to create the sequence STTR. All three types are anomalous because each contains three object names in a row, for which there is no existing syntactic rule.
Journal of Experimental Psychology: General 1993, Vol. 122. No. 2. 184-194
Copyright 1993 by the American Psychological Association. Inc. 00%-3445/93/$3.00
Responses to Anomalous Gestural Sequences by a Language-Trained Dolphin: Evidence for Processing of Semantic Relations and Syntactic Information Louis M. Herman, Stan A. Kuczaj II, and Mark D. Holder This study examined the responses of a bottlenosed dolphin (Tursiops truncatus) to "normal" (semantically and syntactically correct) sequences of gestures and to anomalous sequences given within an artificial gestural language highly familiar to the animal. Anomalous sequences violated the semantic rules or syntactic constraints of the language. The dolphin discriminated anomalous from normal sequences in that rejections (refusals to respond) occurred to some anomalous sequences but never to normal sequences. Rejections rarely occurred, however, if the anomalous sequence contained a subset of gestures that would comprise a normal unit if joined together. Such units were typically perceived by the dolphin and responded to even if they consisted of gestures that were not sequentially adjacent. All semantic elements of a sequence were processed by the dolphin in relation to other elements before the dolphin organized its final response. The results show the importance of both semantic properties and semantic relations of the referents of the gestures and of syntactic (ordering) constraints in the dolphin's interpretations of the anomalies.
In his book on the acquisition of language by children, Ingram (1989) remarked that "the literature on the attempts to characterize the grammars of children is one of the largest, if not the largest, in the field of child language" (p. 261). One useful approach to characterizing children's grammar has been to study their responses to anomalous sentences. In general, anomalous sentences violate a semantic relation or a grammatical rule or use "nonsense" words in place of real words. It is assumed that children interpret anomalous sentences in terms of their grammatical knowledge and their understanding of the semantic features of individual words and of the semantic relations among words. Children's responses to anomalous sentences may therefore be particularly revealing of the grammatical and semantic systems they have developed. Research with anomalous sentences has helped in the understanding of such language phenomena as the importance of word order at various developmental stages (de Villiers &
de Villiers, 1972; Erasure & Entwisle, 1973; Kuczaj & Maratsos, 1975; Tyler & Marslen-Wilson, 1981), the development of semantic rules (de Villiers & de Villiers, 1972; Erasure & Entwisle, 1973; James & Miller, 1973; Tyler & Marslen-Wilson, 1981), the comprehension of causal connectives (Peterson & McCabe, 1985), the development of the concepts of animacy and sentiency (Berzonsky, Miller, Woody-Ramsey, & Harris, 1988; Schwartz, 1980; Tunmer, 1985), and the effect of cognitive and experiential factors on sentence comprehension (Carr, 1979). Despite this fruitful use of anomalous sentences in the study of child language, comparable techniques have rarely been used to study the manner in which language-trained animals process the grammatical or semantic systems of the artificial languages to which they have been exposed. In the extensive language-training work with the great apes, the only instance of the use of anomalous sentences seems to be the analysis of responses to incomplete sentences in the report of Rumbaugh, Gill, and von Glaserfeld (1973). In that study, the chimpanzee Lana, who had been trained to produce sequences of "lexigram" symbols to obtain food or other incentives, was given a choice of several alternative lexigram symbols with which to complete sentence beginnings. For example, she was given the beginning sequence PLEASE MACHINE GIVE and choices of JUICE, M&M, MACHINE, MAKE, and so forth. Lana was able to complete the sequences correctly in most cases by choosing an appropriate term within the constraints of the correlational grammar used (e.g., PLEASE MACHINE GIVE JUICE). Incorrect beginning sequences (e.g., PLEASE BANANA JUICE or PLEASE GIVE MACHINE) were rejected in the large majority of cases. The major purpose of the study, however, was not to examine Lana's grammatical competency but to test her ability to recognize and complete legitimate sequences. Thus, responses to classes of invalid sequences were not explored systematically, nor were the kinds of errors made in completing legitimate sequences presented. A systematic
Louis M. Herman, Department of Psychology and Kewalo Basin Marine Mammal Laboratory, University of Hawaii at Manoa; Stan A. Kuczaj II, Department of Psychology, Southern Methodist University; Mark D. Holder, Department of Psychology, Okanagan College, Victoria, British Columbia, Canada. This research was supported by Contract N00014-85-K-0210 from the Office of Naval Research and by a grant from Earthwatch, both to Louis M. Herman. We thank the many people who helped with this project, including the Earthwatch volunteers at the Kewalo Basin Marine Mammal Laboratory from January to May 1989 and the staff and students of the laboratory. Mark D. Holder and Stan A. Kuczaj II were visiting research associates at the Kewalo Basin Marine Mammal Laboratory at the time of these studies. Correspondence concerning this article should be addressed to Louis M. Herman, University of Hawaii at Manoa, Kewalo Basin Marine Mammal Laboratory, 1129 Ala Moana Boulevard, Honolulu, Hawaii 96814.
