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  • Writer's picturealicepailhes

A psychological classification of forcing techniques

The psychology behind different types of magicians' forces.

Over the last 7 years, I have tried to bridge the gap between the field of magic and the one of academic psychology. I had two aims in mind. As a psychological researcher, my primary objective is to help scientists understand some of the key principles used in magic, so that they can study them scientifically. However, this link between magic and psychology is also useful for magicians: it allows you to draw upon vast amounts of scientific knowledge about human behaviour. I like to think that psychology provides a sort of instruction manual of the human mind, and I personally feel it’s always a good idea to read the manual before operating any complex piece of machinery. I’ve spent the last four years dedicating my research to forcing techniques, and have developed with my former PhD supervisor Dr Gustav Kuhn and my colleague Dr Ron Rensink a formal classification that allows us to identify the key psychological principles that are involved in forcing.

Why create a psychologically-based classification of forcing?

Magicians already have many informal classifications. We distinguish between close-up magic and stage magic, card magic and coin magic, self-working card tricks and sleight-of-hand card tricks. Such categories are important because they allow us to organise our knowledge about magic and they facilitate the communication between magicians. Categorisation helps facilitate communication by letting you know what you are supposed to do if you want to perform these things. For instance, because you know that shuffling involves rearranging your deck of cards, you can find lots of ways of using this principle to get the desired effect. Once you understand the underlying principle, you are free to play with it as you wish.

The Classification

While the magic literature doesn’t offer a universally accepted definition of a force, there seems to be a consensus of two key components: the technique must affect the spectator’s decision or the outcome of their choice, and the spectator involved must feel free in their choice, and in control of the outcome they get.

Because of this, our classification distinguishes between forces in which you either influence the spectator’s decision or the outcome of their decision.

Outcome Forces

Although we generally like to feel in control of our environment, we often fall victim to an illusory sense of control over our own activities. Outcome forces are probably the most widely used forcing techniques, and their success is based on this potentially illusory link between one’s action and the outcome of this action. In these techniques, the spectator makes a genuinely free decision, but unknown to them, this decision has no impact on the outcome of the trick.

We have identified three main kinds of psychological errors that can be exploited to facilitate outcome forces: perceptual, memory, and reasoning errors.

Perceptual Errors

These forces can be achieved through two different mechanisms. The first mechanism relies on secretly switching an item (dissimulation). For example, in the under-the-spread force your spectator can freely touch a card among other cards presented in a spread between your hands, but after the selection is made, you then covertly switch their selected card for the target card. The second type of mechanism involves forces where the spectator makes an error in their perceptual inference, and this often relies on presenting event sequences that are difficult to follow clearly. These forces often involve rapidly presented or otherwise complex events (e.g., Hindu Force).

Memory Errors

There are forces in which the spectator accurately perceives the whole event sequence, but later misremembers crucial parts of the sequence in ways that prevent them from realizing that their actions had no impact on the outcome. These types of forces rely on memory errors. A good example is the Cross-Cut force. I have run numerous experiments to investigate this force and tested it in various ways on hundreds of participants. These systematic investigations support the assertion that most participants failed to remember the correct event sequence of the trick. I’ll go into more details about the results of these experiments in a future article.

Reasoning Errors

The last type of outcome force we have identified exploits the spectator’s reasoning errors: These forces rely on erroneous reasoning about the event sequence that led up to a selection—for example, your spectator can fail to understand that adding up the bottom and top faces of a rolled die always ends up with the number seven; this failure to understand the inevitability of the outcome can occur even if they accurately perceive and remember the event sequence. We have identified four types of reasoning errors that are used in such forcing techniques: ambiguity blindness, limitations in mathematical thinking, logical errors, and wrong assumptions.

  • Ambiguity blindness refers to the spectators’ failure to recognize ambiguous situations, which can create the illusion that their choice has an impact on the outcome of your trick. The most famous example of this type of force is the Equivoque (see my scientific paper about it here).

  • Forces relying on limitations in mathematical thinking are the ones such as asking a spectator to carry out a calculation that always ends up on the same number. For instance, Annemann describes the following technique: Choose a random number (i.e., 32), multiply it by 2 (64), add 10 (74), divide it by 2 (37) and then subtract the originally chosen number from this number (37-32) – the answer will always be 5.

  • In contrast to tricks based on limitations of mathematical thinking, forces based on logical errors don’t rely on arithmetic procedures. Even without using math, some sequences are simply too complex or unusual to follow easily, which results in people failing to understand that their outcome card or item was completely predetermined from the beginning of the trick. The Top Cards dealing force is a nice example of reasoning failure based force.

