Understanding how native speakers acquire the phonological patterns in their language is a key task for the field of phonology. Numerous studies have suggested that phonological learning is a biased process: certain phonological patterns are easily accessed and learned by the speakers, while others show acquisition difficulties. These differences in pattern learnability can partially explain the observed phonological typology: patterns that are easier to learn occur more frequently in the world's languages, whereas patterns that show learning disadvantages may occur less frequently. Therefore, an important aspect of understanding phonological learning and typology is to understand the nature of these learning biases. In this dissertation, I approach the issue of phonological learning bias by focusing on the phenomenon of the Obligatory Contour Principle (OCP), i.e., the avoidance of adjacent similar units in the lexicon. Although this pattern has been attested in a wide range of languages (e.g., Cantonese, Dutch, English, Mandarin, Muna, Quechua, among many others) and supported by psycholinguistic experiments, how the OCP impacts phonological learning has yet to be explored in detail. Using a series of artificial grammar learning experiments, I present evidence that the OCP plays an active role in phonological learning, in that similarity avoidance patterns are easier to learn compared to other patterns. Specifically, an OCP-based phonotactic pattern was better learned than a complexity-matching consonant major place harmony phonotactic pattern, and an arbitrary control pattern (Experiment 1). Similarly, an OCP-triggered alternation pattern was better learned than an arbitrarily conditioned alternation pattern (Experiment 2). Experiment 3 further showed that an OCP effect in stem phonotactics could aid the learning of an OCP-triggered alternation. Typological asymmetries can be observed within the OCP patterns. For example, OCP effects in the labial place of articulation are stronger than other consonant places, and identical sequences sometimes can be exempted from the co-occurrence restriction. Two further artificial grammar learning experiments were conducted to investigate if these asymmetries can be explained by learning biases as well. While a learning bias favoring OCP-Labial was found (Experiment 4), no learning advantage for the identity avoidance was reproduced in a lab setting (Experiment 5).Based on these experimental results, I argue that phonological learning is a biased process: speakers are equipped with a synchronous learning bias that causes the similarity avoidance patterns to receive an advantage during phonological learning. The typological frequency of the OCP patterns is thus explained by this bias. By incorporating the similarity avoidance into the set of possible biases, this dissertation provides further insights into the nature of phonological learning bias, phonological acquisition, language change, and typology. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]