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Robert Mearns Yerkes papers

Call Number: MS 569

Scope and Contents

The Robert M. Yerkes Papers provide a rich resource for anyone interested in the history of twentieth century psychology. They comprehensively document the life and career of Robert Mearns Yerkes, one of the foremost psychologists of the first half of the century. In addition, his extensive correspondence and broad research and professional interests make the papers an indispensable collection for those interested in the development of psychology in the United States. The major portion of the Yerkes Papers were deposited at the Yale Medical Library in 1962, were subsequently transferred to Manuscripts and Archives, and finally donated to Yale University by deed of gift in 1980.

The Yerkes Family, especially Roberta Yerkes Blanshard, daughter of Robert Yerkes, devoted a great deal of attention to processing and arranging the Yerkes Papers, which were originally divided into two major segments. The first part consisted of alphabetically arranged correspondence files for individuals and subject correspondence files. The second segment was designated the Yerkes Supplementary File and consisted primarily of teaching papers, student papers, experiments, publications, photographs, family materials, and diaries. These two segments have been combined and merged to produce the present arrangement for the Robert M. Yerkes Papers. The organizational structure established by Helen Morford, Yerkes' secretary, has essentially been preserved and future researchers owe a great debt of gratitude to her and the family for maintaining such a complete record of the life of Yerkes and for the hundreds of hours of labor required to logically and rationally organize the papers.

The Yerkes Papers provide documentation for researchers interested in a wide variety of subjects and contain correspondence to, from, and about hundreds of people. It is, therefore, only possible to discuss some of the more significant topics addressed in the papers and list the names of just a sample of individuals concerned with these subjects.

The Robert M. Yerkes Papers are divided into six series. Series I, PROFESSIONAL CORRESPONDENCE, contains extensive correspondence relating to anthropoid research and such other subjects as intelligence testing, eugenics and immigration restriction, Yerkes' other research activities, and the growth and development of the discipline of psychology. Series II, SUBJECT FILES, covers the same subjects and has also material on the teaching and publishing activities of Yerkes. Series III consists primarily of notes on experiments with chimpanzees and gorillas, while Series IV, WRITINGS, contains copies of his published books and articles. Series V is composed of photographs, both professional and personal, and Series VI, PERSONAL PAPERS, includes a wide variety of autobiographical and biographical material about Yerkes, family correspondence, and a series of diaries kept by Robert M. Yerkes.

Series I is called PROFESSIONAL CORRESPONDENCE. The material is arranged alphabetically by surname of correspondent and is contained in Boxes 1-54 of the Yerkes Papers. Robert M. Yerkes is best known for his studies of anthropoid apes, in particular for his extensive work on chimpanzee and gorilla behavior. As early as 1913, Yerkes understood the importance of scientific study of anthropoid apes and the need for an anthropoid research station to properly pursue this work. In letters written between 1913 and 1916, he discussed his hopes with such people as Abraham Flexner, Simon Flexner, Gilbert Van Tassel Hamilton, Alfred G. Mayer, Adolph Meyer, Raymond Pearl, Edward W. Scripps, and William H. Welch. Additional information on his plans for the study of anthropoid apes can be found in Series II, Box 57, folders 1088-1091. Not until 1923 and 1924, however, was he given the opportunity to study apes. Through the good offices of William T. Hornaday, director of the New York Zoological Society, folder 2121, Yerkes purchased Chim and Penzee, and the following year travelled to the Cuban estate of Rosalia Abreu to study her primates. See folders 3, 6-10, and 497 and Box 172, folder 2666. These Labors culminated in the publication of his first book on apes, Almost Human, in 1925. That same year Yerkes had the chance to study a young female gorilla called Congo, the results of which appeared in The Mind of a Gorilla, published in three parts between 1926 and 1928. Correspondence concerning Congo can be found in the folders for Benjamin Burbridge, John Ringling, and Richard D. Sparks. See also Series III, EXPERIMENTS, Boxes 114-115.

