Each stimulus PI3K inhibitor comprised the same age-neutral base face modified by a different,

randomly generated template of Gabor noise (see Figure 1, Stimuli; see Experimental Procedures). The effect of adding Gabor noise is that it perceptively changes the appearance of the age-neutral face by altering face features. For example, consider a trial in which adding noise resulted in darkening the wrinkles extending between the nose and the mouth (see Figure 1, Stimulus). The participant might perceive this stimulus as older because darkened wrinkles correspond to their expectation of an “older face.” Thus, when the participant chooses this stimulus among the three noisy faces, we capture the information that this participant expects from an older face (e.g., another participant might expect the jowls). Over trials, we can average the chosen Gabor noise templates and add this average to the age-neutral base face to visualize the information each participant uses to estimate age. We refer to these information images as individual “mental representations” [11, 12 and 13] of age because they capture the expectations of the participant (i.e., their knowledge) of the physical appearance of an aged face—more technically, they project the

participant’s knowledge of an aged face onto the parameters of a recursive organization of Gabor filters. The power of our method to study mental representations of aging is 2-fold. Doxacurium chloride First, we researchers do not RG7420 in vitro need to specify in an a priori manner and subsequently test the aging features that we believe participants should use to judge age, limiting researcher bias. Second, participants do not even need to be consciously aware of these aging features; as long as their age decisions systematically use face features randomly formed by the Gabor noise, the reverse correlation method will capture

them, and our analyses will reveal what the features are. We applied this approach to younger (18–25 years old) and older (56–75 years old) participants performing the choice task independently with three age ranges (20–35 years, 40–55 years, or 60–80 years). For each participant and age range, we computed an individual mental representation. We also computed six averages, one for each condition of the experimental design, to reveal the average information present in the mental representations of each age range in younger and older participants (see Experimental Procedures, Mental Representation Reconstruction). Averages emphasize the aging features common to each participant group, smoothing noise and distinctiveness due to idiosyncratic feature preferences. To understand how younger and older participants represented age, we conducted a validation experiment that used their individual and group average mental representations as stimuli (see Experimental Procedures, Validation).