Twelve participants (6 participants 18–25 years old, three female

Twelve participants (6 participants 18–25 years old, three females; 6 participants 56–75 years old, three females) with normal or corrected-to-normal vision participated in the experiment. Each participant gave informed written consent. We assessed older participants’ visual acuity and contrast sensitivity for normal functional range in the laboratory, on the day find protocol of the first experimental session, using a Colenbrander mixed contrast card set (see Table S3) and a Pelli-Robson chart. Participants reported no cataracts or any neurological condition and

were required to have had a National Health Service eye examination within the year prior to participation. Participants over 65 were also assessed with the Montreal Cognitive selleck chemicals Assessment (MoCa) and were all in the cognitively healthy range (>26). We recruited older participants through a local newspaper article and active-age fitness classes. We recruited younger participants through the Institute of Neuroscience and Psychology website. We compensated participants for their time at the standard rate of £6 per hour. In each trial, we generated an experimental stimulus by adding a recursive Gabor noise mask to a base face. The base face was the average of 84 male and female face pictures (ranging from 18 to 79 years old),

normalized for spatial locations of landmark features (i.e., eyes, nose, and mouth). The recursive Gabor noise mask was comprised of five cycle Morlet wavelets, at six possible orientations, in HAS1 one of two polarities. We tiled the noise with these wavelets, recursively across six spatial scales, increasing the tiling density by a power of two at each spatial scale (see Figure 1, stimulus generation, which shows the systematic spatial structure of the tiling). To illustrate, the second lowest spatial frequency band is tiled with four Gabors per orientation and polarity, for a total of 48 parameters, to independently set the amplitude of each Gabor (4 Gabors × 6 orientations × 2 polarities). Consequently, in each trial, we generated three noise masks by randomly choosing the amplitude parameter of each of the 16,380 Gabor wavelets. The three noise masks were then added

to the base face and simultaneously presented on the computer screen. The experiment comprised three target age ranges (20–35 years, 40–55 years, or 60–80 years), each tested with 60 blocks of 18 consecutive trials, for a total of 3,240 trials. At the start of each block, a target age range was randomly chosen from the set of possible blocks. In each of the following 18 trials, three independent noisy faces, generated as explained above, simultaneously appeared on the computer screen. We instructed participants to choose the noisy face that best fitted the target age range by pressing one of three response keys. The three faces remained on the screen until response. Participants sat in a dimly lit room, their heads maintained at 72 cm from the screen, using a chin rest.

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