Inserting a negative \vspace is most likely the cause behind the overlapping of the \caption and your tabular.
The following removes this and uses a booktabs representation:
\documentclass{article}\usepackage{booktabs}\begin{document}\begin{table} \centering \caption{Results of Ablation Studies: Accuracy of different input settings on KenyanFood13.} \begin{tabular}{ l c c } \toprule& \multicolumn{2}{c}{\bfseries Test accuracy} \\ \cmidrule{2-3} \textbf{Method} & \textbf{Top-1} & \textbf{Top-3} \\ \midrule Image only & $73.18\% \pm 0.79\%$ & $92.04\% \pm 0.44\%$ \\ Caption only & $65.30\% \pm 1.70\%$ & $83.68\% \pm 1.55\%$ \\ \textbf{Ours:} Image + Caption & $81.04\% \pm 0.86\%$ & $95.95\% \pm 0.44\%$ \\ \bottomrule \end{tabular}\end{table}\end{document}