Meditation practices have become mainstream tools for treating and preventing mental health problems. ‘Contemplative psychotherapies’ like Mindfulness Based Cognitive Therapy and Compassion Focused Therapy are effective treatments for a range of neuropsychiatric conditions, including depression, addiction and posttraumatic stress disorder. However, anyone who has tried to meditate will know that it can be hard work, requiring persistence and dedication. Given this, it is important to prevent novices from becoming demoralized as a result of perceived failures (e.g. misconstruing a tendency for mind-wandering as an ‘inability’ to meditate). Strategies for preventing such demoralization – for example, by boosting the early response to meditation – would be a welcome development for therapists and patients alike. In addition, people who meditate for general well-being and self-improvement may also want access to methods that produce greater or faster benefits from meditation.

Biohacking meditation

One increasingly popular, cost-effective and accessible method for hacking brain functioning is neurostimulation. Various non-invasive, direct-to-consumer devices purport to improve psychological functioning by delivering weak and painless electrical pulses to the scalp that modify brain function. One form of this technology, transcutaneous vagus nerve stimulation (tVNS), stimulates a peripheral nerve—the vagus nerve —rather than the brain itself. It does this by activating nerve fibres that pass close to the skin surface of the outer ear, such as the cartilaginous flap just outside the ear canal (the tragus).

The vagus nerve plays a crucial role in the ‘rest-and-digest’ (parasympathetic) system, counteracting the ‘fight-or-flight’ (sympathetic) stress response. It connects the brain and body, allowing the brain to communicate with and regulate all the major organs in the body, while also sending signals about the body’s state back to the brain. These upward projections to the brain also allow the vagus nerve to regulate a range of psychological processes, including those involved in promoting social interactions and emotional control. For example, activation of the vagus nerve is thought to induce physiological states of calm, which are necessary for positive social interactions (e.g., friendliness, kindness, playfulness). These prosocial tendencies can also be directed inwards, towards the self, in the form of self-soothing and self-compassion. These capabilities are a potent antidote to self-critical thinking and shame, and protect against depression, anxiety and general human misery.

Researchers have suggested that the capacity for (self-)compassion relies on the calming influence of the vagus nerve. For example, psychological tasks or exercises designed to increase feelings of (self-)compassion are associated with higher heart rate variability (HRV), which is (supposedly) an indirect marker of the activity of the vagus nerve.

However, this notion of a ‘compassionate vagus‘ has not yet been tested experimentally by stimulating the vagus nerve directly (i.e. transcutaneously). If enhanced vagal activity causes compassionate feelings, stimulating the vagus nerve using tVNS should be sufficient to increase such feelings. Alternatively, if activation of the vagus nerve creates an optimal physiological state in which compassionate feelings can emerge, then tVNS might boost the effects of a compassion meditation training but have no effect on compassionate responding on its own. This question has potentially important implications for augmenting contemplative therapies.

The ear as a compassion-amplifier?

Our recent study with 120 healthy adults set out to test the idea that tVNS could boost the effects of compassion meditation training. Participants were randomly assigned to receive either real tVNS, which involved electrically stimulating the tragus (part of the outer ear), or a sham (placebo) stimulation in which electrical pulses were delivered to the earlobe. These were combined with one of two forms of mental imagery training: a self-compassion meditation (Self-Compassion Mental Imagery Training; SC-MIT), or a control mental imagery training not designed to promote compassion. We wanted to know whether combining tVNS with SC-MIT would produce stronger psychological and physiological effects than either SC-MIT or tVNS alone. We measured participants’ state self-compassion, self-criticism, mindfulness, heart rate variability (HRV), and how their eyes responded to compassionate facial expressions—a measure of the attention they paid to compassionate stimuli in the environment.

One of the promising findings was that participants who received tVNS alongside SC-MIT experienced a larger and more immediate increase in self-compassion than those in the other three groups. This effect was observed during the very first session and was also reflected in increased mindfulness. In fact, the benefits on participants’ states of mindfulness accumulated across multiple sessions, suggesting that while some effects of stimulation and training are immediate, others build over time.

On the other hand, self-criticism – the negative internal voice that many people struggle with – was only reduced with SC-MIT, regardless of the type of stimulation (tVNS or sham). This highlights an important point: while tVNS can enhance some aspects of contemplative practice, it’s not a cure-all, and specific psychological content still matters.

One initially surprising result was that heart rate variability (HRV), a physiological marker often used to assess vagal activity, was unaffected by tVNS or SC-MIT. ‘Negative’ findings like this are often difficult to interpret, but after reviewing related literature, we discovered that this null result was not at all unusual: overall, tVNS studies do not show changes in HRV.

Eyes as Windows to the Heart?

An additional novel aspect of the study involved tracking where participants looked when shown compassionate and neutral facial expressions. This oculomotor attentional bias—essentially, how drawn our eyes are to compassionate cues—was influenced by the type of training participants received. Those who engaged in SC-MIT spent more time looking at compassionate faces, and their pupil size was larger in response to these faces, regardless of whether they received tVNS or sham stimulation.

This type of eye-tracking data might be a powerful new tool for assessing the impact of compassion training, offering an objective, non-verbal marker of internal emotional shifts.

What It All Means

This study provides intriguing preliminary evidence that tVNS may act as an amplifier for contemplative therapies, particularly in cultivating self-compassion and mindfulness. While the expected effects weren’t seen across all measures (like HRV or self-criticism), the findings suggest a new ‘neuroenhancement’ approach to well-being and mental health practices.

Looking Ahead

While these results are promising, more research is needed. How long do the effects last? Are some people more responsive to tVNS than others? And how might this approach benefit people with anxiety, depression, or trauma – not just healthy volunteers? Future research should also consider participants’ attitudes to this kind of ‘contemplative neuroenhancement’. Any form of clinical or well-being application of this kind of neuroenhancement would rely on users viewing such enhancement strategies as practically and ethically acceptable. Some might inaccurately view these developments as part of an unwelcome transhuman trend in which people expect to tap into basic virtues (like compassion) by dialling them into a medical device without effort or a genuine motivation to reduce suffering. Our study dispels this idea (at least for now) by showing that tVNS is generally insufficient for generating self-compassion or mindful states, which only emerged when the stimulation is combined with effortful training.

The open access paper Electroceutical enhancement of self-compassion training using transcutaneous vagus nerve stimulation: results from a preregistered fully factorial randomized controlled trial by Sunjeev K. Kamboj, et al. appears in Volume 55 of the journal, Psychological Medicine.