def selectivity(weights, thresh=0.1):
    """Computes normalized selectivity of a set of `weights`.
    This is something like "peakiness" of the distribution.
    Currently, this is computed by looking at how many weights
    are above the given `thresh`.
    The result is normalized by the length of `weights`.
    """
    return len([w for w in weights if w > thresh])/float(len(weights))