Assessing infant cognition in field settings using eye-tracking: a pilot cohort trial in Sierra Leone

Abstract

ObjectivesTo investigate the feasibility of eye-tracking-based testing of the speed of visual orienting in malnourished young children at rural clinics in Sierra Leone.DesignProspective dual cohort study nested in a cluster-randomised trial.Setting8 sites participating in a cluster-randomised trial of supplementary feeding for moderate acute malnutrition (MAM).ParticipantsFor the MAM cohort, all infants aged 7–11 months at the eight sites were enrolled, 138 altogether. For controls, a convenience sample of all non-malnourished infants aged 7–11 months at the same sites were eligible, 60 altogether. A sample of 30 adults at the sites also underwent eye-tracking tests as a further control.InterventionsInfants with MAM were provided with supplementary feeding.Outcome measuresThe primary outcomes were feasibility and reliability of eye-tracking-based testing of saccadic reaction time (SRT). Feasibility was assessed by the percent of successful tests in the infants. Reliability was measured with intraclass correlation coefficients (ICCs). Secondary outcomes were mean SRT based on nutritional state as well as and changes in mean SRT after supplementary feeding of MAM children.ResultsInfants exhibited consistent orienting to targets on a computer screen (>95% of valid trials). Mean SRTs had moderate stability within visits (ICCs 0.60–0.69) and across the 4-week test–retest interval (0.53) in infants; the adult control group had greater SRT stability (within visit ICC=0.92). MAM infants had a trend toward higher adjusted SRT at baseline (difference=12.4 ms, 95% CI −2 to 26.9, p=0.09) and improvement in SRT 4 weeks thereafter (difference=−14 ms, 95% CI −26.2 to −1.7, p=0.025) compared with age-matched controls.ConclusionsThe results demonstrate the feasibility of eye-tracking-based testing in a resource-poor field setting and suggest eye-tracking measures have utility in the detection of group level effects of supplementary feeding.

Early-emerging gradients in children’s eye movement times in low-resource settings

“…Exposure to poverty is associated with multiple factors that may be influential, including malnutrition and decreased levels of sensory and social stimulation [35]. Preliminary data showing that infant eye movement behaviors are sensitive to nutritional status and nutritional supplementation [21,36] suggest that the gradients may be established and maintained by variations in malnutrition.…”

“…Following the procedure described in ref. [21], SRTs was defined as the time interval from the onset of the saccade target to the first entry of the gaze into the area of the saccade target (Figure 1). SRTs were extracted from data that had been filtered with a 15-sample (128-ms) median filter to remove abrupt spikes, and in which the xy-coordinates for the two eyes had been merged by averaging (if both eyes returned a valid data point), or by using the data of one valid eye.…”

“…Mean SRTs based on ≥10 valid SRTs were retained in the analyses. All inclusion criteria used in the analyses were set a priori and identical to those used in the previous study [21]. Further data on the quality of the SRT measures (e.g., within and cross-session stability) is provided in supplementary data analyses and results.…”

“…Saccadic eye movements are present at birth [14], undergo predictable age-related improvements in speed during the first years of life [15,16], and predict long-term cognitive outcome [17,18]. Because the speed of saccadic eye moevements (i.e., saccadic reaction time, SRT) can be automatically assessed in children across populations and socioeconomic settings [19][20][21][21][22][23][24][25][26][27][28], this measure may have utility in documenting the cognitive dimensions of poverty in children across populations and settings. Indeed, preliminary data show that a large difference in mean SRTs is observed between infants from high-vs. low-income counties by 9 months of age, with slower SRTs in infants from rural, low-resource settings [25].…”

Evaluation of a community health worker home visit intervention to improve child development in South Africa: A cluster-randomized controlled trial

“…P-CR eye trackers are video-based methods that record information about gaze direction based on the coordinates of the pupil and the corneal reflection of an infrared light source in the camera image [20]. Previous studies have confirmed that the expected temporal and empirically verified spatial accuracy of eye-tracking with children is sufficient to reliably quantify SRT [21].…”