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analysis of responses to anomalous sequences in the Rumbaugh et al. study or in other ape language studies might have helped to clarify the grammatical understanding of the ape subjects, a topic that received early prominence but that later aroused a great deal of controversy (cf. Gardner & Gardner, 1975; Terrace, Petitto, Sanders, & Bever, 1979; also, cf. Premack, 1976; Terrace, 1979). Anomalous sequences of gestures or sounds have been used more extensively to explore the grammatical understanding of bottlenosed dolphins (Tursiops truncatus) exposed to artificial gestural or acoustic languages. The results of these studies were first described in detail in Herman, Wolz, and Richards (1983). Portions of these results have also appeared in published sources (Herman, 1986, 1987, 1988; Herman, Richards, & Wolz, 1984). In general, these results have revealed a sensitivity to syntactic (sequential) constraints and to semantic relations among the significates of the gestures or sounds. Gisiner and Schusterman (1992) have recently reported on the use of anomalous sequences of gestures to study a sea lion's (Zalophus californianus) understanding of the artificial language system to which it was exposed. These authors reached the conclusion that the sea lion showed "little, if any, use of logical or semantic properties of the signs" (p. 78), suggesting, perhaps, a fundamental distinction in the way sea lions and dolphins process their respective artificial languages. In this article, we provide the results of further, more detailed tests of responses of a dolphin to selected classes of anomalous sequences that violated semantic relations or syntactic rules within its imposed gestural language. The importance of semantic properties, of semantic relations, and of syntactic constraints to the dolphin's responses are examined. The dolphin subject used here was also a subject in the earlier study of Herman et al. (1983), but was now considerably more experienced in responding to the artificial language.
Background of Normal (Nonanomalous) Language Comprehension Training The artificial languages constructed and the responses of dolphins to instructions given within these languages were first described in Herman et al. (1984). The instructions were conveyed by sequences functionally similar to imperative sentences in human languages. For the dolphin named Akeakamai, a gestural language was used in which discrete visual gestures were the "words" of the language. For the dolphin named Phoenix, an acoustical language was used in which the words were unique electronically generated whistle-like sounds. Within each language the distinct gestures or sounds referred to objects in the dolphin's tank, to actions that might be taken to objects, to relationships that might be constructed among two objects, and to modifiers of place or location. These various semantic categories could be combined and recombined with one another according to a set of syntactic rules to form many hundreds of different sequences, each having a unique meaning. The syntactic rules specified the serial-order relationships among the semantic categories in
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a sequence. The rules also determined the grammatical function of object terms within a sequence as either indirect or direct object and specified which object in a sequence was modified. Sequences could vary in length from two to five items. Two major word-order rules were that modifiers preceded the object modified and that objects preceded actions. Grammatically correct, two-word sequences were thus constructed as object + action (e.g., FRISBEE OVER instructed the dolphin to select the frisbee from among the different objects in the tank and jump over it).1 Three-word "nonrelational" sequences could be constructed by adding the modifier term according to the rule modifier + object + action (e.g., RIGHT FRISBEE OVER instructed Akeakamai to leap over the frisbee to her right and by implication not the one to her left). "Relational" sequences consisted of three or more words and instructed the dolphin to construct a relationship between two objects. In the gestural language, the focus of the present study, a three-word relational sequence was given by the rule objectl + object2 -f- relational term. Two relational terms were available: FETCH required that the second object be brought to the side of the first object, and IN required that the second object be placed inside of or on top of the first object. The first object term (objectl) thus functions grammatically as the indirect object and the second (object2) as the direct object. Examples of three-word relational sequences are SURFBOARD BASKET FETCH, which instructs Akeakamai to bring the basket to the surfboard, and HOOP BALL IN, which instructs her to place the ball inside of the hoop. Four-word relational sequences are formed by modifying one of the two object terms (e.g., LEFT HOOP PIPE FETCH instructs the dolphin to take a pipe to the hoop on her left, but HOOP LEFT PIPE FETCH instructs her to take the pipe on her left to a hoop). Five-word sequences modify both object terms (e.g., RIGHT WATER LEFT BASKET FETCH instructs the dolphin to take the basket on her left to the stream of water on her right). Semantically contrasting sequences can be constructed by changes in word order. Thus, SURFBOARD PERSON FETCH instructs Akeakamai to transport a person (who is in the water) to a surfboard, but PERSON SURFBOARD FETCH requires that the surfboard be taken to the person. A further example of a semantic contrast are the two sequences described earlier: LEFT HOOP PIPE FETCH VCrSUS HOOP LEFT PIPE FETCH.
The results of tests reported in Herman et al. (1984) showed that both dolphins responded to lexically novel sequences almost as well as they responded to familiar sequences. Familiar sequences were those previously given to the dolphins. Novel sequences used familiar vocabulary, but in combinations not previously given to the dolphins. The dolphins also responded reliably to novel syntactic forms, which were logical extensions of familiar syntactic forms (Herman et al., 1984). For example, on the first occasion that Akeakamai was given the new forms modifier + objectl + object2 + relational term and objectl + modifier + object2 + relational term she responded correctly, without hesitation. Also, object names, such as HOOP or BALL, were understood 1
Small capital letters indicate the English gloss corresponding to the unique gesture used to refer to an object or action or modifier.
