Aaccording to charles spearman, it is one's intelligence that produces the positive correlations found between vocabulary, spatial ability, and verbal reasoning tests.

General, g Charles Spearman, an English Psychologist, is best known for the theory of g factor. He argued that general intelligence formed the bedrock from and all other mental abilities are developed from it. Spearman further argued that intelligence as the ability to obtain and use knowledge in a productive way. So, it's general intelligence that produces the positive correlations found between vocabulary, spatial ability, and verbal reasoning tests.

Sorry wish i could