Which of these depressants is most associated with young users?

Young Matthew, only 2 years of age, is learning to use the toilet. First his mother gives him smiles and hugs when he walks into the bathroom. Then his father gives him songs and praise when he points to the potty. When he agrees to sit on his potty seat his parents sing and dance, making him smile and laugh. Finally, when he begins to actually use the potty, his parents give him some candy that he loves. Matthew is being taught to use the potty through the process of

a. extinction. b. stimulus discrimination. c. shaping. d. stimulus generalization.

Who actually found three types of cones in the retina?

a) Young and Helmholtz b) Hering c) Wald and Brown d) Smith and Wesson