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by the dolphin as references to a class of objects rather than to a specific item, as shown by results of tests for object generalization (Herman, 1987). Similarly, action names, such as UNDER or OVER, were broadly generalized. Furthermore, Herman, Pack, and Morrel-Samuels (1993) have argued using many other examples that object words have a referring function. For instance, in the gestural language PERSON can be used in various sequences, which depending on their structure and the other semantic elements present can vary the dolphin's response to a person to include at least all of the following: carrying out an action directly to a person, transporting an object to a person, transporting a person to an object, reporting whether a person is present in the dolphin's tank, requiring an imitation of a person's behavior, or doing nothing at all with respect to a person. Herman et al. (1983) constructed syntactic, semantic, and lexical anomalies to study the grammatical and semantic knowledge of the respective languages possessed by Akeakamai and Phoenix. Syntactic anomalies violated some syntactic rule, such as reversing word order (e.g., OVER FRISBEE rather than FRISBEE OVER); or adding semantic categories to existing rules (e.g., adding an object term after an object + action sequence, as in FRISBEE OVER PIPE); or violating some restriction rule, such as using a nonrelational action term in a location normally requiring a relational action term (e.g., SURFBOARD BASKET TAILTOUCH rather than SURFBOARD BASKET
FETCH). Semantic anomalies were syntactically correct sequences requesting activities that, in fact, could not be performed (e.g., WINDOW THROUGH, a request to swim through the window). Finally, lexical anomalies inserted a novel (nonsense) gesture or sound in the syntactic slot normally reserved for a familiar modifier, object, or action term. The responses of the dolphins to these anomalies included carrying out portions of the anomalous sequence that constituted legitimate grammatical subsets (e.g., responding to the segment FRISBEE OVER in the longer string FRISBEE OVER PIPE), substituting an appropriate instantiation of a category for an inappropriate one (e.g., swimming through a hoop in response to WINDOW THROUGH), and rejecting the entire sequence (i.e., making no attempt to respond or starting to respond but then stopping abruptly). In general, these different types of responses were appropriate to the anomalous type given; for example, rejection commonly occurred for a lexical anomaly having a nonsense gesture in the place of an action term. Recognition of an anomaly is shown by rejection, because such rejections are virtually absent for normal sequences, even when the particular combination of items has not been experienced before (Herman, 1986; Herman et al., 1984). The responses to syntactic anomalies showed that the rules of word order were well learned and exerted control over the dolphins' responses and that legitimate sequences could be extracted from longer anomalous sequences. The responses to semantic anomalies revealed an understanding of some of the pragmatics associated with semantic entities, that is, what actions could and could not be taken to particular objects. In the present study, we were particularly interested in responses to anomalous relational sequences. Relational sequences form the most complex and longest word strings in
Akeakamai's language. Furthermore, such sequences are governed by an "inverse" grammar that guards against simple left-to-right or "word-by-word" processing (Herman et al., 1984). In the earlier study on anomalies (Herman et al., 1983), responses to anomalous relational sequences were not explored in detail, because at that time relational sequences were relatively new to the dolphins' experiences. Also, for the current study we wished to examine how two functionally different categories of objects, those that were transportable by the dolphin and those that were not, affected the responses to anomalous relational sequences. Nontransportable (stationary) objects include such things as underwater speakers, streams of water, and other dolphins, none of which can be or will be transported by the dolphin receiving instructions. Therefore, these objects can only be used as the destination of a transport; grammatically, their function in a sentence can be as indirect object only. Transportable objects—such things as hoops, balls, or baskets— can occupy the direct-object syntactic slot or the indirectobject slot. They can either be transported or be the destination of a transport. Transportable and nontransportable objects appear to be processed somewhat differently by Akeakamai, as shown by differences in error rates when they serve as destinations (Herman, 1986, 1987). Errors to nontransportable objects acting as destinations are less frequent than those to transportable objects acting as destinations. Herman (1987) viewed these differences as arising, in part, from coding conflicts: Two objects placed in different functional or semantic categories (i.e., transportable vs. nontransportable) should produce less interference in memory than two objects from the same category (two transportable objects).2 Method The present study was carried out approximately 7 years after completion of the Herman et al. (1983) study. The dolphin Akeakamai, a female of approximately 13 years of age at the time of this study, was the subject and was one of the two subjects in the earlier studies. She was considerably more experienced in her language than during the earlier study, and the complexities of her language had been extended beyond that available previously (e.g., see Herman et al., 1993).
Testing Conditions and Test Objects Akeakamai lived together with three other bottlenosed dolphins in two interconnected circular outdoor seawater tanks, each 15.2 m in diameter and 1.8 m deep. Akeakamai was tested in sessions of approximately 40 min in duration, seven times per week. Her daily 2
This finding is seemingly analogous to observations in the child language literature that reversible passives (e.g., "The cat was bitten by the dog") are more difficult for young children to interpret correctly than are nonreversible passives (e.g., "The bone was bitten by the dog"; Harris, 1976; Turner & Rommetveit, 1967). However, the children's errors with reversible passives tend to be largely reversals of agent and object, but the dolphin's errors with reversible relational sentences are almost never reversals of the transport object and the destination object.
