sect. 1. Clark L. Hull / by Sigmund Koch -- sect. 2. Edward C. Tolman / by Kenneth MacCorquodale and Paul E. Meehl -- sect. 3. Burrhus F. Skinner / by William S. Verplanck -- sect. 4. Kurt Lewin / by William K. Estes -- sect. 5. Edwin R. Guthrie / by Conrad G. Mueller, Jr., and William N. Schoenfeld.