IKIDS Study Timeline
4-5 Months of Age
Mothers bring their infant to our research lab when they are 4-5 months of age to repeat some measurements done at birth and to complete some new cognitive tests. The data collected are:
- Stool Sample: Mothers collect a sample of their child's stool at home and bring it to the research lab when they come for their child's assessment. Analyses are run to examine the association between prenatal exposure to endocrine disrupting chemicals (EDCs) and the gut microbiota, as well as changes in the microbiota between birth and 5 months.
- Sexually dimorphic indices: Physical measurements that differentiate boys and girls are repeated at this age and the associations between prenatal exposure to EDCs and these physical measurements is analyzed.
- Child's cognition: Two cognitive tasks are administered to assess the relationship between prenatal exposure to EDCs and cognitive function at this age. During both tasks, infants sit in their caregiver's lap and watch videos on a computer screen. Their eye movements are tracked by a hidden observer and an eye tracker. One task involves mental rotation and the other requires they reason about the behavior and properties of an object. The tasks are described next.
Mental Rotation Task
This task was created by Moore and Johnson (2008) and they have generously lent us their stimuli. Infants receive a number of habituation trials in which they see a shape or its mirror image rotate back and forth through a 240 degree arc. For simplicity, one shape is labeled the L shape and the other is labeled the R shape. Infants watch habituation trials until they begin to lose interest as indicated by a decrease in their looking at the videos.
Habituation Stimuli: Babies are habituated to a video of either the L or R stimulus (mirror images of each other) rotating back and forth through a 240 degree arc.
L-SHAPE in HABITUATION TRIAL
Next, infants see two types of videos on alternate test trials. In one trial, they see the same shape they were habituated to (e.g. L-shape) rotate back and forth from 240 to 360 degrees. In the other trial, they may see the mirror image of the shape they were habituated to (e.g., the R-shape) rotating from 240 to 360 degrees.
If infants can identify the shape they saw in haibtuation, they should look longer at the video showing the novel shape. Moore and Johnson found that boys, but not girls, show a preference for the novel shape. Girls tend to look equally at the two stimuli in test. We will examine whether prenatal exposure to EDCs change this sex difference in responses.
L-SHAPE in TEST R-SHAPE in TEST
This task was developed by Renee Baillargeon and colleagues. In the original task, infants watch, on alternate trials, a possible and an impossible event on a puppet stage. In these events an object is placed against a wall and released. In the possible event, the object is placed a few inches above the platform but, surprisingly, it remains stable. Baillargeon found that, at this age, girls but not boys, are surprised by the impossible event as suggested by their looking longer at the impossible than at the possible event. Boys tend to look equally low at the two events, suggesting that they do not find any of the events surprising.
We have developed videotaped versions of Baillargeon's live events, and we will examine whethere prenatal exposure to EDCs alters the pattern of sex differences in infants' responses to these events.
IMPOSSIBLE EVENT POSSIBLE EVENT