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  • We haven't talked about thevaccine debatehere on SciShow because there is no debate

  • to have.

  • Vaccines don't cause autism, and they save millions of lives every year.

  • But there is a debate, whether or not it makes sense.

  • And a lot of people counter this with ridicule, but we at SciShow aren't about judgment,

  • we're about science, and using it to better understand the world.

  • We see the anti-vaccination movement as a phenomenon to be understood.

  • So instead of making yet another statement about how, yes, vaccines are good, and no,

  • they don't cause autism, let's use science to understand why fewer and fewer people are

  • getting their children vaccinated.

  • I'm Hank Green, and this is SciShow.

  • [Intro]

  • First, let's discuss how we ended up with this imagined link between vaccinations and

  • autism in the first place.

  • Autism diagnoses are DEFINITELY on the rise; now many scientists believe that this is largely

  • or even completely because of more effective diagnosis, and changes in how the diagnosis

  • is reported.

  • So while diagnoses of autism are increasing, we can't say for sure whether the incidence

  • of autism is also increasing.

  • If it is, it must be because of some environmental factor.

  • Now, when we talk about autism, we're really referring to range of developmental disorders,

  • which can affect a person's ability to communicate or socialize, or cause them to develop patterns

  • of behavior that become pretty specific and inflexible.

  • The condition can manifest itself in a lot of different ways, but you've probably heard

  • of them referred to together as autism spectrum disorder, or ASD.

  • While ASD has been found to have some strong genetic components to it, there also seem

  • to be environmental factors at work as well.

  • And that's really the root of this controversywe simply don't know precisely what

  • causes autism.

  • And in the absence of an explanations, people try to make sense of it themselves.

  • And the way our brains do that is almost entirely with cognitive bias.

  • A cognitive bias is really just anything that skews how we process and interpret new information.

  • There are tons of different kinds of bias -- some biases cause us to ignore certain

  • data; others lead us to put too much emphasis on certain data; they can even drive us to

  • focus on facts that are actually irrelevant to what we're observing.

  • But essentially, when we hear a hypothesis and think, “Yeah, that 'Makes Sense'”

  • really what we're saying isYeah, that fits with my cognitive biases.”

  • And so people blame all sorts of things for Autism...plastics, pesticides, the use of

  • anti-depressants during pregnancy, GMOs, sugar, gut bacteria, and vaccines.

  • Basically, you start with whatever makes the most sense to the person doing the hypothesizing.

  • The onset of autism typically happens in one of two ways.

  • Either parents notice a delay in language development, typically around the first birthday.

  • Or they notice an apparently sudden loss of existing development, which might happen all

  • the way up through the third birthday.

  • Now, humans are pattern recognition machines.

  • We need to be able to figure out what behaviors and strategies lead to positive outcomes.

  • But, even more than that, we're on the lookout for things that lead to negative outcomes.

  • This over-weighting of negative outcomes is a well known psychological effect callednegativity

  • bias.”

  • So imagine you wake up one morning and your car doesn't work.

  • Your brain is going to want to know what happened.

  • Did you leave your lights on?

  • Did you drive though a huge puddle yesterday that maybe shorted something out?

  • There has to be SOME reason why it won't start!

  • On the other hand, if you get in a 15 year old car and it starts up just fine after having

  • had a bad week of barely getting going, you tend to not wonderWhat went right!?”

  • We spend far more cognitive resources attempting to figure out why a bad thing happened than

  • we do trying to determine why something good happened.

  • In psychology, the search for these explanations is calledExplanatory Attributionand

  • different people have differentexplanatory styles”.

  • Some people are more prone to blame themselves, while others search for an external event

  • to blame.

  • But one thing is clear: we are very bad at not blaming anything.

  • It's not surprising that parents of children with autism, especially parents who notice

  • a sudden loss of previous development, will search for a possible cause.

  • And when the most significant recent event in the health of the child was a vaccination,

  • as can be said for many moments in the life of a young American, we might identify that

  • as a potential cause and deem that link worthy of further examination.

  • Now this, is completely logical.

  • The problem is that over a dozen peer-reviewed papers have found no correlation between autism

  • and the MMR vaccine, or any other vaccine for that matter.

  • And yet, when you Google vaccines and autism, a fair number of the results claim that there

  • is a link between the two, and that that link is being covered up either by the government

  • or by big corporations.

  • A parent, already experiencing frustration with the medical community's inability to

  • tell them why this thing has happened to their child, will, on the internet, find a vibrant

  • community of similarly frustrated people who share their values and experiences.

  • These communities are full of anecdotes that draw connections between vaccines and autism.

  • And so, unsurprisingly, some people become convinced that they have found the reason

  • for their child's disability.

