46
ROTH
standable when we consider a larger time frame and both humans and the machine; that is, Table 3 allows us to attribute particular aspects of the structure of interaction (and therefore of cognition) to users and software. Within the students’ attentional horizon, immediately following the students’ lengthening of one arrow (force) the panel message is displayed. As a result of these actions, the software makes available a trajectory, followed by the panel message. Thus, from the students’ perspective, the message is an immediate consequence of their previous action of lengthening the arrow. The word reduce, when viewed in the context of the previous lengthening, is used as a resource to relate the subsequent time step to the manipulated arrow. However, the interpretive frame of Interactive Physics is different. It is designed to run and display the experiment given a particular specification of the relevant variables (mass, velocity, position, force). The message, based on the size of velocity somewhere along the trajectory, is designed to indicate an action that allowed greater accuracy given the user specifications. Thus, rather than basing its feedback on the history of the interaction or on the specified size of the variables, the system starts with an aspect of the simulation. This aspect is not directly available on the interface, but the program uses it in a default mode and checks whether the simulation is possible with a modified time step. In the hand of a competent user familiar with the design rationale and simulation practices, however, the message is likely to be interpreted differently (e.g., in my own case). My analyses reported in the section “Gesture and Scientific Talk” show how Interactive Physics enables students to use deictic and iconic gestures to make salient certain features (as figure) to which they link their utterances. When viewed against the interface as background, gestures help a speaker to make salient those aspects relevant to his or her explanation. However, as can be seen from Figure 3, when there are three or more individuals oriented toward the interface, there are space constraints on possible physical configurations. Whereas immediate members perceive gestures against background, the same affordance does not always exist for other participants. Thus, although the physical setting does not preclude participation in the conversation, it does preclude the linking function of gestures. However, because gestures are central to scientific laboratory talk (e.g., Lemke, 1998; Ochs, Gonzales, & Jacoby, 1996 ), not having equal access to the representational medium actively interferes with learning. The point is that not being able to handle the computer input appears to be far less important than the exclusion from the ongoing conversation because of limited access to a different mode of communication. This analyses focused on learning in a broader frame considering how physical arrangements, size of social configurations, and nature of focal artifacts interact and affect conversational and participatory patterns. This broader focus then leads us to construct different aspects of cognition than those that emerge from a microanalysis of unfolding activity.