What is a significant effect of oxygen-deficient atmospheres at 12-14% volume?

Oxygen-deficient atmospheres, particularly at levels of 12-14% volume, lead to significant physiological effects primarily affecting cognitive and motor functions. When oxygen concentration drops to this level, individuals typically experience impaired coordination and judgment. This occurs because the brain and body are not receiving adequate oxygen to function optimally, which can compromise mental capacities and physical performance. Individuals may become disoriented, have difficulty thinking clearly, and struggle with fine motor skills. Such symptoms directly relate to the body's reliance on oxygen for neural function and muscular activity, making this option the most relevant and representative of the effects experienced in such environments.