The Palaeoneurology group at the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH) has just published a paper in the American Journal of Human Biology on the relationships between tool shape in Lower Palaeolithic industry and levels of attention during haptic or tactile exploration, whose results show that electrophysiological reaction is more sensitive to specific physical features of the tool than to its general outline.

To conduct this investigation on the influence of features of Palaeolithic tools on their tactile perception, an electrodermal analysis was carried out on a sample of 46 persons without previous knowledge of archaeology, measuring their emotion and attentional responses while handling the tools; in addition, the morphological variability was quantified for a wide range of tools, made up of worked pebbles and handaxes.

On the one hand, electrodermography makes it possible to assess changes in the electrical conductivity of the skin associated to fluctuations in emotions and attention. This methodology is employed in lie detectors and in neuromarketing, to learn the responses of different individuals or groups to commercial stimuli or, as in this case, responses to interaction with Palaeolithic tools.

On the other hand, geometric analysis of tool shape (geometric morphology) makes it possible to quantify the shape of a structure from reference points defined in Cartesian coordinates (landmarks), so that the shape and size of an object can be studied independently.

The main factor involved in shape variation is elongation, followed by the position of maximum thickness. Nonetheless, electrodermal activity is apparently not influenced by general tool shape. Specifically, the size, weight and basic morphology are the principal features eliciting electrodermal reactions.

Therefore, electrophysiological reaction is more sensitive to specific physical features of the tool than to its general outline”, states Maria Silva, lead author of this paper.

Brain-body-object integration

In recent years, the cognitive sciences are putting forward theories which interpret technology as an integrating element of the mental process, rather than as a passive product of this process. In fact, the regions of the cerebral cortex involved in brain-body-object integration are particularly well-developed in the primates, and above all in humans.

“Studying emotional reactions to the hand-object interaction can tell us of variations in perception associated with changes in the influence of technology on our cognitive organization”, affirms Silva.

There are an increasing number of interdisciplinary studies combining archaeology and psychology with a view to understand our behavior. This paper, on which the neuromarketing company Sociograph of Valladolid and the Centro de Arqueología Experimental de Atapuerca (CAREX) collaborated, is the third in a series which the Palaeoneurology group led by Emiliano Bruner has published in this journal.