  • Finally, the spectator’s wrong assumptions about what is happening can create powerful effects. Every spectator enters your performance with a set of prior beliefs about what is going to happen, the objects you are using or even what you are doing. Luckily for you, some of these assumptions are erroneous: your spectator can believe that the card they freely touched is the one you gave them when you in fact covertly switched it, that the deck you are using has fifty-two different cards when it is in fact a one-way deck, or that you have no way of controlling which card they will end up with if they are the one saying ‘stop’ whenever they want…

Decision Forces

Decision forces are often bold or risky, but can be way more rewarding when they succeed. Decision forces are all the techniques in which you try to influence your spectator’s decision by increasing the likelihood that a particular item will be chosen. Here, the spectator’s decision (e.g., to think of a particular card) is not entirely free. For most decision forces, in contrast to outcome forces, there is often a real risk of failure. It is generally wise to use decision forces in situations where you can cover the potential failure through some other technique.

We have identified the main processes by which decision forces influence the spectator’s decision: using their psychological biases and restricting their choices.

Psychological Biases

Most decision forces rely on exploiting people’s natural psychological biases, which basically means exploiting our inherent tendencies to choose particular actions or items over others. Forces that exploit our psychological biases are probably what most magicians mean when they talk about ‘psychological forces’. Very few, if any, of these forces demand physical dexterity.


Priming relates to the idea that specific stimuli can influence people’s subsequent thoughts and behaviours. Priming forces refer to procedures where the magician uses some form of priming to alter the spectator’s tendency to select a target object. These primes can be verbal (e.g., a specific word or sentence) or nonverbal (e.g., a gesture). For example, I have been able to identify some reliable priming effects related to mentalism presentations. I’ll talk about my scientific investigations of Derren Brown’s Three of Diamonds force in a detailed article dedicated to it (in the meanwhile you can find the academic paper here).

Stereotypical Behaviours

The second principle used in decision forces relies on exploiting people’s stereotypical behaviours. Most people will tend to act in certain ways and choose particular options when presented with a specific situation or question. In other words, seemingly free answers to certain questions can actually be highly predictable. A famous example of this type of force involves asking your spectator to name any number between 1 and 10. Far from being even odds of any number being named, when faced with this specific question, people are most likely to name 7. Other stereotypical behaviours rely on physical positioning of the items, such as putting the force item in the middle of a row of three others.


The third psychological bias is based on increasing the saliency of the target item, that is, the extent to which the item visually stands out from its surroundings. Psychological research shows that stimuli with contrasting features (such as a different colour from the background) can automatically capture our attention, and this can happen without our awareness. A famous example of such a technique is the visual riffle force. Ideally the salient card should capture the spectator’s attention, but they should not be consciously aware that its presentation differs from that of the other cards.


Some decision forces are based on the spectators’ reactance: the motivation to restore one’s freedom when we perceive it to be threatened. You can trigger this feeling through different means, such as using reverse psychology in the presentation of the force. A famous example of this is Dai Vernon’s Five-Card Mental Force. We have investigated this technique in four different experiments on 650 participants and found that participants choose the Four of Hearts significantly more often when we used reverse psychology instructions rather than simple instructions (to be discussed in a future article as well!).


Another way to force a particular decision is by restricting your spectator’s options. These restrictions can be verbal, perceptual or physical. Banachek gives several examples of these forces in his books, such as asking your spectator to think of a simple geometric shape but announcing “but don’t take the square, it’s too obvious.” According to Banachek, because you explicitly verbally restrict the decision, this should enhance the probability that the person chooses a triangle. My scientific investigations of such techniques indicate that this principle is not very effective at increasing the chances of the spectator choosing the force item, and simply enhances the likelihood that they will feel restricted in their choice. Perceptual restriction offers a more reliable way of forcing items (for example, spreading the cards on a table and making only one of them fully visible, or literally pushing the force card under the spectator’s index finger during a classic force).

As you might have noticed, the majority of forcing techniques do not fall into one unique category but tend to use a combination of principles to make them effective. For instance, a classic force will use physical restriction by pushing the force card under the spectator’s finger, but is also based on a stereotypical behaviour pushing most people to go along with this card rather than looking for a card at the very bottom of the deck which is not presented to them. The main lesson to take from this classification is that decision and outcome forces rely on different sets of psychological mechanisms, and thus their effectiveness will be influenced by different factors. In future articles, I’ll discuss how to influence each of these mechanisms (i.e., illusory control and psychological biases) in more details.

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