Contributions of head-mounted cameras to studying the visual environments of infants and young children

Abstract

Head-mounted video cameras (with and without an eye camera to track gaze direction) are being increasingly used to study infants' and young children's visual environments and provide new and often unexpected insights about the visual world from a child's point of view. The challenge in using head cameras is principally conceptual and concerns the match between what these cameras measure and the research question. Head cameras record the scene in front of faces and thus answer questions about those head-centered scenes. In this "tools of the trade" article, we consider the unique contributions provided by head-centered video, the limitations and open questions that remain for head-camera methods, and the practical issues of placing head-cameras on infants and analyzing the generated video.

Figure 1

Three spatial scales for measuring the visual environment: The 3^rd person view of the visual environment that may be potentially seen by the child; the 1^st person view of the available visual environment that is directly linked to the child’s bodily location and posture, and the fixated elements of the 1^st person view.

Figure 2

The panels in a show head and eye cameras on a hat (left) and a head camera on a band (right). The four panels in b and c show images from four different cameras with different vertical (V) and horizontal (H) fields of view (and the diagonal, D, measure of field of view). The two views in b were taken with each cameras placed on a tripod 14 inches in front of a toy barn (a reachable distance for a toddler). The two views in c were taken while the head cameras were being worn by toddlers during toy play.

Figure 3

Results from head-camera studies linking visual size and centering of a named object to learning. Panels a and b show examples head-camera images during two naming moments when later testing showed the child had learned the name (a) and not learned the name (b). Panels c and d show the image size (% pixels) of the named target object (black) and the mean of the other in-view, competitor objects (gray) for the 20-second window around the naming utterance (utt) for naming moments that led to the learning of the object name (c) or did not (d). Panels e and f show the overlap of the image of the named target (black) and the mean overlap of the images of the competitor objects (gray) with the center of the head-camera image for the 20-s window around the naming utterance (utt) for naming moments that led to the learning of the object name (e) or did not (f). See Yu and Smith (2012) and Pereira, Smith, and Yu (2013) for technical details and related graphs. Error bars represent standard errors.

Figure 4

Gaze density as measured by an eye camera (low black, white high) within the head- camera images during a 6-minute toy play period for 13- (n=18), 18- (n=18) and 24 month olds (n=16).