top of page

Better Memory by Ice Bath

Updated: Feb 4

How cold plunge activates surprise reflex to boost the brain during training


  • Opera singer Daniel Brevik discovered he can improve his memory by doing ice baths after his practice sessions.

  • The mechanisms of memory enhancement rely on neurotransmitters and glucocorticoids expressed during a stress response.

  • Evolution has prepared humans to consolidate short-term memories when experiencing trauma, surprise, or other strong emotions.

  • An ice bath after strenuous cognitive work may improve acquisition of new knowledge by making the practice experience more memorable.

Opera from the ice bath

The other day I got a surprising notification from Instagram saying I'd been tagged on a comment by award-winning opera singer and vocal coach Daniel Brevik.

Big Brev, as he's known on Insta, was posting videos of himself singing pop songs while submerged up to his neck in a chest freezer. I'd never seen anything like it, so I asked him for a phone call.

Brevik told me he heard something on an Andrew Huberman, PhD podcast about trauma and memory, so he thought he'd start doing ice baths after his opera rehearsals to see if that would improve his memorization.

He said:

In opera, we have so many things to memorize. There are the lines and the music, but also the blocking, the foreign language, the translation of that language, and the direction we're getting. Well, when I was in college I was in a car crash and I remember every detail of the events that led up to that crash -- just like I remember what I was doing on 9/11. There's something about trauma that improves memory. When I get in the ice bath, I feel a lot of adrenaline -- so after a coaching or practice session, I get in the ice bath (to see if that improves my memory). - Daniel Brevik (personal communication, 2023).

Brevik reports that his memorization happens much faster since he adopted the ice bath practice. He no longer needs separate sessions dedicated just to memorizing the libretto (lyrics) and he feels like his retention from his sessions now is way better.

Emotional arousal & memory

Brevik's intuitions about trauma and memory are supported by scientific studies that confirm his experience -- and there are good evolutionary biological reasons for it.

In Ice Bath for PTSD I wrote about the difference between stress and trauma. Not all stressors are traumatic. Trauma is an unresolved, overwhelming emotional state -- i.e., a powerful experience that never gets discharged (e.g. Lane et al. 2015). For example, a stressful situation that traps or immobilizes a victim is much more likely to create trauma and result in PTSD than a stress from which the victim can run or fight back. That's because when we're helpless, the stress has no somatic release from our bodies. Metaphorically, the stress becomes trapped inside our brain just like we were trapped inside the stressful experience.

Evolution has programmed human brains for what Freud called "the compulsion to repeat" -- i.e., an involuntary, unconscious urge to reconstruct the circumstances of trauma to replay the situation from a position of control and resolve it to a satisfactory outcome. It doesn't matter to the cells in our body if the reconstructed trauma is in our imagination, such as in talk therapy or improvisational theater, or in a real life revenge scenario. What's most important is that the brain re-experiences the feeling of helplessness that created the trauma, and resolves it by obtaining control.

In romantic relationships, this is called imago theory (Hendrix 2007). That is, it describes the common phenomenon in which we select romantic partners that unconsciously remind us of the abandonment, neglect, abuse, or pain we suffered at hands of a caregiver -- typically (but not always) an opposite-sex parent. When we find someone our brain recognizes as an opportunity to relive our relational trauma from a position of control that (we hope) will resolve the trauma we experienced as children. that special feeling is called Relationship Chemistry. As you can imagine, it leads to power struggles when each person in the relationship is unconsciously trying to control their partner's behavior.

But from the perspective of memory, you can probably understand why evolution would select for those among our ancestors that could best remember the details that led up to a traumatic experience. The emotional arousal of trauma has a way of consolidating memories from short- into long-term so that every sensory perception remains in vivid recall. The implication is that the sounds, scents, feelings, or other experiences you had before the traumatic experience can be mapped onto your autonomic fight-or-flight activation to ensure that you do not encounter that dangerous situation again. Thus, the compulsion to repeat is an attempt to better understand our circumstances and regain a sense of agency over a situation in which we felt powerless.

When a trauma victim becomes hypersensitive to the sensory perceptions encoded by their trauma, any perception that is unconsciously reminiscent of the trauma can trigger an Emotional Flashback. During a flashback, the victim will not be able to distinguish imagination from reality. That is, when triggered they will experience the same emotions as the original traumatizing situation, regardless of whether their current experience really poses a similar danger.


The negative emotions associated with trauma are not the only ones that sharpen our memory. For example, I still remember my first kiss. Maybe you do, too.

If yours was like mine, the memory of your first kiss was joyful, not traumatic.