LANGUAGE-TRAINED ration of approximately 9 kg of silver smelt (a full, normal ration for an adult female T. truncatus) was fed to her during these sessions and during other daily sessions devoted to additional tasks or to social interactions with trainers. Testing took place in one of the tanks at a location adjoining an elevated deck that was convenient for viewing by observers and for obtaining a videotape record of responses. A supervisor (one of the authors) was located on the deck and controlled each testing session. An assistant manually recorded all trial events, while another assistant obtained a videotape record of all trials involving anomalous sequences. A "blind" observer described Akeakamai's responses using the English glosses for the artificial language. The blind observer had no knowledge of what instruction was given to Akeakamai, but was able to observe her response. A trainer stood on a platform located just outside the tank wall. From that location the trainer was able to interact freely with the dolphin when it too was at the wall. The head, torso, and arms of the trainer were visible to the dolphin at all times. The trainer wore opaque goggles when giving gestural instructions, to guard against eye gaze cues and to prevent the trainer from knowing what actions the dolphin was taking. Two to three trainer's assistants helped to position objects in the tank. There were 11 objects altogether; 6 could be transported by the dolphin and 5 could not. The transportable objects were a blackand-white soccer ball (BALL), a plastic white 160-g Frisbee (FRISBEE), a brown plastic laundry basket kept afloat with four small buoys (BASKET), a surfboard (SURFBOARD), a 117-cm length of a 1.9-cmdiameter plastic pipe (PIPE), and a square hoop made from four 81-cm-long pieces of the same piping (HOOP). The nontransportable objects were a person sitting on the wall of the tank with both feet in the water (PERSON), water pouring from a garden hose tied to the side of the tank (WATER), an underwater speaker suspended from the tank wall (SPEAKER), any of four underwater windows spaced about the tank (WINDOW), and the dolphin Phoenix (PHOENIX). Transportable objects, except for paired objects, were permitted to float freely about the tank and were repositioned only when two or more drifted closely together. The stationary objects remained at fixed locations throughout a session, but these locations changed across sessions (except, of course, for the windows). During each session, 2 of the 11 objects were paired (e.g., in addition to the 9 other objects there were 2 hoops and 2 pipes). One member of each pair was always on the dolphin's left as she faced her trainer, and the other member was on her right. The objects paired were balls, Frisbees, pipes, hoops, persons, and water. The 2 objects selected to be paired varied between sessions with the restrictions that each object was paired for the same number of sessions as every other paired object and that a particular object was never paired for two consecutive sessions.
Procedure During each session the dolphin was given 17 syntactically and semantically correct sequences: six 2-word sequences; four 3-word nonrelational sequences, including two with the modifier LEFT and two with RIGHT; three 3-word relational sequences, including at least one with FETCH and one with IN; and four 4-word relational sequences, including two with FETCH and two with IN, and two with the direct object modified and two with the indirect object modified. In addition to these normal sequences, five of every seven sessions were selected at random to contain two anomalous sequences. The two sequences were embedded among the 17 normal sequences under the restrictions that no gesture used in the previous three
DOLPHIN
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normal sequences could appear in the anomaly, no anomaly could be among the first three or last three sequences of the session, and the pair of anomalies of a session must be separated by at least six normal sequences. In addition, the two anomalies in a session were always different types of anomalies. Each exemplar of an anomalous type was presented only once during the entire experiment. Additionally, anomalous sequences never referred to objects that were currently paired, because modifier terms were not used in the current series of anomalies studied. The low proportion of anomalies, their wide separation from each other within a sequence of trials, and the use of different anomalous types within a session were intended to minimize the probability that Akeakamai would learn to expect anomalies, would become familiar with the types of anomalies, or would develop a response bias. The restrictions on placement of an anomaly within the sequence of normal sentences guarded further against any biasing of responses to anomalies that might occur if some of the same referents had been responded to in the immediately preceding normal sequences. Each session began with Akeakamai positioned at the wall of the tank facing her trainer. While the trainer interacted socially with Akeakamai, the various objects were placed in the tank by the assistants. When all objects were positioned the supervisor gesturally conveyed to the trainer the instructions to be given to the dolphin (i.e., the sequence of gestures to use). The trainer then donned the opaque goggles and gave a "pay attention" signal to the dolphin by extending her index finger upward. In response, Akeakamai brought her head out of the water and watched the trainer intently. The supervisor then gave a verbal "ready" signal to the trainer as a cue to initiate the gestural sequence. Immediately after the last gesture was completed by the trainer, the supervisor vocally cued the blind observer (who was facing away from the tank) to turn and watch the dolphin and label its responses. For normal sequences only, if the labeled response was exactly that given to Akeakamai, the trainer was immediately notified and he/she blew a whistle. Akeakamai then returned to the trainer and was rewarded with a fish and with social reinforcement such as vocalizations (verbal praise), hugs, and hand clapping. If the dolphin's response differed from the labeled response, no reward was given. The trainer simply signaled Akeakamai to return to her by splashing the water or slapping the tank wall. On return, there was a distinct pause by the trainer before reinitiating contact with the dolphin. Before the next trial began, the objects were repositioned if necessary. The procedure after a response to an anomalous sequence was similar to that used by Herman et al. (1983). After the blind observer had labeled Akeakamai's response to an anomaly (including the use of the term erase to indicate no observable or definable response), the supervisor called a halt to the trial so that the position of all objects could be videotaped and notated by the blind observer on a scoring sheet, together with a graphic drawing of the dolphin's path during her response. When this documentation was completed, or nearly so (approximately 1 min), the trainer called the dolphin to her by gently splashing the water. No whistle was blown or fish reward was given, but when the dolphin returned the trainer resumed normal interactions immediately. These procedures guarded against "teaching" the dolphin any particular response to an anomaly and at the same time avoided any strongly aversive consequences of the omission of the whistle sound and the fish. The anomalies were presented to the dolphin in three series. The first consisted of nine different types of anomalies, the second consisted of six types, and the third seven types. There were six exemplars of each anomaly, except for two which contained seven exemplars. The first series required 6.5 weeks for completion, the second 3.5 weeks, and the third 4 weeks. Each series followed
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Table 1 Performance on Grammatically Correct ("Normal") Relational Sequences Sequence type
STR TTR
No.
given
No.
correct (%)
96 170 26 154 73 111
91 (94.8) 93 (54.7) 24 (92.3) MSTR 102(66.2) MTTR 69 (94.5) SMTR 45 (40.5) TMTR Note. Dashes indicate the category is absent. S IO = indirect object; DO = direct object.
