triangle gestalt can readily be seen or not is a separate issue; hence, it is irrelevant to the
validity of Experiment 2.
Can the perceptual grouping hypothesis account for the basic sensory fording? The
perceptual grouping hypothesis prescribes that when the items of the probed category
form a good gestalt (i.e., a triangle in Experiment 2), partial report by category should be
better than when no such good gestalt is available. This theoretical expectation of the
perceptual grouping hypothesis is not met. Moreover, the large-capacity finding is
obtained only when selection is by row, not by category. In other words, results from
Experiment 2 cast doubts on the suggestion that good perceptual organization within a
stimulus may inflate subjects' partial-report performance in a typical partial-report
experiment.
GENERAL DISCUSSION
Merikle (1980) proposed two alternative explanations for the large-capacity and the basic
sensory findings, namely, the display-instruction compatibility and the perceptual
grouping hypotheses. Both of these hypotheses are primarily accounts of some procedural
artifacts that might be operative in Sperling's (1960) partial-report paradigm.
The general thrust of Merikle's (1980) argument is that, if the artifacts are removed, both
the large-capacity and the basic sensory findings should not be obtained. Consequently,
the iconic store, as a hypothetical mechanism, would have to be treated very differently.
Empirical data obtained from a series of experiments devised by Merikle to substantiate
this argument led to the rejection of an underlying mechanism responsible for what
Coltheart (1980) called "information persistence" in favor of a multichannel view of
neural, or visible, persistence.
However, a necessary procedural requirement of the partial-report task was not observed
in Merikle's (1980) study. There is no empirical support for either the display-instruction
compatibility hypothesis or the perceptual grouping hypothesis when the partial-report
cue is presented at or after stimulus offset.
Merikle (1980) also suggested that the absence of any partial-report superiority when
category information is the selection dimension may be attributable to the fact that a
wrong whole-report baseline was used. Merikle noted that, when whole report was made
uncertain in Dick's (1969) study, category selection criterion is effective in bringing
about partial-report superiority. It is suggested that the proper whole-report baseline
should be the subject's whole-report performance when there is uncertainty about when to
carry out the whole report (Merikle, 1980).
The partial-report task is a very unusual and difficult task. It is sometimes necessary to
spend the first quarter of an hour of the first session in assuring the subjects that the
partial-report task is not an impossible one. Partial-report data collected from subjects