What Did Clever Hans Teach Men About Apes?

WE'VE SAID THAT the capacity of human life to receive, supply and transmit the written word is unique to man, and that it has been with us for thousands of years.¹ For example, we find evidence of many distinctive human motifs on temple walls in the form of hieroglyphics,² drawings enunciated in artistic displays along parapets in caves,³ and lunar calendars engraved on prehistoric bones.⁴ In each and every case we find that humans have mentally synthesized abstract elements into ordered composites and then translated these complex patterns into written records that both contain and communicate information that would otherwise be unavailable.

   But if this capacity to lift ourselves up and outside of the time frame of our birth is unique to man and inaccessible to animals, how is it that we read from time to time of experiments indicating that animals are capable of language,⁵ mathematical concepts,⁶ and of even understanding and forming simple sentences?⁷ Papers have been published, for example, saying that dolphins are capable of language,⁸ and that chimps have been trained to communicate with their trainers by making simple sentences using plastic symbols⁹ or computer-generated tokens.¹⁰ If the "word" is unique to man, how can animals also possess it?

   The capacity to assimilate and to communicate information outside of the time period of one's birth is an attribute absolutely unique to human life, a quality that is nonexistent in the animal kingdom. Yet a number of people, particularly in recent years, have made impressive-sounding claims regarding animal speech and animal language.¹¹ One expressed the extreme thought that "even orangutans are all too human,"¹² which seems to imply that were we to give apes the benefit of human culture and education, they

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would begin to take on human qualities. An ape named Lana, for example, allegedly did this in the context of language.¹³ Back in the early 1970s a computer-based language was developed; its purpose was to see whether an ape could use language. In the computer system that was developed, messages could be typed onto a keyboard and then read using a visual display. The early conclusion from this work, which was widely believed as recently as 1980, was that Lana was capable of using symbols in language.¹⁴

   In earlier work with different trainers, a chimp named Sarah also was believed to have the ability to use language.¹⁵ In the case of Sarah, plastic symbols were used, rather than a computer. In the late 1960s much publicity gave the impression that Sarah could create sentences out of the plastic symbols. Furthermore, it was reported that Sarah had a reading and writing vocabulary of about one hundred thirty words, and that her understanding included concepts of actual sentence structure.

   It was said that the chimp understood the use of verbs, adjectives, conditionals, and even compound sentences. Until the 1980s, these beliefs were widely accepted as valid. But their acceptance was premature, and today we know that apes are not capable of language. To see why this is so, let's contrast their so-called language with the waggle dance done by the scout bee discussed in an earlier chapter. In doing so we will acquire insight into the true state of the matter.

Animal Communication

   When a scout bee does the waggle dance to tell other bees in a hive the direction to fly in search of food, it executes a number of sophisticated maneuvers that communicate an impressive amount of information.¹⁶ Not only does it deliver navigational inputs such as target distance, solar direction, and angle of flight, but it actually compensates for the sun's movement in the sky by time-averaging the orientation of its body as it traces out the figure eight.¹⁷ From where does such sophistication come? The answer is from the "software" along the genetic material which the bee receives at birth.

Human Trainers

   Throughout the animal kingdom — regardless of whether bird, fish, animal or scout bee — communication is executed among members of the same species without any interference whatever by human intelligence.¹⁸ In the case of the apes, however, a new ingredient is added, viz., human beings. In this instance animal trainers deploy their human intelligence to see whether animals are capable of using language. Moreover the studies are done in ways that, of necessity, force the apes to intimately interact over extended time periods with human intelligence and expectations.¹⁹ In other words, whereas the scout bee tells other bees in the hive where food is located through genetically controlled chemical odors²⁰ in conjunction with instinctive body

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movements, in the language experiments human intelligence attempts to teach apes the use of language by means of "words" created either as tokens on a computer or in the form of plastic symbols. But consider what it means if you and I engage in such activity, and are successful in teaching these animals language. The ramifications and implications are profound.

