  We present Gemini Multi-Object Spectrograph (GMOS) spectroscopic observations
of 95 galaxies from the Arp & Madore (1987) catalogue of peculiar galaxies.
These galaxies have been selected because they appear to be in pairs and small
groups. These observations have allowed us to confirm that 60 galaxies are
indeed interacting systems. For the confirmed interacting sample, we have built
a matched control sample of isolated galaxies. We present an analysis of the
stellar populations and nuclear activity in the interacting galaxies and
compare them with the isolated galaxies. We find a median light (mass) fraction
of 55% (10%) in the interacting galaxies coming from stellar populations
younger than 2 Gyr and 28% (3%) in the case of the isolated galaxies. More than
half of the interacting galaxies are dominated by this young stellar
population, while the isolated ones have most of their light coming from older
stellar populations. We used a combination of diagnostic diagrams (BPTs and
WHAN) to classify the main ionization mechanisms of the gas. The interacting
galaxies in our sample consistently show a higher fraction of active galactic
nuclei (AGN) relative to the control sample, which ranges between 1.6 and 4
depending on the combination of diagnostic diagrams employed to classify the
galaxies and the number of galaxies considered. Our study provides further
observational evidence that interactions drive star formation and nuclear
activity in galaxies and can have a significant impact on galaxy evolution.
