Much has been discussed about the five “core” emotions chosen to represent the spectrum of a child’s emotional range in Pixar’s Inside Out (2015). How were they selected? How accurate are they to the way a child experiences the world? Choosing a handful of emotions capable of representing the wide spectrum of a child’s inner life is simpler to conceive than to execute. In order to compile the most suitable emotions, Pixar turned to Dacher Keltner, a professor of psychology at the University of California, Berkeley, and Paul Ekman, a pioneer in the study of emotions.

The film depicts the inner-workings of Riley (Kaitlyn Dias), an eleven year-old girl who is dealing with a traumatic move from Minnesota to San Francisco. The move occurs at an important transitional time in her life, and her emotions find themselves working overtime. Each of the characters in Riley's mind represents a facet of her emotional spectrum: Joy (Amy Poehler), Fear (Bill Hader), Disgust (Mindy Kaling), Sadness (Phyllis Smith), and Anger (Lewis Black) are all responsible for manning the “control center” in Riley’s brain and facilitating the understanding and archiving of her memories as they occur.

"I think they really nailed it. The movie does a really good job of portraying what it's like to be 11,” Keltner told NPR. "It zeroes in on one of the most poignant times in an individual's life, which is the transition to the preteen and early teen years, where kids — and, I think, in particular girls — start to really powerfully feel the loss of childhood.”

Psychologist Dan Florell agrees, saying, "The basic emotions that were chosen by the movie makers are ones that universally appear in normally developing infants between the ages of two to seven months." They remain the prominent guiding forces throughout much of childhood.

The film’s representative emotions illuminate the ways in which simple, fundamental feelings can have a profound impact on the way we recall particular memories and how emotions rely on one another to determine their total significance. The film also illustrates the ways in which people's expected emotional reaction to an event and their actual response often fail to align.

Speaking to The Huffington Post, Keltner explained that Pixar was “really interested in what happens with memory. How does my sadness right now color my recollection of my childhood? In our culture, we’re tough on sadness, but it’s a powerful trigger for seeking comfort and bonding. Meanwhile, anger is often about the sense of being treated unfairly, and can be a motivator for social change.” The film also examines how perceptions of memories can change over time, as in the way Riley's memories of Minnesota transform from joyous to sad as she recognizes that that part of her life is over.

Joy is Riley’s dominant emotion, and Keltner asserts that everyone is governed by a primary feeling which evolves over their lifetime through maturity and experiences with other sensations. Keltner told The Huffington Post his primary emotion was once contempt but evolved into compassion. Likewise, when we glimpse into the minds of Riley's parents and school acquaintances, we see that her mother's emotional team is led by sadness, her father's is led by anger, and the school popular girl's is led by fear.

One of Inside Out’s messages is that emotions are not independent and require one another to provide context and depth. While Joy is the central character of Inside Out and Riley’s signature emotion, Sadness, an emotion typically portrayed in a negative light, ultimately comes through as the film’s hero. Keltner calls it "a nice statement about how important sadness is to our understanding of who we are."

In the NPR interview, Keltner continues, “The filmmakers get a lot of other scientific details right. Inside Riley's head, you see memories get locked in during sleep, experiences transformed into abstractions, and guards protecting the subconscious. There are a few departures from the scientific norm. Long-term memories are portrayed as immutable snow globes, though scientists know these memories actually tend to change over time. And Riley gets five basic emotions instead of the six often described in textbooks.”

There are many emotions that aren’t directly depicted in Inside Out - surprise was apparently considered as a core emotion, and even something along the lines of schadenfreude was in the running. Even with the exclusion of several emotions, Inside Out draws on the knowledge of the experts who understand the brain the best to craft an illustrative and comprehensible portrait of a young girl's emotional landscape during a time of dramatic transition.