Form conditional column not working on people column

In my form I have a boolean column called Send Email and a people column for selecting people. I only want the people column to show when the Send email column is checked. I tried this and it does nothing when I press save, no error message. I have tired several different formulae.

=if([$SendEmail],'true','false')

=if([$SendEmail]==true,'true','false')

=if([$SendEmail]=='true','true','false')

Does conditional columns not work with people picker columns?