Program comprehension is an important, but hard to measure cognitive process. This makes it difficult to provide suitable programming languages, tools, or coding conventions to support developers in their everyday work. Here, we explore whether functional magnetic resonance imaging (fMRI) is feasible for soundly measuring program comprehension. To this end, we observed 17 participants inside an fMRI scanner while they were comprehending source code. The results show a clear, distinct activation of five brain regions, which are related to working memory, attention, and language processing, which all fit well to our understanding of program comprehension. Furthermore, we found reduced activity in the default mode network, indicating the cognitive effort necessary for program comprehension. We also observed that familiarity with Java as underlying programming language reduced cognitive effort during program comprehension. To gain confidence in the results and the method, we replicated the study with 11 new participants and largely confirmed our findings. Our results encourage us and, hopefully, others to use fMRI to observe programmers and, in the long run, answer questions, such as: How should we train programmers? Can we train someone to become an excellent programmer? How effective are new languages and tools for program comprehension?

Most modern software programs cannot be understood in their entirety by a single programmer. Instead, programmers must rely on a set of cognitive processes that aid in seeking, filtering, and shaping relevant information for a given programming task. Several theories have been proposed to explain these processes, such as ``beacons,' for locating relevant code, and ``plans,'' for encoding cognitive models. However, these theories are decades old and lack validation with modern cognitive-neuroscience methods. In this paper, we report on a study using functional magnetic resonance imaging (fMRI) with 11 participants who performed program comprehension tasks. We manipulated experimental conditions related to beacons and layout to isolate specific cognitive processes related to bottom-up comprehension and comprehension based on semantic cues. We found evidence of semantic chunking during bottom-up comprehension and lower activation of brain areas during comprehension based on semantic cues, confirming that beacons ease comprehension.

Program comprehension is an important cognitive process that inherently eludes direct measurement. Thus, researchers are struggling with providing suitable programming languages, tools, or coding conventions to support developers in their everyday work. In this paper, we explore whether functional magnetic resonance imaging (fMRI), which is well established in cognitive neuroscience, is feasible to soundly measure program comprehension. In a controlled experiment, we observed 17 participants inside an fMRI scanner while they were comprehending short source-code snippets, which we contrasted with locating syntax errors. We found a clear, distinct activation pattern of five brain regions, which are related to working memory, attention, and language processing---all processes that fit well to our understanding of program comprehension. Our results encourage us and, hopefully, other researchers to use fMRI in future studies to measure program comprehension and, in the long run, answer questions, such as: Can we predict whether someone will be an excellent programmer? How effective are new languages and tools for program understanding? How should we train programmers?