some symbols might not be chosen for use in words in the dictionary; the average number of unused symbols is indicated by the floating contours on the figure. Note that the number of unused symbols tends to be very much higher than for the E- or C- dictionaries, this is because a successful “fork” is now the *only* way for new symbols to appear in the evolving dictionary. Nevertheless, despite this distinct unused-symbol behaviour, the average number of symbols extant in the dictionaries still increases with increasing $\SySize$.

For these B-dictionaries, there is no strong trend with dictionary size, unlike for F- and E-dictionaries; but now higher innovation $\delta_r$ is reported for random discovery order, in this is is like the N-dictionary results; but this is not seen for $\delta_\omega$ or $\delta_\chi$.

To address the effects of fork probability, in fig. \[fig-blinkered-parscaling\] I instead hold $\DcSize$ fixed at $1024$, and vary $\pFfork$. The main feature of note here is that there is a downward trend in reported innovation $\delta_r$ for small $\pFfork$, especially for large symbol lists; in this it is similar to a C-dictionary.

Discussion
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An important feature of the results shown here is the role of discovery 