Participants were first provided with a general overview, followed by the Moral and Control scenarios (randomized presentation order). For each scenario, participants were first provided with a cover story, and then observed one of three possible 48-case sequences—either a generative, neutral, or preventive sequence—where the abstract structure was the same regardless of scenario.15
To eliminate possible familiarity effects, participants saw different (abstract) sequence-types in the different scenarios, and so there were six different possible conditions (e.g., generative in the Moral condition and preventive in the Neutral condition). The frequency distributions for the three 48-case sequences were:
Generative: P(C) = .5; P(E | C) = .75; P(E | ¬C) = .25
Neutral: P(C) = .5; P(E | C) = P(E | ¬C) = .5
Preventive: P(C) = .5; P(E | C) = .25; P(E | ¬C) = .75
For each sequence, participants observed the cases one at a time, and clicked a button to move to the next case. Each case was described both in text (e.g., “Betrafindalis copernicia: Alive”) and with corresponding images. After observing the full sequence, participants were asked to rate “to what extent [the potential cause] causes [the target effect].” Ratings were collected using a slider that ranged from −100 (“Always prevents”) to +100 (“Always produces”) with an anchor at 0 (“No effect”). The slider moved in increments of 5, so actually corresponded to a 21-point scale. The slider began at 0, but had to be moved before the rating could be submitted (i.e., participants could not simply click through without moving the slider).
The global introduction was:
You are about to be presented with two stories. One story is about a man, Smith, and plants that he is growing in his greenhouse. In the story, a liquid has been applied to the plants but the characters in the story do not know what liquid has been applied to the plants. The liquid may either be a fertilizer, poison or water, and so might lead the plants to flower, die, or it has no effect at all. Your job will be to figure out what liquid was applied to the plants.
You must remember that the relationship between the plant dying or flowering and exposure to the liquid could be quite complicated (if there is any relationship at all!). As an example, there are many plants that are very sensitive to fertilizers, and flower very easily if exposed to them. But, some plants that are very sensitive to fertilizers still might not flower when exposed to them. Likewise, there are many plants that are very resilient and thus do not have serious reactions when exposed to a poison. But plants that are resilient may still have a serious reaction when exposed to a poison.
The other story that you will see is about Johnson, a doctor who has traveled to an island to study the outbreak of a skin disease among a particular group of villagers. Villagers have come into contact with various plants on the island and some have contracted rashes. Your job will be to figure out whether exposure to a certain plant causes the skin disease, makes people healthy, or has no effect at all.
You must remember that the relationship between the rashes (a symptom of the disease) and exposure to the plant could be quite complicated (if there is any relationship at all!). And this skin disease is like many other diseases: different villagers might have different levels of immunity or resistance, and there are likely many different causes of the disease. As an example, there are many people who respond readily to vitamins, and very easily become healthy if they take them. But, in some cases people who normally respond to vitamins may still not become healthy when exposed to them. Likewise, there are many people who are allergic to peanuts, and break out in serious reactions if exposed to them. But, in some cases, people who are allergic to peanuts might not have a serious reaction when exposed to them.
For both stories, you will be presented with a series of individual cases. For each case, you will be shown whether the factor (liquid or plant) was present or absent, and what happened to the flower or person. The factor’s absence will be indicated by a red X over the picture of the factor. These cases will help you figure out whether or not exposure to a particular liquid causes the plant to die, causes it to grow, or has no effect at all; and whether exposure to a particular plant causes villagers to contract a skin disease, causes them to be healthy, or has no effect at all. After viewing all of the pictures, you will be asked to evaluate the causal connection between these factors.
The cover story for the Control scenario was:
Johnson is a doctor traveling to the South Pacific Islands to research the rare skin disease Anthrapora that has been reported on various islands. In particular, she is studying the possible effect of native plants have on the contraction of these diseases. On the island of Tongatapu, Johnson is studying the impact (if any) of Solanaceae delisa on the skin disease Anthrapora. The plant may lead to the skin disease, it may cure the disease, or it may have no real effect at all. It is your job to figure this out.
Johnson interviewed various villagers; some have the local disease, and some do not. She can diagnose villagers as suffering from the skin disease by finding the characteristic rashes. Unfortunately, because of language barriers, the only other information she can get from the villagers is whether or not they have come in contact with the local plant, Solanaceae delisa.
