What happens to us when we watch theater? We go into the auditorium, take our seats. The house lights dim, and an actor walks on stage pretending to be someone else. We learn about the characters and story from their gestures, the looks they give, the rhythms and inflections of the language. Their bodies shift in relation to one another and we feel the tension in the room. We hear their words and are drawn into the challenges they face and the compromises they make to conquer them. We know we're not really in front of the palace of Thebes; we're sitting, knees together, in a room full of people, in red velvet seats. That person up there is not really Gertrude—you know her from the TV.

Both audiences and performers play the game of theater. We use the words "illusion" or "realism"—but we're not fooled. "Will you pretend tonight," ask the actors (ludicrously), "that we are fairies in a forest?" And we, the spectators, pretend that we've not just come from a tense day in the office. We imagine what fairies might think, why they might cry or laugh. We, rightly, give credit to the actors for their compelling, coherent, involving work. We should also credit the audience members, who walk in off the street, are lined up in a velvet cocoon, and asked to perform an extraordinary imaginative feat.

What happens, then, when we watch puppets?

In puppetry the character is played, not just by someone else, but by a manikin, a figurine, a doll—an inanimate object, held and moved by human hands. As we watch, the artificiality of theater is even more present. In some productions, the puppeteers are hidden, restricting the puppet characters to limited areas of the stage. In others, the puppeteers move in full view of the audience, so the overall image is populated not just with the characters in the drama, but also with other bodies.

One of the first things I noticed when I started working with puppets was that the audience's energy was different—they lean in.

The puppet is a representation of a person or being, but never an entirely successful one. They can't accurately imitate the movement of a human or an animal—they could never have enough mechanisms to parallel our wonderful muscles, tissue, and skeleton. With their simplified joints and carefully chosen gestures, they sidestep "naturalism." Sometimes they present a full-throated caricature of the way we move, reflecting our passions and appetites; at others it's a gentle and precise style that feels so sensitive that we mistake it for the real thing—those hesitations and suspensions speak to us about anxiety, inner conflict, and the fear of touch. Often the most wonderful puppets look strikingly different from what they represent—distilled sculptures in cane, wood, foam, or fleece. The audience is watching refined, accentuated movements—most often with no alteration at all of the facial features that we rely on so much for nuance and subtlety in our leading players—and imagining a king, or a portrait photographer, or a bull.

And yet we hear from the audience: "How lifelike your puppet was!" What is happening? Why are they so believable?

One of the first things I noticed when I started working with puppets was that the audience's energy was different—they lean in. Perhaps because it's harder to imagine this sculpture as a living person, they commit more to the act of imagining. Puppeteers work to find ways of moving the figure that trigger those responses of recognition in the audience, and this is the "magic" of puppetry. It's a magic not of misdirection, but of precise direction. It's the magic of giving you the right movement at the right moment; the flow of gesture continually suspended by the rhythm of thought. Successful puppeteering requires acting talent as well as technical skill.

For their part, the audience members keep two realities in play, creating for themselves the miracle: This thing, so obviously hard and carved and dead, is alive, thinking, and feeling emotions. It's at once an entirely strange thing to do and completely natural—after all, some of the first strong emotions we ever felt were rehearsed through our dolls and toys. And the magic is between the puppeteer and the audience, an invisible beam that has its focal point in the puppet itself. It's you, the watcher, who makes the character, in the puppet, in that moment. The puppet is not one end of the performance relationship, it is the vessel through which the audiences and performers can mingle their imaginations.

Neurologists have found that the same neurons fire in our brains when we see a smile as when we smile ourselves. What we watch, we also experience. Empathy is innate—it's a biological response to be welcomed, or suppressed, as we prefer. If the theater is a gym designed for us to exercise our empathy, then actors are dumbbells, and the puppet is a crosstrainer. They push us a bit harder, and give our feelings an all-around workout. Watching a piece of theater is feeling it. Feeling a piece of theater is about investing. We find ourselves—sometimes despite our judgment—involved.

We look for the input of the neurologists to try and dig down into the real mechanics of what's happening—after all, we are the type of theater artists who analyze the mechanics of bodies to make them ourselves—but we know what it feels like to be bewitched by a puppet performance. The puppet character seems sometimes abnormally vivid. When we laugh with them, we laugh with relish, and when they make us weep, our sadness seems similarly intense. I like a couple of theories as to why: One is that the puppet gives less away. Without those moving facial features, for instance, it invites the viewer to contribute the imaginative detail of the emotion. To connect these defined gestures and movements we must "fill in" the gaps. And as we do, we find that we are living the story. In contrast, the great Broadway actor fills his or her whole body with emotion (whether suppressed or let loose). We marvel at the display and the technique, and we empathize, but we don’t create it ourselves.

The other is that we cannot escape the cognitive dissonance of this impossibility. We know the puppet is dead, and yet we believe it as an emotional being. And so we are, in every microsecond, repeatedly shocked by the fact that we are exhibiting any response. Our limbic system has cut loose from our rational brain and because we know it has no "real" source, we alert ourselves to this uncanny manifestation—and so the feeling is perceived as intensified.

Watching the puppet can offer a window into new worlds, and a sense of profound emotional connection. When people describe it, they often talk about magic, spirituality, and transcendence. The puppet is an instrument, a tool for the performer to help the audience imagine. When a show really works, you can feel something almost tangible in the air between audience and puppeteer. But if you're wondering what it is, from our side of the footlights I can only say this: It's coming from what you bring into that room as much as what we bring. As puppeteers, designers, directors, and actors, if there’s magic happening, we're doing our best to help it—but you are creating it, fresh, every night.

Mervyn Millar is a director and designer of puppets. He was puppetry director for War Horse at Lincoln Center Theater. www.significantobject.com