Why Scary Experiences Stick

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Think back to a moment that scared you. I will never forget hurtling my then two-year-old daughter towards the pavement as a speeding car came at us. Our pets have these moments too. Like my client, Poppy the Bearded Collie, she was startled by the neighbour’s fireworks, which caused her to become trapped in the hedgerows, resulting in her refusal to enter the garden for weeks. But why do frightening events carve themselves so deeply into memory?

A new review by Tezanos and Trejo (2025) brings together decades of work showing how threatening experiences shape memory. The conclusion is clear: the stronger the fear, the harder the memory is to erase. And far from being useful, this makes fear one of the most damaging forces in an animal’s learning.

Scientists studying memory sometimes use artificial setups where rodents experience mild electric shocks. These laboratory models are designed only to study brain mechanisms of fear. They have never been models for training animals and must never be mistaken as such.

The findings are consistent. Intense fear creates memories that stick and are very resistant to change. For survival, that makes sense. If something is truly dangerous, the brain treats it as unforgettable. The downside is that these memories rarely stay contained. Strong threats tend to spread to safe contexts, a process called generalisation. For an animal, like Poppy the Bearded Collie, although initially frightened by fireworks, she soon began to react fearfully to any sudden noise, including vehicles, rain, and even the sound of the coffee machine. This is trauma, not learning (Dunsmoor et al., 2017; Wiltgen et al., 2006).

What happens in the brain

During a frightening event, stress hormones such as adrenaline and cortisol surge. These act like glue, fixing the memory in place. Brain areas like the amygdala (which processes fear) and the hippocampus (which provides context) become highly active. With stronger threats, additional brain systems also join in, creating a kind of back-up. This makes traumatic memories especially difficult to weaken. Neuroscience confirms this redundancy: even if one chemical pathway for fear memory is blocked, another can compensate. For example, dopamine signalling in the amygdala can take over from stress hormones, keeping the memory intact (Ouyang et al., 2012). The persistence is harmful: the sense of threat lingers even when the animal is safe, preventing relaxation and relearning. This is why using punishment-based training methods is dangerous.

Some argue that because fear creates strong memories, using punishment or shock can make training more effective. The science shows the opposite. These methods do not create reliable learning. They create anxiety, defensive behaviour, and generalised fear that undermines trust and welfare.

In both humans and animals, high-intensity fear has been linked to post-traumatic stress, phobias, and chronic anxiety (Kaouane et al., 2012). Such outcomes are not only unethical, they also exacerbate behaviour problems. No reputable trainer or behaviourist should ever use pain, fear, or intimidation. In the UK, the Animal Behaviour and Training Council (ABTC) exists to prevent exactly that. It sets the benchmark for humane, evidence-based training and behaviour practice, giving pet owners confidence that accredited professionals will safeguard welfare.

The effective alternative is reward-based training. Research across species consistently shows that positive reinforcement builds lasting skills without fear, strengthens trust between animal and human, and reduces the risk of problem behaviours developing later. These approaches protect wellbeing and give both pets and their people the best chance of success.

Humane lessons for practice

So the key takeaways from this latest scientific review, along with the body of research preceding, highlight that we should:

• Always use reward-based training. Positive reinforcement builds behaviour that is reliable and safe without damaging welfare.
• Protect our animals against overwhelming experiences. Plan ahead during fireworks, vet visits, or new events by creating safe spaces and offering comfort.
• Help animals recover gradually. If a scare occurs, use slow, gentle exposure with plenty of positive associations to rebuild confidence, working at your animal’s pace. Science shows that stronger fears are particularly resistant to extinction, so rushing exposure often backfires.
• Rule out pain. Pain makes fear learning even stronger. A veterinary check should always be the first step if behaviour suddenly changes. That’s why clinical animal behaviourists will only work on vet referral to ensure a collaborative and thorough approach is taken.
• Seek the support of an accredited professional. To safeguard both welfare and training outcomes, work with practitioners listed by the Animal Behaviour and Training Council (ABTC). Find your local professional here.

As Tezanos and Trejo’s (2025) review makes clear, fear leaves unusually durable traces in the brain, a consequence of neuroplasticity that cements threat memories and makes them resistant to change. That persistence may once have been vital for survival, but in the context of our pets, it is a liability. It explains why fear-based methods are not only unethical but ineffective, because the very memories they produce are the hardest to undo. Humane, reward-based approaches use the brain’s capacity for change in ways that support confidence, trust, and lasting behaviour. For those seeking help, accredited professionals provide evidence-based guidance that protects both welfare and learning, and will always be ready to explain their methods and the benefits for you and your animals.

References

• Dunsmoor, J.E., Kroes, M.C., Li, J., Daw, N.D., Simpson, H.B. and Phelps, E.A. (2017) Emotional learning selectively and retroactively strengthens memories for related events. Nature Human Behaviour, 1(6), pp.1-10.
• Kaouane, N., Porte, Y., Vallée, M., Brayda-Bruno, L., Mons, N., Calandreau, L., Marighetto, A. and Desmedt, A. (2012) Glucocorticoids can induce PTSD-like memory impairments in mice. Science, 335(6075), pp.1510-1513.
• Ouyang M., Young, M.B., Lestini, M.M., Schutsky, K., Thomas, S.A. (2012) Redundant catecholamine signaling consolidates fear memory via phospholipase C. Journal of Neuroscience, 8;32(6), pp.1932-41.
• Tezanos, P. and Trejo, J.L. (2025) Why are threatening experiences remembered so well? Insights into memory strengthening from protocols of gradual aversive learning. Neuroscience & Biobehavioral Reviews, 162, p.105657.
• Wiltgen, B.J., Sanders, M.J., Behne, N.S. and Fanselow, M.S. (2006) Context fear learning in the absence of the hippocampus. Journal of Neuroscience, 26(20), pp.5484-5491.