"/.b error by category
No.
M
errors
.—.
5 77 2 52 4 66
10
M
DO
R
5.2
— — — — 5.5 8.1
1.0 8.2 3.8 5.2 1.4 3.6
1.0 1.8 3.8 0.6 2.7 0.0
— 3.8
41.8
18.8
28.6
— —
7.7 5.5
49.5 stationary object; T = transportable object; R = relational term; M = modifier;
immediately after completion of the previous one, or nearly so. Results for 12 of the anomalous types most pertinent to the interests discussed earlier are presented in this article. Several controls guarded against any biases within the exemplars of a particular type of anomaly. Particular object-gestures never occurred consistently in the same serial position. For example, given anomalies beginning with two stationary objects (chosen from among PHOENIX, WATER, and SPEAKER), each object appeared approximately equally often in the first and second positions. Additionally, the two relational terms, IN and FETCH, were used an equal number of times. Also, references to the different transportable objects were approximately balanced.
Results The following abbreviations are used to refer to categories of objects and actions in the remaining text: 5 = stationary (nontransportable object; e.g., SPEAKER, PHOENIX); T = transportable object (e.g., BALL, HOOP); M = modifier term (LEFT or RIGHT); R = relational term (FETCH or IN); A = nonrelational action term (e.g., OVER, TAILTOUCH).
Responses to "Normal" Sequences There were a total of 661, 442, and 461 normal sequences given during the first, second, and third series, respectively. The dolphin's responses were 83.1%, 88.5%, and 86.8% correct, respectively, during these three series. There were very few errors made to any of the nonrelational sequences: Only five errors were made in responding to 560 object + action sequences (the wrong object was chosen four times and the wrong action was performed once), and 13 errors were made in responding to 374 modifier + object + action sequences. The latter included nine modifier errors, three object errors, and two action errors (there were two errors in response to one of the sequences). Table 1 summarizes the results for normal relational sequences for the three series combined. As we stressed earlier, relational sequences were of primary interest for the present study. The table categorizes the sequences by whether the destination object (the indirect object in the grammatical sequence) was a stationary (S) object or was capable of transport (T). It is apparent that this variable produced marked differences in performance. As was reported in the results of earlier studies (Herman, 1986, 1987; Herman et al., 1984), the dolphin experienced considerably greater difficulty in
choosing the correct destination object if that object was itself potentially transportable (T) than if it was not (S). The dolphin responded correctly to 94.4% of 195 sequences in which the destination was an S object, but to only 55.2% of 435 sequences in which it was a T object, t(628) = 11.5, p < .001.3 The error analysis shown in Table 1 reveals that choice of the wrong destination object was by far the major problem in TTR, MTTR, or TMTR sequences, as contrasted with STR, MSTR, or SMTR sequences. That these differences were more a result of the function of the object than of the object itself was shown by the very low error rate to objects referenced in nonrelational sentences (only seven object errors in 934 nonrelational sequences). Both S and T objects appeared in nonrelational sequences, in roughly a ratio of 5 references to S objects to 6 references to T objects (although S objects cannot be transported, they can be the object of a nonrelational action such as touching or leaping over). Finally, regardless of the type of sequence illustrated in Table 1, the dolphin never refused to respond, even when the particular exemplar of the sequence was new to her experience. As will be seen in subsequent results, outright rejections of anomalous sequences did occur.
Responses to Anomalous Sequences Requests to transport stationary objects. Three relational forms, shown in Table 2, placed a nontransportable (S) object in the sequential position normally occupied by a transportable (T) object, as contrasted with the normal sequences STR or TTR shown previously in Table 1. In effect, the anomalous sequences violated a semantic relation by directing the dolphin to transport a nontransportable object. The first sequence type, SSR, directs the dolphin to transport one stationary object to another, and the second type, TSR, requires the dolphin to transport a stationary object to a transportable object. This second type is an inversion of the normal STR sequence and it was of interest to see whether the dolphin would reinvert the sequence to construct the normal form. 3
The probability of responding correctly to a three-item relational sequence by chance alone is very much less than 50% (see discussion in Herman et al., 1984, Appendix).
