a magnetic power supply and a fast clock speed, a hot computer temperature results.
A bright screen image and wireless video output together cause a short battery life. Because a bright screen image and wireless video output both require extra memory on the video card, the presence of both activates the video card’s overflow buffer. The overflow buffer causes the battery to drain more quickly, and the constant charging and recharging of the battery shortens its life.

Table S6

Materials for Lake Victoria Shrimp.

Features / Independent
Causal Relationships / Conjunctive
Causal Relationships
High quantity of ACh neurotransmitter
A long-lasting flight response
An accelerated sleep cycle
A high body weight
A low level of insulin
Elevated blood pressure / A high quantity of ACh neurotransmitter causes an accelerated sleep cycle. The neurotransmitter speeds up all neural activity, including the internal "clock" which puts the shrimp to sleep on a regular cycle.
A long-lasting flight response causes an accelerated sleep cycle. The long-lasting flight response causes the muscles to be fatigued, and this fatigue triggers the shrimp's sleep center.
A high body weight causes elevated blood pressure. The excess fat resulting from a high body weight circulates in the blood stream. As a result, cholesterol attaches to the walls of the blood vessels, increasing blood pressure.
Low insulin causes elevated blood pressure. Insulin is a hormone that regulates glucose uptake from the blood. Thus, when insulin is low, blood glucose is high. Higher glucose thickens the blood, which in turn results in higher blood pressure. / A high quantity of the ACh neurotransmitter and a long lasting flight response together cause an accelerated sleep cycle. When Lake Victoria shrimp perceive a threat their flight response is triggered. This flight response produces muscle fatigue and so the need for rest. However, the perception of threat also increases the production of ACh that acts as a long-lasting stimulant. The shrimp's sleep cycle is accelerated because the ACh causes the shrimp to wake soon after the onset of sleep. Thus, if a long lasting flight response and high amounts of ACh are both present, an accelerated sleep cycle results.
A high body weight and low insulin together cause elevated blood pressure. The excess fat that results from a high body weight circulates in the blood stream, resulting in cholesterol attaching to the walls of the blood vessels. Although this would normally increase blood pressure, the elastic tissue in the blood vessels of Lake Victoria Shrimp allows them to expand so as to maintain constant blood pressure. However, this expansion is prevented by insulin, which tends to increase the rigidity of blood vessels. Thus, if a high body weight and low insulin are both present, elevated blood pressure results.