  Background: Despite similar education and background, programmers can exhibit
vast differences in efficacy. While research has identified some potential
factors, such as programming experience and domain knowledge, the effect of
these factors on programmers' efficacy is not well understood.
  Aims: We aim at unraveling the relationship between efficacy (speed and
correctness) and measures of programming experience. We further investigate the
correlates of programmer efficacy in terms of reading behavior and cognitive
load.
  Method: For this purpose, we conducted a controlled experiment with
37~participants using electroencephalography (EEG) and eye tracking. We asked
participants to comprehend up to 32 Java source-code snippets and observed
their eye gaze and neural correlates of cognitive load. We analyzed the
correlation of participants' efficacy with popular programming experience
measures.
  Results: We found that programmers with high efficacy read source code more
targeted and with lower cognitive load. Commonly used experience levels do not
predict programmer efficacy well, but self-estimation and indicators of
learning eagerness are fairly accurate.
  Implications: The identified correlates of programmer efficacy can be used
for future research and practice (e.g., hiring). Future research should also
consider efficacy as a group sampling method, rather than using simple
experience measures.
