Right-handed subjects were tested on a bimanual task that required :he concurreni production of two different isochronous sequences. The direction of attention was manipulated by having subjects count out loud either one or the other of the sequences. Attention interacted with task performance; subjects performed very much better when attending to the faster of the two sequences. Handedness effects were seen in preference but not in performance. A fine-grained analysis of the succession of movements suggests that subjects do not perform the two sequences independently; the initiation of movement in one hand is more clearly dependent on the preceding movement in the other hand than on preceding movement by the same hand. The findings arecompatible with a unitary scheduler that provides movement initiations for both hands.

In a typical study, pairs of participants are shown an event and then are tested. One of the participants in a pair reports first, and then the second participant reports. Sometimes the first participant is accurate and sometimes inaccurate. Therefore, the second person is exposed to both 1077© 2010 The Psychonomic Society, Inc. Conformity effects in memory for actions DANIEL B. WRIGHT AND SHARI L. SCHWARTZ Florida International University, Miami, FloridaThe goal of this research was to examine whether memories for actions can be affected by information reported by another person. In two studies, pairs of participants performed 48 of a set of 96 actions. In Study 1, both members of the pairs performed the same actions, and in Study 2, they performed different actions. One week later, the members of the pairs were questioned together about whether they had or had not done all 96 actions. What one person reported greatly influenced what the other person reported for both correct and incorrect responses. This influence was maintained when the participants were later tested individually, and the participants described having pictorial memories for doing many of the actions that they had not done but had merely been suggested.

Memory conformity for images was examined using a mixed factorial design. Participants were presented with 50 images then later completed an old/new recognition test on these plus 50 fillers. Some received post-event information (PEI) attributed to a co-witness that was introduced either soon after the original 50 images were presented or 2 days later. The memory test was either soon after the co-witness PEI was shown or 2 days later. When the memory test was 2 days after receiving PEI, the PEI had no effect. PEI had a large effect when presented just before testing. The memory conformity effect was largest when PEI was presented, and the when memory test was completed 2 days after the initial presentation. Memory conformity effects were larger for new items than for old when PEI immediately preceded the test. Thus, the PEI affected the false alarm rate more than the hit rate.

People's reports are affected by what others say. The current study compared memory conformity effects of people who interacted with a confederate, and of bystanders to that interaction. A second goal was to observe if memory conformity occurs in a naturalistic setting. A male confederate approached a group of people at the beach and had a brief interaction. About a minute later a research assistant approached the group and administered a target-absent lineup to each person in the group. Memory conformity was observed. Bystanders were twice as likely to conform as those who interacted with the confederate. Forensic investigators should take into consideration the role a person plays in an event when assessing eyewitness evidence.

Although it is well-known that biased lineup instructions (i.e., those that do not inform witnesses the perpetrator may not be in the lineup) inflate false identifications, their effects on witness confidence are less well understood due to methodological limitations of past studies. We report two studies that use novel methodologies to obviate these limitations. Study 1 (N = 177) demonstrated that biased lineup instructions increased witnesses' average estimates of the likelihood that a lineup member is guilty. Study 2 (N = 137) introduces a novel debiasing paradigm that allows a parsing of choosers into those who made an identification only because of the biased instructions (induced choosers), and those who would have chosen despite the instructions (inherent choosers). Biased lineup instructions inflated confidence only among induced choosers, but not among inherent choosers. Contrary to legal reasoning, witness confidence is an insufficient metric to determine the suggestiveness of biased instructions.