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LANGUAGE-TRAINED DOLPHIN Table 2 Three-Item Semantically Anomalous Relational Sequences Requesting a Transport of a Nontransportable Object, and Closely Related Four-Item Semantically and Syntactically Anomalous Sequence R
R
R
SP PH IN [reject] WT PH FT OV [reject] PP WT IN [reject] WT SP IN [reject] WT SP IN TT [reject] BL SP FT [reject] WT PH FT [WT//PFT] SB PH FT [SB LT FZ FT] SP WT IN PT [reject] PH WT IN [reject] PH WT FT UN [reject] BK SP FT [BKLrPPFT] PH SP FT [reject] PH SP FT MT [reject] FZ WT IN [BKLTBLW] SP WT FT [reject] SP PH IN TT [reject] HP PH IN [LTFZTS] Note. Stationary (S) objects: Phoenix (PH), speaker (SP), and water (WT). Transportable (T) objects: basket (BK), ball (BL), Frisbee (FZ), hoop (HP), pipe (PP), and surfboard (SB). Relational (R) terms: fetch (FT) and in (IN). Nonrelational actions (A): mouth (MT), over (OV), pec-touch (PT), spit (ST), tail-touch (TT), toss (TS), and under (UN). Modifiers: left (LT) and right (RT). Anomalous sequence is given on left; a rejection or a "divergent" response, if any, is on right, in brackets. Underlining indicates items responded to by dolphin. Divergent responses use objects or actions not referred to in the anomalous sequence (shown in italics). Thus, in response to WT PH FT ("take Phoenix to the stream of water"), the dolphin took the hoop to the stream of water (WT HP FT). "Reject" indicates that the dolphin remained at her station. The third sequence, SSRA, again contains the three-item sequence SSR but the addition of the action term (A) creates a syntactic anomaly in addition to the semantic anomaly. At the same time, however, the action term allows for the possibility of taking that action to one of the previously referenced objects (or to some other object). That is, although the overall SSRA sequence is anomalous, two normal two-item subsets, Si A and S2A, are embedded within the sequence although each is composed of nonadjacent terms. For example, in the anomalous sequence WATER PHOENIX FETCH OVER, the two embedded normal sequences are WATER OVER and PHOENIX OVER ("jump over the stream of water" and "jump over Phoenix"), although the gestures that form these sequences are separated by one or two additional gestures. Table 2 shows that Akeakamai rejected five of the six SSR sequences, making no attempt to respond.4 The exception was the substitution of a transportable object, the hoop, for the nontransportable dolphin Phoenix in the SSR sequence WT PH FT ("take Phoenix to the stream of water"). Instead, the hoop was taken to the water. In contrast to the results for SSR sequences, only two of six TSR sequences were rejected, but in no case did the dolphin reinvert the sequence. Relational responses were constructed for three of the remaining four sequences: The transportable object, which always occupied the indirect object slot, was never transported, but in two cases was used as the destination of the transport of some other possibly conveniently positioned transportable object. The final sequence resulted in an apparent irrelevancy, although the action of "tossing," as carried out by Akeakamai, is a component of her response topography to IN, when she places one object inside of or on top of another. There was no indication that responses to objects other than those referred to in the anomaly were governed by semantic similarities or gestural sign confusions. For example, in Table 3 the TSR anomaly SB PH FT requires that the dolphin Phoenix be taken to the surfboard, but the Frisbee to Akeakamai's left was taken instead (SB LT FZ FT). There is no semantic similarity between Phoenix and a Frisbee, nor are the gestures used for these two items similar to each other, as is the case for all object gestures (and all action gestures).
Akeakamai rejected all six SSRA sequences, despite the presence of the embedded nonrelational subsets. It appears, therefore, that rejection of these sequences was governed by the presence of the SSR semantic anomaly, or by the preeminence of the R term, demanding that a relational construction be formed and leading to an apparent rejection of the A term. Overall, the results from these three sequence types suggest that Akeakamai's responses were highly constrained by her interpretation of semantic relations, by what seems to be a recognition that certain objects cannot be transported. The anomalous semantic relation in the TSR sequences apparently overrode any attempt to reinvert the sequence, but it should be noted that inversion of normal relational sequences (i.e., using the second object as the destination and the first as the object to be transported) has always been an extremely rare event for Akeakamai. Herman et al. (1984), for example, reported an inversion rate in normal three-item relational sequences of only 1%. Preserving sequential order: Adding a transportable object to the anomalous sequence. What responses would occur if a transportable object (T) were added to the SSR sequence in an appropriate location sequentially? Table 3 summarizes Akeakamai's responses to three four-item sequences in which a T term has been embedded within the SSR sequence as either the second item (STSR) or the third (SSTR). In the remaining case, two transportable objects were added, one of which took the place of the second S item to create the sequence STTR. All three types are anomalous because each contains three object names in a row, for which there is no existing syntactic rule. However, the presence of a transportable object or objects placed after one or more of the S terms allows, in principle, for a normal STR sequence to be formed without inversion of sequence order. The STSR sequences contain one normal subset (STR), the SSTR sequences contain two 4
In studies of young children's responses to anomalous sentences, rejection is typically indicated through a predetermined verbal response, such as labeling a sentence as "silly" (e.g., James & Miller, 1973).
