Polygraphy is associated with the technique used in interrogations to detect lies
The Greek word polygraphía came to our language as polygraphy . The first meaning included in the Royal Spanish Academy ( RAE ) refers to the technique that allows writing in a hidden way , in such a way that what is written is intelligible only to those who are in a position to discover the content . The notion also refers to the skill to decipher messages of this type .
Detect lies
Another use of polygraphy is linked to the measurement of physical magnitudes . In this context, a device that simultaneously measures different psychosomatic variables is known as a polygraph , which is used to try to confirm whether a testimony is true or not .
In colloquial language, this polygraph is known as a lie detector . In this case, polygraphy involves monitoring physiological responses to different questions.
The polygraph is capable of recording changes in breathing rate , heart rate and blood pressure . The data collected can be used as a reference to determine whether a person is telling the truth or lying.
Fundamental assumptions
Polygraphy is based on two assumptions that underlie the way it works and its effectiveness:
* reactivity : when an individual is in a difficult and stressful situation, such as an interrogation by police authorities, they are expected to feel nervous, restless and scared. These are the typical symptoms of an anxiety disorder, which also involves the activation of the sympathetic nervous system , which acts in moments of danger or alert;
* truly : when a person tells a lie, it is inevitable that he or she will become nervous, even if only at a minimal level. Therefore, the polygraph can detect your abnormal state and assume that it is a false response.
Scientific stance
It is important to note that, from a scientific point of view, these polygraphy machines are not reliable. The scientific consensus indicates that there is no artifact that makes it possible to accurately detect a lie. This is curious, since the use of the polygraph is very common in the police field and even in the army.
Precisely, its success on so many occasions serves as a statistical source to try to demonstrate its validity as a lie detection method to the scientific community. However, the latter refutes all statements by pointing out that the subject responds in the expected manner only if he believes in the effectiveness of the polygraph.
For science, the two fundamental assumptions mentioned above are not enough, but to accept polygraphy, and more precisely the polygraph, as a tool to detect lies, the test should meet the following two points:
* sensitivity : this is the percentage number of positive results in cases in which the authorities know that the subject has lied;
* specificity : it is practically the opposite of the previous point, the number of negative results when it is known that the subject is not lying.
Cardiorespiratory polygraphy
On the other hand, respiratory polygraphy - also known as cardiorespiratory polygraphy - is a study performed to diagnose sleep apnea . What is done is to control variables while the patient is sleeping to discover if oxygenation remains constant, if breathing pauses occur or if the subject snores, for example.
Cardiorespiratory polygraphy helps diagnose sleep apnea
Through cardiorespiratory polygraphy, these variables are also measured throughout the apnea episodes:
* oxygen saturation : to know if there are alterations in the amount of oxygen that reaches the blood;
* heart rate : what is its variation;
* air flow : to know if the air is entering the lungs properly;
* movements of the thorax and abdomen : those of breathing , which are perceived with the help of belts.