This post initially appeared on Science Blogs[This fall, I'm estimated human population over the last millenium. That enormous dip during around 1350 is not a result of people having less babies - as much as 10-20% of the entire human population may have been wiped out in that decade in the mid 14th century by a tiny bacterium called Yersinia pestis. In this course, we're going to be talking about a lot of unpleasant things, from viruses that make you bleed from your eyes, to bacteria that give you such terrible diarrhea that you die from dehydration, to infectious diseases with the potential to wipe out humanity.
But we're also going to discuss some really great things like vaccines, turning viruses into antibiotics, and even sex. I realize that sex in the context of infectious disease doesn't sound like a pleasant topic, but I'm talking about a theory that suggests that the whole reason sex evolved in the first place was to help us evade infectious microorganisms. And of course, we're going to be discussing science itself, which is awesome.
Why is Science Awesome?
Principally, science is awesome because we are not. Our ability to perceive things is limited and flawed, our memories are limited and flawed, and our minds are filled with biases that distort reality even when the information is right in front of us. Science helps us overcome our own limitations (to the extent we are able).
Take a look at this image:
Click image for the source
The squares marked "A" and "B" are actually the same shade of grey, but no matter how long you stare at it, you can't convince your brain of the truth.
This is the same image with the rest of the board covered in white.
We like to think that what we perceive is an accurate representation of the world, but it is just an interpretation of the world. Our brains have been wired by evolution to expect certain patterns - things that appear to be in shade are interpreted to have a lighter tone for instance - but when those patterns are violated, our brains end up distorting reality.
Our brains also have limited attention to devote to perception. In the following video, two teams (white and black), are passing a basketball between one another while moving around each other. Try just counting the number of passes made by the white team. You can't do it - there's too much else going on (don't read on until you've tried it).
Were you able to count the number of passes? Of course, that's not the real thing being tested - it's your ability to see something unexpected that you weren't paying attention to. In this study, about half of participants completely fail to see the gorilla walking through the middle of the players.
Besides being presented with a limited and often distorted view of the world, our recall of what we perceive also has serious flaws.
In 1974, psychologists Elizabeth Loftus and her mentor John Palmer showed test subjects a series of videos of car crashes, and then later asked to recall about how fast the cars were going at the time of the accident. But they weren't testing how well people could estimate speed, they were testing their own ability to subtly manipulate the participant's memory. The participants had been randomly assigned to 5 groups, and asked
About how fast were the cars going when they contacted?
But that final word varied - some participants were asked how fast the cars were going when they "hit," "bumped," "collided" or "smashed." The only thing that varied was that final word in the question, yet the memories of participants were dramatically different.
Further, participants were asked a week later whether they remembered seeing broken glass (there was no broken glass). If the participants had originally been asked how fast the cars were going when they "smashed," they were nearly 3 times as likely to remember seeing broken glass. In other words, the simple act of changing the word used to ask a question can have lasting impacts on people's memories.
Examples like this abound in the scientific literature. We like to believe that our memories are more or less carbon copies of our experiences, that we store memories away like files on a hard-drive, and that we can pull them up intact and unsullied. In fact, our memories are highly maleable, and are re-formed each time we access them. Scientists have shown that memories can be erased or invented out of whole-cloth. (For more, check out the Radiolab episode "Memory and Forgetting")
To top it all off, biases can insert, remove or alter the information in our memories at every stage of formation and retrieval.
Just check out the wikipedia page on cognitive bias, and you begin to grasp what fallible creatures we are. Just to name a few of my favorites - we tend to remember information that supports our beliefs and ignore what contradicts them (confirmation bias), we apply logic that will allow us to draw the conclusions we want to draw (motivated reasoning), and we believe that things that are correlated must be causally linked.
Science is awesome because it attempts an end-run around our failings by forcing us to be more systematic in our search for knowledge. We confront confirmation bias by intentionally trying to disprove our own hypotheses. We confront motivated reasoning by getting others with different motivations to vett our ideas and our results. We don't let correlation imply causation - we run experiments to test causal links.
Of course, science is done by humans, so it's not exactly perfect. But as Carl Sagan wrote in Demon Haunted World, science is "by far the most successful claim to knowledge accessible to humans."
If you're a scienceblogs reader, chances are this post hasn't told you anything you don't already know. My aim with this lecture was to give students who might not have the best relationship with science a different type of introduction. Science is so often taught as a fixed body of knowledge. "There's your biology textbook filled with facts, now go and learn those facts and repeat them back to me on a test." I wanted to give a sense of why we need science, and impress upon them that science is a process of discover, not a discrete set of information to be memorized.
Next up: Intro to evolution and basic biology.