I've been using the n-back protocol for over a year and it's definitely improved my cognitive abilities. I don't know if my IQ has increased, but on days where I use this protocol(20-25 minutes) I see a marked improvement in the clarity and vibrancy of my thoughts- put another way this protocol's biggest benefit is it's effectiveness in clearing the mental fog in my head. I've tried experimenting with other protocols…
How are you sure that the perceived improvement is due to the n-back and not that you only do n-back on days with abnormally good cognition? Like if you slept very little you obviously wouldn't not perform well nor do the n-back.
Tbh I use the dual n-back protocol most vigorously on days where I feel cognitively sluggish as it's benefits are most apparent to me then.