If there’s a lot of low-quality evidence, the rate of accumulation is slower and our decisions are slower but they are also potentially more accurate.

Not yet possible to explain all the biases

This basic model can be extended into simple consumer choices: imagine that there are two competing products sitting side-by-side on a supermarket shelf. Your eyes flip back and forth between looking at one than the other, with each eye movement bias the process of evidence accumulation toward the product are currently viewing.

Again, when the evidence for one product over the other becomes large enough, you’ll make your decision and you take the selected product off the shelf and place it in your basket. There’s still much more to be learned about this process: we don’t yet know whether they are the basic mechanisms that help explain the choices are also used for much slower and more complex choices and it’s not yet possible to explain all the biases.

Wanting to believe and ignoring the contrary

But this very simple sort of model holds promise: it’s consistent with power neurons work, it’s consistent with basic psychological experiments and it’s consistent with simple economic choices. So there’s good reason to believe that more complex decisions work in much the same way. Maybe you know the story of Percival Lowell, an ambitious and talented astronomer who believed something in spite of all evidence to the contrary.

He believed that on the planet Venus were cities and canals, an entire alien civilization. He drew pictures of that civilization and he took his belief to his grave. Why did he make this mistake? The natural answer has always been confirmation bias. He wanted to believe in something and he ignored or reinterpreted evidence to the contrary. He believed what he wanted to believe.

Solving the mystery

But, there was something always mysterious about the fact that Lowell’s drawings of Venus were so detailed: he was an exceptional observer using one of the best telescopes in the world in day after day he drew the same pattern of hubs and spokes, none of which others saw. Almost 90 years after his death Lowell’s drawings were published in a magazine for amateur astronomers in several of those amateur sent letters each solving the mystery.

You see, Lowell had indeed worked on the largest telescope in the world a refractor with the light gathering lens 24 inches across. Through that telescope Venus was blindingly bright, it was so bright that one cannot look at it directly. So what Lowell did what astronomers often do when observing very bright objects he covered up all but 3 inches of its lands that dim the image of Venus enough to be viewable but it also made that image very small like light coming through a pinhole.

We need to be skeptical about ourselves

You’ve probably experienced what Lowell saw yourself, when you have your eyes checked the eye doctor will waive a very small light in front of your eyes and you’ll see both the light in the shadows it casts of the blood vessels in your. You’ll see a central dark spot and then a set of lines radiating from the spot those are blood vessels. You’ll see the same thing the Percival Lowell saw.

He wasn’t looking at canals on Venus he was looking at blood vessels in his own eye. We want to find evidence that supports our beliefs that helps us make dramatic discoveries or when arguments. We’re very good at seeking out the supporting evidence and we were very good at developing counter arguments against evidence in which we don’t believe.

But, we need to be skeptical not just about others but about ourselves, sometimes we just shouldn’t believe her own eyes.