My initial wording was sloppy. There were 50 trials in each session; so I counted a session completed if they did more than 40 in that session. They needed to

My initial wording was sloppy. There were 50 trials in each session; so I counted a session completed if they did more than 40 in that session. They needed to have completed at least six sessions. The mutate is unnecessary. I forget why I did that.