In April 2014, the MIT Technology Review published an article titled “How the Internet is Taking Away America’s Religion”. This article reported on the results of a study which purported to show that “using the internet can destroy your religious faith”.

This claim was primarily based on the fact that, as the proportion of Americans who use the internet has increased, so has the proportion who report that they are not affiliated with any particular religion.

Does the evidence presented support this claim?

Toxoplasma Gondii is a small parasitic organism that lives inside the cells of warm-blooded animals. Toxoplasma has an interesting life cycle. It commonly infects mice, but it can only reproduce sexually inside the body of a cat. And this is where it gets interesting: mice who are infected with the parasite appear not to be afraid of cats. For example, a study by researchers at the University of California, Berkeley, found that, while uninfected mice instinctively avoided the smell of cat urine, mice infected with Toxoplasma Gondii were unfazed. The theory goes that the parasite is changing the mice’s brains (and therefore behaviour) in order to get itself into the belly of a cat, so it can reproduce.

Toxoplasma can also infect humans. Its creepy, mind-altering properties when it comes to mice have therefore led to speculation that it might affect human behaviour as well. The most common source of infection is cat faeces (a risk for cat owners), but you can also catch Toxoplasma from unwashed vegetables, undercooked meat, or contaminated water sources.

In 2012, a group of Danish researchers examined a sample of 45,000 mothers who had given birth between 1992 and 1995, looking for signs that they we infected with the Toxoplasma parasite. They then used Danish hospital records to keep track of the women until 2006. They found that women who had the parasite were around 50% more likely to have been later treated for self-harm.

Media coverage (for example in the Daily Mail and the British Daily Telegraph) claimed that “female cat owners” were more likely to self-harm “because they can be infected with a common parasite that can be caught from cat litter”.

Does the evidence from the Danish study support this claim?

As a local government politician, you are considering a law banning disposable plastic grocery bags in your constituency.

An organisation opposed to the law has argued that plastic bag bans increase rates of food poisoning. The organisation claims that, because people do not clean out reusable bags, meat, vegetables and other goods mix together – increasing the risk of foodborne illnesses.

As evidence for this claim the organisation has collected statistics on emergency hospital admissions in a city which had implemented a plastic bag ban. The city’s ban came into force on 1 June 2015. The statistics showed that emergency admissions for food poisoning were 40% higher in the three months after the introduction of the bag ban than they were in the three months prior to the law coming into effect.

Does the evidence from this study support the claim the organisation is making?

In the year 2000, Robert Putnam, an American political scientist, released a highly influential book called Bowling Alone: The Collapse and Revival of American Community. In it he argues that the USA (in common with other Western countries) has seen a dramatic decline in the kinds of in-person social interaction that used to be the bedrock of American social life. This includes membership of clubs and hobby groups, participation in local politics, and just plain hanging out together in public.

One of the potential causes Putnam cites is the introduction and increasing popularity of television – primarily because television competes for people’s time. Put simply, people don’t go out and participate in society because they are inside watching TV.

As evidence for his hypothesis, he cites a study conducted in the 1970s in three isolated communities in northern Canada. The three communities were very similar in terms of their demographic makeup and their accessibility by road. However, one of the towns, nicknamed ‘Notel’ by the researchers “just happened to be located in a valley in such a way that the transmitter meant to serve the area did not provide television for most residents”. The other two towns were nicknamed ‘Unitel’ (the town only received one channel), and ‘Multitel’ (multiple channels).

The researchers found that:

“Before Notel had television, residents in the longitudinal sample attended a greater variety of club and other meetings than did the residents of both Unitel and Multitel, who did not differ [in this respect]. There was a significant decline in Notel following the introduction of television, but no change in either Unitel or Multitel.”

Does the evidence from this study support Putnam’s hypothesis?

Note that it might be helpful to contrast this research with the research cited in Exercise 2.