Repeated encounters with unfamiliar conspecifics in large groups of domestic birds create a potentially stressful social environment which can affect the birds' emotional reactivity and consequently their welfare. As social relationships between young quail are particularly influenced by their social motivation (i.e., the motivation to seek close proximity with conspecifics), it is likely that the reaction of quail to repeated encounters with strangers depends on their social motivation. The aim of this study was to assess the emotional reactivity of quail chicks with high (HSR) or low (LSR) social motivation housed under stable and unstable social conditions. Quail chicks were housed either in stable pairs, i.e. remaining with the same cagemate until testing (N(HSR) = 19 and N(LSR) = 18 pairs), or in unstable pairs, i.e. changing cagemate daily from 6 to 13 days of age (N(HSR) 20 and N(LSR) = 19 pairs). Emotional reactivity was measured using a novel object test on day 14, and an emergence test and a tonic immobility test on day 15. The social condition affected the number of induction attempts of quail chicks in the tonic immobility test but only in the LSR ones. This number of inductions was lower under the stable than under the unstable social condition in this line. Moreover, the HSR chicks showed greater disturbance than the LSR ones in the three behavioural tests. In conclusion, social instability did not affect the emotional reactivity of HSR quail chicks, which was high, regardless of social condition. In contrast, repeated cagemate changes seemed to decrease the emotional reactivity of LSR quail chicks. These results suggest that low social motivation makes easier the adaptation to the potential social instability encountered in large flocks. (c) 2010 Elsevier B.V. All rights reserved.