Tuesday, 24 May 2016

Study of firefighters shows our body schema isn't always as flexible as we need it to be

The results could help explain some of the many injuries
incurred by firefighters each year
Your brain has a representation of where your body extends in space. It's how you know whether you can fit through a doorway or not, among other things. This representation – the "body schema" as some scientists call it – is flexible. For example if you're using a grabbing tool or swinging a tennis raquet, your sense of how far you can reach is updated accordingly. But there are limits to the accuracy and speed with which the body schema can be adjusted, as shown by an intriguing new study in Ecological Psychology about the inability of firefighters to adapt to their protective clothing.

Indeed, the researchers at the University of Illinois at Urbana-Champaign and the Illinois Fire Service Institute believe their findings may help explain some of the many injuries sustained by firefighters (of which there were over 65,000 in 2013 alone), and that they could have implications for training.

The participants were 24 firefighters (23 men) with an average age 29 and an average of 6 years experience in the job, all of whom were recruited through the University of Illinois Fire Service. The researchers led by Matthew Petrucci asked the participants to don the full protective kit, including bunker-style coat, helmet and breathing apparatus. As well as the weight and bulk of the gear affecting the participants'  ability to move freely, it also changed the participants' physical dimensions – for instance, the helmet added 21cm to their height, and the breathing apparatus added 21cm of depth to their body.

The researchers created three main obstacles designed to simulate situations in a real-life fire: a horizontal bar that the firefighters had to go under, a bar that they had to go over, and a vertical gap between a mock door and wall that they had to squeeze through. All of these were adjustable, and the participants' first task was to estimate what height bar they could manoeuvre over, what height they could manoeuvre under, and what width gap they could squeeze through. To make these judgments, the researchers adjusted the obstacles' in height or width, and for each setting the firefighters said whether they thought they could safely pass the obstacle.

For the next stage, the firefighters actually attempted to manoeuvre over, under or through the different obstacles, which were adjusted to make them progressively harder to complete. The idea was to find the lowest, highest and narrowest settings that the firefighters could pass through safely and quickly. To count as a safe passage, the firefighters had to avoid knocking off the delicately balanced horizontal bar for the over and under obstacles, and avoid touching their hands to the floor, or dumping their gear.

Despite having many years experience wearing protective gear and breathing apparatus, the results showed that there was little correspondence between the firefighters' judgments about the dimensions of the obstacles they could safely pass under, over or through, and their actual physical performance. In psychological jargon, the firefighters made repeated "affordance judgment errors", misperceiving the movements "afforded" to them by different environments.

The participants' judgments were most awry for passing under a horizontal bar – on average they thought they could pass under a bar that was 15cm lower than the height they could actually go under. Errors related to the over obstacle were a mix of over- and underestimations, and for the through obstacle 80 per cent of participants underestimated their ability by four to five cm – in other words, they thought they couldn't pass through, when actually they could. In a real life situation, this could lead to time wasting or unnecessary danger as they sought a more circuitous route.

The results suggest that the firefighters struggled to adjust their body schemas to account for their gear, and it's easy to see how this problem could lead to accidents in a burning building. It seems strange that they hadn't learnt to take account of their gear through experience, but in fact the converse was true – the more experienced firefighters made more errors. The researchers propose several explanations for this, including that specific experiences may be needed to recalibrate the body schema to specific obstacles. Also, the firefighters training in manoeuvring in their gear mostly comes at the start of their career and the benefits may have faded. Refresher training may be helpful, especially to learn one's changing capabilities with ageing.

The researchers said that their results were important because "affordance judgment errors made on a fireground could contribute to injuries attributed to contact with ceilings, doors, structural components of buildings, and other objects with slips, trips, and falls."

_________________________________ ResearchBlogging.org

Petrucci, M., Horn, G., Rosengren, K., & Hsiao-Wecksler, E. (2016). Inaccuracy of Affordance Judgments for Firefighters Wearing Personal Protective Equipment Ecological Psychology, 28 (2), 108-126 DOI: 10.1080/

Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.

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