Environment affects every human characteristic; without environment, no gene could be expressed

Which of the following pairs of wavelengths is the most difficult for children and adults to discriminate?

a. 480 nm and 510 nm b. 540 nm and 570 nm c. 590 nm and 620 nm d. 620 nm and 650 nm

Observational research allows a researcher to

a. make statements about causality. b. make predictions about one variable based on knowledge of another. c. provide a description of a phenomenon. d. randomly assign participants to conditions of an experiment.