Yerkes came to Yale in 1924, due largely to the efforts of Yale President James R. Angell, who was able to provide research facilities in the recently established Institute of Psychology. The university's support proved essential for the realization of Yerkes' dream to establish a primate research center. With additional support from foundations, his Anthropoid Experiment Station was established in Orange Park, Florida in 1929. It soon became known as the Yale Laboratories of Primate Biology and after his retirement as the Yerkes Laboratories of Primate Biology. For information about the establishment of and developments at the research station see the files for James R. Angell, Roswell P. Angier, Harold C. Bingham, Raymond Dodge, John C. Merriam and Herbert W. Rand. Additional material on research carried on at the laboratories can be found in the folders For such research assistants as James H. Elder, Louis W. Gellerman, Carlyle F. Jacobsen, Thomas L. McCulloch, Austin H. Riesen, Kenneth W. Spence and Otto L. Tinklepaugh. A great deal of further material on the Yerkes Laboratories can be found in Series II, Boxes 107-112. Until Yerkes' retirement in 1941, Yale served as the sponsoring institution for the Orange Park facility, but with the appointment of Karl S. Lashley as director, sponsorship of the laboratories was jointly shared by Harvard and Yale. See Box 109, folders 2038-2039. By the early 1950's, however, both institutions sought to be relieved of their responsibilities for the Yerkes Laboratories. Professor Yerkes was, of course, concerned about the future of the laboratories, a subject discussed in the period 1951-1955 in the correspondence of such individuals as Leonard Carmichael, Donald Hebb, Robert S. Morison, Arthur F. Perry, Jr., and Arthur J. Riopelle. See also Box 110, folders 2057-2060 for correspondence with Karl S. Lashley and Henry W. Nissen on the same subject. In 1956 title to the Yerkes Laboratories was transferred to Emory University. Eight years later they were moved to Atlanta and rededicated on October 27, 1965 as the Yerkes Regional Primate Research Center. See the files for Arthur J. Riopelle in Series I and Box 111, folders 2061-2063 and Box 112, folder 2110 for information on the history of the Yerkes Laboratories after the death of Robert M. Yerkes.

Yerkes was also known for his psychological testing of military personnel in World War I, in reality intelligence testing. These matters, in particular Yerkes' testing work in World War I, are treated at length in Series II, SUBJECT FILES. Some information on psychological testing in World War I, however, can be found in the correspondence of Yerkes with Walter B. Cannon and Henry A. Shaw. Yerkes had been interested in intelligence testing prior to World War I, having published A Point Scale for Measuring Mental Ability with James W. Bridges and Rose S. Hardwick in 1915. Material on intelligence testing can be found in the correspondence of such individuals as John F. Anderson, J. W. Baird, Edwin G. Boring, James W. Bridges, Carl C. Brigham, Mabel R. Fernald, Rose S. Hardwick, William Healy, A. A. Roback, Celio S. Rossi, Carl E. Seashore, Lewis M. Terman, William H. Welch and Helen T. Woolley. The results of these tests, in particular the massive and seemingly authoritative World War I ones, appeared to confirm racial and ethnic stereotypes of the hereditary superiority of Nordic peoples over Slaves and South Europeans and provided a strong impetus to the eugenics and immigration restriction movements. These two subjects are discussed in the files of Charles B. Davenport, Charles W. Eliot, Samuel F. Fels, Henry H. Goddard, Charles W. Gould, Walter Lippmann, Herbert A. Miller, Helen C. Putnam, Gino Speranza, Victor C. Vaughan, Robert Ward (folder 961) and Leon F. Whitney.

For some twenty-five years, from 1922 to 1947, Robert M. Yerkes served as chair of the National Research Council's Committee for Research in Problems of Sex. The greater part of the material concerning the work of the committee can be found in Series II, Boxes 77-79, but additional information is scattered throughout PROFESSIONAL CORRESPONDENCE, in the files for such people as Sophie D. Aberle, Edgar Allen, Chester I. Barnard, Walter B. Cannon, George W. Corner, Gilbert Van Tassel Hamilton, Ruth Hershberger, Alfred C. Kinsey, Frank R. Lillie, Amram Scheinfeld, Lewis M. Terman, and Earl F. Zinn. The best known works sponsored by the Committee are Alfred C. Kinsey's Sexual Behavior in the Human Male (1948) and Sexual Behavior in the Human Female (1953). The first controversial work is discussed in the correspondence of Yerkes with Barnard, Corner, Hamilton, Kinsey, and Terman.