The fact is that any stress-related emotional arousal can improve memory, whether that's positive or negative, and one of the best emotions for creating memorable experiences is surprise.

In my role as an engineering professor at Arizona State University, I do a lot of research for the military. I recently completed a new paper on what happens to personnel at military installations under conditions of surprise.

Here's an excerpt from that research paper:

When confronted by surprise, a cascade of reactions in the autonomic nervous system interrupts attention, opens perception, and creates conditions that heighten sensory awareness. For example, expressions of surprise often include raised eyebrows, a slack jaw, perking of the ears, and open body language. Although these are not always visible, other physiological markers are reliably present, including increased heart rate, perspiration, and cortisol release (Ekman & Oster 1979, Souza-Talarico et al. 2011, Noordewier & Van Dijk 2019). The fact that surprise is observed in all human cultures suggests it is an innate (rather than learned) instinctive response with origins in evolutionary biology. Psychologists describe surprise as a “basic” human emotion, like anger, fear, sadness, enjoyment, and disgust (Ekman 1992). These responses happen automatically – i.e., without thought, training, or pre-meditation – suggesting that they have their origins deep within the nervous system and have been guided by evolutionary/reproductive selection pressures. For example, research in cognitive psychology shows that an amplified emotional state improves memory. Thus, the surprise response might prepare and motivate the human psyche to investigate and understand novel conditions, thereby accelerating the rate at which false beliefs can be updated to create new expectations that persist in memory. To the extent that surprise accelerates learning, it may be critical to evolutionary success. - Seager et al. (2023).

The surprise response (sometimes called surprise syndrome) is triggered when our experience is discordant with our expectations. In that moment, our attention is interrupted and our autonomic nervous system opens up our senses for greater perception. Our eyebrows raise involuntarily and we often pull our head back so we can better see. Our mouths open wide, jaw agape, and we gasp so we can better smell and taste the air. Even our hands and limbs typically open wide to open up our bodies to the new experience.

A young Judy Garland, as Dorothy in the Wizard of Oz (1936), portrayed the typical surprise response when she took her first tentative steps in the technicolor world of Oz and delivered one of the most famous lines in 20th century pop culture, "Toto, I have a feeling we're not in Kansas anymore."

The evolutionary purpose of surprise is to gather new information for updating our beliefs (e.g., expectations) as fast as possible. For example, it takes Dorothy about two minutes of wandering around Munchkinland to conclude "We must be over the rainbow." In the movie, she is called upon to integrate every new experience into this single, sense-making sentence, or she would never be prepared for the adventures that are yet to come in Oz.

Surprise can have positive or negative emotional valence. For our ancient ancestors, it didn't matter whether the surprise was a hidden blueberry patch or a sudden bear attack.

Surprise is an autonomic nervous system response that primes the brain for learning.

The evolutionary purpose of surprise is to prepare our brains for a better understanding of new situations. The emotional arousal of surprise sharpens our awareness and consolidates our recent experiences into long-term memory so that we can learn faster and be better prepared the next time we're confronted with similar sensory cues.

Feeling surprised is intrinsically related to the acquisition of new knowledge. - Hu & Chen 2019.


I call the successful resolution of surprise the resilience response in my research for the Navy. However, it is not the only possible outcome.

There is also the shock response. In shock, our senses shut down and we often deny the experience. You know someone is in shock when they say things like "This can't be happening!"

It is happening, but when a person is in shock, they defend their old, outdated misconceptions against their own experience. The shock response typically devolves into blaming and scapegoating others, and when it is observed in military situations it almost always makes conditions worse.

Ice bath brain

To Brevik's credit, he realized that the ice bath excites the autonomic nervous system and creates a state of emotional arousal. That is, you don't have to be traumatized or surprised to initiate the fight-or-flight responses within your body. The cold will do that for you, as long as the temperature is cold enough to frighten you.

When thermoreceptors in Brevik's skin sense the cold water, they signal an emergency to the hypothalamus in his brain, which then works through the central nervous system to prepare his body for fight-or-flight. His liver releases glycogen into the blood stream, temporarily spiking his blood sugar to ensure that his muscles have the fuel they need to power escape from what his hypothalamus thinks is a life-threatening danger. Moroever, Brevik's brown fat will receive signals to begin burning excess blood sugar and triglycerides to create heat for defending his core temperature. His norepinephrine, dopamine, and oxytocin levels all spike, and his heart will typically beat faster.

These cold shock responses happen in all of us, because it is how our bodies are hard-wired to keep us safe from harm.

Norepinephrine, in particular, enhances neuroplasticity.

