The breadth and depth of cognitive insights gleaned from gaz

The breadth and depth of cognitive insights gleaned from gaze analyses motivates the expansion of eye-tracking methodology in several directions. Regarding gaze analyses, longitudinal studies examining the development of cognitive skills are relatively rare (exceptions include Huestegge et al., 2009; Schneider et al., 2004). Such studies would enable us to illuminate the shift in strategies as children and adults construct new concepts, build new skills, and gain expertise across a variety of cognitive domains. Additionally, two methodologies now widely available via standard eye-tracking technology have the potential to augment the insights of gaze analyses: pupillometry and spontaneous blink rate. The analysis of pupil dilation has been used for over a century in the scientific study of cognitive processes (Kahneman and Beatty, 1966; Löwenstein, 1920; Schweitzer, 1956), but obtaining these data required hand-measurement of photographs taken of the pupil every 0.5–1s, or the use of infrared pupillometers that obscured the participant’s vision. Similarly, measures of blink rate have informed cognitive and clinical studies since the 1920s (e.g., Ponder and Kennedy, 1927), but required hand-counting of visually observed blinks, the use of electrooculography (EOG), or other custom-made devices. Now that both of these measures can be obtained with modern eye-trackers and analyzed with automated data processing software, we recommend the expansion of their use in developmental studies. As the use of eyetrackers becomes more widespread, it is important that researchers who are just beginning to use this methodology understand both its affordances and its limitations. Just as fMRI indirectly measures caffeic acid activity by measuring blood oxygenation, necessitating that researchers mitigate and account for the effects of the physiological and idiosyncratic factors that affect blood flow, there are also many potential influences on ocular responses that must be considered (Gredebäck et al., 2009). Below, we provide an introduction to these ocular measures, the neural mechanisms they reflect, and the opportunities they present for new insights into cognition and cognitive development.
Pupil dilation Changes in pupil size are caused by two antagonistic muscles (Fig. 1b): the dilator pupillae, which is located in the outer parts of the iris and dilates the pupil, and the sphincter pupillae, located in the central parts and constricting it. The constricting sphincter muscle receives input from brain systems involved in the pupillary light reflex (Loewenfeld and Lowenstein, 1993), but both pupillary muscles also receive inputs from brain systems involved in cognitive and autonomic functions (Samuels and Szabadi, 2008). As a result, changes in cognitive and autonomic activity influence pupil diameters. Pupil dilations cannot be inhibited voluntarily, although it is possible to dilate one’s own pupils, for example by doing mental arithmetic (Loewenfeld and Lowenstein, 1993). Neuroscientists and cognitive psychologists have exploited the pupillary response to cognitive effort to study the unfolding of cognitive processes over time by observing fluctuations in pupil diameters. A large number of studies has used this method for at least 6 decades in human adults (e.g., Lowenstein and Loewenfeld, 1958) and – to a lesser extent – in infants (for a review, see Hepach and Westermann, 2016). But despite its many advantages, pupillometry has been underrepresented in the study of children and adolescents so far.
Spontaneous eyeblink rate Dopamine (DA) is an important neurotransmitter involved in learning, working memory, and goal-oriented behavior (for a recent review see Westbrook and Braver, 2016). Despite decades of research on animal models and adult samples, we currently lack suitable methods for directly measuring DA activity in children and adolescents.
Conclusion