Prior to his interest in intelligence testing and anthropoid apes, Yerkes published extensively on his research into the behavior of lower animals, including the earthworm, fiddler crab, crawfish, frog, rat, and ring-dove. He also published one book, The Dancing Mouse, in 1907. See Series IV, WRITINGS, for copies of published books and articles. Yerkes discussed these and other similar research topics with such professional colleagues as J. W. Baird, Lawrence W. Cole, Wallace Craig, Philip B. Hadley, Charles S. Minot, Raymond Pearl, R. Myron Strong, Francis B. Sumner, and John B. Watson. The correspondence of these men and other scholars portray efforts to make psychology an experimental science, a discipline Yerkes often called psychobiology.

Like many others of his generation, Yerkes was involved in the effort to establish psychology as a discipline. He was active, therefore, in the American Psychological Association, served on the editorial boards of several psychology journals, and was interested in the nature of the field of psychology. A great deal of material on these related subjects can be found in Series II, especially in the files for the American Psychological Association, Boxes 56-57; Editor of Journals and Series, Boxes 61-63; and Psychological Corporation, Boxes 83-84. Additional information can be found in the folders for such people as Walter V. Bingham, Milton J. Greenman, Francis H. Herrick, Walter S. Hunter, E.B. Titchener, Howard C. Warren, Margaret F. Washburn, and John B. Watson. Yerkes was also concerned with promoting the professional careers of former students, research assistants and younger colleagues. See for examples the files for Clarence Ray Carpenter, George M. Haslerud, and Kenneth W. Spence. As Haslerud stated in a 1945 letter, "you have not only helped me get out of this blind alley . . . but have helped me get much more confidence in my ability." The letters between Yerkes and Donald K. Adams and Harold C. Bingham, together with related correspondence in the files of Edwin G. Boring and Raymond Dodge, highlight the career difficulties of scholars in the 1920's who were not of independent means.

Researchers can also find information in Series I on Yerkes' politics. He can, perhaps, be accurately described as a liberal Democrat, but was never strongly engaged in political activity. Information on his political views can be gleaned from the files for Burton E. Eames, Charles W. Eliot, Raymond F. Fosdick, Ernest R. Hilgard, Walter Lippmann, Lucius E. Marple, Franklin Delano Roosevelt, Fillmore H. Sanford, Harlow Shapley, Harry S. Truman, Henry A. Wallace, and in letters to Drew Pearson and John P. Peters (folder 722). Further material on this subject is in Series II in the subject files for Causes, Box 59; and Organizations, Boxes 80-82. Yerkes knew and corresponded with such eminent Russian scientists as Nadie Kohts, Ivan P. Pavlov, and Alexandre P. Sellheim and travelled to the Soviet Union in 1929 in search of information about Soviet primate research. (See also the section Experiment Stations, Box 69, folders 1188 and 1195.) Due, therefore, to considerations of personal friendship and a wish to perhaps return to Russia, Yerkes was publicly "sympathetic with the experiment" and equally sympathetic of "socialistic ideals." See the correspondence of Yerkes with George S. Counts and W. Horsley Gantt. In private, however, in a confidential June 30, 1929 letter to his brother William Augustus Yerkes, he was much more candid, stating that to "Leave Russia is somewhat like escaping from a prison camp" and that "grosser injustice and inhumanity would be difficult to imagine." (Box 168, folder 2639).

