concentrative

From concentrate +‎ -ive.

• (UK) IPA^(key): /kənˈsɛntɹətɪv/

concentrative (comparative more concentrative, superlative most concentrative)

1. Characterised by concentration.
   • 1841 March, Edgar A[llan] Poe, “The Murders in the Rue Morgue”, in George R[ex] Graham, Rufus W[ilmot] Griswold, editors, Graham’s Lady’s and Gentleman’s Magazine. […], volume XVIII, number 4, Philadelphia, Pa.: George R. Graham, published April 1841, →OCLC, pages 166–167:

     To observe attentively is to remember distinctly; and so far the concentrative chess-player will do very well at whist; […].