Arnaud Badets

Recent studies have demonstrated that conceptual and abstract knowledge could rely on and could be influenced by sensory-motor processing of usual goal-directed actions. In line with this, interactions have been reported between number magnitude and finger grip with, for example, small-magnitude numbers priming grip closure and large-magnitude numbers priming grip aperture. Here, we assessed whether observing a closing or opening grip was able to influence the magnitude of the numbers produced in a random number generation task, and we tested whether this effect was specific to biological hand actions by using non-biological fake hands with the same closure or aperture amplitude. The participants were asked to produce as randomly as possible numbers between 1 and 10 after they observed a change in posture (i.e. grip closing or grip opening) or in colour (i.e. red or blue hand). The results revealed that the participants produced more often small numbers than large ones after observing a grip closing, whereas they produced equally often small and large numbers after observing a grip opening or colour changes. Importantly, this effect was only present for the biological hands but not for the non-biological fake hands. This finding demonstrates that observing a biological grip closing conveys small-magnitude information, which, in turn, influences the mental selection of a numerical response. We discuss our results in the light of the internal random generator process proposed in the domain of numerical cognition and argue that number semantics is stored with a code governed by sensory-motor mechanisms.

Besides language, the contribution of Broca’s area to motor cognition is now widely accepted. In this study, we investigated the role of its posterior part (left Brodmann area 44) in learning of a motor sequence by altering its functioning with a continuous theta-burst transcranial magnetic stimulation (cTBS) in 12 healthy participants before they learned the sequence by observation. Twelve control individuals underwent the same experiment with cTBS applied over the vertex. Although cTBS over Brodmann area 44 did not impair sequence learning, it significantly increased the response latency as measured during the retention test, performed 24 h later. This finding suggests that Broca's area might be critically involved in organizing, and/or storing, the individual components of a motor sequence before its execution.

The present study aimed at testing, by means of a response–effect compatibility paradigm, whether finger–numeral representations derived from finger counting may underlie simple arithmetic problem solving in adults. Participants were asked to provide a verbal response to simple additions, which triggered the presentation of the correct (Experiment 1) or an incorrect (Experiment 2) response, displayed either as a configuration of fingers or as a series of rods. Answers were faster with finger configurations than with rods, and only when the finger configuration showed the correct result. These findings support the idea that, even in adults, simple arithmetic operations are still unconsciously underlain by finger–numeral representations.