Response of various co-localization algorithms to correlation and co-occurrence. The sensitivity of various co-localization algorithms to varying levels of correlation and co-occurrence is tested. Sets of synthetic dual channel images with varying levels of co-occurrence and correlation are analyzed with Manders', Pearson's and RWC algorithms. (A) The Manders' co-localization coefficient is found to be insensitive to correlation. (B) Pearson correlation is insensitive to co-occurrence as shown by a poor linear response to varying levels of co-occurrence. The response is skewed as a result of correlation in the non-co-occurring pixels. (C) The RWC co-localization algorithm shows a linear response and is sensitive to both correlation and co-occurrence.