Final answer:
The theory most likely to state that the brain is the biggest sexual organ is the Cognitive theory, as it emphasizes internal thought processes that are central to experiencing sexual arousal and desire.
Step-by-step explanation:
The theory that would state that the biggest sexual organ is the brain is not explicitly named among the traditional psychological perspectives provided in the options. However, the notion that the brain plays a critical role in sexual experiences could align with elements from several theories. The Cognitive theory focuses on internal thought processes and might suggest that the brain is central to interpreting and experiencing sexual arousal and desire. The Humanistic theory, with its emphasis on individual experience and subjective perception, could also imply that the brain, as the seat of consciousness, is critical in sexual experiences. However, the Social Learning theory, which involves learning through observation and imitation, does not, in particular, emphasize the significance of the brain as an organ in sexual behavior. The Evolutionary perspective might suggest the brain's role in sexual behavior is important due to its involvement in mate selection and reproduction, but it does not typically characterize the brain as a 'sexual organ' per se. Therefore, if one must choose from the options listed, the Cognitive theory is most likely to view the brain as the largest sexual organ due to its role in our thoughts, feelings, and arousal.