Researchers have quantified Muhammad Ali’s mental decline as he took more punches throughout his career:
In 1968, Ali spoke at a rate of 4.1 syllables per second, which is close to average for healthy adults. By 1971, his rate of speech had fallen to 3.8 syllables per second, and it continued sliding steadily, year by year, fight by fight. An ordinary adult would see little or no decline in his speaking rate between the ages of 25 and 40, but Ali experienced a drop of more than 26% in that same period. Slowing his speaking rate couldn’t indefinitely compensate for the deterioration of signals between his brain and his speech muscles. The paper suggests that by 1978, six years before his Parkinson’s syndrome diagnosis and three years before his retirement from boxing, Ali was slurring his words.
In addition to this overall decline in speech, researchers found a strong relationship between Ali’s activity in the ring and his verbal skills. The more punches he took, the more steeply his speaking abilities declined. (Listen to a sample of Ali’s speech changes.)
In 1977, the 35-year-old Ali fought a brutal, 15-round bout with Earnie Shavers. One of the strongest punchers in boxing history, Shavers hit Ali with 266 punches, including 209 power punches, according to the new CompuBox data. Before his fight with Shavers, Ali spoke at a rate of 3.7 syllables per sec. After the fight, his speaking rate fell 16% to 3.1 syllables per sec. His voice also became less animated in the immediate aftermath of fights.