You might wonder what relevance jokes about an erstwhile Playboy centrefold might have to a science blog, but bear with me – all will soon become clear. Many readers of science blogs such as Layscience will be familiar with the singularity that is Jenny McCarthy, autism activist and antivaccine campaigner. Jenny’s point of view regarding science in general and vaccines in particular is that her own experiences trump those of orthodox science, and that her opinions, backed up with her diploma in logic from the University of Google, matter far more than the views of others with specific clinical and research experience and established authority in the field. As is often the case in debates with antivaccine campaigners (or pseudoscience apologists in general), their arguments tend to be littered with logical fallacies.

Sometimes all it takes is a simple joke to neatly illustrate the philosophical principle behind a logical fallacy. This is something that has been developed in the delightful books by Cathcart and Klein (e.g. “Plato and a Platypus walked into a bar”) which I can heartily recommend. Most of Jenny McCarthy’s arguments about vaccines are similarly fallacious, and rather than criticising them individually (others have done this before far better than I could, and there are too many anyway), I thought I’d borrow the methods (and a couple of the stories) of Cathcart and Klein, and look at a few Jenny McCarthy jokes.

Joke #1
Jenny has a friend over for morning coffee. As she makes some toast for them both, she remarks “Did you ever notice that if you drop a piece of toast, it always lands butter side down?”
Her friend says: “I think you’ll find that is only your perception, and it will probably land butter side up just as often as butter side down. It may seem that way because if it does happen, it’s a real hassle getting a new slice and quite a job cleaning up all the mess, so that episode lingers in your memory for longer.”
“Oh yeah?” retorts Jenny. “Watch this!” She drops a slice of toast to the floor, where it lands butter side up.
Jenny’s friend says: “See, I told you.”
Jenny replies: “Oh, I see what happened. I buttered the wrong side!”

According to the Karl Popper’s scientific philosophy of critical rationalism, for a hypothesis to hold water, it must be testable and falsifiable. Jenny’s hypothesis certainly is, but the irony is that for some people, no amount of evidence will falsify their pet theory.

Joke #2
Feeling rather out of sorts, Jenny goes to see her psychiatrist As part of his assessment, he decides to show her a series of Rorschach blots to help interpret her state of mind. Putting the first one in front of her, he asks “And what do you see in this picture?”
“A child screaming as it is injected with toxic vaccines” she replies.
“And this one?” asks the shrink.
“That’s a doctor eating a baby with a knife and fork” Jenny says.
The psychiatrist shakes his head slowly, muttering under his breath. “Ms McCarthy,” he says, “I think you are seriously disturbed.”
“What do you mean I am disturbed?” shouts Jenny. “You are the one showing me all these pictures of child abuse!”

Here Jenny is merely seeing what she wants to see. This is one of the commoner logical fallacies employed in arguments, namely that of “wishful thinking”, where one misinterprets evidence according to what one want to see, rather than what the evidence states. It may not necessarily be intentional, but a form of unconscious self-deception. However, sometimes it can be a deliberate process, known as “confirmation bias”, which occurs when a more calculated form of selective thinking is applied and one only considers as evidence as valid if it already conforms to one’s preconceptions.

Joke #3
Jenny goes to see her doctor.
“I’ve not been feeling so well”, she explains. “I have diagnosed myself as having Polymyalgia rheumatica, and I need a referral for some reflexology and reiki.”
“Hang on a second” responds her doctor. “First tell me what seems to be the matter.”
“Well” explains Jenny. “I’ve spent hours on the Internet Googling all my symptoms and I’ve even checked on Whale.to. It just has to be Polymyalgia. I’ll show you. If I touch myself here it hurts” she says, poking her thigh. “And it also hurts here, and also here”, she demonstrates, prodding her arms and then her neck.
“Ahhh….. I understand.” says her doctor, realisation dawning. “I see now what the problem is. You’ve broken your finger.”

