To gain physical insight on the particle dynamics, we transform the correlation function into the particle mean squared displacement (MSD), *\(<\Delta r^2(\tau)>\)*, which we plot as a function of the lag time in Figure 2(c). Since the chosen *q*-vector nearly corresponds to the structure factor peak position, the msqd describes single-particle dynamics. It is characterized by sub-diffusive behavior at short lag times followed by a plateau reminiscent of kinetic arrest. However, for even larger lag times, the msqd increases with time again. The sub-diffusive behavior corresponds to *\(<\Delta r^2(\tau)>\sim \tau^{0.62}\)*, while the long time behavior is consistent with *\(<\Delta r^2(\tau)>\sim \tau\)**, w*hich corresponds to diffusion. The plateau in the msqd at intermediate times is typical of systems approaching a kinetically arrested state, such as super cooled liquids on the approach to the glass or a transient colloidal gel [10, 11]. We find a plateau value, *\( \delta ^2\sim 0.1 R_h^2 \)*. The diffusive dynamics at long lag time dynamics results from particles escaping from the surrounding cage formed by their neighbors [12]. Finally, we note that the dynamic measurements were performed for 14 hours with absence of significant aging. This could be interpreted as suggesting that within the length of the experiment, cage escape results from the break-up of the associative structures suggested by the low-q increase of the effective structure factor. However, more experiments are under way to fully explore the behavior of this soft-particle system.

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^{ }