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Table 3 Syntactic Anomalies: Four-Item Anomalous Relational Sequences Involving Combinations of Stationary Objects and Transportable Objects S 5 T S R S T R S T T R PH HP SP IN [reject] SP HP PP IN [BK PP IN] SP PH HP FT WT PH BK IN WT FZ SP FT WT FZ BL FT WT PH FZ FT PH FZ WT IN [PH FZ FT] PH BK SB FT WT SP BL IN [SB BL IN] SP HP PH FT SP SB BK FT SP FZ WT IN WT PP HP IN SP WT PP IN WT HP PH IN [HP BL IN] PH SP BL FT [reject] PH BL FZ FT [PH FZ IN] PH WT FZ IN Note. Stationary (S) objects: Phoenix (PH), speaker (SP), and water (WT). Transportable (T) objects: basket (BK), ball (BL), Frisbee (FZ), hoop (HP), pipe (PP), and surfboard (SB). Relational (R) terms: fetch (FT) and in (IN). Nonrelational actions (A): mouth (MT), over (OV), pec-touch (PT), spit (ST), tail-touch (TT), toss (TS), and under (UN). Modifiers: left (LT) and right (RT). Anomalous sequence is given on left; a rejection or a "divergent" response, if any, is on right, in brackets. Underlining indicates items responded to by dolphin. Example: SP PH HP FT indicates that Akeakamai transported the hoop to the dolphin Phoenix and ignored the first item (speaker). Divergent responses use objects or actions not referred to in the anomalous sequence (shown in italics). Thus, in response to WT SP BL IN, the dolphin placed the ball on top of the surfboard (SB BL IN). "Reject" indicates that the dolphin remained at her station.
(S,TR and S2TR), and the STTR sequences contain three (ST,R, ST2R, T,T2R). As an example, the SSTR sequence SP PH HP FT contains the normal subsets SP HP FT and PH HP FT (respectively, "take the hoop to the speaker" and "take the hoop to Phoenix"). The STTR sequence SP HP PP IN contains the subsets SP HP IN, SP PP IN, and HP PP IN (respectively, "put the hoop on the speaker," "put the pipe on the speaker," and "put the pipe in the hoop"). To form some of these subsets, nonadjacent terms must be placed together, a process that did not occur in the SSRA sequences discussed in the previous section. Overwhelmingly, the data show that Akeakamai was able to extract a normal subset from these sequences or that she attempted to do so. This occurred for 17 of the 19 anomalous sequences in Table 3. In 12 of these 17 cases, she extracted wholly normal three-item subsets (STR or TTR), using only objects referred to in the sequence, and for 10 of the 12 she conjoined nonadjacent items. For example, she placed the basket in the stream of water (WT BK IN) in response to the sequence WT PH BK IN. Altogether, of the 12 three-item sequences extracted from the anomalies she conjoined the first, second, and fourth items five times and the first, third, and fourth items five times. Clearly, then, adjacency of items was not a requisite for organizing a response to a subset of items in an anomaly. There were five cases in which only two items were used from the anomalous sequence. Of these five, Akeakamai twice used two objects from the anomaly but constructed the wrong relationship (substituting FETCH for IN and IN for FETCH). On another two occasions she selected a transportable object from the sequence, constructed the requested relationship, but used a destination object not referred to in the anomalous sequence. Finally, in the remaining case she chose an object for transport that was not referred to in the sequence, but arrived at a referenced destination and constructed the referenced relationship. She rejected only 2 of 19 sequences as compared with 5 of 6 of the SSR sequences. Hence, in most cases the addition of transportable objects to the SSR sequences resulted
in the reliable use of those objects to construct relational responses. The SSTR sequences in Table 3 provided a choice between the first or second item as the destination of transport. Akeakamai chose the first item on four of the five occasions when she extracted a normal three-item subset. Similarly, the STTR sequences allowed for a choice of either of the first two items as destination, but also allowed for a choice of either the second or third item for the transport. Again, in four of five cases of construction of normal subsets, the first item was chosen as the destination. However, insofar as the limited data allow, Akeakamai appeared indifferent to a choice of the second or third item for transport in STTR sequences. She chose the second item twice and the third item twice among the four normal sequences constructed beginning with the first item as destination (she additionally constructed one normal TTR sequence). These data again make clear that adjacency of items is not a compelling reason for selection of subsets by Akeakamai. A comparison of the SSR sequences (or the SSRA sequences) of Table 2 with the sequences of Table 3 shows that rejection was based more on the absence of a transportable object than on the presence of two consecutive stationary objects. Thus, the dolphin's responses to particular objects were constrained both by their functional role (as S or as T) and by the location, in the sequence of gestures, of the reference to those objects. Substituting a nonrelational action for a relational term. Table 4 shows three sequence types that begin with two object terms (either SS, ST, or TS) but end with an action term (A) rather than a relational term (R). The sequence SSA may be contrasted with the sequence SSR of Table 2, the sequence STA stands in contrast to the normal sequence STR, and the sequence TS A is in contrast to the inverted sequence TSR of Table 2. All of these sequences (SSA, STA, and TSA) are anomalous, but embedded normal two-item subsets are present in all cases (either as S A or TA or both). For example, the STA sequence PH PP TT contains the embedded normal subsets PH TT and PP TT ("touch Phoenix with your tail" and
LANGUAGE-TRAINED DOLPHIN
191
Table 4 Three-Item Syntactic Anomalies Consisting of Two Object Terms Followed by a Nonrelational Action Term S
T
A
T
S
A
S
S
A
