Paramount Pictures

The recently released movie "Paranormal Activity 3" focuses on the boundary between dreaming and waking - which psychologist Richard Wiseman says is prime territory for perfectly normal "paranormal" experiences.

Halloween is the peak time to dwell on ghosts, spooky noises, weird premonitions and other "paranormal activities" — but despite that label, such phenomena are totally normal. You can even create them yourself.

That's the message of Richard Wiseman's latest book, "Paranormality: Why We See What Isn't There." Wiseman, who began his career as a magician and is now an experimental psychologist at the University of Hertfordshire, reveals the tricks of the paranormal trade — including the methods used by on-air psychics to make themselves seem, well, psychic. (To try them out, download Wiseman's "Instant Superhero Kit.") 

Wiseman wishes normal people had a better understanding of the psychology behind seemingly paranormal activities.

"There's an enormous problem," he told me today, "actually more in America than in Britain, because the level of belief in the States is huge. We're talking about more than three-quarters of the population believing in some sort of paranormal phenomena — even with the rise in technology and science over the past 20 years or so. It's really quite staggering."

There are so many stories about chilling premonitions of doom, or alien visitations, or high-tech studies of haunted houses. Surely there must be some reality behind all those scary tales. It turns out that there is, but Wiseman says you don't have to turn to supernatural explanations. Here are five examples:

1. Selective memory: Can dreams predict future events? Actually, psychologists have found that people tend to have far more dreams than they consciously remember. A significant event — say, a death or dramatic change of fortune — can trigger the memory of a past dream that may seem to relate to that event. Also, you're more likely to hear about the one seemingly prophetic dream than about the many other dreams that went nowhere. In this essay for The Guardian, Wiseman delves more deeply into the selective nature of dream recall.

The  fact that we often hear only what we want to hear, or remember only what fits our expectations, also plays into psychic readings. Wiseman refers to this as "fishing and forking": The psychic throws out some generalities as a fishing expedition, watches to see which of those observations you pick up on, and then follows that fork in the road to build up the reading. The Skeptic's Dictionary outlines the process here.

2. Ideomotor action: Sometimes zombies really are in control of our brains — but those zombies are our own mental processes that buzz along beneath our consciousness. For example, experiments have shown that unconscious muscle movements can guide your hands to rock a table during a seance, or move a Ouija board pointer to spell out a message, or twist a dousing twig to point to an underground water source (or not). But it works only if your zombie brain can process the results of the motor movements. If you're blindfolded, the effect is spoiled. The Straight Dope provides further discussion of the Ouija connection.

3. Sleep paralysis: For thousands of years, tales have been told about strange beings who visit in the middle of the night and have their way with sleepers. In the old days, these were demons known as succubi and incubi. Nowadays, they're aliens or ghosts (like the ghosts in the "Paranormal Activity" movies). Such experiences are associated with a psychological phenomenon known as sleep paralysis, in which the brain hovers at the edge of consciousness but keeps the mind-body connection turned off (except for the connection to the genitalia, which may explain why those succubi were so sex-crazed). "The body paralyzes itself," Wiseman said.

Researchers recently reported that they were able to train volunteers to experience out-of-body experiences as well as alien encounters during their semi-waking states.

4. Cold spots and infrasound: Ghostbusters often report feeling "cold spots," or suddenly becoming anxious, or getting weird readings on high-tech sensors when a specter makes its presence known. Wiseman said such sudden changes are due to natural rather than supernatural causes. Ten years ago, he and his colleagues used an array of thermal cameras and air movement detectors to figure out what was behind a "haunting" at Hampton Court Palace, near London. It turned out that chilly drafts blowing through cracks in the palace's concealed doorways created the unsettling sounds and the plummeting temperatures.

Low-frequency sounds, created by changes in the weather or even appliances such as air conditioners, can also create a sense of uneasiness in listeners, even if they can't consciously sense the sound.  Wiseman conducted an experiment on the effects of "infrasound" during a concert and found that 22 percent of the listeners felt chills or other unusual sensations when they listened to music that was laced with the low-frequency tones. 

5. Hyper-vigilance: All these effects are accentuated when visitors think they're in a haunted house. "Basically, when we become afraid, we become very vigilant. ... It feeds on itself," Wiseman said. He and many other scientists believe that such hyper-vigilance came in handy when our ancestors were in the midst of a mammoth hunt or a host of unseen threats. The same hard-wired instinct may explains why we seek out an eek by visiting a haunted house or watching a scary movie. "It's the way we've evolved," Wiseman said.

Although Wiseman doesn't see anything supernatural in paranormal activities, he does see a lot of value in studying them. "Trying to understand why people have these experiences is very instructive," he said. In fact, research has shown that some concepts, such as mind-reading and out-of-body experiences, are rooted in solid neuroscience. Just as science fiction can give rise to real-life innovations, so can tales of the paranormal.

"Whenever science has done well, so has the paranormal. ... You get this interesting relationship," Wiseman said.

More Halloween tales from the Cosmic Log files:

• 2002: Ghostly mysteries solved
• 2003: Why we seek out an eek
• 2004: Sharing your scares
• 2005: Ghosts on the rise
• 2006: Bring me your ghost stories!
• 2007: The science of spooks
• 2008: Chasing phantoms on film
• 2008: The science of bloodsuckers
• 2009: Seven ghoulish discoveries
• 2010: Spooky stuff from NASA
• 2010: How your brain handles terror scares

Check out Wiseman's "Paranormality" website for more about the book, plus lots of spooky photos and videos.

Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding me to your Google+ circle. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for other worlds.