Abstract
Background: It has been suggested that infants rely on low spatial frequency (SF) mechanisms for face processing. Using stimuli that were equated for detectability, we recently reported that 4-month old infants' larger upright preference for faces than objects was greater for “high” than “low” SF-filtered stimuli (Dobkins & Sampath, VSS 2010). Here, we asked if this pattern in 4-month-olds is adult-like by testing adults in the same paradigm. Methods: Adults (n = 5) were presented with an upright stimulus and its inverted image on the left and right side of a monitor, respectively (or vice versa). The stimulus was either a face or an object (the latter being a stroller). Using forced choice preferential looking, wherein the adult observed the stimuli passively, we determined the percentage of trials the adult looked preferentially at the upright stimulus. Six conditions were presented: 2 stimulus types (faces vs. objects) × 2 cutoff SFs (1 & 2 c/deg) × 2 SF filters (1 c/deg cutoff: “low” < 0.8 c/deg vs. “high” > 0.1.2 c/deg; 2 c/deg cutoff: “low” < 1.6 c/deg vs. “high” > 2.4 c/deg). In our previous study of 4-month-old infants, the cutoff SF was 0.4 c/deg. For both infants and adults, all stimuli were presented at 3.3× contrast threshold. Results: For cutoffs of both 1 and 2 c/deg, adults' larger upright preference for faces than objects was greater for “high” (1 and 2 cpd cutoff, p = 0.02 and 0.005, respectively) than “low” (1 and 2 cpd cutoff, p = NS and 0.02, respectively) SF-filtered stimuli. Conclusions: In adults and 4-month old infants, the mechanisms underlying upright face preferences appear to be preferentially selective for high SFs. This indicates that the mechanisms for face processing are fairly mature at 4-months of age.
NIH/NEI R01-EY12153-06 (KRD).