Heuristic Traps

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The paper "Evidence of heuristic traps in recreational avalanche accidents" presented at the 2002 International Snow Science Workshop by Ian McCammon gives some interesting insights into the decisions making process in the backcountry. A heuristic is a rule that people apply when they recognize some common pattern in a complex set of data. Analysing avalanche risk a a complex judgement call involving variables such as new snowfall, predominant wind direction and speed, humidity, temperature history, slope gradient and steepness. A heuristic trap is where the backcountry skier ignores this large data set and incorrectly applies a rule of thumb.

McCammon investigated 622 accidents in the United States between 1972 and 2001 and identified four common traps: Familiarity, Social Proof, Commitment and Scarcity. What was surprising was that experienced backcountry users were as likely to be caught by these traps as inexperienced

Familiarity

is where a group is skiing slopes they have skied many times in the past. It seems when we are skiing terrain we know well we let our guard down and ignore warning signs. When groups of experienced and inexperienced backcountry travellers were compared, experienced skiers were at a distinct advantage on unfamiliar terrain where they critically examined available data. On familiar slopes there was no difference between experienced and inexperienced groups. The familiarity heuristic may actually have a sound basis. Slopes that are skied regularly are stabilized by the passage of skiers.

Social Proof

We tend to believe behaviour is correct or can be justified when we witness other people engaged in it. This can range from people crossing piste-closed markings to decisions on whether to ski a slope. McCammon found that social proof affected even groups with significant avalanche awareness where they witnessed groups similar to themselves on a slope.

Commitment

This is the tendency to carry on with a course of action whatever the indications to the contrary. Groups that had a high commitment were trying to achieve a stated goal with the pressure of darkness, timing or weather constraints. These groups were more likely to expose themselves to danger. cf/ Orres and Durrand glacier accidents.

Scarcity

When we perceive resources to be in short supply: Beenie Dolls, Luxury Goods or Powder Snow we tend to compete for them more aggressively. McCammon found that the presence of untracked powder snow within easy reach of other skiers to have a significant effect on the evaluation of risk.

Munter (3x3 method), Bolgonesi (Nivotest) and the Red/Green Light method are attempts to codify risk. For example

• Always use the latest avalanche bulletin
• Set absolute limits: 40 degrees in NW N and NE facing slopes when the danger is moderate, 40 degrees on all slopes when considerable and 30 degrees when the danger is high.
• Spacing out on slopes to reduce the forces on the snow pack and risk of multiple burials
• Evaluate the experience and capacity of the group

Categories: Snow Safety