Memory and testimony: the psychology of the witness

Memory and testimony: the psychology of the witness

Since the emergence and first development of psychology as a scientific discipline, some researchers were aware that the knowledge that was beginning to be generated in the field of human memory could be used to solve some unknowns and problems that arose in applied fields. One of these areas is that of testimony that people make when they testify before the courts of justice or for the police.


  • 1 Psychology in legal contexts
  • 2 The effect of misleading information
  • 3 Variables that affect the accuracy of the testimony

Psychology in legal contexts

At the beginning of the century, authors such as Münsterberg, Binet or Stern published research papers on witness psychology and raised the need for judges, as well as being advised by different professionals on issues that fall outside their sphere of knowledge, to have expert psychologists to advise them on different psychological aspects involved in legal contexts.

Today, it is getting a little more normalized than ever forensic psychologists, participation that materializes in very diverse fields, such as the following:

  • The criminology.
  • The selection of jurors.
  • The attribution of responsibility.
  • The formation of the police.
  • The prison setting.
  • The attention to the victims.
  • The assessment of psychological damage.
  • The assessment of the witness.

When a person, at the police station or before a judge, explains the facts that he has witnessed or lived, or when he is subjected to an identification wheel in which he must try to recognize a suspicious person, he is doing a memory exercise.

This exercise of memory can be extraordinarily transcendent because of its consequences.However, it does not differ substantially from what we do when we try to tell a friend about the episode of a movie that we have seen or anything else, more or less trivial that has happened to us.

That our story of a movie is not very faithful does not usually have much significance. Nevertheless, errors in testimony can determine that people guilty of crimes are acquitted or, worse, innocent people are convicted. For this reason, judges, lawyers and prosecutors increasingly rely on psychological expertise to try to determine the degree of accuracy that should be attributed to a witness's account, or an identification process.

The effect of misleading information

The effect of misleading information occurs when the person distorts the original memory of an episode due to the subsequent processing of contradictory information with what has actually been perceived.

When we perceive any event, the processes that operate in the different memory systems elaborate a representation of what we have perceived in our memory. However, if subsequently, by any means, we receive information that does not match the original episode we perceive, the likelihood of distorting the representation of the original episode in some way is increased so that, when we remember it later, we introduce inaccuracies or Mistakes in our memory.

Psychologists interested in the subject of testimony accuracy have revealed from many experiments the effect of misleading information.

In an experiment by Loftus, Miller and Burns (1978), for example, a sequence of slides representing a traffic accident was presented to the subjects. In this sequence of slides there was one in which the subjects saw a car stopped at a stop sign.

Seen the sequence, the subjects were given a questionnaire of twenty questions about what they had seen. For half of the subjects one of these questions was: Did you advance another car in the red car while standing at the Stop sign? (Information consistent with what the subject had seen); For the other half of the subjects, the critical question was: Did another car pass in the red car while it was standing at the yield signal? (Information misleading or inconsistent with what the subjects had seen).

Subsequently, the participants performed a twenty-minute distracting task that involves reading a text and answering some questions.

Finally, the subjects were subjected to a recognition test in which they were presented with simultaneous pairs of slides from which the subjects had to select the one that had been previously presented to them in the accident sequence.

The critical pair of slides, in which the subjects had to choose the slide seen in the original sequence, presented the car stopped at the Stop sign, on one slide, and stopped before the yield signal, on the other.

The results showed that in the group of participants in which the question was consistent with the information seen, the percentage of subjects who chose the original slide was 75%, clearly above 50% that would mark the effect of chance; while in the group that received misleading information in the question the percentage of correct answers was 41%.

An experiment by Loftus and Palmer (1974) shows us how the information after the event, subtly introduced according to the linguistic expression used, can alter people's testimony.

In this experiment, a film was presented to the subjects in which two cars colliding with each other were seen. Subsequently, the following question was asked to the subjects:

At what speed were the vehicles going when…?

For a part of the participants the verb used was crashed; in the other group the verb was collided; in another dent, in another collide against, finally in another group of subjects the verb that was used was to contact.

We must bear in mind that the different verbs used in the question imply a gradation of more to less violence in the clash and, therefore, of a greater speed prior to the clash.

The average of the results in the estimation of the speed of the cars of the different groups according to the verb that was used was the following:

Verb used in the questionEstimated speed (km / h)
Bump against34.0

Although the variation in the speed estimation made by the subjects may seem small, he thinks that there is enough for a real situation to go from a legal speed to an illegal one.

The effect of misleading information, which has been demonstrated in many experiments, reveals interesting problems both applied and theoretical.

In the applied field, the problem arises of how to avoid that, when a person has witnessed or suffered a crime as a victim, the subsequent information he receives distorts his memory in some way.

The information of an event can come from very different sources: the same police interrogations, conversations with other people, or even the information provided by the media.

In the theoretical field, the fundamental question is: What mental processes determine the effect of misleading information?

Several explanations are currently being investigated:

  • It may happen that subsequent misleading information deletes and replaces part of the original representation of the event in the subject's memory.
  • It may happen that both the original information of the event, and the subsequent misleading information coexist in the representation of the subject and several factors determine that the subject accesses one or the other.
  • It may happen that, although the subject retains in its representation the original information perceived in the event, several factors force it to give a biased response with information that is not represented in its memory.

Variables that affect the accuracy of the testimony

The witness psychology researchers have specifically addressed what factors or variables particularly affect the specific situation in which a person has to testify and how these factors and variables make the witness tend to be more or less accurate. Different classifications of the variables that influence the testimony have been developed and here we will review some of these variables have been the classification made by Ibabe (2000).

Variables related to the event

In the first place, we have the physical conditions such as the time that the perception of the event on the part of the subject has lasted, the distance in which this perception has occurred and the degree of illumination that was. Obviously, the less exposure time, the more distance and lighting the more bad, the less likely the witness is accurate.

On the other hand, we have the characteristics of the event. For example, it has been shown that the witness of violent events is usually worse than that of events that do not involve violence. In addition, within an episode not all the actions and objects involved have the same relevance and the witness tends to get worse when it affects less important elements.

Variables related to the witness

In the first place we find a whole series of physical variables related to the witness. One of these is age. For example, it is known that the testimony of very young children, of preschool age, and that of the elderly tends to be worse than that of people who are between these age limits.

Another variable of a physical nature is the race of witness in relation to the race of the person to whom he must testify. We tend to code more elements and details, and consequently to remember better, the physical appearance of people of our same race.

Differences in the quality of the witness have also been demonstrated according to the sex of the witness. Among others, it is known that women remember violent events worse than men. Although the testimony of women is better.

Many cognitive variables related to the control have also been investigated.

One of these refers to individual differences in memory skills for remembering events or remembering people. It has been shown that remembering events or identifying people are skills that do not have to match a person. That is, we can be very skilled in the memory of events and very little in the identification processes or vice versa.

Another important variable for witness accuracy is the Attention. If you have been very focused on particular aspects of an episode (for example, the weapon carried by the offender), the memory of other aspects of the event will tend to be very poor. This is what is known as the targeting effect on the weapon.

A very important element in relation to the accuracy of the testimony is the degree of emotional activation that the event provoked in the witness. Although we have said before that both to tell an episode of a movie to a friend, and to testify about a crime of which we have been victims or eyewitnesses are memory exercises, we cannot ignore that in many cases the witness of a crime in a real case He lived the event with a high stress component.

The question is: will an episode that arouses a high degree of stress in those who perceive it be better or worse remembered than a neutral fact? Unfortunately, today we do not have a clear and simple answer.