The Effect of Poor Source Code Lexicon and Readability on Developers' Cognitive Load

Abstract

It has been well documented that a large portion of the cost of any software lies in the time spent by developers in understanding a program's source code before any changes can be undertaken. One of the main contributors to software comprehension, by subsequent developers or by the authors themselves, has to do with the quality of the lexicon, (i.e., the identifiers and comments) that is used by developers to embed domain concepts and to communicate with their teammates. In fact, previous research shows that there is a positive correlation between the quality of identifiers and the quality of a software project. Results suggest that poor quality lexicon impairs program comprehension and consequently increases the effort that developers must spend to maintain the software. However, we do not yet know or have any empirical evidence, of the relationship between the quality of the lexicon and the cognitive load that developers experience when trying to understand a piece of software. Given the associated costs, there is a critical need to empirically characterize the impact of the quality of the lexicon on developers' ability to comprehend a program. In this study, we explore the effect of poor source code lexicon and readability on developers' cognitive load as measured by a cutting-edge and minimally invasive functional brain imaging technique called functional Near Infrared Spectroscopy (fNIRS). Additionally, while developers perform software comprehension tasks, we map cognitive load data to source code identifiers using an eye tracking device. Our results show that the presence of linguistic antipatterns in source code significantly increases the developers' cognitive load.