A study of behavior (sic) at breakfast buffets showed that the first item in the buffet was taken by 75% of the diners (even when the order of the items was reversed) and that two-thirds of all the food taken came from the first three items, regardless of how long the buffet is.
The study Seth mentions is an interesting read but only cites one small experiment. However I have noticed similar behaviour on our client websites, such as; the first menu items often get the most visits, the first few at the top are clicked on most but, unlike the study, I have no science to support this.