ADHD can slow down ability to understand speech - Israeli study

Attention-deficit hyperactivity disorder (ADHD) can cause a delay in speech perception and difficulty in understanding the meaning of spoken sentences, according to a new study done at Reichman University in Herzliya, which suggests that background noise takes a heavy toll.

Prof. Boaz Ben-David and Rony Lemel of the university’s Ivcher School of Psychology carried out the first-ever study to examine real-time speech processing in young people with ADHD by using an eye tracker (a device for tracking eye movements), just published in the journal Science Direct of the National Library of Medicine at US National Institutes of Health, entitled “Listen up! ADHD slows spoken-word processing in adverse listening conditions: Evidence from eye movements.”

Understanding speech is an ability that enables interpersonal communication and is essential for an active life and emotional well-being. While hearing is seemingly a passive act that allows access to the auditory world while perceiving sounds, listening to speech is an active function that requires auditory-stream segregation, attention to the target information, suppression of irrelevant information and processing over time.

Speech processing in a noisy environment is necessary in everyday conditions and frameworks such as school, work and social interactions. The understanding of speech involves the executive functions of inhibition (delaying a response), sustained attention, selective attention, working memory and planning and executing tasks. People with ADHD often have difficulty controlling and managing these actions, but there has been almost no research in the scientific literature to date that has studied the relationship between speech and the disorder.

The study was carried out at the communication, aging and neuropsychology lab (CANlab) at Reichman, in collaboration with the attention lab headed by Prof. Lilach Shalev Mevorach at Tel Aviv University.

Studying the link between speech and ADHD

The researchers conducted an experiment with subjects from a group of 24 young adults with ADHD and another 22 without it. They were asked to perform a task in noisy conditions simulating common situations such as a classroom or a family meal. The experiment was conducted using an eye-tracker device, the only method that enables analysis of processes in real-time.

The findings showed that the people in the ADHD group had a delay/slowdown of half a second in performing the task, that is, a delay in processing speech. When it comes to speech, half a second is a long time; when people lose a word here and a word there, it adds up, and they may end up missing the context and meaning of the sentence.

Previous studies have found that people with ADHD need an optimal signal-to-noise ratio to properly process and recognize spoken words. Given the results of the study, it seems that young people with ADHD are impaired both in recognizing and processing speech in environments with a lot of background talk and noise. Recognition and processing demand attention, resource mobilization, inhibition and working memory capacity. People with ADHD have to make more effort to listen in noisy conditions and mobilize more resources than are available to them, which leads to a delay in understanding. This impairment may have serious consequences that will negatively affect the quality of life of those who suffer from it.

Other studies have shown impaired working memory in people with ADHD, but in the current study, the researchers found that all the subjects – both those with and without the disorder – had the same level of working memory, which was tested before the experiment. Yet, in situations with high cognitive demands, there were differences in working memory between the two groups, with the subjects having ADHD experiencing memory impairment.

 “People with ADHD ‘miss’ words during a conversation or lecture, and once that accumulates, they have difficulty understanding the meaning of the sentences that have been said,” according to Ben-David, the speech scientist and head of the CANlab. “The effort people with ADHD have to make in order to cope with distractions dilutes their cognitive resources, affects their ability to use their working memory effectively, and impairs their perception and processing of speech.

“Communication is vital for active living and well-being. We suggest paying attention to speech processing in ADHD in treatment and when considering accessibility and inclusion.”