Where is the focus of attention? An eye tracking study of stone tools

Abstract

Humans are obligatory tool-users. Our culture and cognition are tool-dependent, and a co-evolution between brain and technology is expected. The parietal cortex is crucial for the integration between body and tools. Simply watching a tool does stimulate the motor cortex and triggers action plans according to its implicit affordances, even when there is no intention to act with it. Also, humans integrate objects in the body scheme when handled. Actually, when a tool is touched, it is included in the personal space and it induces an expansion of the peripersonal space. Traditionally, tools have been interpreted as the output of the evolving cognitive system, while more recent hypotheses suggest that they can be a functional part of the cognitive network. Vision is the first input channelling action and body-environment relationships, particularly influencing attention engagement. We have applied eye tracking technology during visual exploration of Paleolithic stone tools, as to investigate salient their visual features and to find differences between different morphotypes associated with early hominids. Our results suggest that worked pebbles require more attentional burden than handaxes. The main focus of attention concerns the center of the upper half of the tool for the former technology, and on the midline for the latter. Attention is influenced by the width of the base in worked pebbles, and by the oval shape in handaxes. Knapped surface triggers more attentional exploration than natural cortex. These visual patterns are directly related to the tool’s affordances, and can supply information on the brain-tool evolutionary relationships.