The newest Pixar film, “Inside Out”  —  called “a delight,” “thrilling,” and a “stunningly original concept” by critics — offers a fresh take on old theories of learning and memory.

“Inside Out” explores the inner workings of the mind of an 11-year-old girl named Riley, voiced by Kaitlyn Dias. Her emotions, anthropomorphized and voiced by actors such as Amy Poehler and Mindy Kaling, wander around Riley’s brain, affecting her memories, moods and thoughts.

The ideas of sensory input, short-term and long-term memory play a central role in the movie’s  plot and design. In “Inside Out,” sensory input —  information a person gains from touching, tasting, hearing, smelling or seeing — is shown by small, colorful glass spheres that show flickers of Riley’s memories. Short-term memories are kept in “headquarters,” which Riley has immediate access to. Long-term memories are shipped out to endless rows of shelves, which colorful workers have to send back to headquarters for Riley to access with her conscious mind.

This setup draws on the work of Richard Atkinson and Richard Shiffrin, who were the first two scientists to solidify a model of memory in terms of long-term and short-term in 1968. They published a chapter in the book The Psychology of Learning and Motivation that proposed a memory system with three parts: sensory input, short-term memory and long-term memory.

The Atkinson-Shiffrin model has been the basis of decades of subsequent research, but fellow scientists criticized it from the time it was proposed. Atkinson and Shiffrin believed rehearsal was the main method by which memories were moved to long-term storage. But, this theory doesn’t fit with Riley’s experiences – she is never seen rehearsing anything in order to memorize it.

Instead, the organization of Riley’s memories better reflect the theory that psychologists Ferguson Craik and Robert Lockhart proposed in 1972. They argued that thoroughly analyzed sensory input is more likely to be stored in long-term memory. If Riley’s sensory input is especially emotional, she internalizes it more deeply and her brain files it away automatically.

Another criticism with the Atkinson-Shiffrin model is that the brain does not store all memories in the same way. In terms of the movie metaphor, not all the colorful glass spheres are kept on the same shelves. The brain stores the memories of how to ride a bike and Shakespeare’s 18th sonnet in different places.

The fascinating case study of a man named Henry Molaison, who died in 2008, supports this theory. After a surgery, Molaison began to suffer from severe amnesia. He could not name the current president, or the doctor he had been introduced to moments before. However, he could learn and remember complicated motor activities – tasks he carried out with his body. For example, he was able to learn how to draw a star by looking at its reflection in a mirror.

In “Inside Out”, all kinds of memories seem to be stored in the same shelves. If this case study of Henry Molaison had been represented in the movie, Riley’s hockey moves should have been stored in a separate area from her more verbal memories, such as the jingle that pops up irritatingly in her consciousness. The annoying song moves from Riley’s long-term storage to her short-term working memory through a long chute.

In the human brain, memories travel a little differently. After all the debate in the 1970s, the Atkinson-Shiffrin model was revised into the Search of Associative Memory model (SAM). In this system, memories are retrieved based on their associations with other ideas. The more connections a memory has, the more deeply it is entrenched in long-term memory.

If the Pixar team had used SAM, the main character’s memories might be intertwined in webs of connections instead of stacked on shelves. Those with the fewest connections could drop off into the chasm of forgotten memories.  

The writers and designers of “Inside Out” thoughtfully drew on a long tradition of psychology and neuroscience in order to build their brain-world. By bringing these ideas to a larger audience, Pixar got viewers thinking deeply about their own thinking.