How much can children see and report about their experience of a brief glance at a natural scene?

Recent studies on brief scene perception have revealed that adults discriminate between what they see and do not see in a photograph with varying degrees of confidence. In this study, we attempt to extend previous studies by asking if these perceptual/cognitive abilities are already established in preschool and school-aged children. In Experiment 1 (<i>n</i> = 122) and 2 (<i>n</i> = 205, registered report), using an online experiment, we briefly presented a natural scene (267 ms in Experiment 1 and 133 ms in Experiment 2) to participants and, subsequently, asked them if a small patch was included in the original scene. Experiment 2 was a registered report. We tested various patch locations to probe "how much" the participants can see and report about it with graded levels of confidence. In Experiment 1, discriminative performance was nearly saturated (the area under the receiver operating characteristic curve (AUC)) = 0.9 across age groups) with no effects of ages, but metacognition slightly improved across ages (AUC = 0.74 in 5-6-year-olds to 0.79 in adults). In a critical registered report (Experiment 2), with reduced stimulus duration, we found a developmental effect (AUC = 0.73 in 5-6-year-olds to 0.91 in adults), and, again, metacognitive accuracy was constant across development (AUC = 0.73 in 5-6-year-olds to 0.75 in adults). Additionally, our analysis of semantic congruence between objects and scenes revealed age-related differences in performance. Contrary to our expectation, the size of the image modification strongly affected task performance, uniformly across ages. Overall, we conclude that 5-6-year-olds' perceptual and metacognitive abilities are much better than we expected when they were tested with briefly presented natural scenes, although their performances were generally lower than adults.