General second language proficiency continues to intrigue researchers. This study investigates the relationships between general second language proficiency (SLP) and selected cognitive abilities (i.e. foreign language aptitude, verbal intelligence, and reasoning) in 160 EFL Japanese college students. Structural equation modeling disconfirmed the hypothesis that general SLP forms the center of what has traditionally been called general intelligence. However, it suggests a strong relation between SLP and other cognitive abilities. The study also analyzed the protocol data provided by the actual text takers, revealing that SLP is related to the ability to assess, plan, and execute in problem solving processes.