There are thus four different observations Johnson might make: the villager was exposed to the plant and suffers from the disease; the villager was exposed to the plant and is healthy; the villager was not exposed to the plant and suffers from the disease; the villager was not exposed to the plant and is healthy.
You will now see the information – both plant contact and disease status – that Johnson collected for several villagers. After seeing all of the individuals, you will be asked to evaluate the causal connection between the plant and the skin disease on a scale from −100 to +100. Respond with −100 if you think that exposure to the plant (Solanaceae delisa) always prevents the skin disease (Anthrapora). Respond with +100 if you think that exposure to the plant always produces the rashes. And respond 0 if you think the plant is irrelevant for whether the person suffers from the disease or is healthy. Please give your best estimate of the causal strength, even if you are uncertain about what is actually happening.
The cover story for the Moralized scenario was:
Smith is an elderly man who has devoted his life to cancer research. He has been involved in the development of various treatments, which have helped to save the lives of thousands of people. Recently, Smith traveled deep into the Amazon in order to recover a nearly extinct species of orchids called Betrafindalis copernicia.
Betrafindalis copernicia contains a highly concentrated form of the chemical dispofignila. Smith has been experimenting with a synthetic form of dispofignila and has found that it slows down the growth of cancer. While synthetic doses slow the growth down somewhat, only the strongest form of dispofignila, which cannot be synthetically produced and is only found in the orchid Betrafindalis copernicia, slows down the growth substantially, almost to the point of stopping growth altogether. As a matter of fact, Smith was actually able to experiment with one Betrafindalis copernicia. He found that the dispofignila found in the Betrafindalis copernicia was in fact more potent than the synthetic form of dispofignila and that it lead to a significantly greater decrease in cancer growth than the synthetic form of dispofignila.
Betrafindalis copernicias are very rare. They are only found in a remote part of the Amazon, and, because of global warming, only a few dozen plants survive even there. Smith is sure that if he can preserve these plants, then he can develop a cure for cancer. Thus, Smith traveled to the Amazon, returned home safely with all of the orchids, and placed them in his greenhouse.
Smith’s neighbor, Jones, hates Smith. Jones has always despised Smith for no good reason. Jones knows that Smith has recently returned with the only remaining orchids in the world and he wants to kill all of the plants and destroy Smith’s hopes for finding a cure for cancer.
Jones wants to kill the orchids, but he doesn’t want to get caught. He knows that he could simply uproot the plants and kill them, but in order to do that he would have to get into the greenhouse, which is secured by an alarm. However, there is one way that Jones can kill the plants without leaving any evidence. There are several hoses that run a steady flow of water into the greenhouse. Jones knows that if he can inject poison into the hoses, it will kill all of the plants, and no evidence will be left behind.
One night, Jones breaks into an old farmer’s shed and finds several bottles with the label “poison”; Jones grabs one of the bottles and discretely leaves the shed. Unbeknownst to Jones, however, the farmer reuses his bottles: some of the ones labeled “poison” have fertilizers, others simply have water, and of course, some actually do have poison. (The farmer has a system for knowing what each bottle contains, though Jones obviously does not know this system.)
A few days later, Jones fills a syringe with the liquid from the stolen bottle. He then goes to Smith’s greenhouse, pushes the needle through one of the hoses, and injects the liquid into that particular hose.
Your job is to find out whether the liquid that Jones injected into the hose was a poison, a fertilizer, or water (in which case it has no effect). There are thus four different observations you might make: the plant was exposed to the liquid and dies; the plant was exposed to the liquid and produces flowers; the plant was not exposed to the liquid and dies; the plant was not exposed to the liquid and produces flowers.
You will see the relevant information – both liquid contact and whether the plant died or flowered – for several of the plants in Smith’s greenhouse. After seeing all of the plants, you will be asked to evaluate the causal connection between the liquid and the plant flowering on a scale from −100 to +100. Respond with −100 if you think that exposure to the liquid always kills the plant. Respond with +100 if you think that exposure to the liquid always makes the plant flower. And respond 0 if you think the liquid is irrelevant for whether the plant dies or flowers. Please give your best estimate of the causal strength, even if you are uncertain about what is actually happening.
After only the Moralized scenario, participants were asked two further questions with responses on a 9-point scale: a Blame question (“How blameworthy do you think Jones is for attempting to kill Smith’s plants?” from “Not at all blameworthy” to “Extremely blameworthy”) and a Knowledge question (“Do you think that Jones knew what was in the bottle of liquid that he stole?” from “He did not know at all” to “He definitely knew”).