Cold Water and Decision-Making

Inclusion Criteria: * 18-40 years of age * Consent to participate * Fluency in German * Physically and mentally healthy * BMI 18-30 kg/m2 * Normal day-night rhythm Exclusion Criteria: * Raynaud syndrome * Cold urticaria * High resting heart rate (\>160 beats per minute) * Acute infection * Diagnosed current or former illnesses of * Brain and mind * Heart and blood circulation * Gastrointestinal system * Endocrine system * Other serious past or present medical conditions * Wearing of medical devices (e.g., pacemaker) * Fear of blood, needles, or phlebotomy * Allergies to plasters, gels, and other medical equipment * Allergies to commercially available liquid meals (e.g., shakes, yfood Labs GmbH) * Recurrent intake of medication which affect metabolism * Regular nicotine consumption (e.g., vaping, cigarettes) * Excessive alcohol consumption (\>14 servings/week) * Recent illegal drug consumption (within 2 weeks prior) * Strong mental or physical stress * Excessive exercise (\>2 h high-intensity exercise/day) * Pregnancy or breastfeeding * Inability to wear skin-exposing swimwear, e.g., for religious reasons * Affinity for winter swimming, cryotherapy, breathwork (\>3 times/year)