Post hoc analysis revealed that 17‐ and 23‐month‐old mice spent a longer time in contact with the unfamiliar conspecific of the same age than 2‐month‐old mice, although the behavioral differences among the age groups failed to reach significance after the Bonferroni correction (17 and 23 mo > 2 mo, P = 0.0365 and P = 0.0314, respectively).
For the third footshock, there was a nominally significant effect of age on the distance traveled (age effect, F 3,56 = 2.88, P = 0.0441; age × time interaction, F 42,784 = 1.76, P = 0.0025), and post hoc comparisons revealed that there were no significant differences in the total distance traveled during and after the footshock between age groups.
A marginally significant effect of age was found on the total duration of contacts (Figure 3 C: F 3,35 = 2.92, P = 0.0477).
Some cases in which behavioral differences were observed between age groups did not reach statistical significance, possibly due to the relatively small number of animals in each age group in this study.
The present study also showed that vertical activity and center time in the open field test significantly increased in middle‐aged (11 mo) mice compared to those in young (2 mo) mice, whereas our previous study found no significant differences in these behaviors between young (2‐3 mo) and middle‐aged (8‐12 mo) mice, although middle‐aged mice showed a trend toward an increase in those behaviors.