= Laterality index
{title2=$\mathrm{LI}=(L-R)/(L+R)$}
For nonnegative measurements $L,R$ with $L+R>0$, one convention is $\mathrm{LI}=(L-R)/(L+R)$. The bound $|L-R|\leq L+R$ gives $-1\leq\mathrm{LI}\leq1$. Multiplying both measurements by the same positive factor leaves the index unchanged. A change from $(L,R)=(20,10)$ to $(10,10)$ changes the index from $1/3$ to $0$ without increasing $R$. Thus a reduced leftward index alone cannot establish right-side recruitment. Baseline, threshold and negative-response conventions must be specified.
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