You can predict how well a toddler will perform academically at age eight with a dried grape and a plastic cup, according to a recent study.

Researchers from the University of Warwick devised a test based on how long a 20-month-old child can wait to pick up a raisin in front of them.

"An easy, five-minute raisin game task represents a promising new tool for follow-up assessments to predict attention regulation and learning in preterm and term born children. The results also point to potential innovative avenues to early intervention after preterm birth," Professor Dieter Wolke, senior author of the study, said in a statement.

For the study, researchers collected and analyzed data from more than 500 children who were born at 25 to 41 weeks gestation and assessed for self-control once they were 20 months old. The results of those born preterm 25 to 38 weeks were compared to those born a healthy full term between 39-41weeks.

The toddlers were given a raisin that was placed under an opaque cup within easy reach. After three training runs toddlers were asked to wait until they were told (60 seconds) they could touch and eat the raisin. During the study it was found that those who were born very prematurely were more likely to take the raisin before the allotted time. In a follow on study the academics found that those who couldn't inhibit their behavior as toddlers weren't performing as well in school as their full-term peers seven years later.

Around age eight, the same children were evaluated by a team of psychologists and pediatricians using three different behavior ratings of attention from mothers, psychologists and the whole research team. Academic achievement -- including mathematics, reading and spelling/writing -- was assessed utilizing standardized tests.

The findings concluded that the lower the gestational age, the lower a toddler's inhibitory control -- and the more likely those children would have poor attention skills and low academic achievement at eight years old

"This new finding is a key piece in the puzzle of long-term underachievement after preterm birth," Julia Jaekel, lead author of the study and honorary research fellow at the University of Warwick and assistant professor of child and family studies at University of Tennessee, Knoxville, said in a statement.

The findings are detailed in the Journal of Pediatrics.