Distant learning: objects falling slower than expected makes us feel taller

Thursday 28 June 2018

Believe it or not, your hearing has a lot to do with how tall you feel you are according to new research

Our perceptions of our height are based on lifetimes of sensory feedback. But researchers have found that disrupting auditory feedback can confuse us into re-evaluating how tall we think we are.

Sound and object motion can be used to change perceptions of our own bodies, according to a new study by an international team involving researchers from the School of Advanced Study (SAS), University of London. 

The report, published today in PLOS ONE, found that introducing a mismatch between the predicted and actual outcome of an action, such as dropping a ball, can make people feel taller. Taking into consideration the height from which the object is released, the brain can predict with high acuity when it will hit the floor.

The experiment played with this prediction: Participants were handed a ball, which they had to let fall from their head’s height and could not see landing on the floor. Instead, they just heard and felt the impact at their feet, but this took longer than expected. As a result, the brain had to revise its expectations and concluded that the object had fallen from a higher point – which meant from a taller body!

In the study, a collaboration between UCL, Universidad Carlos III de Madrid, NTT Communication Science Laboratories, the University of London, Ludwig Maximilian University, Ritsumeikan University and Yoshika Institute of Psychology, participants were required to drop a ball from head height. The actual sound of the ball dropping was masked and a simulated sound was played at longer and shorter intervals.

Participants were then asked to take a step backwards to an already memorised point and visually estimate their body size. Results show that the time the ball was perceived to have taken to drop to the floor affected participants’ perception of their body height and leg length.

Our brains keep a remarkable and a highly flexible perception of our body size, even beyond the ages when we grow. Previous studies have been able to ‘trick’ the brain to quickly change body representations, making people perceive themselves as taller than they normally do. However, most of them relied on artificial feedback related to one’s own body. This study shows that even objects around us are used to compute our body size. It also shows the surprising role of audition on how we perceive ourselves.

‘These results reveal the surprising importance that sound and movement have on body representation,’ explains lead researcher Dr Ana Tajadura-Jiménez (UCL Interaction Centre and Universidad Carlos III de Madrid).

‘We don’t just feel and see our bodies, we also hear ourselves whenever we interact with solid objects. This is a really promising avenue for applications. Think of clinical conditions where people suffer from chronic pain or other conditions linked to distorted mental body representations such as anorexia nervosa. Making them “hear” themselves differently might sometimes be more successful than directly trying to change how they feel or see themselves.’

Dr Norimichi Kitagawa, one of the researchers from Tokyo's NTT Communication Science Laboratory, adds that, ‘This could also inform the development of technologies for motion controlled games where players take on a larger character on screen.’

Underscoring the importance of the findings, Dr Ophelia Deroy, a research fellow at the Institute of Philosophy at SAS who contributed to the study, says ‘We tend to think that what we know about our bodily selves comes uniquely from the feedback we get from our bodies. That’s an easy assumption – but here, we show that our brains are not so selective, and also use distant objects to learn about the body. It is like distant learning.’

The project was supported by the Economic and Social Research Council (UK), The Nippon Telegraph and Telephone Corporation of Japan, Ministerio de Economía, Industria y Competividad of Spain and the Arts and Humanities Research Council.