The collection contains useful information on a wide variety of additional subjects. Reflections upon aging, retirement, and life in general, for example, can be discovered in the correspondence of personal friends and colleagues who through the years became close friends. There are, perhaps, a couple of dozen such people, including Peter Frandsen, Lucius E. Marple, Herbert W. Rand, R. Myron Strong, and Lewis M. Terman, Insight can be gained into conditions at Boston Psychopathic Hospital under the directorship of E.E. Southard by reading the files for Elizabeth Chapman, Frederick Gay, and Elmer Ernest Southard. (See also the folder for Boston Psychopathic Hospital in Series II, Box 80, folder 1532.) The dim view that Yerkes held toward the Roman Catholic Church can be seen in correspondence with Paul Blanshard, Henry P. Van Dusen (folder 953), and Harry S. Truman (Box 59, folder 1133). In 1952 Yerkes read and was fascinated by Herbert J. Muller's The Uses of the Past, a heavily annotated copy of which is found in Series IV, Box 126. He discussed the book in letters to Muller (folder 612) and old friends like Richard M. Elliott, C. Judson Herrick, and Lewis M. Terman.

Another way of looking at the PROFESSIONAL CORRESPONDENCE in Series I is by identifying the kinds of people with whom he corresponded. Any division is somewhat arbitrary, but some of the major types of correspondents are professional colleagues of Yerkes' generation, younger psychologists, associates at Harvard and Yale, foreign scientists, personal friends, former students and research assistants, possible benefactors and officials of private funding agencies, chimpanzee and gorilla enthusiasts, naturalists and zoologists, and Yerkes' own professors. Professional colleagues of the Yerkes generation, many of whom were pioneers in the field of psychology, include James R. Angell, Walter V. Bingham, Edwin G. Boring, Carl C. Brigham, C. Judson Herrick, Walter S. Hunter, Raymond Pearl, Lewis M. Terman, Edward L. Thorndike, E.B. Titchener, Margaret F. Washburn, and John B. Watson. Younger professional colleagues include such figures as Gordon W. Allport, Leonard Carmichael, Harold J. Coolidge, Jr., George W. Corner, Richard M. Elliott and Alfred C. Kinsey. Among Professor Yerkes' associates at Harvard University, Boston Psychopathic Hospital, Yale University, and the Yerkes Laboratories are such people as Roswell P. Angier, Walter B. Cannon, Raymond Dodge, John F. Fulton, Arnold Gesell, Earnest A. Hooten, Clark L. Hull, Karl S. Lashley, Walter R. Miles, Henry W. Nissen, Ralph Barton Perry, Sidney L. Pressey, Herbert W. Rand, and E.E. Southard.

Yerkes corresponded with foreign scientists like Maurice Delorme, Julian Huxley, Wolfgang Koehler, Nadie Kohts, Ivan P. Pavlov, Margaretha Selenka, Niko Tinbergen, and Hans Weinert, primarily concerning primate research. Numbered among the many personal friends of the Yerkes family are Burton E. Eames, Louisa Eyre, Peter Frandsen, T. Harry Haines, Gilbert Van Tassel Hamilton, Lucius E. Marple, Arthur F. Perry, Jr., Ralph H. Spangler, R. Myron Strong, and Charles F. Whiting. The series also contains the correspondence of many former student and research assistants, including Donald K. Adams, Meredith P. Crawford, James H. Elder, Louis W. Gellerman, Donald Hebb, Margaret Child Lewis, Vincent Nowlis, Austin H. Riesen, Kenneth W. Spence, and Joseph G. Yoshioka. In his search for financial support for his anthropoid experiment station, Yerkes corresponded with many officers of private foundations and with possible benefactors, such as Chester I. Bernard, Edwin R. Embree, Abraham Flexner, Charles W. Gould, Alan Gregg, William S. Learned, John C. Merriam, Robert S. Morison, Edward W. Scripps, and George E. Vincent. Yerkes also corresponded with people who were enamoured with chimpanzees and gorillas, like Benjamin Burbridge, Martin Johnson, Cathy Hayes, Keith Hayes, Mrs. Robert Noell, and Richard D. Sparks. Sparks expressed the sentiments of all in a 1939 letter, when he asserted, "gorillas, with me, are like liquor with an addict." A common interest in anthropoid apes prompted Yerkes to correspond with many naturalists and zoologists, including Carl E. Akeley, Mary L. Jobe Akeley, W.C. Allee, Frank M. Chapman, William T. Hornaday, Herbert S. Jennings, Lorus J. Milne, William E. Ritter, and Clark Wissler.

