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\begin{document}

\begin{table}
\begin{center}

{\bfseries\strut Fraction of time in modes}

\begin{tabular}{cccc}
    \toprule
    \textbf{Mode} & 
    \begin{tabular}{@{}c@{}}\textbf{rewarded}\end{tabular} & 
    \begin{tabular}{@{}c@{}}\textbf{unrewarded}\end{tabular} \\
    \midrule
    \bf{leave}    & $0.053 \pm 0.014$ & $0.054 \pm 0.013$ \\
    \bf{drink}    & $0.103 \pm 0.026$ &  \\
    \bf{explore}    & $0.844 \pm 0.032$ & $0.946 \pm 0.013$ \\
    \bottomrule
\end{tabular}
\end{center}
\end{table}
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