Jacqueline Woolley is a professor and chair of the Department of Psychology who studies children's understanding of reality at The University of Texas at Austin. The opinions expressed in this commentary are solely those of the author. View more opinion at CNN.

(CNN) You might have noticed that Halloween decorations have changed since you were a little kid.

Things have taken a dark turn, and alongside the jack o' lanterns, bedsheet ghosts and startling ghouls, it's not so unusual now to find, even in the placid suburbs, grisly decorations featuring too-real-looking humans meeting a violent end: hooks in their skulls, knives in their bodies, or even depictions of human victims of hangings.

Jacqueline Woolley

What's wrong with this, you might ask, if the goal of Halloween is to scare and be scared? The answer is that this crosses the line from the fantastical realm into reality. And that's not what Halloween is all about.

I'm a developmental psychologist who studies how children distinguish fantasy from reality. My take on Halloween is that it's a playground in which children can contemplate and navigate the distinction between life and death, and between fantasy and reality.

Think about the costumed creatures that populate the streets on this holiday -- ghosts, skeletons, vampires and zombies (we'll leave out the pop culture figures for the purposes of this discussion: your "Elsa", from Frozen, your Spider-Man...). These beings toe the line between the living and the dead, with one foot in the real and one in the imaginary world.

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