  The Contextuality-by-Default (CbD) theory allows one to separate
contextuality from context-dependent errors and violations of selective
influences (aka "no-signaling" or "no-disturbance" principles). This makes the
theory especially applicable to behavioral systems, where violations of
selective influences are ubiquitous. For cyclic systems with binary random
variables, CbD provides necessary and sufficient conditions for
noncontextuality, and these conditions are known to be breached in certain
quantum systems. We apply the theory of cyclic systems to a psychophysical
double-detection experiment, in which observers were asked to determine
presence or absence of a signal property in each of two simultaneously
presented stimuli. The results, as in all other behavioral and social systems
previous analyzed, indicate lack of contextuality. The role of context in
double-detection is confined to lack of selectiveness: the distribution of
responses to one of the stimuli is influenced by the state of the other
stimulus.
