Children born prematurely: Cognitive outcomes and preliminary findings for subsequent intervention

Well-established evidence shows that children born preterm/low birth weight (LBW) are at increased risk of academic difficulties (Lee, Yeatman, Luna, & Feldman, 2011; Pritchard et al., 2009) and, despite global IQ scores within the normal range, nonetheless display lower academic performance than their same age peers (Bhutta, Cleves, Casey, Cradock, & Anand, 2002; Kerr-Wilson, Mackay, Smith, & Pell, 2011). This is not fully understood and previous attempts to improve these circumstances through means of cognitive intervention have met with little success. Therefore, the current thesis investigates possible underlying mechanisms of this intellectual disparity and tests the effectiveness of one potential intervention. In doing so, the studies presented focus specifically on fluid intelligence (Taub, 2002). The investigation through fluid intelligence is relatively novel in the current literature and therefore worthy of further exploration. Normal individual differences in fluid intelligence have been explained with reference to information processing parameters. Previous studies have shown that children born preterm/LBW have impairments in basic processes identified with executive function (Aarnoudse-Moens, Smidts, Oosterlaan, Duivenvoorden, & Weisglas-Kuperus, 2009; Mulder, Pitchford, Hagger, & Marlow, 2009). However, the current study is the first to test whether differences in fluid intelligence, as measured by the Cattell Culture Fair Tests, between preterm (n = 217) and typically developing children (n = 145) could be accounted for by differences in working memory and cognitive flexibility, as measured by the digit span tasks and the Wisconsin Card Sorting Test respectively. Results indicate that the seven to nine years old preterm cohort performed less well on measures of fluid intelligence than their peers across all age groups and their differences were partially mediated by both working memory and cognitive flexibility in a multiple mediation analysis. It also identified at least one year of developmental delay in fluid intelligence between the clinical group and their peers. Provided with evidence from Study 1 and parallel research suggesting that computerized working memory training may enhance working memory and fluid intelligence in non-clinical groups (Jaeggi, Buschkuehl, Jonides, & Perrig, 2008; Klingberg, Forssberg, & Westerberg, 2002; Studer et al., 2009), the second goal of this thesis was to conduct a preliminary study to investigate the feasibility of cognitive training for children born preterm/LBW. Therefore, in the second study, the utility of a brief adaptive working memory span training program (Buschkuehl, Jaeggi, Kobel, & Perrig, 2008) was tested in typically developing children. Sixty-three children, aged seven to nine years, were randomly assigned to one of three groups: Intervention, active control and passive control. The intervention group was trained in the adaptive version of the working memory span task and the active control group was trained in the nonadaptive version. Both groups trained for 15 minutes each day for a duration of 20 days. Participants in the passive control group participated only in pre and post assessments. All participants were assessed using the digit span and spatial span tasks for measuring working memory, the Stroop task for measuring executive control, a reaction time task for measuring processing speed and the Raven’s Standard Progressive Matrices for measuring fluid intelligence. Results indicate that children in the intervention group improved on their trained task and demonstrated significant far transfer effects on the assessment of fluid intelligence compared to both control groups. However, no near transfer to other measures was found. The reason behind the occurrence of far transfer effect without evidence of near transfer effects was unclear. However, given that the adaptive complex working memory training task was not in any way similar to the fluid intelligence measure, significant differences in fluid intelligence gains were unlikely to have been a consequence of practice or general familiarity effects but, rather, a consequence of the training. Although Study 1 identified that working memory and cognitive flexibility partially mediate birth status-related differences in Gf, the impact of these variables on academic performance in children born preterm is still unknown. Nonetheless, current evidence of far transfer to fluid intelligence after adaptive complex working memory span training provides support for the utility of WM training and modifiability in Gf. This in turn provides a preliminary evidence-base approach for psychologists to work toward providing neuro-remediation treatment options to targeted clinical groups, such as those born preterm with fluid intelligence deficiencies. In combination, the outcomes of these two studies provide both a theoretical contribution to our understanding of the deficits observed in children born preterm and an applied contribution to beginning the process of developing appropriate intervention programmes suitable for this clinical group in the future, with hopeful prospects for improving cognitive outcomes.