In this research, I used a mixed-methods approach employing both autobiographical reasoning and psychometric instruments through a survey design to explore how the four cognitive mechanisms of Work Identity Theory (WIT) were developed in 754 college-educated participants' lives. WIT is a vocational identity theory, which posits that, four cognitive mechanism: Effort, Reflection, Appraisal and Fusion are used by individuals to define their vocational identities. By vocational identity, I am referring to the sum total of a person's self-thoughts, attitudes, beliefs and actions that are informed by work experience. By cognitive mechanisms, I am referring to the mental processes used to develop a vocational identity. Multiple theories have emerged over the past one hundred years to explain the concept of a vocational identity. This study seeks to make two new contributions to the set of existing theories. First, the definition I propose of vocational identity does not have an implied, positive valence for having a well-developed vocational identity, but it encompass the many ways people define themselves in relation to their work. In contrast, the most frequently cited vocational identity theories are stage theories in which the highest stage is regarded as optimal. I posit this difference is important because it permits individuals to have different attitudes toward work and themselves without being stigmatized by the theory. Second, the focus of this research is to identify how the cognitive mechanisms come to exist through the study of participants' self-identified most important developmental experiences in relation to each WIT cognitive mechanism. In addition to experiences, I also study the participants' Need for Cognition (NFC), the propensity to engage in and enjoy thinking. This study has two key findings. First, people who think more deeply about their own lives, experience more development, at least in the cognitive mechanisms of WIT. Second, our life experiences do not matter as much as the depth of thought we give to them and subsequently what we take from them concerning the development of WIT's cognitive mechanisms. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]