The conductors of this experiment used eye-tracking technology to test two hypotheses: (1) that larger breasts should receive the greatest number of visual fixations and longest dwell times, as well as being rated the most attractive; (2) that lightly pigmented areolae (ring of pigmented skin circling the nipple), indicative of youth and nubility should receive most visual attention and be rated as most attractive.  To learn how this study was conducted and its results, check the link below:

Eye Tracking of Men’s Preferences For Female Breast Size And Areola Pigmentation