Specific star-formation rate versus stellar mass for star-forming galaxies in groups (red) and the field (yellow). Individual points are re-binned in hexagons and only bins with more than two counts are shown. Black filled points show the median for the groups, empty ones for the field. Inset histograms show the distribution of the difference between the median relation in groups and in the field. Green symbols at z = 0.8–1.0 are obtained from MIPS stacking by Patel et al. (2009) and represent the field (crosses), groups (plus sign) and clusters (diamonds).