White eyes are the window to the pure soul: metaphorical association and overgeneralization effects for spokespeople with limbal rings

We introduce limbal rings (dark annulus around the iris of the eye) as a biological facial cue that illuminates the sclera (white of eye) and subsequently acts as a signal for source purity, a construct we distinguish from source trustworthiness. We argue the phenomenon observed is due to an eye purity metaphorical association effect, whereby consumers use the illuminated white of an eye as a metaphorical representation of purity. We also illustrate a source purity overgeneralization hypothesis, where source purity acts as the mechanism that consumers use to judge the purity of a source, and overgeneralize to other source and endorsement-based judgments. Across four experiments we manipulate the presence and type (thick versus thin; transparent versus opaque) of limbal rings (no limbal ring versus limbal ring), while controlling for product attractiveness, perceived spokesperson-product fit, and eye characteristics including eye shape, pupil, color, and gaze. Results demonstrate that a biological (or authentic) facial contrast cue (i.e., thick, opaque limbal rings) increases perceptions of source purity, which, in turn, enhances source trustworthiness judgments, attitude toward the advertisement, and attitude toward the brand. We demonstrate that source purity is a stronger predictor of source and endorsement-based judgments than source attractiveness. We also determine that the addition of an artificial (or inauthentic) facial contrast cue (i.e., cosmetic adornment on the eyes) attenuates the limbal ring effect, resulting in the dilution of source purity judgments, as well as trustworthiness and attractiveness perceptions, and advertisement and brand-based attitudes.