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Neurophysiology

The impact of horror

A study gives dimension to the tension generated by violent images

ReproductionThe Scream, Edvard MunchReproduction

To see a baby sleeping or a happy face, which conveys peace, can bring about physical relaxation or set off the desire of getting close. Inversely, images of death or of wounded bodies cause tension and bring defensive actions into play, as if we were faced with imminent danger, according to a study coordinated by the neurobiologist Eliane Volchan, a professor at the Biophysics Institute of the Federal University of Rio de Janeiro (UFRJ).

Eliane and her group reached these after having carried out an experiment in which 48 men observed 72 images divided into three categories: the first was with positive scenes, with people swimming, running, playing ball or practicing sport in a general manner; the second was neutral, with photos of inanimate objects such as a telephone, a hydrant or a cake mixer; and the third involved negative images, with bodies of people without arms or legs, dead or with serious wounds. The participants in the study remained standing, with their feet together and barefoot and their arms placed at the side of their body, standing on a metallic base, called the force platform. This device, similar to a scale, registers the oscillations of the body when faced with the images, successively shown for three seconds on a computer screen, without any interval between them.

In this work, carried out by Tatiana Azevedo under the supervision of Eliane, and in conjunction with researchers from the Biophysics Institute and the Physical Education school of UFRJ, the subtle movements of the body registered by the platform, added to the variation in the frequency of heart beats, revealed the changes in body posture caused by the three groups of images. Among the results, published in May in the magazine Psychophysiology, that which most called attention is the fact that the disaster or mutilation scenes bring about immobility: faced with them, the observers oscillated less to the sides than when they were looking at neutral or pleasant images. They also registered an increase in muscular tension – the so-called freezing, already investigated in rodents and now confirmed in human beings. “The period of immobility and tension is characterized by an increase in attention and vigilance and by a reduction of the frequency of heart beats, as if the observer felt himself faced with imminent danger”, comments Eliane.

Survival instinct
“We and other animals produce a freezing reaction when faced with distant threats or even those non-concrete yet”, she says. One is dealing with an adaptive response: when faced with a predator, who as yet has not detected its prey, the best thing to do, if we were to be the prey, is to remain immobile and not call attention. According to the researcher, the visualization of photos in the laboratory can correspond to this situation, since it causes the impression that the danger is there, but it is not concrete. “If the danger becomes concrete, an action will probably occur, such as fleeing movements, and the acceleration of the heart beat”, she analyzes. “Both of the reactions, freezing and fleeing, make up part of our ancestral defensive repertoire, just like the other animals.”

Other studies have already indicated that seeing images of wounded or incomplete bodies increases the liberation of hormones such as cortisol and reflex action heightens – the fright. The human brain seems to have preserved ancestral defense mechanisms, which are brought into action under specific circumstances, but these responses vary among people. In this experiment not all of the observers of the negative images clearly showed the reactions typical of freezing, which apparently depends on each person’s ability to deal with the disagreeable stimuli. By way of another study, published in March of last year in the Brazilian Journal of Medical and Biological Research, Mirtes Garcia Pereira, currently with the Federal Fluminense University (UFF), Eliane and other researchers from UFRJ and UFF had already verified that people become slower to detect a light circle after having been exposed to photos of mutilated bodies.

Repressed fear
Through studies such as these, Eliane and another group with whom she is working in conjunction, coordinated by Ivan Figueira, from the Psychiatry Institute of the UFRJ, are particularly interested in better knowing the variability of emotional responses of people in situations that are more dramatic, such as post traumatic stress disorder (PTSD). It is known that anyone that lives through a terrorizing situation involving risk of life, such as an robbery, an accident, or rape, can have difficulties to free themselves from the fear or the memories that can come to the surface with a conversation or a film on television. The memory of the traumatic situation can lead to the loss of emotional control, but it is as yet unknown exactly how the memory can be brought into action nor what are the best alternatives to combat this problem.

In a complementary line of research, Eliane’s team arrived at other interesting conclusions concerning the changes in the body’s posture in situations that signal safety. One of the group’s researchers, Lívia Facchinetti, under the co-supervision of Claudia Vargas, from the Biophysics Institute and one of the co-authors of this study, verified that exposure to agreeable photos of babies and family changed the body posture in a manner that surprised the researchers: the body’s center of gravity moved a little backwards, indicating that the people were literally withdrawing themselves. “Even though tense, these very small but significant movements register the predisposition to bring something or someone closer”, says Eliane. She and other specialists in organic reactions caused by images are arriving at the conclusion that human beings and even other animals constantly search the environment looking for danger or safety signals. “The detection of clues of a threat activates the defensive system”, she says, “whilst the detection of safety clues promotes social interactions”.

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