The series contains some correspondence with Charles B. Davenport, William James, Hugo Münsterberg, George H. Palmer, George H. Parker, and Josiah Royce, Yerkes' professors at Harvard University. In the period before World War I, it was not uncommon for Americans to pursue graduate studies abroad, particularly in Germany. The files contain letters written from Germany by Charles Scott Berry, Frederick S. Breed, Harold C. Brown, Richard M. Elliott, and John E. Rouse. As might be expected, Series I also includes correspondence on a variety of other subjects. For example, the papers contain a 1937 letter from Yerkes to Thurman Arnold, giving his reaction to The Folklore of Capitalism and a four page answer from the author. Scotland G. Highland wrote Yerkes in 1945 asking about bloodsucking by war prisoners to satisfy thirst, while a small folder for Fritz M. Urban gives an interesting account of the trials of a Czech psychologist during Nazi occupation.

The correspondence in Series I, therefore, provides extensive documentation on the growth and development of psychology as seen through the lives and careers of scores of scholars and researchers and gives a great deal of information about the life, career, and interests of Robert Mearns Yerkes. Researchers wanting to study the subjects discussed above must remember, however, that the examples cited are by no means inclusive or exhaustive. They are listed to give direction to scholars and provide information on some of the major subject areas covered in the papers.

Series II, SUBJECT FILES, fills Boxes 55-113. The SUBJECT FILES consist of correspondence, plus reports, memoranda and proposals, minutes of meetings, and other similar papers arranged alphabetically by broad subject area in accordance with the organizational system established by Helen S. Morford. The major subject areas are similar to those in Series I, except that the papers are arranged by subject instead of by correspondent.

Those interested in primate research should examine the files under the subjects of Anthropoid Research, Chimpanzees, Experiment Stations, Gorillas, Gorilla Studies, Works by Yerkes, Yerkes Laboratories of Primate Biology, and Zoos.

The subject of intelligence testing is treated in several parts of Series II, most important being in the section, War: World War I, Psychological Examining in the U.S. Army. Additional material is to be found under the headings for National Research Council, Box 76, folders 1446-1448; Research: Test materials, Box 87; and Works by Yerkes, Boxes 96 and 98-99. The subject of immigration restriction is discussed in the files for National Research Council: Committee on Scientific Problems of Human Migration. Yerkes served as chair of this committee from 1922 to 1925. For material on the subject of eugenics, see Causes: Eugenics, Committees, and Organizations. Among the several committees and organizations concerned with eugenics which Yerkes was associated with are the American Breeders' Association, Eugenics Research Association, American Eugenics Society, Massachusetts Society for Mental Hygiene, and the National Committee for Mental Hygiene. Of related interest was population control. See the folders for Planned Parenthood Federation of American and Population Association of America under the heading for Organizations.

Series II also includes material useful for documenting the other research interests of Yerkes. See the headings for Research and Works by Yerkes. Robert M. Yerkes was one of the most distinguished psychologists of his era. It is not surprising, therefore, to find extensive files that document his interest and stature in his field, the most important being American Psychological Association, Committees, Conferences, Congresses, Fels (Samuel) Research Institute, Intersociety Constitutional Convention, National Research Council, Organizations, Psychological Corporation, and Society of Experimental Psychologists. Due to his prominence, he also belonged to and was active in several learned societies, like the American Academy of Arts and Sciences, American Association for the Advancement of Science, American Philosophical Society, and the National Academy of Sciences. The section Editor of Journals and Series is also relevant in this regard.

Information on Yerkes' politics is located in two sections of Series II - Causes and Organizations. Information about Yerkes' institutional affiliations and teaching can also be found in Series II. See the files under the headings for Harvard University, Johns Hopkins University, University of Minnesota, Teaching, Ursinus College, and Yale University. The University of Minnesota and Johns Hopkins University files are particularly interesting. By 1916, Yerkes, still an assistant professor, felt that his career at Harvard was at a standstill and he began searching for a new position. The University of Minnesota in the spring of 1916, which was in the process of separating psychology from philosophy, offered Yerkes the position of chair of the new psychology department together with the post of director of the psychological laboratory at the rank of full professor. Yerkes declined the offer, but it was renewed in 1917 and he accepted. The war, however, intervened and afterwards Yerkes became employed by the National Research Council. He resigned a position that he never filled in March 1919. The next year he negotiated unsuccessfully with Johns Hopkins University in the hope of developing psychobiological and anthropoid research there. Not until 1924 did he find a university position that would allow him to pursue primate studies, negotiations found in Series I in the correspondence of James R. Angell and Roswell P. Angier.

