When do you know what you know? The emergence of memory monitoring

•Nonverbal tasks adapted from the work of Kornell, Son, and Terrace (2007) and Hampton (2001) are used.•Four-year-old children begin to make accurate confidence judgments retrospectively.•Children at approximately 4.5 years of age begin to demonstrate prospective memory-monitoring skills.

Recent research on comparative metacognition shows that animals, like humans, can differentiate between what they know and what they do not know. However, not much is known about the metacognitive behaviors of human children during their early years. To explore the emergence of memory-monitoring skills, two experiments were conducted using nonverbal tasks adapted from the work of Kornell, Son, and Terrace (2007) and Hampton (2001). Experiment 1 endeavored to determine when children began to show the ability to monitor their memories retrospectively. Experiment 2 aimed to reveal when young children knew what they knew by assessing their prospective monitoring. The results suggested that 4- to 5-year-olds had the ability to judge retrospectively their accuracy in a serial position task, whereas 3- to 4-year-olds did not. In contrast, 4.5- to 5-year-olds could discern items present in and absent from their memory before recognition, whereas 4- to 4.5-year-olds could not. In conclusion, 4-year-olds began to make accurate confidence judgments retrospectively, and children who are approximately 4.5 years old began to demonstrate prospective memory-monitoring skills.