ResearchBlogging.orgOr rather, I probably do…  Let me explain.

Social scientist Eric Rassin and legal scholar Simone van der Heijden of Erasmus University in the Netherlands had a question: what efect does swearing have on legal testimony? They had two equally likely hypotheses: that swearing is a sign of weakness and undermines the believability of testimony, or that swearing is a sign of heightened emotions or, as they put it, swearing indicates “that the narrator is sincerely motivated to transmit the message.” So they devised a set of experiments to see what effect swearing had on the believability of both defendant and victim testimony.

First, though, they decided to test people’s expectations. They asked 76 undergraduate students to tell them whether they thought that swearing was characteristic of lying, characteristic of truthfulness or whether it was impossible to say. Only  16 percent said they thought that swearing was a sign of credibility: 38 percent said they thought that swearing indicated deceit and 46 percent said it was impossible to tell.

But something told Rassin and van der Heijden that there was more to it than that – previous psychological studies had shown that innocent people tend to become more hostile than guilty ones when accused of a crime. Even though the students believed otherwise, was it possible that they’d react differently when faced with “real” swearing? Would they trust a swearer more, recognising that hostility is a sign of outraged innocence? Or would they continue to believe that swearing is an indication of untrustworthiness?

The researchers devised another test: they gave the students one of two (fabricated) defendant statements, identical except for the absence or presence of swearing:

Investigator: I ask you again… were you involved in the burglary in the Havenstreet last month?

Suspect: No. As I have stated ten times, I have nothing to do with that. What’s this all about? I have been in this room for two hours now. I want to go home, or I want to be allowed to talk to my attorney. What a mess.

Or

Investigator: I ask you again… were you involved in the burglary in the Havenstreet last month?

Suspect: No, God damn it. As I have stated ten times, I have nothing to do with that. What’s this all about? I have been in this shitty room for two hours now. I want to go home, or I want to be allowed to talk to my attorney. What a fucking mess.

The students were asked to rate how believable the suspect’s denial was, from 1 (not at all believable) to 10 (extremely believable). The mean score was 5.2 for the statement with the swearwords in but only 4.2 for the statement without the swearing. The difference was small but significant. It turns out that, whatever they may say that they think about swearing, a vociferous denial is more credible than an even tempered one.

Intrigued, the researchers decided to perform one last test. This time they gave the students a statement from a (fictional) victim of crime.

Victim: That man pulled my bag out of my hands and ran away. He even dragged me several metres because I wouldn’t let go of my bag. And who is going to pay for all that? I suggest that man does.

Or

Victim: That asshole pulled my bag out of my hands and ran away. He even dragged me several metres because I wouldn’t let go of my bag. God damn it. And who is going to pay for all that? I suggest that mister dirtbag* does.

Again,  a set of students ranked the credibility of the statements and again, the statement with the swearing in it was seen as significantly more credible (6.33 vs 5.11 out of 10 on average).

So it’s not just vociferous denials that are more credible. No matter what people think they think, a few oaths under oath might help!


*Possibly the epithet loses something in translation. Can any Dutch speakers help me out here? Does it sound as twee in Dutch?

Rassin, E., & Heijden, S. (2005). Appearing credible? Swearing helps! Psychology, Crime & Law, 11 (2), 177-182 DOI: 10.1080/106831605160512331329952