We investigated the effort associated with incidental- and intentional-memory encoding of repeated human faces (Experiment 1) and car fronts (Experiment 2). Some stimuli were repeated, and the lag (number of intervening items) was varied. Encoding effort

1
THE SPACING EFFECT EVIDENCE FROM
DURATION PRODUCTIONS AND RECOGNITION
MEMORY Richard A. Block, Frank A. Bosco, Travis
S. Schanz Montana State University, Bozeman, MT
Discussion
Experiment 1 Faces
Experiment 2 Cars
Abstract
We investigated the effort associated with
incidental- and intentional-memory encoding of
repeated human faces (Experiment 1) and car
fronts (Experiment 2). Some stimuli were
repeated, and the lag (number of intervening
items) was varied. Encoding effort was inferred
by secondary task costs associated with
concurrently performed temporal productions, a
sensitive index of effort. Recognition memory
performance results were typical however,
temporal productions of the second presentation
were about 80 ms shorter for massed (immediate)
repetitions than for all other lags. These
findings clarify models of the spacing effect.
The stimuli were frontal views of cars. As
before, 64 subjects were assigned to each memory
condition (intentional vs. incidental).
In both experiments, recognition memory showed
typical spacing and lag effects Performance was
a monotonically increasing, but decelerating
function of lag between the two presentations (P1
and P2). However, temporal productions of P2
showed a different effect They were about 80 ms
shorter for massed repetitions than for all other
lags. One exception was the incidental-memory
condition in Experiment 2, which showed no
spacing effect. Perhaps this reflects the
relatively less automatic processing of cars
versus faces. Compared to subjects in the
incidental-memory condition, subjects in the
intentional-memory condition made longer temporal
productions and showed better recognition-memory
performance. These findings clarify models of
the spacing effect. The spacing effect and the
lag effect result from separable processes. The
spacing effect is explainable in terms of a
habituation-recovery model or an
attentional-deficiency model. However, the lag
effect is apparently not a consequence of varying
attentional demands, because the temporal
productions did not vary as a function of lag
(beyond that of an immediate repetition). An
encoding-variability model of the lag effect is
one viable model in the light of our data.
The stimuli were unfamiliar human faces. A total
of 64 subjects was assigned to each memory
condition (intentional vs. incidental).
The temporal productions show a spacing effect
(in the intentional condition), but no lag
effect. In addition, they were longer in the
intentional than in the incidental condition.
The temporal productions show a spacing effect,
but no lag effect. In addition, they were longer
in the intentional than in the incidental
condition.
Introduction
Memory improves if two or more presentations of
an event are separated by other events. This
finding is called the spacing effect, or
distributed practice effect. It is a reliable
effect on memory with many practical
consequences. A spacing effect has been found for
a wide variety of materials, ages of subjects,
and memory tests. Because it is so ubiquitous, it
is not well understood. Researchers have proposed
several models. The spacing effect may result
from two or more processes, one involving massed
(immediately repeated) presentations versus
distributed presentations and the other involving
the number of items intervening between the first
and second presentation. We call the first effect
the spacing effect and the latter effect the lag
effect. We used a concurrent task to investigate
the spacing effect. Subjects were asked to
delimit a specific stimulus exposure duration.
This method, called temporal production, is
considered to be a sensitive measure of
attentional demands. Subjects received brief
training (with feedback) on producing 2-s
durations. Then they self-paced the exposure of
100 stimuli (including some filler items),
attempting to expose each for 2 s. Some stimuli
were presented once (P1 only), and some were
presented twice (P1 and P2) at lags of 0, 1, 5,
or 13 intervening stimuli. Memory condition was
also manipulated Some subjects received
intentional-memory instructions, and others
received incidental-memory instructions. Finally,
we tested recognition memory for presented
stimuli, along with nonpresented stimuli.
In contrast, the recognition data show both
spacing and lag effects. As in Experiment 1,
memory was better in the intentional than in the
incidental condition.
In contrast, the recognition data show both
spacing and lag effects. As expected, memory was
better in the intentional than in the incidental
condition.
References
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