Off-campus UMass Amherst users: To download campus access dissertations, please use the following link to log into our proxy server with your UMass Amherst user name and password.

Non-UMass Amherst users: Please talk to your librarian about requesting this dissertation through interlibrary loan.

Dissertations that have an embargo placed on them will not be available to anyone until the embargo expires.



Access Type

Open Access Thesis

Document Type


Degree Program


Degree Type

Master of Science (M.S.)

Year Degree Awarded


Month Degree Awarded



Developmental studies have revealed that preschool-aged children believe that an agent’s internal properties are more important than its external properties for determining its identity over time. The current study examined the developmental origins of this understanding using a manual-search individuation task with 13-month-old infants. Subjects observed semi-transparent objects that looked and behaved like animate agents placed into box that they could reach but not see into. Across trials infants observed objects with either the same- or different-colored insides placed into the box. We found that infants used internal property differences more than external property differences to determine how many agents were involved in the event. A second experiment confirmed that this effect was specific to the domain of animate entities. These results suggest that infants are biased to see an agent’s ‘insides’ as more important for determining its identity over time than its outside properties.


First Advisor

Erik W Cheries

Second Advisor

Neil Berthier

Fourth Advisor

Adrian Staub