Shaw, John S. III; Zerr, Tana K. (2003). Extra effort during memory retrieval may be associated with
increases in eyewitness confidence. Law & Human
Behavior, 27, 315-329.
INTRODUCTION:
Eyewitnesses often try to work hard to perform
well when testifying in court and their motivation may be selfish or
unselfish. Some may try to work hard
because they understand the importance of their testimony. Others may try to work hard to impress their
peers and themselves, which could improve their self-esteem. Most witnesses believe that extra effort
on their part will result in increased accuracy. However, simply trying harder is not sufficient to produce more
accurate memories. Poor encoding can
alter memories so that any type of retrieval will have no effect on the
accuracy of memories. Also, there is
very little any type of retrieval can do to recover the effects the delay
between the event and trial has on memory.
While extra effort may not increase accuracy, it
can however increase confidence. Most
witnesses are likely to conclude that because the worked harder at being a
“good” witness, they will produce accurate testimony. According to the self-perception theory, this will result in high
confidence ratings. Shaw, Woythaler, et
al. (2001) found evidence to support the theory that extra effort leads to
higher confidence on a memory test.
Participants were informed, just before the memory test, some test items
“counted” and some did not. Those that
did not count were part of a future study.
Participants reported higher confidence on the items that “counted” than
those that did not. Response accuracy
was the same, regardless of confidence ratings.
OVERVIEW:
This study was designed to add to Shaw,
Woythaler, et al. (2001) in three ways.
Shaw, Woythaler et al. (2001) did not measure effort so this study was
designed to measure whether extra effort increased eyewitness confidence. Another aspect the authors wanted to measure
the effect of selfish motivation to use more effort on witness confidence.
The event to be tested was a presentation by a
visitor to an intro to psych class. A
surprise memory test was given five days later with questions about the
visitor’s presentation and appearance (eyewitness and ear-witness memory). The subjects were tested over incidental, as
opposed to intentional, learning. Half
of the subjects could potentially earn prizes (such as candy or money) which
constituted the high-motivation condition.
The other half were not eligible for prizes (low-motivation
condition). While this kind of selfish
motivation may not directly parallel the types of selfish motivation in the
courtroom, it was designed to provide selfish motivation to cause the witnesses
to expend more effort. Also, witnesses
were not rewarded for expending more effort but for higher levels of
performance that might come about as a result of this extra effort.
Using the self-perception theory (Bem, 1967,
1972), the authors hypothesized that confidence would be higher in the high-motivation
condition than in the low-motivation condition. Participants should give higher confidence ratings because they
believe that extra effort correlates with increased accuracy. However, the authors did not expect an
actual effect of effort on accuracy.
They also believed that there would be a positive correlation between
confidence and effort and that there would be a negative correlation between
difficulty of questions and confidence.
Another hypothesis was that the confidence-accuracy and effort-accuracy
correlations would be larger in the low-motivation condition rather than the
high motivation condition. This
prediction was made on the basis that the authors expected individual
differences to play a part in the motivation manipulation. (The presence of reward would cause some
participants to work harder while it would not have any effect on those who
naturally work hard.)
METHODS:
During the third week of classes, 75 undergrad
students in an intro to psych class heard a short, 9 minute talk given by the
director of the counseling center. She
described the roles of counselors and discussed educational programs. Five days later, the students were given a
surprise memory test about the speaker.
There were 12 multiple choice questions about the speaker’s appearance
and presentation. There were three
possible answers for each of the questions.
Before working on the questions, students were told that half of the
class was eligible for prizes and the other half was not. A random drawing determined which half
(based on the color of paper the questionnaire was printed on) was eligible for
the prizes ($25 for first place and candy bars for the next 10 highest). After going through the questionnaire at
their own pace, the students received a form for indicating amount of effort
and confidence ratings, both of which were on 11-point scales. Students also indicated how many questions
they believed the answered correctly.
RESULTS:
The motivation condition in which students were
placed did not affect accuracy, which was expected (M=46.6% correct for high, M=46.5% correct for
low). However, motivation had no effect
on confidence ratings, which was not expected (M=3.46 for high, M=3.44 for low). Motivation also did not affect the mean
accuracy estimate. Response accuracy
was significantly correlated with confidence and effort in the low-motivation
condition, but was completely unrelated in the high-motivation condition (Table
1, p. 321). Consistent with the
authors’ hypothesis, confidence was positively correlated to effort and
negatively correlated with difficulty.
Also, accuracy estimate was positively correlated with effort and
negatively correlated with difficulty in the low-motivation condition. (The same pattern seemed to appear in the high-motivation
as well, but was not statistically reliable.)
Finally, confidence and accuracy estimate were highly correlated for
both conditions.
Figure 1 (p. 323) shows the mean confidence
ratings as a function of motivation and effort and Figure 2 (p. 324) shows the
data for accuracy estimate. There was a
main effect of effort for both confidence and accuracy. And in Figure 2 there was an interaction
between motivation and effort for the accuracy estimate.
DISCUSSION:
This study shows that although witnesses may
expend extra effort and report higher confidence, it does not result in higher
accuracy. The high-effort group had
much larger confidence ratings and accuracy estimates than the low-effort group. However, accuracy did not differ between the
groups. These results follow the
self-perception explanation (Bem, 1967, 1972) where students may believe that
extra work will result in higher accuracy which increased confidence even
though there was no change in accuracy.
Another explanation is that post event
questioning or reflective thought can lead to higher confidence (Wells and
Bradfield, 1999). Another possible
explanation is that participants may have subjected to demand characteristics
and thought that since they put more effort into the memory test that they should report higher confidence.
The fact that motivation did not affect witness
confidence may have been due to the fact that the motivation manipulation
simply was not powerful enough.
However, this does not take away from the importance of the finding that
witness effort was significantly correlated with witness confidence.
IMPLICATIONS:
Jurors typically consider eyewitness confidence
as an indicator of accuracy (Cutler, Penrod, & Dexter, 1990; Cutler,
Penrod, & Stuve, 1998; Wells, Lindsay, & Ferguson, 1979). The results from this study provide
troubling implications that even though an eyewitness may be extremely
confident about their testimony; it may simply be due to extra effort, not to
accuracy. This situation does not occur
only in the courtroom but also during police interviews and while viewing
lineups. There is a lot of pressure on
the witness to “get it right,” and because of this, the witnesses will put
extra effort into their testimony which in turn, will result in high
confidence. But as this study shows,
increased accuracy may not go along with this increased confidence.