Environmental intervention can raise general intelligence in young children but the effects are not permanent, a new study has found.
John Protzko from University of California, Santa Barbara (UCSB) analysed an existing study to determine whether and how environmental interventions impacted the intelligence levels of low birth weight children.
The findings showed that interventions did raise intelligence levels, but not permanently. When the interventions ended, their effects diminished over time in what psychologists describe as "the fadeout effect."
"Certain environmental interventions can raise general intelligence. It is not just pushing scores around on a test; it is deep changes to underlying general intelligence. The fadeout effect, however, applies the same way," said Protzko.
Scientists make a distinction between Intelligence quotient (IQ) scores, a quantitative measure of intelligence, and general intelligence, which reflects underlying cognitive abilities.
Protzko reviewed the results of the Infant Health and Development Programme involving 985 children, all of whom experienced an intense and cognitively demanding environment during the first three years of their lives.
Three main interventions had been employed to reduce the negative effects of being born at low birth weight.
At age three, the children were given the Stanford-Binet Intelligence Scales as a baseline measure of their intelligence.
At ages five and eight - at least two years after the interventions had ended - they were again given intelligence tests.
The results showed that the interventions had raised the children's general intelligence at age three.
However, by age five the increases were no longer evident. According to Protzko, this demonstrates that the fadeout effect applies to general intelligence.
One theory regarding the development of intelligence suggests that the trait can be correlated between two ages because there is a causal connection - intelligence at one age causes intelligence at another age.
"However, my analysis starts to bring evidence to the idea that intelligence may not be the causal factor we suppose it to be from the correlation work - at least not in children," said Protzko.
"It is unlikely that given an increase in intelligence, I would live my life any differently than I do right now. This work will have to be done in adults to really pull that apart, but I think that this analysis starts to bring evidence against that idea of causality," he said.
"Raising IQ is not an instance of raising test scores with no concomitant effects on the latent underlying intelligence," said Protzko.
"While both IQ scores and general intelligence can be raised through targeted environmental interventions, any gains are not permanent and fade over time," he said.
The findings were published in the journal Intelligence.