When Kids Stop Believing in Santa

Warning: This post contains spoilers about reality.

Earlier this week, a woman wrote in to Slate's Dear Prudence advice chat asking whether it's considered lying to allow her daughter, who is three, to continue to believe in Santa Claus.
Prudie's take: Nah.
"Reality will eventually out," wrote the columnist, Emily Yoffe, "but there’s so much reality in this life, that one of the delights of childhood, and of being a parent, is to spread a little fairy dust occasionally."
Later in the chat, though, another person wrote in saying that his or her parents kept the Santa thing going until the writer was nine, at which point this person found out and felt "incredibly embarrassed" that he or she had been "duped" for so long.
The takeaway is clear: There is no way to not traumatize your children.
So, barring an early reality check from an elementary-school Scrooge, when is a normal age for kids to realize who's actually leaving those presents under the tree?
In studies for which she interviewed children, University of Texas psychologist Jacqueline Woolley noticed a drop-off in belief in Santa after the age of five. That's also when belief in the Tooth Fairy peaked, as well:

Percent Who Believe, by Age

Her findings resembled a 1978 study that found that 85 percent of 4-year-olds believe in Santa, but only 65 percent of 6-year-olds and 25 percent of 8-year-olds do.
But as Woolley told NPR, it also depends on how hard parents try to maintain the Santa illusion—and how hard kids try to discover the truth:

Two Christmases ago [Woolley's] daughter's doubts were growing, so, taking after her mom, she set up an experiment. She left a camera on a table with a note telling Santa to take a picture of himself if he was real. Woolley played along that year, writing back that Santa couldn't figure out the buttons on the camera, but by last year she stopped being so careful and let her daughter see the "Santa presents" being put under the tree.

Interestingly, when adults are interviewed, they say they remember believing for much longer. An AP poll from 2011 found that among adult respondents, 84 percent of people had ever believed in Santa, but the mean age at which they stopped thinking he was real was 8.8. Similarly, an earlier AP poll found that the age at which kids stopped believing varied by religion, but a good third to half of people across religions said they stopped believing between the ages of 9 and 12—much later than what the kids told Woolley:

Age When Stopped Believing in Santa
Among those who ever believed. (2006 AP-Ipsos Poll/Nineteensixty-four)

Apparently, just as kids might believe in Santa longer than absolutely necessary, adults like to believe that they believed for longer than they actually did. So unless your kid is leaving out milk and cookies in his college dorm room, it's a safe bet that you're probably not scarring him by keeping the magic alive for a few more years.