The research used a sample of 10,419 children born in the early 1990s, and took into account a range of background factors, including parental educational levels, family income, a child's sex and age, maternal health and parenting styles.
Dr Maria Iacovou, from the ISER, who led the research, said: "The difference between schedule and demand-fed children is found both in breast-fed and in bottle-fed babies.
"The difference in IQ levels of around four to five points, though statistically highly significant, would not make a child at the bottom of the class move to the top.
"But it would be noticeable."
The research compared babies fed to a schedule at 4 weeks old with those whose mothers tried but did not manage to feed to a schedule, and with those who were fed on demand.
The children of mothers who had tried but failed to feed to a schedule were found to have similar higher levels of attainment in standard assessment tasks tests and IQ scores as demand-fed babies.
Iacovou said: "This is significant because the mothers who tried but did not manage to feed to a schedule are similar to schedule-feeding mothers.
"It seems that it is actually having been fed to a schedule, rather than having the type of mother who attempted to feed to a schedule - successfully or not - which makes the difference."
- OBSERVER