Animal Implications

   For example, one thing it means is that human intelligence has succeeded in freeing animals from some of the instincts they receive at birth. It also implies that with sufficient training and environmental input, their linguistic ability could improve to the point where animals might converse with one another. Given enough time, their improved language ability could be imagined to resemble that of humans. Moreover, once dialogue occurred it might generate insights showing that their present state of affairs is the result of "adverse" evolutionary circumstances. If animal conversation became common, laws against discrimination and for equal opportunity could be developed to protect animals from the environmental factors that victimized them into a disadvantaged position relative to humans.

   Indeed, one writer went so far as to suggest that although humans differ profoundly from animals, it's easy for people to be blind to special circumstances which, according to this idea, brought about the "seemingly God-given division" that separates man and animal.²¹ He also alleged that, except for human culture and education, man's mind "is not so different from an ape's." He then expressed the corollary that were people to expose an ape's mind to human culture, then apes might acquire human qualities. Furthermore, were humans to speak to apes "in the right way," they might also speak back.

   Are these informed opinions? Or do they show undiscerning acceptance of the rubbish that has passed for science in the area of animal language? These views have so little factual content, yet they provide perhaps the strongest evidence thus far for the common ground that is thought possible between a human and ape mind. Yet even here the apparently small distance between the two is by human choice and not necessity. In light of the recent indisputable evidence now available on this subject,²² it is no longer tenable to believe that natural circumstances can decrease the infinity that exists between the human and the ape mind. Monkeys land on trees while man lands on the moon, and to believe that special circumstances produced the difference is to invent past events that are unknown and unexplained, and that contradict present evidence.

Historical Perspective

   The question is, of course, are apes really capable of using language? Up to about 1980, the answer was believed to be yes, and by a large number

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of investigators.²³ Many experiments had been done. Apes named Austin and Sherman, as well as Lana, were taught to label different foods and tools.²⁴ The chimp, Sarah, then fourteen years old, was even said to be able to infer the nature of problems and to recognize potential solutions to them.²⁵ Furthermore, six wild-born chimpanzees, five to seven years of age, were reported to be capable of humanlike spatial memory organization.²⁶ Paper-marking tests were devised for chimpanzees ²⁷ three years after "social conditions" were believed to determine the rates at which the chimps approached "hidden, distant goals." ²⁸ This was a time period when it was thought that language in children and chimpanzees could be compared.²⁹

   But as with all questions, it's often quite helpful to establish a perspective. In this case we need an historical perspective. How new are these claims that allege that animals are capable of using language? The answer is not very new at all. In fact, in 1661 Samuel Pepys wrote that it was his opinion that apes might be taught to speak,³⁰ an impression obtained when he met a baboon for the first time. Somewhat more recently, in 1885, Sir John Lubbock wrote that rather than trying to teach animals our ideas, it might be better to devise a code of signals so that the animal could communicate its ideas to us.³¹ Twenty years later, and colored by the alleged academic antics of a horse named Clever Hans, a psychiatrist said that an animal can think in human ways and express human ideas in human language.³²

   Notwithstanding asinine views of animal efficacy, the observable facts show that animals are organic machines energized by instincts. In the absence of human intelligence, animal behavior expresses itself under a dictatorial genetic system that imposes common controls from generation to generation. This is why the language experiments with apes required training so structured as to be logically equivalent to teaching a child to swing through trees while supporting him with cables, harnesses, and nets.³³ In fact, the training of animals to perform longer and longer sequences of signs for rewards is not at all new or even novel. It has been done with pigeons³⁴ and even with worms.³⁵ It certainly does not imply the use of language. Furthermore, all such sign behavior on the part of animals is mechanistic in that it can be essentially duplicated on a computer.³⁶ The alleged "language" of the chimp Lana has been reported attributable to only two basic processes called paired associate learning and conditional discrimination learning.³⁷ This means that, as a practical matter, a computer can be programmed to simulate the alleged language behavior of the chimp, a result that underscores the machine-like character of animal behavior.

