The Bell Curve : Reaction time and IQ

Arun Gupta (
Sun, 2 Apr 1995 13:26:17 GMT

People may remember the claim that reaction time experiments (which
have no built-in bias, by their very nature) show that there is a
significant black/white difference. Furthermore, it is claimed that
these tests correlate significantly with IQ. [see for example page
282-283 of Murray and Herrnstein's TBC ].

Well, in a compilation "The Bell Curve Debate : History, Documents,
Opinions", an essay by Leon Kamin contains the following :

"Here is another example of mis-citation in The Bell Curve, this
time part of the effort to convince readers that blacks are less
intelligent than whites. Hernnstein and Murray maintain that "smarter
people process [information] faster than less smart people," and that
reaction time, requiring "no concious thought", indexes an underlying
"neurologic processing speed...akin to the speed of the microprocessor
in a computer".

"Reaction time" is the time elapsing between onset of a signal light
and a subject's lifting a finger to initiate a required response;
"movement time" is the additional time needed to execute the response.

Herrnstein and Murray report, "In modern studies, reaction time is
correlated with the g factor in IQ tests .... Movement time is much
less correlated with IQ...." The cognitive processing, they explain,
is measured by reaction time, while movement time measures "small
motor skills".

The work of Arthur Jensen is cited as follows : "The consistent
result of many studies is that white reaction time is faster than
black reaction time, but black movement time is faster than white
movement time." White men can't jump, but they have faster computer
chips inside their heads.

The cited Jensen paper (1993) presents data for blacks and whites,
for both reaction time and movement time, for three different
"elementary cognitive tasks."

The results are not, despite Herrnstein and Murray's contention,
"consistent". Blacks are reported to have faster movement times
on only two of the three tasks; and they have faster reaction times
than whites on one task, "choice reaction time".

Simple reaction time merely requires the subject to respond as quickly
as possible to a given stimulus each time it occurs. Choice reaction
time requires him/her to react differently to various stimuli as they
are presented in an unpredictable order. Thus it is said to be
cognitively more complex, and to require more processing, than simple
reaction time.

When Jensen first used reaction time in 1975 as a measure of racial
differences in intelligence, he claimed that blacks and whites did
not differ in simple reaction time, but that whites, with their
higher intelligence, were faster in choice reaction time.

He repeated this ludicrous claim incessantly while refusing to make
the raw data of his study available for inspection. Then in a
subsequent 1984 paper, he was unable to repeat his earlier finding
in a new study described as "inexplicably inconsistent" with his
1975 results.

Now, in the still newer 1993 study cited by Herrnstein and Murray,
Jensen reports as "an apparent anomaly" that (once again !) blacks
are slightly faster in choice reaction time than whites.

Those swift couriers, Hernnstein and Murray, are not stayed from their
appointed rounds by anomalies and inconsistencies. Two out of three
is not conclusive. Why not make the series three out of five ?


Any comments, anybody ?
-arun gupta