Two other major subjects are covered in Series II. Correspondence, reports, and articles on psychology in World War II are found in Boxes 94-96. Information on the extensive publishing activities of Yerkes is located in the sections Periodicals, Publishers, Reprints and Reproducing, Research, and Works by Yerkes. What is found in Series II, however, is primarily correspondence about his research and publications, not copies of the publications. For copies of his publications, see Series IV, WRITINGS.

Series III, EXPERIMENTS, is contained in Boxes 114-120 of the Robert M. Yerkes Papers. It consists of notebooks of observations on chimpanzees and the gorilla Congo, notes on experiments with chimpanzees, and a laboratory log covering the period 1925-1942. These materials are housed in Boxes 114-117 and 120. A variety of other materials is found from the end of Box 117 through Box 119, including announcements for Yale's Institute of Psychology, pro-seminar syllabi, and several bound typescripts. One of the bound typescripts is The Biojonnismith, a publication "containing short tales for the juvenile mind," edited and produced by Yerkes, R. Myron Strong, Helen Makepeace, C.A. Holbrook, and Ada Watterson at Woods Hole in 1900-1901. The other bound typescripts date from the first decade of the twentieth century and consist of pseudonymous manuscripts written under the names C.J. Blix and Romby.

Series IV consists of WRITINGS and is divided into two sections. The first section, Books, is housed in Boxes 121-127 and the second section, Papers, is in Boxes 127-130. WRITINGS contain copies of books, articles, and reviews of Robert M. and Ada Watterson Yerkes, plus a handful of related materials by others. Books has copies of such major publications as The Dancing Mouse (1907), A Point Scale of Measuring Mental Ability (1915) with James W. Bridges and Rose S. Hardwick, Psychological Examining in the United States Arm (1921), Almost Human (1925), The Mind of a Gorilla (1926-1928), and The Great Apes (1929). Also included is John Dewey's Psychology, third revised edition 1893, about which Yerkes states, "this little books gave me my introduction to psychology as science," The Uses of the Past (1952) by Herbert J. Muller, and several other items. The section on Papers has nine bound volumes of articles and reviews by Robert M. Yerkes and Ada Watterson Yerkes published between 1899 and 1956, plus a binder containing publications too large to be included in the bound papers, publications about Yerkes including biographical memoirs, and items printed after his death. Each bound volume contains an index to all items included within the volume. A complete listing to all the publications of Robert M. and Ada Watterson Yerkes is found in Box 130, folder 2235.

The Robert M. Yerkes Papers contains fifteen boxes of photographs and these make up Series V. PHOTOGRAPHS. Boxes 131-136 house professional photographs and they consist primarily of albums of chimpanzee and gorilla pictures plus book illustrations and World War I photos. Personal photographs are contained in Boxes 137-145 and also largely consist of albums. Most of the pictures were taken by Ada Watterson Yerkes and Roberts Yerkes Blanshard, virtually all pictures are clearly identified, and the albums contain contents listings.

The final series, PERSONAL PAPERS, fills Boxes 146-177. The material is arranged under broad headings, the most important being Autobiographical, Biographical, Family, Family: Relatives, and Diaries.