Clever Hans

   This raises an important question. Why have some intelligent people wrongly believed (some still do) that apes have the ability to use these signs in ways that are characteristic of true language? How were they fooled into accepting the idea that animals could do things that they really can't do? The answer lies in an ability that animals do have, an ability that is relatively

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unknown but which played a major part in the hoax apes have unknowingly perpetuated on their trainers. Although trainers have been fooled by this ability in many varied situations, over a good number of years, the effect is best illustrated in the story of the trotting horse, Clever Hans, from the early 1900s.³⁸

   Clever Hans was not your ordinary horse. His owner was so captivated by the extreme degree of intelligence the horse appeared to possess that he exposed the horse to the equivalent of several years' high-school education. People traveled for miles to see the horse, and to view first hand the near miraculous intellectual wonders that it ostensibly performed. Clever Hans astounded audiences with his ability to solve very complex math problems. He could also answer nonmathematical questions as well.

   When asked a question involving numbers, the horse would answer by pawing the ground with his hoof. Questions that demanded a yes or no response were answered by shaking his head up and down or left and right. Furthermore, the horse could also name colors. This was done by picking up colored rags. The horse drew worldwide attention, and large numbers of people — including medical doctors, animal experts and even circus trainers — attempted to discover how he could be so smart. They studied the horse, investigated its owner, and questioned the people who asked questions of the horse. All attempts at discovering the source of the intelligence the horse displayed failed. Cavalry officers, psychologists, and well-known scholars got into the act, but none was able to learn why the horse was so bright.

   One day, when it seemed there was nothing left but accept the seemingly scholarly horse at face value, the mystery was abruptly solved. Someone thought to ask the horse a question whose answer was not known by either the questioner nor anyone else physically close to the horse. Suddenly the horse became dumb. Not only did it not know the answer³⁸ to the question, it became obvious that it had not known the answer to any question ever asked of it.

   Years of intimate familiarity between the horse and its trainer during many teaching sessions had enabled the horse to interpret extremely small movements of his trainer's head and body. At each demonstration, when the horse reached the correct answer, it had been able to detect an ever-so-slight unconscious movement of his trainer's body. For example, the horse answered number problems by pawing the ground with its hoof. While it did so, the trainer habitually leaned forward ever so slightly until the paw strokes equalled the correct answer; then, imperceptibly, he would relax somewhat. This small movement was an unconscious thing on the part of the trainer, and although unseen by humans, it proved a clear signal to Clever Hans.

   Likewise with head movements to yes and no questions. When the horse started to answer by moving its head in the wrong direction, a slight twitch of discomfort by its trainer was signal for it to reverse the direction of its head movements.

   Animals make exquisite observers, and over the course of many training

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sessions Clever Hans had acquired such familiarity with his owner that he could decisively distinguish human head movements well under one hundredth of an inch.³⁸ Thus, for example, when the horse's nose passed over the correct colored rag, the inadvertent expectation of its owner produced more than enough motion for the horse to detect.

   Despite the discovery that Clever Hans wasn't clever, a profusion of pet owners seemed to come out of the woodwork, making all kinds of claims on behalf of their four-legged companions. Cats, dogs, and other domestic animals suddenly had become instant oracles of wisdom as their owners vouched for their IQ. In the next thirty years over seventy animals that were alleged to "think" made their appearance with their two-legged counterparts in hope of stardom.³⁹ But all were doomed to failure. The energizing agent behind the performance of each animal proved to be the intelligence of its master. To eliminate the newly discovered effect in scientific studies, European psychologists demanded that all contact between the experimenter and the animal be eliminated.⁴⁰

   This precaution was voiced at least twenty years before serious language experiments with animals had begun, and yet it was not heeded. As a result, the animals' ultrasensitive and unseen perception of human expressions and mannerisms became the dominant mechanism behind ill-founded language claims that followed. An animal's discernment of its trainer's expectations coupled with its superior sensory organization explains what has been happening for years in the language experiments with apes.⁴¹

Video Exposure

   Only recently has it been realized that apes do not display linguistic ability.⁴² Rather, like Clever Hans, they mirror the human intelligence of their trainers.⁴³ Indeed, so subtle is the effect of this mirroring with apes that it was discovered only after many hours of careful study of videotapes by an able researcher whose mind was open to learning the truth about the matter.⁴⁴ The breakthrough came when a young chimp named Nim⁴⁵ was trained with sign language.⁴⁶ Initially the chimp appeared to use signs in ways characteristic of true language, much as humans do. But later, when videotapes of the results were carefully and repeatedly studied, it was discovered that the chimp used the signs only when prompted by the trainer. Moreover, when the chimp did this, it repeated the trainer's signs without adding any new ones of its own. This occurred as much as 40 percent of the time.

