Naming conventions are generally adopted in an effort to improve program comprehension. Two of the most popular conventions are alternatives for composing multi-word identifiers: the use of underscores and the use of camel casing. While most programmers have a personal opinion as to which style is better, empirical study forms a more appropriate basis for choosing between them. The central hypothesis considered herein is that identifier style affects the speed and accuracy of manipulating programs. An empirical study of 135 programmers and non-programmers was conducted to better understand the impact of identifier style on code readability. The experiment builds on past work of others who study how readers of natural language perform such tasks. Results indicate that camel casing leads to higher accuracy among all subjects regardless of training, and those trained in camel casing are able to recognize identifiers in the camel case style faster than identifiers in the underscore style.