Since the 50s in the U.S., you have to pass a literacy test to join the Armed Services. From such a test and others, the military learns a lot about your aptitudes, cognitive skills, and ability to perform on the job.

It took a while for the military to develop these tests. Over the years, it changed the content of the tests and what they measure. Testing literacy advanced in these general stages:

1. During World War I, they focused on testing native intelligence.
2. The military decided that what they were testing was not so much raw intelligence as reading skills. By World War II, they were focusing on classifying general learning ability for job placement.
3. In the 1950s, Congress mandated a literacy requirement for all the armed services. The resulting Armed Forces Qualification Test (AFQT) prevented people of the lowest 10% of reading ability from entering military service. The military then combined AFQT subtest with other tests, which differed for each service and sorted recruits into different jobs.
4. In 1976, with the arrival of the All-Volunteer Force, the military introduced the Armed Services Vocational Aptitude Battery (ASVAB). All military services used this test battery for both screening qualified candidates and assessing trainability for classified jobs.
5. In 1978, an error resulted in the recruitment of more than 200,000 candidates in the lowest 10% category. The military, with the aid of Congress, decided to keep them. The four military services each created workplace literacy programs, with contract and student costs over $70 million. This was a greater enrollment in adult basic education than in all such programs of 25 states combined. The results of the workplace literacy programs were considered highly successful, with performance and promotions "almost normal."
6. In 1980, the military further launched the largest study ever in job literacy, the Job Performance Measurement/Enlistment Standards Project. They invested $36 million in developing measures of job performance. Over ten years, the project involved more than 15,000 troops from all four military services. Dozens of professionals in psychological measurement took part in this study.
7. In 1991, based on these findings, the military raised its standards and combined the ASVAB with the AFQT and special aptitude tests from all the services into one battery of 10 tests. Both the Army and Navy continue to provide workplace-literacy programs for entering recruits and for upgrading the literacy skills of experienced personnel (Sticht 1995, pp 37-38).

The major findings of the military research were:

1. Measures of literacy correlate closely with measures of intelligence and aptitude.
2. Measures of literacy correlate closely with the breadth of one's knowledge.
3. Measures of literacy correlate closely to job performance. Hundreds of military studies found no gap between literacy and job performance.
4. Workplace literacy programs are highly effective in producing, in a brief period, significant improvements in job-related reading.
5. Advanced readers have vast bodies of knowledge and perform well across a large set of domains of knowledge. Poor readers perform poorly across these domains of knowledge. This means that, if programs of adult literacy are to move students to high levels of literacy, they must help them explore and learn across a wide range of knowledge (Sticht and Armstrong 1994, pp. 37-38).