   Furthermore, when new signs were added, they were found to contain no new information. The data reported in this work⁴⁷ show that the chimp's use of signs was merely the result of cues it obtained from its trainer.⁴⁸ When the researcher studied films of the other apes that were supposedly capable of using language, he discovered the same thing, viz., that apes were responding to the motions and gestures of their trainers. These experiments

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underscored something that has been known since Clever Hans. Having sensory ability vastly superior to humans, animals make excellent observers and often are extremely skillful at interpreting human expression.

   These recent analyses are sobering and show that the conclusions that apes have linguistic ability are without substantive evidence; they are, in fact, wrong.⁴⁹ This isn't true of only Lana and Sarah. Another category of investigators has been at work raising both chimps and gorillas in a highly social, family-type environment in which the trainers attempt to teach the animals sign language as mentioned earlier.⁵⁰ The first chimp, allegedly proficient in producing sounds of this kind, was Washoe. What may not be so widely known is that about sixty people were involved in attempting to train this chimp, although a core of about eight did most of the work.

   In the early 1970s a female gorilla named Koko was also trained at doing the same thing.⁵¹ In this case forty people were involved, with an estimated core group of about six. That's quite a "teacher-to-student" ratio. Can you imagine what the linguistic ability of an ordinary child would be with such an educational blessing? It's interesting that when the same techniques used to teach apes language were applied to mentally retarded patients at the Georgia State Retardation Center,⁵² the retarded patients were much easier to teach than the chimps, despite all of the problems these patients had, including extremely low IQs of between 20 and 40.

Other Language Experiments

   Thus, beginning in 1661 with Samuel Pepys's first encounter with a baboon, and extending all the way into the twentieth century with much serious work beginning in the 1960s and continuing through the late 1970s, it was almost unanimously (if erroneously) agreed upon that apes are actually capable of using language in much the same way as man. A number of factors contributed to the misleading of the investigators. For example, after the chimps had been taught to communicate with each other there were times when their success rate reached 95 percent. But these experiments used word symbols generated by a computer. When it was turned off, communication dropped to about 10 percent, thereby indicating that apes do not have the capacity of abstract cognition. When they communicate, they do so by using a computer or plastic symbols, i.e., things supplied by human intelligence. Moreover, the linguistic ability they display does not reflect language ability. Instead, it is the ape's response to miniscule motions by its trainer whose linguistic expectations are then mirrored as "language."

   In the early 1960s, dolphins were reported to be capable of language.⁵³ At that time people foolishly speculated that since dolphins had larger brains than any other mammal, they might even be more intelligent than man. Sober inquiry, however, has shown that this is not the case.⁵⁴ This dolphin mystique was elevated to a cultlike fanaticism, having nothing whatever to do with reality.⁵⁵ Today it is recognized as complete nonsense.

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   Since apes were thought to be intelligent and capable of language, one wonders why no one thought to train them at least to clean their own cages? No one has ever succeeded in getting even one of the thousands of apes in zoos all over the world to prepare its own food or clean up after itself. One may argue that apes have no interest in such work. If so, then we are forced to conclude that neither apes, nor dolphins, nor any of these animals seem to show interest in anything that humans find worthwhile. Where then does their intelligence lie? Humans are the ones who prepare the food and clean the cages and do all kinds of other work. Animals work only when they are forced to.

Abstract Cognition

   Humans are able to force animals to work because man has dominion over planet earth by virtue of his ability to receive and transmit information through time. This ability is unique to human life and it gives each of us the capacity to comprehend the message that perpetuates through time, promising eternal life to those who will trust it. The message is briefly discussed in Appendix 10.

