Provided by Cognitive Sciences ePrint Archive
Memory & Cognition, 1985, 13 (3), 256-264
Iconic store and partial report
SIU L. CHOW
University of Wollongong, Wollongong, New South Wales, Australia1
The iconic store has recently been challenged on the grounds that data in
its favor may have resulted from some procedural artifacts. The
display-instruction compatibility and perceptual grouping hypotheses were
reexamined in two experiments with the partial-report paradigm. When
care was taken to rectify some procedural problems found in Merikle's
(1980) study, it was established that the iconic store (as a hypothetical
mechanism) can still be validly entertained. This report demonstrates one
important procedural point in studying the iconic store with the partial-
report task, namely, that subjects must be given more than token training
on the partial-report task.
An example is useful in illustrating the meaning of "iconic store." A subject is given a
five-letter array for 50 msec and is asked to recall as many letters as possible. In the
absence of any masking (forward or backward), the subject can do the task quite easily.
Of interest is the interval between the onset of the stimulus array and the time at which
the subject finishes responding. The typical estimate is about 1.5 sec. Because the
stimulus is present for only .05 sec, the subject is responding to something that is
physically absent much of the time. This phenomenon suggests that information about the
stimulus array must have been preserved long enough for the subject to respond. The
crucial question is how the mechanism underlying such a feat should be characterized.
There are currently two schools of thought. Some investigators (e.g., Holding, 1970,
1971, 1973, 1975; Merikle, 1980), although they accept the phenomenon that a briefly
shown stimulus may appear to persist longer than the actual stimulus duration, suggest
that the inferred preservation of information can easily be accounted for in terms of the
physical properties of the visual system. Moreover, such a hypothetical mechanism is
deemed theoretically irrelevant because it does not have any ecological validity (Haber,
1983). The term "visual persistence" is used to stand for the underlying mechanism
(Merikle, 1980). Relevant to this position is the finding that the locus of visual
persistence may be at the retinal level (Haber, 1983; Sakitt, 1975, 1976a, 1976b; Sakitt &
Appelman, 1978; Sakitt & Long, 1978, 1979). The term "visual persistence" seems to be
compatible with either "neural persistence" or "visible persistence" as recognized by
Coltheart (1980).
Other investigators (notably Coltheart, 1975, 1980, 1983; Coltheart, Lea, & Thompson,
1974; Haber, 1971; Neisser, 1967) are willing to ascribe to the underlying mechanism
some properties not definable in terms of the physical properties of the visual system qua