These data were obtained in a paper-and-pencil classroom exercise.
Subjects were participants in the 2002 Annual Summer Cognitive Science Workshop for college students,
sponsored by the Institute for Research in Cognitive Science, and the Center for Cognitive Neuroscience,
at the University of Pennsylvania.
Each subject ran in twelve conditions:
three sizes of target set (1, 2, 4) within each of
two frequencies of target, within each of
two levels of preview (no preview, full preview).
The order of the two preview conditions was balanced across subjects.
Within each preview condition, the order of the frequency conditions was balanced across subjects.
Within each frequency condition, subjects started with a target set of size 3 (practice),
and then worked with sets of size 1, 2, and 4,
whose order varied across subjects according to a latin square.
In each condition, the display contained five rows of twenty digits.
The subjects' task was to mark each digit, underlining it if it was a target, crossing it out if not.
In the no-preview condition, subjects made their marks through a hole in a "mask" that they slid over the display.
In the full preview condition they did not use the mask.
(A better procedure would have used a mask containing a hole under both conditions,
the mask being opaque and transparent in the two conditions, respectively.)
An hour-minute-second time display (nist.time.gov) was projected on a screen;
for each condition, subjects wrote down their starting and ending times, obtained by consulting the screen.
For purposes of this analysis, data were averaged over the two target-frequency conditions.
This classroom exercise was a partial approximate replication of an
described in an unpublished PhD dissertation
(William G. Chase (1969) Parameters of visual and memory search. PhD dissertation, University of Wisconsin.)
Chase's experiments are described in Section 14.5.14 of Sternberg, S. (1998) Discovering mental processing stages:
The method of additive factors.
In D. Scarborough & S. Sternberg (Eds.) An Invitation to Cognitive Science,
Volume 4: Methods, Models, and Conceptual Issues. Cambridge, MA : MIT Press. Pp. 703-863.