   Whereas you or I can close our eyes and mentally reconstruct abstract representations of reality, an animal seems incapable of doing this. For example, we can close our eyes and yet, in our mind's eye, visualize Christ hanging on a cross as a sin payment for our failure to do all that God requires. Furthermore, we each have the power to understand that event as a passport into eternal life, and to make a decision apart from instinct regarding whether or not to take advantage of it. Irrespective of one's response to this example, the point is that an animal is incapable of the visualization, the understanding, and even of the decision. Man alone, of all the known species within the universe, has this distinctive attribute — the capacity of the "word."

The Word

   Why should man, of all the known life forms, possess this incredible capacity to receive and comprehend information from a time period in the past, and to assimilate and transmit that information into the future? Stated differently, why does only human life have the capacity of the "word"? Why is there absolute disunion between us and all other known species on our planet? In five thousand years of human record, the Bible is the only writing that clearly answers the question. Its answer is that human life is made in the image of the Supreme Intelligence who designed and brought it into existence. It's clear from the empirical facts that human life, as a species, is indeed distinct and different from all of the other known species in the world.

   Is there any evidence that relates this distinctive attribute of human life with the creation of human beings? Is there evidence that correlates man's capacity to manage information outside the time frame of his existence, and the unique informational specification we now know resides within the particular

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sequence of nucleotide bases along the DNA strand of his body? The answer appears to be yes. Data were obtained from six adult patients who needed to undergo surgery in the left hemisphere of their brains. By studying electrical impulses within the brain, scientists were able to establish that the neurological and physiological correlations unique to human language are "specific" to the language cortex in the left hemisphere of the human brain.⁵⁶

   In that same year, computer experts in artificial intelligence recognized that human beings assign meaning to verbal utterances — meaning that depends not only on the words but also on the state of mind and knowledge of those deploying language.⁵⁷ This inescapable intimacy between language and mind was anticipated ten years earlier. One of the greatest thinkers of our time in the field of human language identified a unique feature of the human mind. He found that a child seems to possess at birth an innate structure that enables a natural understanding of the spoken word.⁵⁸ What this means is that the capacity of the "word," the unique distinction that gives man the faculty of human language, is itself genetically traceable to the informational specification along the DNA strand which encodes human life and which, therefore, came into existence at the time human life was created.

   This aligns with the biblical doctrine that portrays the Creator as the Word, and man as his image. If the divine attribute of man's Creator is the Word, then the human capacity to perpetuate an absolute moral code through time is itself an ever-present shadow of the moral image overlaying all generations of human life. Man is thus illuminated as life's singular moral species with access to eternity. This "passport" is embodied in a Creator's timeless message that only man can receive. Although man is free to disregard it, the message contains assurances that the purpose for which it was sent will nonetheless succeed. This means that failure to accept one's destiny cannot be the fault of the message,⁵⁹ but rather lies in its rejection.

Chapter Twenty  ||  Table of Contents

1. Cyrus G. Orietalia (1968) 37:75.

2. Thompson J. Maya Hieroglyphic Writing (1950) Washington.

3. Phillips P. The Prehistory of Europe (1980) London.

4. Corliss W. ed. Ancient Man: A Handbook of Puzzling Artifacts (1980) Sourcebook Project (Glen Arm, Md) references NY Times (1971 Jan 20) and reports: Marshack A. (Peabody Museum Of Archeology & Ethnology — Harvard) analyzed pit marks engraved in prehistoric bone and stone objects and concluded the inscriptions represent a lunar calendar; the notations were reportedly used in most of Europe from 34,000 to 10,000 years ago.

5. Hediger H. Image Roche (1974) 62:27. Fouts R. Science (1973) 180:978. Schrier A. & Stollnitz F. ed. Behavior of Non-Human Primates (1971) viz., V.4 Academic Press.

6. Woodruff G. & Premack D. Nature (1981) 293:568 Oct 15.

7. Gardner B. & Gardner R. Science (1969) 162:664. Gardner R. & Gardner B. Jour. Exp. Psych. Gen. (1975) 104:244.

8. Lilly J. The Mind of the Dolphin — A Non-Human Intelligence (1967) Doubleday.

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10. Rumbaugh D. et.al. Science (1973) 182:731.

