## 2 Theoretical Background  
### Lie and Deception  
To deceive means \"to lie, mislead or otherwise hide or distort the truth\". Although the term lie is often regarded similar to the term deception, there is a certain distinction between the two. Lying is just one of many forms of deception, which does not only mean uttering an untrue claim, but also manifests itself in \"omitting the truth or more complicated covering-up the truth\" commonly with the intention to mislead or deceive someone [8]. The traditional definition states that to deceive means \"to cause to believe what is false\", which naturally leads to the question of whether this includes the case of mistakenly or unintentionally deceiving another person, on which many have conflicting views [9]. However, the majority believes that lying and deception necessarily manifest themselves with intent, so the definition itself has been modified to define deception as \"intentionally causing to have a false belief that is known or believed to be false\" [9]. The definition also implies the success of the act of deception since otherwise, the goal of creating a \"false belief\" in another person is not fulfilled. This is precisely one of the differences between deception and lying, where lying does not necessarily mean convincing another person was done successfully; it only refers to \"making a false statement with the intention of deceiving\". A slightly broader, generally accepted definition of lying is the following: \"A lie is a statement made by one who does not believe it with the intention that someone else shall be led to believe it\" [10]. According to the stated statement, four main conditions are defined that must be fulfilled in order for a certain statement to be identified as a lie: the person should make the statement (statement condition), the person making the statement should believe that the statement is false (untruthfulness condition), an untrue statement must be given to another person--the recipient of the statement (addressee condition)--and lastly, the person making the statement must lie with the intention to convince the recipient of the statement to believe the untruthful statement to be true (intention to deceive the addressee condition) [9]. Here, too, there are debates regarding the very definition of \"lying\", and they concern the intention with which a person lies; these debates lead to two opposing groups, namely the theories of Deceptionism and Non-Deceptionism. The former group believes that intention is necessary for lying while the latter believe the opposite. The theory of Deceptionism is further divided into Simple Deceptionism, Complex Deceptionism, and Moral Deceptionism. Simple Deceptionists believe that for lying, it is necessary to make an untrue statement with the intention of deceiving another person while Complex Deceptionists additionally believe that the intention to deceive must be manifested in the form of a breach of trust or belief. Moral Deceptionism state that lying not only requires making an untrue statement with the intention of deceiving, but also violating the moral rights of another person. On the other hand, the theory of Non-Deception dictates that lying is a necessary and sufficient condition to make an untrue claim, and it is further divided into the theory of Simple Non-Deceptionism and Complex Non-Deceptionism [9]. Unlike lying, deception itself does not only involve verbal communication, but also manifests itself through various non-verbal signs, such as leading another person to the wrong conclusion by certain behavior, using non-linguistic conventional symbols or symbols that determine similarity (icons), etc. It is also possible to deceive someone with an exclamation, a question, a command, an omission of an important statement, and even silence [9]. This leads to the conclusion that the statement condition does not apply to deception.