If someone breaks out the Ouija board at the Halloween party you’re attending in attempts to contact and converse with their late Uncle Bernie, do them a favor, and tell them any movements they make on the board can be explained by the theory of ideomotor action (I’m sure it’ll make you the life of the party). The gist of ideomotor action is that people are prepared to initiate movements they think about performing even if they are not going to actually enact the movement, and most importantly, that there is a tendency to enact the movement the more vividly it is imagined. 
Ideomotor action has been used as far back as the 1800s to explain various psychic phenomena such as water witching (using a diving rod to find water underground, a debunked practice which is still very much in practice today), magic pendulums (used to ascertain the sex of an unborn baby; also debunked), and yes, those seemingly involuntary movements made on Ouija boards. There is support for a particular type of ideomotor action that is called intentional induction, which entails the greater likelihood of instigating a movement if it results in something we would like to see happen. One could liken intentional induction to a confirmation bias or self-fulfilling prophecy. Applied to the Ouija board, if your friend expects Uncle Bernie’s psychic powers to move their hands, the intentional induction facet of ideomotor action theory suggests their hands will be more likely to move across the board and spell out what they think is Bernie’s message. It turns out Bernie’s message is merely what you would like to hear from Bernie.
Interestingly, there is some knowledge to be gleaned from Ouija boards. In a study involving a memory task that specifically examined implicit sematic memory, which is not accessible to conscious recall, participants providing volitional responses to questions they had to guess the answers to were accurate at chance levels (about 50%). However, participants who used a Ouija board to respond to questions they were guessing the answers to were accurate 65% of the time, a significant difference from the volitional response group. It turns out ideomotor actions can tap into knowledge we have but don’t know we have. Ouija boards can be a useful tool to communicate information about ourselves to ourselves, but falls short of tapping the communication lines of ancestral ghosts. In short, belief in the traditional powers of Ouija boards is plain, old superstitious.
Superstitions. What are they? Why do so many of us believe in them? And how is it that people will do seemingly irrational things in order to continue their good fortune and not invite misfortune? Superstition is defined as an irrational belief that an object, action, or circumstance not logically related to a course of event influences its outcome. It’s October, and it seems the month of October is bombarded with superstitions like “playoff beards” in baseball and the ominous sign of black cats on Halloween night. What these things have in common are people engaging in behaviors to support the belief that they are somehow in control of the outcome.
Fifty years ago, one of the greats in Experimental Psychology, B.F. Skinner shaped superstitious behavior in pigeons. In his paper published in 1948, titled "Superstition in the Pigeon," Skinner explained how reinforcing pigeons on an interval schedule (delivering a treat after a certain amount of time has passed) produced superstitious behavior in the pigeon. For example, Skinner would deliver a food pellet to the pigeon after a certain amount of time. He found that the pigeon would then continue to perform any behavior that occurred immediately before the food pellet was delivered. The pigeon's behavior did not control the delivery of the food pellet, but the pigeons began to walk in counter-clockwise circles, bob their heads, or toss their heads as if the pigeon was lifting an "imaginary lever." Although the pigeon's behavior had no control over the outcome, the pigeons continued to engage in the behavior that may have resulted in their fortune. The pigeon’s behaviors sound a lot like lucky socks before a game, a lucky tie before a job interview, never again wearing the shoes that resulted in a particularly bad day. Want to make someone engage in irrational behaviors in their attempt to control the outcome of an event they actually have no control over? Just deliver treats on a time schedule and see what types of behaviors you begin to see.
And if you want to get a gruesome image stuck in someone’s head while they are performing these irrational behaviors, just tell them not to think of flesh-eating zombies of The Walking Dead ilk. In a study of thought suppression, where participants were instructed not to think of a white bear, what do you think happened? You guessed it, they reporting having intrusive thoughts of a white polar bear. This is explained by ironic process theory, which states that there is a dual process of cognition: one is automatic and effortless and is responsible for looking for a failure of control, while the other is the conscious operating process. In the polar bear experiment, participants tried to consciously think of something else, but the automatic, effortless process of looking for a failure of control (thinking of a white bear) often kicked in and this restarted the cycle of consciously attempting not to think of the bear yet again…until the automatic, effortless process looking for failure of control forced the white bear back into consciousness (hence the name ironic effects of mental control). It is important to note that these effects are most pronounced under high cognitive load where resources are taxed thereby making those automatic, effortless processes much more influential. This doesn’t take away from the effects of ironic processing theory because in everyday life, we are typically cognitively taxed with the billions of bits of information flooding our senses. In point of fact, the ironic effect of mental control has been demonstrated in several facets of life such as depression, sleep disorders, and even sexual deviancy, which makes this theory one of clinical relevance.
So there you have it, the psychology behind Halloween-related phenomena. Hopefully, a black cat will not cross your path this Halloween night as you are stepping on a crack on the sidewalk, fingers crossed! -just in case. Boo!
 Pfister, R., Janczyk, M., Kunde, W. (2013), Action Effects in Perception and Action: The Ideomotor Approach. Frontiers in Cognition.
 Knuf, L., Aschersleben, G., Prinz, W. (2001), An Analysis of Ideomotor Action. Journal of Experimental Psychology General, 130(4): 779-98
 Gauchou, H.L., Rensink, R.A., Fels, S. Expression of Non-conscious Knowledge via Ideomotor Actions,Consciousness and Cognition: An International Journal, Vol 21(2), Jun, 2012. pp. 976-982
 Wegner, D. M. (1989), White bears and other unwanted thoughts: Suppression, obsession, and the psychology of mental control, New York: Viking/Penguin
 Wegner, D. M. (1994), Ironic Processes of Mental Control, Psychological Review 101 (1): 34–52
 Johnston, L., Ward, T., Hudson, S. (1997). Deviant Sexual Thoughts: Mental Control and the Treatment of Sexual Offenders, 34(2).