Models offer visual support for analyzing complex domains such
as business processes and information systems. In both cases,
models are developed using graphical modelling languages. In our
study we focus on usability evaluation of modelling languages for
the model interpretation scenario. The study is based on a causal
model of hypotheses, which was developed under consideration of
psychological cognitive theories and usability theory. Survey data
is collected and the causal relations hypotheses are assessed using
a structure equation modelling approach. Our study shows
important findings for practical and theoretical issues of how
differing modelling languages are influencing usability attributes
on causal stages in model interpretation.