11. Woodruff G. & Premack D. (1981) op. cit. Galdikas B. "Living with the Great Orange Apes" (1980) Nat. Geo. Jun. Patterson F. "Linguistic Capabilities of a Lowland Gorilla" (1979) Ph.D. Dissertation (Stanford Univ.). Fouts R. et.al. in Understanding Language Through Sign Language Research (1978) Siple P. ed. Academic Press. Lilly J. Communication Between Man and Dolphin — The Possibilities of Talking with Other Species (1978) Crown Pub. Miles H. "Conversations with Apes: the Use of Sign Language by Two Chimpanzees" Ph.D. Dissertation (1978) Connecticut Univ. Patterson F. Brain Lang. (1978) 5:56. Premack D. et.al. Science (1978) 202:903 Nov 24. Rumbaugh D. ed. Language Learning by a Chimpanzee: the Lana Project (1977) Academic P. Premack D. Intelligence in Ape and Man (1976) Wiley.

12. Galdikas B. (1980) op. cit.

13. Rumbaugh D. et.al. (1973) op. cit.

14. Marx J. rp. Science (1980) 207:1330 Mar 21.

15. Premack D. (1971) op. cit.

16. Brines M. & Gould J. Science (1979) 206:571 Nov 2. von Frisch K. Science (1967) 168:1072. von Frisch K. Dance Language and Orientation of Bees (1967) Harvard U. Press.

17. Gould J. Science (1980) 207:545.

18. Sebeok T. (1977) ibid. ch. 25.

19. Bouissac P. "Behavior in Context: In What Sense Is A Circus Animal Performing?" in Sebeok T Annals Of The New York Academy Of Sciences (1981) Sebeok T. & Rosenthal R. ed. (364:18).

20. Gould J. Science (1975) 189:685 Aug 29.

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22. Sebeok T. & Rosenthal R. The Clever Hans Phenomenon: Communication with Horses, Whales, Apes, and People (1981) New York Academy Of Sciences V.364.

23. Woodruff G. & Premack D. (1981); Galdikas B. (1980); Patterson F. (1979); Fouts R. et.al. (1978); Lilly J. (1978); Miles H. (1978); Patterson F. (1978); Premack D. et.al. (1978) op.cit.

24. Savage-Rumbaugh S. et.al. Science (1980) 210:922.

25. Premack D. & Woodruff G. Science (1978) 202:532 Nov 3.

26. Menzel E. Science (1973) 182:943 Nov 30.

27. Premack D. et.al. (1978) op. cit.

28. Menzel E. & Halperin S. Science (1975) 189:652 Aug 22.

29. Gardner B. & Gardner B. Science (1975) 187:752 Feb 28.

30. Pepys S. in Marx J. (1980) op. cit.

31. Lubbock J. Note On The Intelligence Of The Dog (1885) Report to the British Assoc. for the Advanc. Sci.

32. Wolff G. Die dendenden Tiere von Elberfield und Mannheim :456 (1914) Suddeutsche Manatshefte, Berlin.

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34. Epstein R. et.al. Science (1980) 207:543 Feb 1.

35. McConnell J. New Scientist (1961) 9:318.

36. Sedelow W. & Sedelow S. ed. Current Trends In Computer Uses for Language Research (1975) Mouton (The Hague).

37. Thompson C. & Church R. Science (1980) 208:313 Apr 18.

38. Pfungst O. Das Pferd des Herrn von Osten (Der kluge Hans) (1907) J. Ambrosius Barth (Leipzig) reprinted: Rosenthal R. ed. Clever Hans: The Horse Of Mr. von Osten (1965) Holt, Rinehart & Winston.

39. Koehler O. Die "zahlenden" Tauben unk die "zahlsprechenden" Hunde Der Biologe (1937) 6:13.

40. Koehler O. ibid. :24

41. Sebeok T. & Umiker-Sebeok J. ed. Speaking of Apes: A Critical Anthology of Two-Way Communication with Man (1980) Plenum Press.

