A group of mountain climbers was studied to determine how they were affected by diminished oxygen in the air at high altitudes  As they climbed past 6, 100 meters above sea level, the climbers slurred words, took longer to understand simple sentences, and demonstrated poor judgment
This combination of worsened performances disproves the theory that the area of the brain controlling speech is distinct from that controlling other functions
many of the climbers had engaged in special training before the climb because they wanted to improve the efficiency with which their bodies use oxygen