First, the maximum likelihood estimator of PMI add scores deduct scores Table 3: Comparison of estimators of PMI and PHSIC in terms of methods of matching the given (x, y) and the observed (x i , y i ) in D. PMI matches them in an exact manner, while PHSIC smooths the matching using kernels.
pHSIC is expected to be robust to data sparsity (Section 4).