This joke is similar in some respects to the first, in that it involves the misinterpretation of evidence, but where the facts are initially considered in an apparently quite objective fashion without any form of preconceived bias looking for a particular inference. However, in this case, ignorance and inexperience (aided by the misdirection of information from unreliable sources) the incorrect conclusion has been reached.

Joke #4
Jenny died and duly arrived outside the Pearly Gates, hoping to get in.
“I’m sorry,” St Peter said; “But Heaven is nearly full and we have been forced to put up an entrance exam to ease the burden of Heavenly arrivals.”
“OK, that's cool” said Jenny, “What does the entrance exam consist of?”
“Just three questions” said St Peter. “The first is: Which two days of the week start with the letter 'T'? The second is: How many seconds are there in a year? The third is: What is the name of the swagman in the song Waltzing Matilda?”
Jenny asked for a bit of time to think the answers over, and a couple of days later returned to the Pearly Gates.
“Well then,” said St Peter, “Are you ready to answer the questions?”
“Yes” replied Jenny.
“Which two days of the week start with the letter T?”
Jenny responded: “Today and tomorrow.”
St Peter pondered this answer for some time, and decided that indeed it could be regarded as valid considering the question’s terms of reference.
“Very well then, could I have your answer to the second of the three questions?” St Peter asked, “How many seconds are there in a year?”
Jenny replied, “Twelve.”
“Only twelve?” exclaimed St Peter, “How’d you figure that?”
“Well,” said Jenny, “there’s the second of January, the second of February, and right through to the second of December, giving a total of twelve seconds.”
St Peter looked nonplussed for a moment, and shook his head in disbelief
“I suppose I can also let that answer stand, but you need to get the third and final question absolutely correct to be allowed into Heaven. Now, can you tell me the name of the swagman in Waltzing Matilda?”
Jenny replied; “Of the three questions, I found that the easiest to answer.”
“Really!” exclaimed St Peter, “And what is the answer?”
“It's Andy.”
“Andy??”
“Yes, Andy,” said Jenny with complete conviction.
This totally floored St Peter, and he paced this way and that, deliberating her answer. Finally, he turned back to Jenny and asked “How in God's name did you arrive at THAT answer?”
“Simple,” came the reply. “Andy sat, Andy watched, Andy waited ’til his billy boiled….”
St Peter sank to his knees with a low moan, tearing at his hair in frustration. Triumphantly, Jenny forcefully pushed past him and swept past him into Heaven.

Rightly or wrongly, I put this joke into the category of a deductive fallacy. The premise can be (loosely) regarded as true for each of Jenny’s arguments, but the conclusion is wrong.

Joke #5
Jenny and Jim’s sex life seems rather dull. Whatever they do, she can’t achieve an orgasm. Jim, thinking it might be to do with his rather lacklustre performance between the sheets, goes to get advice from his doctor.
After hearing Jim’s story, the doctor suggests: “I’ve an idea. Get a well-hung porn star to play some bongo drums in your room while you and Jenny make love.”
Fired with enthusiasm, Jim rings up one of Jenny’s old flames and to his delight he agrees to help. That night, Jim and Jenny go at it like a pair of rabbits, while the porn actor plays the bongos in the corner of their bedroom. Unfortunately, nothing happens, and Jenny remains as unsatisfied as usual.
In despair, Jim visits his doctor the next day, explaining what happened.
“Tell you what,” his doctor says. “Tonight, let the porn star have sex with Jenny, while you play the drums.”
So that evening, Jim has a go on the drums while the porn star does his business. As Jenny’s cries of pleasure get louder and louder, Jim pounds away ever more feverishly. Finally the porn star brings Jenny to an earth-shattering climax.
Triumphantly, Jim rushes up to the exhausted actor and cries: “See! That’s how you play the bongos!”

This joke neatly demonstrates the post hoc ergo propter hoc fallacy, a common entity encountered in debates, particularly when one discusses events that “follow” vaccination. It is a form of faulty reasoning where because one event preceded another, it is erroneously viewed as being the cause, even though the events are unrelated and other factors are far more likely to be responsible.

I think I’ll leave it there for now. My brain is starting to hurt.