A surge of norepinephrine before, during, or after encoding enhances synaptic plasticity at norepinephrine hotspots, triggering local protein synthesis processes that enhance selective memory consolidation. - Mather et al. 2016.

In other words, Brevik discovered that the ice bath stimulates endogenous production of the stress-related neurotransmitters that enhance memory.


Hans Selye, PhD, MD is credited with inventing the concept of stress as we understand it today and identifying its biochemical markers in the body. He was among the first to recognize that cold exposure elicits a general stress response that elicits a neuro-physiological response. For example, in Ice Bath Stress: Resilience I explained how psychologists use the cold pressor test to observe their patient stress response. That may be why I often get reports from ice bathers who experience a powerful, non-specific emotional release during their plunge. Sometimes, people write to me to say they they were sobbing uncontrollably while in the water, and is that OK?

It sure is OK. It's what your body is programmed to do.

If it's your first time in the cold, you will probably experience a cold shock response. That is, you might not believe you're doing this! At that moment, it will help to remind yourself that "This is what cold feels like."

Then, as you structure your breathing, you calm your body down. Your heart rate will drop back down and typically your gasp reflex subsides.

With experience, you become calm in the cold. In other words, you resolve the stress of cold exposure by regaining control.

Brevik says that when he first started his ice bath practice, he couldn't relax enough to sing. First, he needed to be able to deal with the stress of the cold, learn to control his breathing, and keep himself calm enough to control his voice.

Now, he takes requests. He's convinced that singing in the ice bath better prepares him to deal with the anxiety of performance. He reports that still gets excited when he's going on stage, but he doesn't get scared anymore. Instead, he recalls the sense of calm he constructed while cold plunging.

Also, it's important to know that Brevik doesn't do his opera practice in the ice bath. That's not the way that emotional arousal sharpens our memory. In fact, the biochemical release that helps us consolidate recent experiences into memory can also temporarily block the recall of other things we've already memorized. That's why we can't do crosswords puzzles or math problems while we're in the ice bath.

Human brains have evolved to consolidate the memory of everything that happened just before an activating experience, so that we can better recall the circumstances that preceded our stress. For Brevik, the ice bath prepares the brain to store everything he was memorizing in his opera practice just before he goes into the ice bath.

Although I wrote about the long-term benefits of ice baths for the brain in Cognition & Cold Exposure, and I've written about the short-term benefits of pre-cooling your exercise with cold exposure in Precool Your Workout, Brevik is the first person to discover that post-cooling your study session is likely to improve memory and speed learning.

His experience has me wondering, could ice baths help other performers? Could football players improve their retention of the playbook if they went straight from the classroom to the ice bath? Could my students improve their exam scores if they studied right before an ice bath? Or might I better consolidate the material I'm reading if I follow up my own research sessions with a plunge?

I know how to find out.


  • Ekman P. An argument for basic emotions. Cognition & emotion. 1992 May 1;6(3-4):169-200.

  • Ekman P, Oster H. Facial expressions of emotion. Annual review of psychology. 1979 Feb;30(1):527-54.

  • Hendrix H. Getting the love you want: A guide for couples. St. Martin's Griffin; 2007.

  • Hu G, Chen L. “To our great surprise…”: A frame-based analysis of surprise markers in research articles. Journal of Pragmatics. 2019 Apr 1;143:156-68.

  • Lane RD, Ryan L, Nadel L, Greenberg L. Memory reconsolidation, emotional arousal, and the process of change in psychotherapy: New insights from brain science. Behavioral and brain sciences. 2015;38:e1.

  • Mather M, Clewett D, Sakaki M, Harley CW. Norepinephrine ignites local hotspots of neuronal excitation: How arousal amplifies selectivity in perception and memory. Behavioral and Brain Sciences. 2016;39:e200.

  • Noordewier MK, van Dijk E. Surprise: unfolding of facial expressions. Cognition and Emotion. 2019 Jul 4;33(5):915-30.

  • Seager TP, Pesicka EA, Eisenberg DA, Alderson DL. Infrastructure resilience to surprise. Prepublication draft. 2023.

  • Souza-Talarico JN, Marin MF, Sindi S, Lupien SJ. Effects of stress hormones on the brain and cognition: Evidence from normal to pathological aging. Dementia & Neuropsychologia. 2011 Jan;5:8-16.


About the Author

Thomas P Seager, PhD is an Associate Professor in the School of Sustainable Engineering at Arizona State University. Seager co-founded the Morozko Forge ice bath company and is an expert in the use of ice baths for building metabolic and psychological resilience.

497 views0 comments

Recent Posts

See All


bottom of page