  Indistinguishable quantum emitters confined to length scales smaller than the
wavelength of the light become superradiant. Compared to uncorrelated and
distinguishable emitters, superradiance results in qualitative modifications of
optical signals such as photon coincidences. However, recent experiments
revealed that similar signatures can also be obtained in situations where
emitters are too far separated to be superradiant if correlations between
emitters are induced by the wave function collapse during an
emission-angle-selective photon detection event. Here, we compare two sources
for cooperative emission, superradiance and measurement-induced cooperativity,
and analyze their impact on time-dependent optical signals. We find that an
anti-dip in photon coincidences at zero time delay is a signature of
inter-emitter correlations in general but does not unambiguously prove the
presence of superradiance. This suggests that photon coincidences at zero time
delay alone are not sufficient and time-dependent data is necessary to clearly
demonstrate a superradiant enhancement of the spontaneous radiative decay rate.
