I simulated some results that look like this:

but I don't want to include the plot (my advisor is keeping me to a strict limit on figures and these are minor intermediate results).
Is there a name for this type of curve? I'm thinking of saying something like "increases sigmoidally 0 to -0.2 and from 0 to 0.2" but that sounds very clumsy to me.
I would say something like "an upside down bell curve". Or Gaussian function.