Body Schema Experiment Wrap-Up: What Happens in Your Muscles During Pinocchio Illusion?

— Written by Milica Manojlovic —

Aaaand the results are in!

So, just a quick recap – we were hoping to get as much data on the way we process the Pinocchio illusion by measuring different behavioral outcomes as well as the EMG in three timepoints. As far as the behavioral measures are concerned, we questioned participants on the illusion vividity (see my introductory blog post!), the extent of the nose elongation as well as through a recently published Pinocchio questionnaire (Prucell et al., 2021). On the neural side, we were comparing the EMG activity on the biceps and triceps between resting state, state of the illusion and the situation where the participants were actually instructed to contract the muscles. 

Firstly, we found that all the participants reported sensation of the illusion and described it as moderately vivid – the average score was 2.6 on the five-point Likert type scale. They felt their nose extending by at least 50% and the questionnaire data suggest that sensations regarding arm tingling, nose and arm elongation represent the best predictors of the illusion vividity, whereas nose widening, pulsation in arm/nose/fingers or tingling in nose and fingers turned out to be less relevant. 

When it comes to EMG data, we found comparable results on the biceps and triceps. As shown in figure one, there were a lot of EMG spikes while the muscle was actually contracting and almost none during the resting state. As expected, the signal recorded while participants were sensing the illusion resembled the resting state recordings. This implies that the illusory effect happens completely due to cortical processing of the illusion rather than muscle activity per se.

Lastly, during this internship we created a mini conference presented our findings to the public and the press by making posters that depict the project. Figure 3 shows the poster regarding the Pinocchio illusion, hopefully you like it!