Horizontal beats vertical
Assortment variety is essential for retailer listings and, as we have shown before, for brand penetration. At the same time, choice overload is frustrating and may decrease consumer satisfaction. Research shows that not only assortment size, but also how products are presented (i.e., horizontal vs. vertical) impacts choice: Horizontal displays are easier to process and increase the number of items selected (see figure). Horizontal product displays better match our binocular vision field and correspond to the dominant direction of eye movements. Higher processing efficiency results in higher perceived assortment variety relative to assortments of the same size presented vertically. Retailers should therefore use horizontal displays especially in product categories where consumers seek variety and desire to shop for more than one item (snacks, cereals, or beer).
Source: Xiaoyan Deng, Barbara E. Kahn, H. Rao Unnava, and Hyojin Lee (2016) A “Wide” Variety: Effects of Horizontal Versus Vertical Display on Assortment Processing, Perceived Variety, and Choice. Journal of Marketing Research: October 2016, Vol. 53, No. 5, pp. 682-698.