Scottish children whose parents have no formal educational qualifications arrive at school lagging 18 months behind the vocabulary skills of children of university-educated parents.
Research published this week finds that the gap in terms of problem- solving abilities is 13 months.
The findings come from the Growing Up in Scotland study, which since 2005 has been tracking the experiences of 8,000 families as they deal with education, childcare, parenting and health.
Former Scottish health minister Susan Deacon, author of a Government- commissioned report on how to improve early years, said the GUS findings reinforced the need for action on early intervention.
Her report Joining the Dots: A Better Start for Scotland's Children had underlined the need to "get beyond rediscovering the evidence and get on with acting on it". She told TESS: "I remain genuinely concerned about our apparent inability to move out of a comfort of ever-finessing the evidence base without making the step change necessary in investment and practice which it points to."
Greater provision of children and family centres was one of the keys to making the difference, said Professor Deacon.
Angela Constance, Minister for Children and Young People, said the Government would draw upon the GUS research to achieve better decision making for Scotland's most vulnerable young people.
The gap in "school readiness" at the age of five identified by the research can continue to affect children as they move through primary school and beyond, said the report's author, Dr Paul Bradshaw, research director at the Scottish Centre for Social Research.
"Additional research from the UK and the US suggests that children from `better off' socio-economic backgrounds move up in terms of their ability as they go through school," he said.
But there was a "downward pattern" in the ranking of children from poorer backgrounds as they got older because their initial ability is "not built on in the way it could be".
The report identified a "rich home learning environment" as key in shaping better cognitive ability in the pre-school period.
Attending a private nursery school for pre-school education and having some experience of primary school were also associated with positive development. It was unclear why private nurseries made a positive impact - although social mix might be a factor - and further research on this would be valuable, the report said.
Improving children's school readiness relies on enhancing both the home learning environment offered by parents and the quality of pre-school services used by families, it added.
But home environment and parents' behaviour were factors "more difficult for policy to affect" than pre-school and primary education, it stated.
"What we are finding is that social background is important but home has a significant impact, as do external factors," said Dr Bradshaw. "The data suggests that simply tackling one element may not have as much impact as tackling multiple issues in unison."
FACTORS LINKED TO CHANGE IN COGNITIVE SKILL
Knowledge of vocabulary
- mother aged under 25 at child's birth
- having a non-white parent
- frequency of home learning activities at age two to three
- level of rule setting in household at age five
- level of infant-maternal attachment at 10 months
- parent's perception of child's readiness for pre-school at age three
- language and communicative development at age 1
- attendance at ante-natal classes
- maternal mental health
- experience of material deprivation
- frequency of home learning activities at two to three
- type of pre-school attended
- whether child had started primary school
- child's health between 10 months and two years
- area deprivation
Source: GUS report.