Availability Heuristic
People judge how likely something is by how easily an example comes to mind, which favours the recent and the vivid.
Definition
Tversky and Kahneman (1973) described the tendency to estimate frequency or probability by the ease with which instances can be recalled. Memorable, recent and emotionally charged events are over-weighted.
Established research. Originates in published research and has been replicated. The effect is real. Its size in your product still needs measuring.
On this plate
Reach for this when
- Prioritising bugs and features.
- Synthesising research.
- Evaluating risk.
- A prioritisation meeting is being driven by what people remember rather than what they measured.
Common mistakes
- Acting on the most recent input.
- Reporting behaviours without frequencies.
- Confusing vividness with prevalence.
It distorts prioritisation more than it distorts users
The most consequential appearance of this bias in product work is internal. The bug reported yesterday by a senior stakeholder feels more urgent than the one affecting thousands of users silently. The complaint that arrived vividly outranks the pattern in the data.
The countermeasure is to make the base rate as available as the anecdote: put the numbers next to the story in every prioritisation discussion.
Practical responses
- Pair every anecdote with its frequency before deciding anything.
- Keep a standing dashboard of the top recurring issues so they are as available as the newest one.
- In research readouts, state how many participants exhibited a behaviour, not just that it occurred.
- Be suspicious of the phrase 'users are saying', and ask how many.
Keeping it out of prioritisation
Do
- Count how many people hit an issue before ranking it.
- Keep a written backlog with dates, so old evidence does not fade against new noise.
- Ask how common this is before asking how bad it sounded.
- Weight a vivid report as one observation, which is what it is.
Do not
- Reprioritise on the strength of the most recent complaint.
- Treat a memorable session as representative of the sample it came from.
- Let the loudest customer set the roadmap and call it customer focus.
In practice
- i.
The loudest bug
PrioritisationA vividly described issue affecting a handful of users routinely displaces a quiet issue affecting thousands. Attaching frequency data to every incoming report is the structural fix.
- ii.
Research recency
Research synthesisThe last session watched disproportionately shapes the readout. Coding all sessions before synthesis, rather than writing from memory, corrects for it.
- iii.
The bug from the demo
Recency and vividnessA crash seen once during a leadership demo outranked an issue affecting four percent of sessions daily for two sprints. Nothing about the comparison was written down, which is precisely how the heuristic wins.
Local chart
BIAS·011 · Region I · Grid A1
This entry and the entries it is stated to connect with. Each line is labelled with what the connection means.
Sources
Where a source establishes something narrower than the popular reading of it, the note says so.
- [1]
Availability: A heuristic for judging frequency and probability
A. Tversky and D. Kahneman, Cognitive Psychology, 1973
The original demonstration that ease of recall is substituted for actual frequency.
Continue from here
Each link says what the connection is, so you can tell a principle from an alternative from a thing people mix this up with.
Applied through
Where this shows up as a concrete interface decision.
- Product AnalyticsRES·010 · Research method
- Research SynthesisRES·014 · Research method
- Prioritising Design WorkFLOW·006 · Workflow
Related concept
Connected closely enough to change how you apply this.
- Confirmation BiasBIAS·009 · Cognitive bias
- Survivorship BiasBIAS·010 · Cognitive bias