In the mid 1980s a group of people experimented with 2C-D specifically in regards to its effects on learning and cognition. Most of the test subjects were graduate students who were voluntarily taking 2C-D. Their results were recorded in the work Certain Exotic Transmitters as SMART PILLS or Compounds that Increase the Capacity for Mental Work in Humans A story about LAZAR as told by Hosteen Nez
Unfortunately, the body of research appears to end there. Wikipedia has mention to therapeutic studies of 2C-D in Germany under the name “LE-25”.
Caution: In the United States, 2C-D is potentially covered under the Federal Analog Act. Selling or purchasing 2C-D with the intent of human consumption is potentially punishable as a felony.