Shocking fact: Sometimes people lie. Interesting fact: Research shows that sometimes — more often than simple chance would predict — listeners can tell when people are lying to them. Logically, therefore, it is shown that the information about lying is present in the voice, and consequently a machine should theoretically be able to pick up this information and detect lies from the voice.
So-called “psychological stress detectors”: Over the years, many attempts have been made to invent such a machine. By and large, these attempts have been failures — or worse, if you believe that scams are worse than simple failures. Nonetheless, my research has shown that under some circumstances machines can indeed, sometimes, detect lies. Situational factors: First, it is important to recognize that the situation is an important factor in detecting deception. For example, if only the investigator and the person who committed the crime know how much money was taken, or certain other information about the crime, almost any unusual or distinctive reaction to the relevant information can be taken as indicating guilty knowledge. An interesting variation on this approach was used by the psychologist Jung. In that case, only he and the guilty party knew what was stolen. He asked the suspect to respond with as many words as possible when presented with objects of the sort that might have been stolen. When presented with the item actually stolen, the subject came up with fewer responses than when presented with other items. When confronted with this result, the subject confessed.
Research: My research has shown that in a controlled situation, such as a job interview, in which the subject is instructed to lie about which number he selected, it is possible to detect the invited lie in more cases than would be predicted by chance, but with less than perfect accuracy. An important aspect of the results is that they are based on ordinary measurements such as how long it takes the person to respond, and the pitch and loudness of the voice, rather than mysterious vibrations such as some other systems depend on.