Two studies on measurement of M capacity are reported. Study 1, with 1
91 subjects aged 6-11, found factor-analytical and correlational evide
nce that five M capacity tests share a common source of variance, and
that, with age, they increase at a similar rate. Study 2, with 124 sub
jects aged 6-10 years, replicated the previous findings. It is suggest
ed that, in this age range, M capacity can be measured with a battery
of tests.