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
the climbers' performance in speech, comprehension, and reasoning was impaired because oxygen deprivation affected their entire brains