This study illustrates, quite dramatically, a fairly common deception which is usually the object of memory: the suggestionabilità. The experiment, developed by the Iowa State University, shows a very simple design whose repercussions are immense in the field of Forensic Psychology. Participants were shown a video taken by a security camera of a man walking towards a store. The video lasted only 8 seconds but played slowly so that people could appreciate as much detail as possible, although to be honest, given the poor quality of the video itself, very few peculiarities could be noticed. After watching the video, the participants were told that the man was a killer and that the moment he disappeared from sight he entered the shop and killed a guard. This information was true, based on a real case. Participants were told that their purpose was to identify the killer from five photos that were shown to them, which had actually been used in the original case except that the photo of the real killer was excluded from the experiment. At this point the group was divided into three subgroups: - The first group was not given any information that could condition the choice. - The second group was told they were wrong. - The third group was led to believe that they had identified the real killer. Each was then asked how many factors and characteristics he had used to identify the suspect, how confident he was of his decision, how well he had seen the man in the video, and if he could describe details of his face. The results showed that simply complimenting people on choosing the suspect correctly had a great effect on their relationships: they automatically recognized that they were very confident in their choice and therefore their judgments were reliable, they were convinced that they had a good overview of the killer and that identification had been very easy. So that offering good feedback to these people greatly strengthened their self-confidence by making them truly believe their judgment was entirely safe. Only 15% of the people who were told that they were wrong in the identification accepted the judgment while that 50% of the people who were given positive feedback increased their certainty in having identified the culprit. In the second part of the experiment we wanted to consider how conscious the alleged witnesses were on the influence of the conditioning feedback. As if to say, if they had realized that after listening to the words of the researchers their confidence increased or decreased. The results can be imagined: people did not consider themselves deluded nor did they believe that the words of approval or disapproval of scholars could affect what they had "seen". The researchers assure that the phenomenon of positive conditioning does not need to be verbal, it can also be simple extraverbal signals of satisfaction from the police forces.