42. Greenfield P. & Savage-Rumbaugh E.J. Comp. Psy. (1984) 98:201. De Luce J. & Wilder H. ed. Language in Primates (1983) Springer-Verlag. Ristau C. & Robbins D. Adv. Study Behav. (1982) 12:141. Terrace H. "A Report To An Academy" in Annals of the New York Academy of Sciences (1981) Sebeok T. & Rosenthal R. ed. (364:94). Seidenberg M. & Petitto L. Ape Signing: Problems of Method and Interpretation in Annals of the New York Academy of Sciences (1981) Sebeok T. & Rosenthal R. ed. (364:115). Scheibe K. in Annals of the New York Academy of Sciences (364:160). Thompson C. & Church R. (1980) op. cit. Terrace H. et.al. Science (1979a) 206:891. Hill J. Ann. Rev. Anthrop. (1978) 7:89. Limber J. Am. Psych. (1977) 32:280. Seidenberg M. There Is No Evidence for Linguistic Abilities in Signing Apes (1976) Master's Thesis Columbia Univ.

43. Terrace H. et.al. (1979a) op. cit.

44. Terrace H. (1981) op.cit.

45. Terrace H. et.al. "On the Grammatical Capacity of Apes" in Nelson K. ed. Children's Language (1980) V.2 Gardner Press (NY). Terrace H. J. Exp. Anal. Behav. (1979b) 31:161. Terrace H. Psych Today (1979c) 13:65.

46. American Sign Language (ASL) is a gestural means of communication common to North American deaf people; a good discussion in its use with apes is found in: Terrace H. et.al. (1980) op.cit.

47. Terrace H. (1980) op. cit. Terrace H. et.al. (1979a) op. cit.

48. Chevalier-Skolnikoff S. "The Clever Hans Phenomenon, Cuing, and Ape Signing: A Piagetian Analysis of Methods for Instructing Animals" in Annals of the New York Academy of Sciences (364:60). (Note: Aspects of ape signing believed due by the writer to other than cuing and Han's effects can be explained as statistical noise on the data).

49. Savage-Rumbaugh S. in Annals of the New York Academy of Sciences (1981) (364:36) indicates that an ape is separated from man by the absence in its natural state of the simultaneous array of representational and referential skills that emerge within humans. Terrace H. (1981) ibid. (364:112) indicates that a child's sophisticated (language) ability, against which language in ape experiments should be measured, stands as an important definition of the human species. Seidenberg M. & Petitto L. (1981) ibid. (364:127) indicate that there is nothing to warrant the conclusion that apes acquired linguistic skills in language experiments involving signs. Scheibe K. (1981) ibid. (364:166) indicates that there is no compelling argument or evidence to believe that apes possess true conversational capacity.

50. Gardner B. & Gardner R. "Comparing the Early Utterances of Child and Chimpanzee" in Pick A. ed. Minn. Symp. On Child Psychology (1974) Minn. Univ. (V.8). Register No. 16802-"Teaching Sign Language to the Chimpanzee Washoe" (1973) Psych. Cinema Reg. Univ. Park (PA). Gardner R. & Gardner B. "Communication With A Young Chimpanzee: Washoe's Vocabulary" in Chauvin R. ed. Modeles Animaux du Comportement Humain (1972) Centre National de la Recherche Scientifique (Paris).

51. Rumbaugh D. & Savage-Rumbaugh S. Behav. Res. Method. Instrum. (1978) 10:119.

52. Romski M. et.al. Amer. J. Ment. Defic. (1985) 89(4):441. Romski M. et.al. Psychol. Rec. (1984) 34:39.

53. Lilly J. (1961) op. cit.

54. Gish S. Quantitative Analysis of Two-Way Communication Between Captive Dolphins (1979) Ph.D. Diss. Cal. U. (Santa Cruz).

55. Lilly J. (1978) op. cit.

56. Fried I. et.al. Science (1981) 212:353 Apr 17.

57. Roberts S. BYTE (1981) 6(9):164.

58. Chomsky N. Language and Mind (1972) Harcourt Brace Jovanovich.

59. Romans 9:16.

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