Gardner asserts that each intelligence should be measurable to some extent by psychometric tests. However, he also criticizes the overreliance on such tests in traditional intelligence testing. Psychometric support means that standardized tests should be able to reliably measure and differentiate between the various intelligences. This criterion is important for validating the theory within the scientific community and for practical applications, like educational assessments. It ensures that the concept of multiple intelligences is not just theoretical but has practical, measurable implications.

The criterion "Potential Isolation by Brain Damage" refers to the notion that distinct intelligences can be independently affected by brain damage. This means that a specific type of intelligence can be impaired or lost while others remain intact, indicating its unique neurological basis. For instance, a person might suffer damage to a part of the brain responsible for linguistic abilities, losing their capacity to use language, while their mathematical or musical abilities remain unaffected. This criterion supports Gardner's idea that multiple intelligences are separate from each other, each residing in different areas of the brain.

The criterion "Existence of Savants, Prodigies, and Other Exceptional Individuals" highlights the presence of individuals with extraordinary abilities in specific cognitive domains as evidence of distinct intelligences. Savants and prodigies often display remarkable skills in areas like music, mathematics, or art, despite potential deficits in other cognitive functions. This extraordinary proficiency in a particular area suggests that intelligences are modular and independent.

Each intelligence has its own unique developmental trajectory. This means that these intelligences emerge and develop at different stages and rates in an individual's life. For instance, linguistic intelligence develops rapidly in early childhood, while interpersonal intelligence might evolve more significantly during later childhood or adolescence. This criterion underscores the belief that intelligences are not static but evolve with age and experience. The distinct developmental paths of each intelligence imply that educational strategies should be tailored to the maturity level of each intelligence in an individual.