“So, while we cannot trust the stories we are told, tradition, faith, convenient or reassuring narratives, charismatic figures, or even our own memories, we can slowly and carefully build a process by which to evaluate all claims to truth or knowledge. A big part of that process is science, which systematically tests our ideas against reality, using the most objective data possible. Science is still a messy and flawed process, but it is a process. It has, at least, the capacity for self-correction, to move our beliefs incrementally in the direction of reality. In essence, science is the process of making our best effort to know what’s really real.”

The Skeptics’ Guide to the Universe is a handy guide to skepticism from the same people behind the The Skeptics’ Guide to the Universe podcast. I get the impression Dr. Steven Novella wrote most of it, although the other co-hosts of the podcast contribute as well. Fans of the podcast (which I highly recommend everyone listen to) will find much of this material familiar, although there are a few new bits. Even if you already know most of this information, it’s still nice to have the biggest take-aways from the 700+ episodes all in one place. So, for those unfamiliar with the term, what is skepticism?

Scientific skepticism isn’t simply doubting everything, but rather doubting ideas which are not supported by science. Science isn’t perfect, but as long as it’s done correctly, it’s the best method we have for eliminating bias. In addition to promoting science, Skepticism also promotes reason and critical thinking in order to expose fraud and pseudoscience.

The book starts with some core skeptical concepts everyone should know, including some cautionary tales from history. Each one of the hosts of the podcast then provides a chapter detailing examples of skeptical thinking that have affected their own lives. There’s then a section on fake news and how to be skeptical of the media, a section concerning some of the tragic deaths caused by pseudoscience, and a final section on how to apply skepticism to your own life.

The first core concept that is covered is memory. Something everyone needs to accept in order to be a skeptic is that our memories are unreliable. Each time we recall a memory, we change it. This is why the fish that got away keeps getting bigger with every telling of the story. The way our brains store memories is messy. Different memories get combined together. Sometimes you remember something you observed or someone else’s memory as if it’s your own. We invent details to fill in gaps. False memories can be created through hypnosis, guided imagery, suggestion, or group pressure. Police can convince innocent people they committed a crime through lengthy interrogation. Confidence in a memory doesn’t make it more likely to be true.

In the 1980s, many therapists believed traumatic memories get repressed and can be uncovered through hypnosis and other techniques. In actuality, the therapists were creating false memories in their patients without realizing they were doing it. These false memories led to the Satanic Panic in which many people remembered witnessing child sacrifices and being abused by satanic cults, even though nobody has ever uncovered any evidence that satanic cults such as these even exist. Many innocent people were sent to jail and many families were torn apart as a result of false memory syndrome.

Optical illusions demonstrate that we can’t always trust our senses. Our perceptions are constructed by our brains. Your brain actually changes what you see based on what it’s expecting to see, projects movement into the future, fills in your blind spots, makes your two dimensional perception appear three dimensional, makes the blurry images around the center of your vision appear clear, and more. We can easily mistake something small and close for something big and far away, especially when we’re looking into the sky.

Your brain also changes what you hear to match how lips appear to be moving. Our brains tell us we’re inside our body, but virtual reality can make us feel like we’re out of our body. Our brains also give us the sensation that we control our body, but this circuit can be interrupted, making us think our hand has a mind of its own. When sleepy, we’re especially susceptible to hearing or seeing things that aren’t there.

We also have limited attention and can miss something happening right in front of us if we aren’t paying attention to it. This is called attentional blindness. We don’t see what we aren’t looking for. Change blindness is not noticing changes in detail that occur outside our direct view such as one person being swapped for another. This is one of the reasons eye witness testimony can’t be trusted.

Pareidolia is seeing an image in random noise such as the man in the moon or images in clouds. It also applies to sound, such as hearing messages in songs played backwards. Expectation plays a huge role, so you’ll see or hear what someone else tells you to expect. Our brains are especially disposed to see faces, which is why so many peoples see the Virgin Mary in tree bark or Jesus in a piece of toast.

Hyperactive agency detection is assigning emotions to non-living objects such as children assigning emotions to a favorite toy, or the way all of us assign emotions to cartoon characters. It’s also part of why conspiracy theorists assign agency behind chaotic events like the JFK assassination.

Hypnagogia is a state when you’re still dreaming, but feel like you’re awake. It’s sometimes associated with sleep paralysis, in which you can’t move your body even though you’re mostly awake. Depending on culture, people can interpret sleep paralysis as being caused by demons, ghosts, witches, or aliens.

The ideomotor effect is a subtle muscle movement driven by expectation that can be found in dowsing, facilitated communication, or people using Ouija boards. This may seem like harmless fun, but businessman James McCormick made millions selling a modified dowsing rod to detect bombs. It didn’t work and likely resulted in hundreds of deaths in Iraq alone.

The Dunning-Kruger Effect is everyone’s tendency to overestimate their own knowledge in areas outside their expertise due to the fact we’re ignorant of how ignorant we are. Everyone thinks they’re above average. Those who know the most in a subject underestimate their knowledge a little bit. Those who know the least overestimate how much they know the most. This is because ignorance isn’t a lack of knowledge, but rather possession of incorrect knowledge which gives us unwarranted confidence.