Interest in inspection time (IT), uniformly thought to index 'speed-of
-processing', has been maintained because of its established empirical
correlation with general mental ability and performance IQ measures.
The IT procedure generally consists of a simple visual discrimination
task displayed at various critical exposure durations and immediately
followed by a suitable mask. Processing is assumed to terminate at mas
k onset, which seems inappropriate in light of the target/mask composi
te necessarily available with integration theories of backward masking
. The present paper reports five experiments involving attended and un
attended secondary stimuli and additional factor analyses of previous
studies involving IT. From these it is proposed that IT is better thou
ght of as indexing the power an individual can bring to bear within a
specific cognitive domain rather than 'speed-of-processing' per se. Th
e consequence is that the observed IT-IQ correlation is merely the ine
vitable outcome of measuring the same domain with two different tasks;
rather than due to some elemental factor such as mental speed underly
ing both tasks. Ways in which this model could be tested are discussed
. Copyright (C) 1996 Elsevier Science Ltd.