The findings of this new study, led by Lancaster University, appear in the journal Child Development.

Children with intellectual disabilities – significantly low cognitive functioning coupled with significant deficits in adaptive or everyday functioning – make up 2 to 3 percent of the population, and it’s estimated that 1 in 3 children with disabilities experiences some form of maltreatment. However, in many cases, the disclosures of children with intellectual disabilities aren’t investigated or taken to court, in part because of concern over whether these children can describe their experiences sufficiently and be believed by juries.

Dr Deirdre Brown, who was the co-investigator of the study, said: “Our findings show that children with intellectual disabilities can provide accurate and detailed information about their experiences when interviewed properly.

“Children with more severe intellectual disabilities (those in the moderate range) could still provide useful descriptions of their experiences, but were less able than typically developing children of the same developmental level and those with mild levels of intellectual disability.

“Interviewers should interview children with intellectual disabilities as soon as possible after a disclosure of maltreatment, and they should consider developmental level and severity of impairments when evaluating eyewitness testimony.”

The study aimed to determine how well children with intellectual disabilities could recall an experience when they were interviewed later, compared with typically developing children.

Children were interviewed using a protocol very similar to that used by investigators assessing allegations of child maltreatment; the researchers also used leading and misleading questions similar to those that might be encountered during cross examination in a court proceeding.

The study included 194 children from Lancashire schools: two groups had intellectual disabilities that fit with diagnostic categories of either mild or moderate impairment and were 7 to 12 years old. The remainder of the children were typically developing children and were 4 to 12 years old.

The children with intellectual disabilities were compared with two groups of typically developing children—one group was the same chronological age, while the other was the same developmental age. For example, a 12-year-old with a mild intellectual disability may function at about the level of a 9-year-old and would be compared with a 12-year-old (chronological age match) and a 9-year-old (developmental age match).

All of the children took part in a team event made up of several activities related to health and safety. Partway through the event, they witnessed an argument about the equipment. Half of the children were interviewed a week after the event and then interviewed again six months after the event; half were interviewed only once, six months after the event.

The team found that children with mild levels of intellectual disability did as well as their typically developing counterparts of the same developmental level or mental age in terms of how much they recalled, how accurate their accounts were, and how they responded to suggestive questions.

Children who were classified as having moderate levels of intellectual disability – those with more severe cognitive impairments – could still provide useful descriptions of their experiences, but were less able to do so than typically developing children of the same developmental level.

All of the children recalled more information in the six-month interview and were more accurate and less suggestible when they had been interviewed previously (one week after the event) than children who had been interviewed only once, at six months.

Younger typically developing children and those with mild levels of intellectual disability were very similar, with both groups recalling the event, but not recalling it as well as the typically developing children who were older.

The picture was different for children with more severe intellectual disabilities: they recalled less than even the youngest typically developing children.

Dr Brown concluded: “There is no reason why children with mild to moderate intellectual disabilities should not be provided with the same access to the investigative and judicial processes that would be initiated when typically developing children make disclosures of maltreatment – that may include repeated interviews as well as using an open-ended style of questioning, with more focused questioning delayed until later in the interview.”

Dr Brown, who worked on the research while at Lancaster University, is now at the Victoria University of Wellington. Professor Charlie Lewis of Lancaster University was the principal investigator of the research and Professor Michael Lamb of the University of Cambridge was a consultant.

The study was funded by the Economic and Social Research Council.