Blips and Biases…How your emotion and memory don’t work so well!

The last couple of weeks have seen a number of fatalities which some have said is unprecedented and that something should be done about improving diving safety because ‘divers are dropping like flies’.

The human psyche is a funny thing and we have a number of cognitive biases which help us survive and save time but they can also confuse us a little. Fundamentally, there is not enough time to think through every problem, so we try to take short-cuts through our memory and decision making to help us get to a decision quickly.  

Recency Bias. Recency Bias is where community participants evaluate their future performance based on recent results or on their perspective of recent results and make incorrect conclusions that ultimately lead to incorrect decisions about how the environment or risk behaves. 

Recall Bias. Recall bias is a systematic error caused by differences in the accuracy or completeness of the recollections retrieved (“recalled”) by study participants regarding events or experiences from the past.  Therefore , if we are exposed to social media (Facebook, Twitter, Forums, Newsfeeds from Media Outlets) which shows diving fatalities, we might think it happens all the time, but what about the hundreds of dives which take place without incident or accident? 

Small Number Bias: This is where we think we try to extrapolate from what we know now into the future, but the numbers we have are so small (1s, 2s, 3s etc) such that if they only increase by one, we think there is a major shift and yet it might just be noise.

Truisms:  This is where something is repeated so often that it becomes truth, even when there is no evidence to back it up.

  • Nitrox reduces narcosis, no it doesn’t, O2 is more narcotic than N2 but we metabolise it.
  • Reverse dive profiles are bad for you, no they aren’t (as long as you stay within recognised limits).  
  • There is a peak of fatalities in the spring because people are not prepared…

…and that leads onto the image below.  I went went through the 2000-2013 BSAC Annual Reports plus what data I have for 2014 and produced the following graph (click on it to get a larger image).  The raw data is available to download from here.   

Screen Shot 2014-09-02 at 20.37.45

Looking at the individual months themselves (also in the spreadsheet), the following data comes out of the 179 months examined with a total of 224 fatalities (some data from Nov 13 to Sep 14 might be missing). Months with:

  • Zero fatalities – 74 months, 41.3%
  • 1 fatality – 44 months, 24.6%
  • 2 fatalities – 30 months, 16.8%
  • 3 fatalities – 18 months, 10.1%
  • 4 fatalities – 6 months, 3.4%
  • 5 fatalities – 6 months, 3.4%
  • 6 fatalities – 2 months, 1.1%

Note that it is not possible to determine when in a month an incident occurred from the annual reports, therefore a rolling month value might be higher than a calendar month value.

So you can see, there is a spread of incidents throughout the year. More diving, more likelihood for incidents. Ageing population, more likelihood of health related issues in diving. Either way, the risk is relatively small but you, as the diver, are in control of mostly what happens and that there are very few fatalities which could not be prevented by a proactive approach to improved skills, knowledge, preparedness, situational awareness or decision making.  Human error is a cop-out term! We, as divers are part of system which includes peers, instructors, their equipment and the environment.

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Safe Diving…


2 responses to “Blips and Biases…How your emotion and memory don’t work so well!

  1. Personally I think this re-enforces the need for agencies to limit certifications, c-cards should NOT be for life, and renewals requiring a medical would help with the aging diver population health risks…
    Steve Craig-Murray, CEO ITDA Group International

  2. C-card renewal sounds nice but would have no effect. The dive industry is self-regulated in the US; there is no requirement to even be certified before scuba diving. There’s no way to validate the medical form so if the individual wants to dive he/she is going to dive. The best way to insure safer diving is to encourage divers to continue training. Practice basic skills as part of your dive club activities, service your gear and never dive solo.

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