Reading, we assume, is a skill that kids tend to get out of the way by their seventh or eighth birthday. Sure, they may pick up several thousand words before they ever truly master the skill, but the broad strokes are there. Popular neuroscience theories have long held this belief, arguing reading skills top off around the fourth grade.

A new study cuts across these theories. Published in the journal Developmental Science, the new research suggests adolescent brains aren’t savvy enough to recognize real words from non-words — abstract strings of letters cooked up by a research team. Many of the automatic processes do, in fact, develop and concretize by the fourth grade. It’s the precise, speed-based mechanisms, a difference the brain makes in a matter of milliseconds, that takes longer to catch on.

"Until now, we lacked neurological evidence about the supposed fourth-grade shift," said Donna Coch, a principal investigator for Dartmouth's Reading Brains Lab, in a statement. Instead, eachers tend to rely on anecdotal evidence. They see a group of students meeting the curriculum standard and assume reading is one less thing they need to worry about. What they don’t see is how those students transition over the next couple years. It’s in those years, Coch says, that weigh heavily on future literacy.

So the team turned to lab tests. They took for their small study 96 third-, fourth-, and fifth-graders along with a group of college students. Each subject viewed a screen that either showed a word (“bed,” for example), a pseudo-word (“bem”), a string of letters (“mbe”), and strings of meaningless symbols one at a time. Using an electrode cap to measure each subject’s neural activity, the team could generate a reasonable picture of how each age group reads unconsciously.

Students also took a written test to judge their conscious reading abilities. The two tests were meant to tease out just how much reading ability was automatic. In theory, a more advanced reader would look at “bem” and spend just as little time reading it as she would a string of nonsense letters. Less advanced readers would look at “bem” and process the letters more as if it were an actual word. In written tests, these pseudo-words were no-brainers, even for most of the third-graders. But the electrode cap told a different story: Young students’ brains got fooled.

“We can see from brain waves that students in those grades are still learning to process words automatically,” Coch said. “Their neurological reading system is not yet adult-like."

Even fifth-graders, the supposed elders of the group, whose brains should demonstrate far superior neural output than the puny third-graders, reacted to meaningless symbols as if they were actual words. In real-time they may have understood the symbols had no meaning, but on a cognitive level the brain scans showed no difference. The mechanism that controls quick, glancing interpretation — the ability that lets us accelerate our reading to its maximum speed — still fails as late as fifth grade.

Teachers need to be aware of these neural shortcomings, the researchers say. It isn’t enough that Johnny reads his book faster than the rest of the class. All that means is his fifth-grade brain is getting better at being a fifth-grade brain. Just because a student shows advanced reading ability, teachers shouldn’t quit teaching that skill. It still needs nurturing if it is ever to stay engrained for life.

"There is value to the theory of the fourth-grade shift in that it highlights how reading skills and abilities develop at different times," Coch said. "But the neural data suggest that teachers should not expect their fourth-graders, or even their fifth-graders, to be completely automatic, adult-like readers."

Source: Coch D. The N400 and the fourth grade shift. Developmental Science. 2014.