The Autobiographical section, located in Box 146, folders 2311-2319, contains a typescript of Robert M. Yerkes "Testament," a document that is both an autobiography and a statement of his belief in the efficacy of science. A microfilm copy of the "Testament" is available as HM Film 133. The Biographical section, Boxes 146-157, contains biographical memoirs and obituaries, reminiscences, school memorabilia, college and graduate school materials, honorary degrees, address books, a report on the 1976 Yerkes Centennial Conference, and a variety of similar materials. Under the heading for Family, Boxes 159-165, one finds correspondence, biographical material, writings, research notes, and miscellanea on Ada Watterson Yerkes; correspondence of son David Norton Yerkes and his wife and daughter; letters of Robert M. Yerkes to his wife Ada, son David, and daughter Roberta; and correspondence of Roberta Watterson Yerkes Blanshard. Family: Relatives, Boxes 165-168, contains letters to and from Carrell, Diebitsch, Hughes, Krusen, Mearns, Norton, Watterson, and Yerkes relatives together with letters of members of the immediate family of Robert N. Yerkes, his parents Susanna Addis Carrell and Silas Marshall Yerkes and younger brothers Miles and William Augustus Yerkes. The final section, Diaries, is housed in Boxes 169-177. Robert M. Yerkes began keeping a diary in 1893, a practice he faithfully continued to 1906. The collection contains five diaries covering some of the years between 1908 and 1920 and a final series of diaries covering the period 1940-1954. In addition there are lists of and annotations for books read between 1891 and 1893, a daily record of his anthropoid research at the Abreu plantation in 1924, a log and notes from his 1929 European and African journey, five diaries of Ada Watterson Yerkes, a date book, and record of household accounts for the period 1905-1912.

Researchers can find information in Series VI on the research and professional interests of Professor Yerkes. Those interested in the subject of anthropoid research should examine family correspondence, particularly letters from Robert M. Yerkes to his wife, Boxes 163-164; letters to other family members; the "Testament," Box 146; writings and notes of Ada Watterson Yerkes, Box 161; and his 1924 notes taken at the plantation of Madame Rosalia Abreu, Box 172, folder 2666. Yerkes' World War I military experiences in psychological testing can likewise be traced through the "Testament," correspondence with his wife, and his 1917-1918 war journal, Box 171, folder 2663.

PERSONAL PAPERS contain a great deal of material documenting the educational growth of Robert M. Yerkes at West Chester State Normal School, Ursinus College, and Harvard University. The diaries of Yerkes, Boxes 169-170, are especially useful in this context. The documentation for his years at Ursinus College and Harvard University, Boxes 147-155, is particularly rich. Yerkes' Ursinus College years, 1893-1897, are represented by course grades, papers, notebooks, essays and exercises, exams, and a variety of printed materials. For further information on his devotion to Ursinus, see the small section for Ursinus College in Series II, Box 91, folders 1739-1742. The Harvard University material, 1897-1902, includes bills, grades, exams, fellowships, etc. plus an extensive collection of philosophy, psychology, and zoology notebooks and papers. The diaries and the Woods Hole files, Boxes 155-156, folders 2436-2344, provide a useful record of his early research activities.

The Real Estate section and correspondence in the Family sections have material on the Franklin, New Hampshire farm owned by Yerkes. Purchased in 1911, the farm served as a family retreat and site for early chimpanzee research. Additional information about the Franklin property is scattered throughout Series I. See, for example, the files for Walter B. Cannon, Burton E. Eames, Louisa Eyre, and Lee Russell.

The sections devoted to Family and Family: Relatives are housed in Boxes 159-168. They consist primarily of correspondence and all of it to, from, and about Yerkes and Watterson relatives, except for four folders of correspondence of Ada Watterson Yerkes with friends, one of whom, Elizabeth Cutter Morrow, was the mother of Anne Morrow Lindbergh. Although the collection contains a great deal of correspondence between Robert and Ada Yerkes, Boxes 159 and 163-164, few letters date from the period before their September 1905 marriage. Most of these letters were destroyed by the family.

The family correspondence and diaries, supplemented by the "Testament," give information about a wide variety of domestic topics. The letters between husband and wife reveal the deep feelings of love and respect they had for each other and also the sense that their marriage was a true partnership. Ada Watterson Yerkes authored or coauthored ten articles, four of which concerned primates, and also coauthored The Great Apes: A Study of Anthropoid Life (1929). Yerkes enjoyed warm relationships with his children, two brothers, many cousins, uncles and aunts, and his mother, who died of cancer in 1913, but he was not close to his father, Silas M. Yerkes. Father and son disagreed on the relative importance of education and farm work, a situation made more difficult by financial problems caused by a fire that destroyed the Yerkes farm in 1893. From these same sources researchers can also find useful material about farm life and rural conditions in Bucks County, Pennsylvania at the end of the nineteenth century and about youthful activities and college life. After retirement Yerkes became increasingly interested in family history and delighted in recalling the events of his youth, thus readers interested in these subjects should examine the "round robin" letters to his brothers Miles and William Augustus Yerkes in Boxes 167-168. See also Box 147, folders 2329-2334 for additional material on life in Bucks County in the late nineteenth century.

