Lesson 14: Probability Overestimation

The previous lesson looked at the tendency to jump to the worst outcome. This lesson focuses on a related bias: overestimating how likely that outcome is. Anxiety doesn’t just make you think about bad things — it makes bad things feel probable.

Module: 5, Working with behavior

Learning objective

By the end of this lesson, you should be able to explain probability overestimation, understand why anxiety distorts likelihood judgments, and use practical techniques to recalibrate.

The concept: when anxiety inflates the odds

Research from the early 1980s showed that anxious individuals consistently rate negative events as more likely to happen to them than non-anxious individuals do. Crucially, this bias was specific to personally threatening events — anxious participants didn’t overestimate the likelihood of negative events happening to other people [1].

This makes sense if you consider what anxiety does to information processing. An information-processing model of anxiety describes how threat-relevant material is prioritized at every stage: attention, interpretation, and memory [5]. When threat-related information is more accessible, it feels more probable. This is the availability heuristic in action: the easier it is to imagine something, the more likely it seems.

Two biases working together

Probability overestimation rarely works alone. It often pairs with catastrophizing from Lesson 13:

Bias	What it does	Example
Probability overestimation	Inflates how likely the outcome is	“There’s a good chance the plane will crash”
Catastrophizing	Inflates how bad the outcome will be	“If there’s turbulence, the wing will snap off”

Together, they create a distorted picture: a terrible thing that feels almost certain. Correcting either one reduces the overall threat estimate.

Why the bias persists

Anxiety creates a feedback loop that maintains the overestimation:

• Avoidance prevents correction. If you avoid flying because you believe it’s dangerous, you never accumulate the evidence of safe flights that would correct the estimate. This connects directly to the avoidance cycle from Lesson 10.
• Emotional reasoning reinforces it. “I feel terrified, so it must be dangerous” — a pattern Arntz described as ex-consequentia reasoning [2]. The intensity of the emotion is taken as evidence for the probability.
• Selective attention confirms it. You notice the turbulence article in the news and skip the safety statistics.

Recalibrating: practical exercises

1. The evidence test

For a specific feared outcome, list:

• Evidence that it will happen.
• Evidence that it won’t.
• How many times you’ve been in similar situations and the feared outcome didn’t happen.

2. Base rates

Where possible, look up the actual statistics. Fear of flying? The odds of a fatal accident are roughly 1 in 11 million flights. Fear of public speaking going catastrophically wrong? Ask how many presentations you’ve attended where someone collapsed or was ridiculed.

3. The prediction log

Keep a notebook. Each time you notice a probability overestimation, write down the predicted outcome and your estimated likelihood. A week later, check what actually happened. Over time, the log builds concrete evidence of how often your predictions are wrong.

A worked example

The following is a fictional example used for teaching.

Fatima has a medical appointment next week. She’s convinced the doctor will find something seriously wrong. She estimates the probability at “about 70%.”

Using the evidence test:

• Evidence for: She’s had a headache for a few days.
• Evidence against: She’s had similar headaches before that resolved. Her last check-up was normal. She has no other symptoms.
• Base rate: Most headaches are tension-type or migraine, not signs of serious illness.
• Prediction log: She reviews three previous times she was convinced something was wrong. Each time, the appointment was routine.

Revised estimate: “Maybe 5–10%, and probably worth checking but not worth three days of dread.”

A common misunderstanding

“Thinking about probability means I’m dismissing my feelings.” Recalibrating a probability estimate doesn’t invalidate the emotion. The anxiety is real. The technique questions the accuracy of the prediction, not the legitimacy of the feeling. Foa and Kozak described how exposure to corrective information updates the fear structure without denying the original experience [3].

Optional reflection

Pick a feared outcome you’ve been overestimating. Write down your estimated probability (as a percentage). Then list the evidence for and against, and check if any base rate data is available. Re-estimate. Notice the difference.

When to get support. If overestimated probabilities dominate your daily decisions — you avoid travel, medical appointments, social events or work because of inflated risk estimates — a therapist can help you test these predictions systematically through behavioral experiments. If you are in crisis, contact emergency services or a crisis line: in the UK and Ireland, Samaritans on 116 123; in the US, call or text 988.

Recap

• Probability overestimation is the tendency to judge feared outcomes as more likely than they are.
• It is specific to personally relevant threats and maintained by avoidance, emotional reasoning and selective attention.
• Recalibrating involves examining evidence, checking base rates, and keeping a prediction log.
• The bias often pairs with catastrophizing: one inflates likelihood, the other inflates severity.
• Correcting the estimate doesn’t dismiss the feeling — it questions the prediction.

Previous lesson: Lesson 13: Catastrophizing and Decatastrophizing | Next lesson: Lesson 15: Thought Records