to cue action. This kind of cueing has been observed in other domains. Flor ( 1994) showed how two programmers working side-by-side used their ability to easily see (access) each others' computer screens to opportunistically coordinate a task that would otherwise require a high degree of prior planning.
These findings have several implications for the design of computing technologies intended to support cooperative learning between remote participants. First, such technology needs to make the performance of others globally accessible. This means more than merely providing a context switch that allows remote participants to access information about each others' performance on demand. Ideally, performance information should be constantly presented to all participants since they may not have prior knowledge about which global cues are relevant. The constant presentation of performance information allows participants to opportunistically take advantage of any relevant cues that emerge. This is not a problem when the performance information is represented in an "open" medium, such as auditory information, where co-present participants cannot help but hear each others' performance. However, performance information may be visual, such as when the participants engage in a joint writing task. When information is represented in such a "closed" medium, it is non-trivial to constantly present the information to all participants. Fortunately, computing technology allows information to be re-represented and simultaneously presented in different media. Consider the writing task. As a participant types a word, it can be simultaneously broadcast to a voice synthesizer on the co-participants' computer and each participant can have a different synthesized voice. A less complex approach is for participants to have an editor that shows their co-participants' typing activity as faded-text overlaid in the editor's background using different colors for each participant. Thus, although visual information is not typically open to all participants, technology that either places the information in another medium or overlays information of others in the same medium, provides constant presentation of group performance.
A second design implication of this research is that participants should have the ability to draw attention to those cues in the group performance that can help individual participants learn their performances. For instance, in the music covering case, the bass player turned to the drummer and used a visual cue to temporarily substitute for the auditory cues (from the singer and other band members) that the drummer had not yet learned. Performance information was auditory and the temporary learning cue was visual. The multimedia aspect of computing technology makes such cross-media abilities possible. If the performance information is auditory, visual media can be used to simultaneously provide temporary learning cues. Similarly, if the performance information is visual, audio media can be used to provide the temporary learning cues. Technology may also allow the actual performance medium to hold these. temporary learning cues. For example, the programming environment described previously, which visually overlays participants' screens, could also be used to overlay temporary visual learning cues.
Both design implications suggest working environments that may be distracting for participants and, thus, negatively effect performance. Empirical will be able to quantify whether the benefits of using global cues to direct local performance outweighs the distractions which result from either the constant presentation of performance information to all participants or the introduction of temporary learning cues.
To summarize, we have shown that the computational problem of song covering lends itself to a more efficient and effective solution in the case of group performance than in the case of individual performance. This follows because by working together in a group, individuals can use cues that emerge to help sequence actions. In the musical group studied, we found that in fact that the group uses the simpler solution that makes use of emergent cues. We believe our findings are not specific to cover bands, but generalize to all group activities in which individuals perform actions in parallel and have access to the on-going activities of others.
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