= Speech timing lag
A <speech timing lag> is the time difference between corresponding events in two <speech> recordings. Define $\Delta_i=t_{B,i}-t_{A,i}$ for landmark $i$. Positive values mean speaker B's event occurs later; negative values mean B leads. The landmark might be a specified syllable onset or phrase boundary, so its definition is part of the measurement.
In <synchronous speech> experiments, <Fred Cummins> recorded paired readings and compared corresponding events. Typical differences were about $40\,\mathrm{ms}$ on average, with larger mismatches at phrase beginnings.<Practice and performance in speech produced synchronously by Fred Cummins>[Abstract and phrasal-position results]{ref}
Different summaries answer different questions. For illustrative lags $10,20,-30\,\mathrm{ms}$, the <arithmetic mean> is zero, the mean <absolute value> is $20\,\mathrm{ms}$, and the <root mean square> is
$$
\sqrt{(10^2+20^2+30^2)/3}\approx21.6\,\mathrm{ms}.
$$
Zero average leadership therefore does not imply close alignment at every event. The square gives larger mismatches more influence on the final statistic.
Recording delays also matter. If channel B adds a known $12\,\mathrm{ms}$ delay relative to channel A, then $\Delta_{\mathrm{recorded}}=\Delta_{\mathrm{speech}}+12\,\mathrm{ms}$ under this sign convention. Subtracting that calibrated offset separates equipment delay from speaker timing. Consistent landmark annotation and synchronized recording are consequently necessary for interpreting the measured lag.
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