Additional Study Information: The purpose of this research study is to better understand how processing speed affects depression and antidepressant non-response in older adults. We are combining cognitive training with antidepressant treatment to determine whether improving processing speed will result in an increased response to medication in individuals who exhibit processing speed deficits. Before beginning medication treatment with either Escitalopram, Duloxetine, or a placebo for 8 weeks, participants will partake in one of two forms of cognitive training daily for 4 weeks.