USE OF PHYSIOLOGICAL MEASURES TO ASSESS INDIVIDUAL-DIFFERENCES IN REACTIVITY

Individual differences in reactivity are relevant to animal welfare st udies. Since reactivity refers not only to behavioural, but also to ph ysiological responses, the latter could be used to assess such individ ual differences. Both changes in heart rate and in glucocorticoid conc entration in plasma have been used with somewhat contradictory results . This may be due to the following causes: ( 1 ) differences in the ex act methodology used, (2) use in the same experiment of animals reared in different environments and (3) use of physiological measures that may be affected by many different causes. It is suggested that althoug h physiological measures may be used to assess individual differences in reactivity, particular attention must be paid to the exact methodol ogy used. Furthermore, the results are likely to be more meaningful wh en animals reared in the same environment are used and when behavioura l measures are also taken.