The final Oversize section contains a sound recording of vocalization of baby gorillas, a microfilm copy of correspondence between Yerkes and E.B. Titchener found at Cornell University, one trunk of World War I era psychological testing materials, and a roll of charts on psychological examining in World War I.

Those seeking additional background information on Robert M. Yerkes should consult his Testament, Box 146, folders 2311-2317 and Memoirs, Box 146, folder 2323. The biographical memoirs written by Edwin G. Boring for the Year Book of the American Philosophical Society,1956 and Ernest R. Hilgard for the National Academy of Sciences in 1965 are particularly good. The latter essay has a twenty-four page biographical sketch, chronology, and bibliography of the publications of Robert M. Yerkes.


  • 1822-1985


Conditions Governing Access

The materials are open for research.

Existence and Location of Copies

Testament, Yerkes' autobiography is also available on microfilm (500 frames on 1 reel, 35mm.) from Manuscripts and Archives, Yale University Library, at cost. Order no. HM133.

Conditions Governing Use

Copyright for unpublished materials authored or otherwise produced by Robert Mearns Yerkes has been transferred to Yale University. These materials may be used for non-commercial purposes without seeking permission from Yale University as the copyright holder. For other uses of these materials, please contact

Copyright status for other collection materials is unknown. Transmission or reproduction of materials protected by U.S. Copyright Law (Title 17, U.S.C.) beyond that allowed by fair use requires the written permission of the copyright owners. Works not in the public domain cannot be commercially exploited without permission of the copyright owners. Responsibility for any use rests exclusively with the user.

Immediate Source of Acquisition

Gift of Roberta Yerkes Blanshard, 1980, 1984-1986, 1988, and 1993; gift of David Yerkes, 1989.


Arranged in six series and subsequent additions: I. Professional Correspondence. II. Subject Files. III. Experiments. IV. Writings. V. Photographs. VI. Personal Papers.


83.75 Linear Feet

Language of Materials


Catalog Record

A record for this collection is available in Orbis, the Yale University Library catalog

Persistent URL


The papers contain correspondence, reports, minutes of meetings, research notes, writings, photographs, diaries, and other materials documenting the professional career and personal life of Robert Mearns Yerkes. The papers document the broad range of psychological activities undertaken by Yerkes in the first half of the twentieth century. The papers contain correspondence and other materials on chimpanzee and gorilla behavior, intelligence testing in World War I, eugenics and immigration restriction, sex research under the auspices of the National Research Council's Committee for Research in Problems of Sex, research into the behavior of lower animals, and efforts to establish psychology as an experimental science. The papers include notes on chimpanzee and gorilla research, a complete set of his published writings, professional and personal photographs, and extensive files providing information on family life.

Biographical / Historical

Robert Mearns Yerkes was born on May 26, 1876 in Breadysville, Pennsylvania. He was one of the most eminent psychologists of his day, noted chiefly for his studies of primate behavior and his psychological testing in World War I. He died in New Haven, Connecticut on February 3, 1956. Yerkes graduated from Ursinus College in 1897, received a second A.B. from Harvard in 1898, and a Ph.D in psychology in 1902. He taught at Harvard University, 1902-1917; served in World War I, 1917-1919; worked at the National Research Council, 1919-1924; and was professor of psychology and psychobiology at Yale University, 1924-1944.

Guide to the Robert Mearns Yerkes Papers
Under Revision
compiled by Bruce P. Stark
December 1983
Description rules
Finding Aid Created In Accordance With Manuscripts And Archives Processing Manual
Language of description note
Finding aid written in English.

Part of the Manuscripts and Archives Repository

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