Figures of Speech: Through computational modeling Professor Bonnie Nozari illuminates the invisible systems of language production

Professor Bonnie Nozari Photo by Jordan Morning

“How can something so hard be so easy for us?” That is the question at the center of newly arrived PBS Professor Bonnie Nozari’s work on how we put thoughts into words, the process of language production. Words flow almost like magic. In the blink of an eye, they become sentences and paragraphs, back to back, seemingly on their own. Until one day, a stroke or brain injury occurs, and a single act of speech becomes a monumental struggle.

Nozari has encountered many such patients. At the age of 25, having just graduated with an M.D. from the Tehran University of Medical Sciences, she was working as a research assistant in a psychiatric hospital at the University when one such encounter, as she says, “changed everything for me.” During a picture naming task, the patient misidentified the image of a sheep with a series of words that had a curious pattern to them: “wolf, no, steep, no sleep.” So intrigued was Nozari by this pattern that she went back to her computer and started searching for information on speech errors and the brain. What she found was a study by psycholinguist Gary Dell presenting a computational model of the brain which imitated speech errors. “I was absolutely fascinated,” she says.

Having accidentally stumbled into the field of cognitive psychology, not widely known in Iran at that time, she began an email correspondence with Dell, who shared his knowledge and explained how she could ultimately become a practitioner in the field. As she puts it, “This generous man patiently addressed my very naïve questions over the next couple of months.” And before long she was on her way to becoming a Ph.D. student at the University of Illinois Urbana-Champaign with Dell as her advisor. As she sees it, “He really did take a chance on me and I’m really grateful that he did.”

She clearly thrived in that environment, picking up other interests in areas such as visual processing and attention, and continuing to work with patients. Some 15 years, several positions and much professional recognition later, her interests have expanded even further. But at Indiana University, another Midwestern intellectual enclave, she says, “I feel like I’ve come full circle.”


We think there’s something internal to the language production system that makes it self-regulating, that monitors itself.

– Professor Bonnie Nozari


She now leads the Language Production and Executive Control Lab in PBS, bringing together two areas to understand how we perform this difficult act of producing words so easily, as well as to find ways to restore this ability to those who have lost it. 

“There’s a lot going on under the hood that makes language production so efficient that we’re not even aware of it,” she explains. And one of the ways she sheds light on those invisible processes is to look at error-monitoring in word production, a language process which also entails capacities of executive control. As she explains, “You mean to say ‘cat’ and a lot of other words come to mind, ‘dog,’ ‘cap’ and other things. How do we keep all of them apart and say the things we want to say?”

Every now and then, however, people will inadvertently say a word they did not intend and no sooner does it slip out than we are already correcting it. “All of us sometimes make speech errors,” she explains. “But you don’t need my help to correct your speech errors. You have the ability to understand you said something that is not what you meant. How do we do it so quickly? That’s one of the things we study in the lab.”

Nozari’s theories about how this happens hinge on the fact that “catching an error is not contingent on you consciously thinking about it. You don’t need your comprehension system to tell you that you made an error. That would be “like waiting for an accident to happen and saying, ‘Oops, I should have put my foot on the brake. That’s going to be too slow.” Instead, she says, “we think there’s something internal to the language production system that makes it self-regulating, that monitors itself.”

To test their theories about how this self-monitoring system works, she and her team develop computational models that they think work the same way as the system, plugging in data from a variety of sources – from neurotypical individuals, children, patients, EEG and fMRI studies – to test it out.

Two of Nozari’s major contributions to the field include a computational model of error detection and a new model for error repair, the ability to instantaneously correct our own speech errors. To test and refine these models, she is building a large multilingual database of human speech error detection and repair with support from a recent National Science Foundation grant.

In coming to PBS, she also hopes to take her work in new directions through new collaborations with people in the department, in particular those who work on decision making. “My view on language production is that it’s a goal-oriented task that entails decisions just like any other human cognitive task. So, applying some of the cutting-edge work that has been done here to model linguistic phenomena is one of the highlights for me.” She and her postdoctoral fellow Arella Gussow are already discussing collaborative possibilities.

But as she sees it, the PBS community enhances her life as well as her work, as does IU and Bloomington communities beyond it. “I think midwestern culture in the U.S. is my favorite culture in many ways, because I like talking to people, I like having lunch with my colleagues. I like a community of people who enjoy hanging out with one another. Can you get luckier than that? The smartest people on the planet actually like spending time with one another. It’s the true definition of a community that lifts you up. I just started teaching but the class that I just started teaching, the graduate seminar, has some of the smartest, most brilliant students I have ever encountered.”

And beyond her PBS colleagues and students, she loves having the IU Jacobs School of Music at her doorstep. “That both the science and the arts scene are just so topnotch, that for me kind of completes the picture. It gives me the two things I love most in life, science and art. And there are lots of connections with people who are also interested in literature. It’s kind of the ideal university for me and the ideal environment. It’s a really nice community to live in.”

Hear Professor Nozari talk about her work and goals!


Science Writer