Research Ear, Hearing and Vestibular

Studying the impact of reward on speech processing

Neuroscientist Jonathan Peelle, PhD, was awarded a one-year $479,000 grant from the National Institute on Aging to look at the influence of reward and motivation in speech processing. The project, called, “Age-related changes in language processing,” will study whether offering listeners explicit rewards result in greater speech intelligibility among older adults.

The study is a collaboration between Peelle and Dennis Barbour, MD, PhD, associate professor in the Department of Biomedical Engineering, Ryan Bogdan, PhD, associate professor, and Todd Braver, PhD, professor, both in the Department of Psychological and Brain Sciences.

Normal aging involves changes to sensory and cognitive systems that affect many aspects of life, including spoken communication, according to Peelle who is an associate professor in the Department of Otolaryngology. Speech comprehension involves rapidly mapping a complex acoustic signal to our knowledge of words and extracting higher-order meaning from sentence or story structure.

When the sound signal is degraded—for example, due to background noise, or a listener’s poor hearing—this task is made more difficult. Peelle says there is good evidence that in such cases of acoustic challenge listeners must engage additional cognitive resources supported by domain-general executive networks.

Older adult listeners frequently have greater difficulty understanding and remembering speech in noise compared to young adults. Although some of this difficulty is due to age-related hearing loss, hearing ability alone cannot account for all of the comprehension changes that occur with age, according to Peelle.

One appealing explanation for older adults’ increased speech comprehension difficulty is a more limited set of cognitive resources, making them unable to meet the cognitive demands of challenging listening situations. However, it is important to consider that a listener’s motivation to understand plays a critical role in communication, which is why Peelle and his colleagues are pursuing this study.

In the NIA grant, Peelle and his colleagues will test the role of reward on language processing by varying the amount listeners are rewarded for correct responses during speech comprehension tasks. Reward is linked to dopamine-mediated pathways important for guiding learning and behavior. For this study, the rewards will be money and food, but the goal is to eventually examine the impact of social rewards.

They hypothesize that increased reward (associated with greater motivation) will increase a listener’s use of executive processing resources and result in greater speech intelligibility. Because normal aging is associated with changes in dopamine responsiveness, they expect that age differences and reward sensitivity may explain a portion of the age difference in speech comprehension.

The results will improve our understanding of factors that contribute to successful aging and will help identify mechanisms for intervention to improve performance when necessary.