“We will continue until we no longer have questions and hypotheses that our C.L.S. population can help to address,” Sally said.

Among those questions: What are some of the specific factors that might ameliorate or exacerbate the effects of dyslexia over a lifetime? What are the specific adult outcomes of early reading difficulties? What do the participants wish they had known about their dyslexia early on?

They plan to invite a subset of the participants back for brain imaging to investigate, among other things, whether there has been a change in the neural signature of dyslexia — an anomaly in the brain that shows up in imaging — now that the participants are mature adults.

It is a follow-up to work they did in the early 1990s, when Bennett, who trained as a pediatric neurologist, suggested they scan the brains of 100 of the study’s participants. They were among the first researchers to describe a neural signature for dyslexia, which is characterized by inefficient functioning of neural systems for skilled, fluent reading.

People with dyslexia have trouble separating words into phonemes, the sounds that correspond with each part of a word. For example, the word “dog” is broken down into the phonemes “duh,” “aah” and “guh.”

Hearing these discrete sounds is a vital part of learning to read. But people with dyslexia hear the word only in its entirety: “dog.”

“Perhaps the most important contribution of brain imaging to dyslexia is that it made visible this previously hidden disability,” said Bennett, who was chief of pediatric neurology at Yale for 40 years.