Date of Award


Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy (PhD)


Developmental and Brain Sciences

First Advisor

Erik Blaser

Second Advisor

Zsuzsa Kaldy

Third Advisor

Susan Zup


In the first two years of life, infants interact with the environment around them in complex and dynamic ways, and rapidly pick up new knowledge and skills through observation and reasoning (Gweon & Schulz, 2011; Stahl & Feigenson, 2015; Téglás et al., 2011; Xu, Cote, & Baker, 2005). One of the most fundamental systems that support all their daily explorations is Visual Working Memory (VWM) - a mechanism that holds information actively in mind and allows for manipulating visual information during ongoing cognitive tasks (Baddeley, 1986). Early development of VWM plays an important role on later cognitive abilities (Conway, Kane, & Engle, 2003) and reading comprehension and academic achievement (Bull, Espy, & Wiebe, 2008; De Smedt et al., 2009; Krajewski & Schneider, 2009; Swanson, 2011).

Attention is the mechanism that “turns looking into seeing” (Carrasco, 2011). Yet, little developmental research has examined the interface of attention and visual working memory, where what is seen is maintained for use in ongoing visual tasks (Baddeley, 1996). In Chapter 1, using the task-evoked pupil response – a sensitive, real-time, involuntary measure of focused attention that has been shown to correlate with VWM performance in adults and older children – I examined the relationship between focused attention and VWM in 13-month-olds. I used a Delayed Match Retrieval paradigm (Kaldy, Guillory, & Blaser, 2016), to test infants’ VWM for object-location bindings – what went where – while recording anticipatory gaze responses and pupil dilation. Results showed that infants with greater focused attention during memory encoding showed significantly better memory performance. As well, trials that ended in a correct response had significantly greater pupil response during memory encoding than incorrect trials. Taken together, this shows that pupillometry can be used as a measure of focused attention in infants, and a means to identify those individuals, or moments, where cognitive effort is maximized.

Infants’ ability to remember objects and their locations emerges during the first year of life (Kaldy & Leslie, 2005; Richardson & Kirkham, 2004; Ross-sheehy, Oakes, & Luck, 2003). However, not much is known about infants’ ability to track objects’ identities in a dynamic environment. In Chapter 2, I tailored the Delayed Match Retrieval eye-tracking paradigm (Kaldy et al., 2016) to study infants’ ability to track two object identities during occlusion - an infant version of Multiple Identity Tracking (MIT) (Oksama & Hyönä, 2004). Delayed Match Retrieval uses virtual ‘cards’ as stimuli that are first shown face-up, exposing to-be-remembered information, then turned face-down, occluding it. Here, cards were subject to movement during the face-down occlusion period. I used complex, non-nameable objects as card faces to discourage verbal rehearsal. In three experiments (N = 110), I compared infants’ ability to track object identities when two, previously exposed, cards were static (Experiment 1), were moved into new positions along the same trajectory (Experiment 2), or were moved along different trajectories (Experiment 3), while face down. I found that 20-month-olds could remember two object identities when static, however, it was not until 25 months of age that infants could track when movement was introduced. The results show that the ability to track multiple identities in visual working memory is present by 25 months of age.

The number of objects that infants can remember in their visual working memory increases rapidly during the first few years of life (Oakes, Baumgartner, Barrett, Messenger, & Luck, 2013; Ross-Sheehy et al., 2003). However, less is understood about their visual working memory representational format - whether they represent an object as a whole, or as multiple features that are combined into an object? In Chapter 3, I adopted the Delayed Match Retrieval eye-tracking paradigm (Kaldy et al., 2016) to examine this question. I tested 30-month-old toddlers’ ability to remember three object-location bindings when the stimuli are all unique (Experiment 1) and when the stimuli are similar (Experiment 2), where I modified the stimuli to share features such as color and shape. Results in Experiment 1 showed that 30-month-olds could remember three object-location bindings in their visual working memory when the stimuli were unique. Similar, but less robust results were found when the to-be-remembered objects shared features (Experiment 2). Further analysis suggested the less robust performance in Experiment 2 was not due to the loss of a subset of information about each object, but a less precise representation overall, as well as a potential limiting factor of object-location misbinding. By adopting the Delayed Match Retrieval paradigm to examine visual working memory development from 1 to 3 years of age, I reveal the role of focused attention on visual working memory performance (Chapter 1), developmental increases in infants’ ability to track multiple objects in visual working memory (Chapter 2), and toddlers’ representational format of visual working memory (Chapter 3). Taken together, these findings further our understanding of the underlying mechanism of visual working memory in early development.


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