For everyone, understanding speech in crowded environments such as busy workplaces or social gatherings requires concentration. New RNID‑funded research from Professor Maria Chait’s lab at University College London is helping to explain the hidden effort involved.
The study has shown how subtle changes in eye behaviour – such as pupil size, blinking and tiny eye movements – can reveal how much mental effort the brain uses to focus on sounds and ignore distractions.
Why listening takes more than just hearing
Listening in noisy environments depends not only on how well the ears process sound, but also on cognitive abilities such as attention and memory. This extra mental work – known as listening effort – is often greater for people with hearing loss and can lead to fatigue, stress and withdrawal from social situations.
Developing reliable, objective ways to measure listening effort is critical for understanding these challenges more precisely.
PhD student Xena Liu is investigating whether changes in pupil size, eye movements and blinking can provide new insights into the challenges people face when listening.
How the study tested listening effort
The researchers asked participants to complete a challenging listening task while their pupil size and eye movements were recorded using eye‑tracking technology. Participants had to:
- remember a sequence of sounds
- actively ignore a distracting sequence
- compare a third sequence to the original one
Importantly, the distracting sounds contained the same tones as the important sounds, making them especially difficult to ignore. This closely mirrors real‑world listening situations, such as trying to follow a conversation in a busy café while other voices are a constant distraction.
They measured four eye-related signals:
- pupil diameter: how large the pupils are
- pupil dilation rate: how quickly pupil dilations happen
- blink rate: how frequently participants blinked
- microsaccade rate: tiny, involuntary eye movements
What eye movements reveal about attention and effort
The results showed that listening effort is not a single process, but is made up of several different components, each reflected by different eye behaviours. Changes in pupil size and blinking revealed increases in effort and alertness, particularly when participants were actively trying to suppress distracting sounds.
In contrast, microsaccades were reduced only when participants were focusing their attention on important sounds. Crucially, these tiny eye movements did not change when participants were ignoring distractions.
This demonstrates that blocking out background noise is not automatic – it requires mental effort – and that it is distinct from the process of actively focusing attention.
Next, the researchers are further developing these measures during natural listening conditions, as well as investigating the brain processes involved in listening.
Why this matters
For people with hearing loss, listening often requires greater mental effort, particularly in noisy environments. By showing that ignoring background noise is itself demanding, this research helps explain why listening can feel so fatiguing, even when hearing aids or other technologies make sounds audible.
Importantly, the study highlights the potential for objective, non‑invasive ways to measure listening effort using the eyes. In the future, this could help researchers and clinicians better understand individual listening difficulties, assess fatigue, and evaluate hearing technologies more effectively.
By deepening our understanding of the hidden demands involved in listening, this research supports RNID’s wider goal of improving assessment tools, developing better hearing technologies, and helping people communicate with confidence in everyday life.
This work was supported by an RNID PhD studentship awarded to Professor Maria Chait, and it was published in the Journal of Neuroscience. Explore more about this project.