  • Once their mind has been made up, confirmation bias sets in.

  • Confirmation bias is simply our tendency to more readily, and with less scrutiny, accept

  • information, anecdotes, and worldviews that confirm our existing beliefs.

  • And, again, it is a completely normal thing that every person does.

  • Indeed, trying to convince someone that a previously held belief is incorrect has been

  • proven to actually increase their affinity for that idea.

  • And so a community is born, and the safety of vaccines is called into question.

  • And once the procedure for getting a vaccine goes from the doctor telling you that it is

  • now time for a vaccine -- and 99% of parents agreeing because that person went through

  • medical school -- to it being a question to ponder, vaccination rates will go down.

  • A 2011 study showed that parents who think about vaccines before their child is born

  • are eight times less likely to vaccinate their children.

  • Basically, when given an opportunity to research on their own, what they find is confusing.

  • And when confused, the default choice is to simply take no action.

  • This is an example of yet another bias, called omission bias.

  • In effect, we judge harmful actions as less moral than harmful inactions, or omissions.

  • In fact, a frequently cited study found that, when the choice to vaccinate is framed as

  • an action, the average parent will only vaccinate their child if not vaccinating is at least

  • TWO TIMES more dangerous than vaccinating.

  • This has to do with our perception of future regret.

  • Parents report that they'll feel worse if they take an action and it harms their child,

  • than if they don't act and the child is harmed by a failure to act.

  • This perception of potential regret can be so strong that even bringing up the choice

  • of acting versus not acting seems to be counter-productive.

  • A 2013 study found that attempts to convince parents to vaccinate their children actually

  • decreased the percentage who went on to choose vaccination.

  • If vaccination is presented as a personal choice, instead of a necessity for good public

  • health, then potentially harmful inaction can seem more moral than potentially harmful

  • action, and vaccination rates go down.

  • Parents are choosing tolet nature take its course.”

  • And as you might expect, this effect is much stronger in people with a measurablenaturalness

  • bias.”

  • This is just a tendency to perceive things that come from nature as being inherently

  • less threatening than things that we invent ourselves.

  • One way psychologists measure this bias is by asking a subject if they'd prefer a substance

  • extracted from an herb or one synthesized in a lab, even if they're chemically identical.

  • And of course, others have biases against big government or big corporations, and these

  • ideas about vaccinations fit well with those worldviews.

  • Confirmation bias at work again.

  • But even people who don't hold those biases end up being more likely not to vaccinate

  • if they start doing research before their baby is born.

  • This is because of another failure of the human brain.

  • We are terrible at what psychologists callRisk Perception.”

  • Given the merest sliver of a possibility that vaccines will cause developmental disorders,

  • parents are now weighing a disease they have seen, autism, against diseases they have never

  • seen.

  • Since the 1970s, measles has been pretty much unheard of.

  • Measles doesn't scare people my age for the same reason a giant man-eating squirrel

  • doesn't scare us...we've never seen it.

  • Risk perception is basically a science all on its own, and we have found that vague,

  • future hazards, like the future probability of an illness, are far less frightening than

  • immediate, specific hazards, like the sudden onset of autism.

  • So, amazingly, the success of vaccines is one of the reasons that people are less likely

  • to vaccinate their children.

  • So yes, it turns out humans are complicated, and this is a complicated problem.

  • Humans are inherently bad at understanding the effects of self-selecting samples -- like

  • online anti-vaccine forums -- and often completely unable to accept that a negative outcome could

  • really be the result of something that's beyond their control -- and still not very

  • well understood.

  • This is not a “anti-vaxxerproblem; it's a human problem.

  • Those of us who trust science or have built an understanding of statistics and bias simply

  • have had different lives than people who more heavily weight anecdotes or the opinions of

  • their friends, or strangers they meet online who feel the same way.

  • So next time you find yourself frustrated about the decline in vaccinations in America,

  • remember that it's only because of the dramatic success of vaccines that we could even think

  • of having this debate, and that those anti-vaccine activists are being driven by the exact same

  • logic traps and cognitive biases that every one of us suffers from.

  • Only by understanding and accepting these psychological pitfalls that we're all so

  • susceptible to will we be able to solve this problem.

  • And that's what science is all about.

  • Thanks for watching this episode of SciShow, where we really do try to be objective.

  • And we objectively believe that the universe is amazing and fantastic.

  • And if you want to join us in understanding it and all of the stuff in it, including our

  • brains, you can go to youtube.com/scishow and subscribe.

We haven't talked about thevaccine debatehere on SciShow because there is no debate

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B1 中級 美國腔

反疫苗科学(The Science of Anti-Vaccination)

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    joey joey 發佈於 2021 年 06 月 04 日
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