Various researchers have criticised this two-group method, not only for resulting in less statistical power but also for risking spurious type D effects. A four-group method was commonly applied to solve this issue by distinguishing individuals without Type D personality from those with high scores on either negative affectivity or social inhibition alone.
Several researchers have raised concerns about the two-group methodology, citing its limitations in terms of statistical power and the potential for false Type D effects. To overcome these issues, a four-group approach was commonly used to differentiate between individuals without Type D personality and those with high scores on either negative affectivity or social inhibition.