BK SP OV [SBOV] WT HP TS [WTHPW] WT PH OV [reject] SB WT ST [reject] PH PP TT SP WT MT [LT//FMT] FZ PH MT [//PMT] WT BK OV PH SP MT [LTFZMT] BL WT TT [SBTT] SP FZ PT PH WT UN [reject] PH SB MT HP PH PT WT SP TT [reject] SP BL UN PP SP UN [SB UN] SP PH PT [reject] Note. Stationary (S) objects: Phoenix (PH), speaker (SP), and water (WT). Transportable (T) objects: basket (BK), ball (BL), Frisbee (FZ), hoop (HP), pipe (PP), and surfboard (SB). Relational (R) terms: fetch (FT) and in (IN). Nonrelational actions (A): mouth (MT), over (OV), pec-touch (PT), spit (ST), tail-touch (TT), toss (TS), and under (UN). Modifiers: left (LT) and right (RT). Anomalous sequence is given on left; a rejection or a "divergent" response, if any, is on right, in brackets. Underlining indicates items responded to by dolphin. Example: SP BL UN indicates that Akeakamai swam under the ball, ignoring the speaker. Divergent responses use objects or actions not referred to in the anomalous sequence (shown in italics). Thus, in response to BK SP OV, the dolphin leaped over the surfboard (SB OV). "Reject" indicates that the dolphin remained at her station. "touch the pipe with your tail"). The table shows some interesting differences among the sequences. First, rejections occurred for four SS A sequences, two TSA sequences, and no STA sequences. Second, only in the STA sequences were responses made consistently to objects referenced in the anomalous string. In five of six cases Akeakamai responded to the grammatically correct embedded TA subset. For the remaining case (WT HP TS), she constructed a relation between S and T (WT HP IN meaning "put the hoop in the stream of water"). Possibly, this relationship was constructed because, as noted earlier, tossing (TS) of an object is a typical initial component of putting one object in or on another. The action term was responded to only twice in the SSA sequences. Each time the action was MT ("to mouth") and each time the object used was not contained within the anomaly. For the TSA anomalies, the action term was responded to in five of six cases, but in only one case was the object chosen contained in the anomaly. Thus, there is clear hierarchy of response trends to referenced objects across the sequences: Responses to a referenced object occurred for all six STA sequences, but for only one TSA sequence, and for no SSA sequences. Clearly, the categorical nature and the semantic relations of the objects preceding the action terms strongly influenced how and whether the response was directed to the object. Only transportable objects were responded to, and, with one exception, only if they were in the normal ST sequence rather than the reversed TS sequence. It appears as if the TS (and ,SS) sequences are analyzed as a pair and rejected because they do not form a legitimate (or familiar) two-object subset and because no relational term is present. As we saw in Table 3, however, both items of an SS sequence are not necessarily rejected if a transportable object is available later in the sequence and if a relational term ends the sequence. Hence, processing of anomalous sequences continues until some legitimate subset can be found. A terminal nonrelational action is usually sufficient, however, for a response, with or without use of one of the object terms in the anomalous sequence. The exception to this rule appeared when the action term followed a relational term (Table 2), resulting in rejection of the entire sequence. The effect of the terminal term: Relational or nonrela-
tional. Evidence that Akeakamai evaluates an entire sequence before organizing a response, accounting for both forward and backward relationships among items in a sequence, is found in the comparisons in Table 5. Here, responses to each of the four-item anomalous relational sequences previously described in Table 2 are compared with responses to similar sequences ending with an action term. The sequences contrasted are SSTR and SSTA, STSR and STSA, and STTR and STTA. Does responding change with substitution of the A term for the R term? The change produced a dramatic effect on responding. Except for two rejected sequences, each anomaly ending with R resulted in the construction of a relationship between two objects. In contrast, no relationship was ever constructed when an A term ended the sequence. Instead, except for four rejected sequences, the terminal action response was carried out to a single object. The presence of a T term as the penultimate item resulted in the selection of that object in seven of nine cases when an action was performed (e.g., the SSTA sequence PH SP BK UN resulted in the response BK UN, glossed as "swim under the basket"). In contrast, if an S term was the penultimate item (STSA), it was never selected. Instead, an arbitrary object was selected or the earlier occurring T item was selected. Overall, the results in Table 5 are very similar to the results shown in Table 4 for the simpler threeitem STA and SSA sequences.
Discussion Analyses of Akeakamai's responses to anomalous sequences suggest that both semantic relations and syntactic constraints influence her processing of the information contained in the artificial language she has been taught. In general, our justification for this conclusion rests on two broad response categories: (a) rejections, and .(b) responses that incorporated subsets of the anomalous sequence. Rejection of anomalies occurred most commonly in response to the SSR, SSA, and SSRA sequences. These rejections demonstrate, first, that Akeakamai was able to discriminate anomalous sequences from normal sequences. Normal sequences, even when the particular instantiation
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Table 5 Contrast of Four-Item Anomalous Sequences Terminating With a Relational or Nonrelational Term 5 ~ S T ~R 5 5 T ~A SP WT WT WT SP PH PH
PH WT PH SP SP WT
PH PH PH SP WT SP WT
HP FT BK IN FZ FT BL IN [SfiBLIN] PP IN BL FT [reject] FZ IN
HP FZ FZ HP FZ HP
R SP IN [reject] SP FT WT IN [PH FZ FT] PH FT WT IN PH IN [HPBLIN]
PH SP SP WT PH WT
SP PH WT SP WT PH
BK UN FZ MT HP OV BL ST [reject] SB PT [5ATPT] PP TT [LTFZTT]
SP WT PH WT PH SP
PP BK BL SB FZ HP
WT SP SP PH WT PH
MT [HPMT] UN [LTFZUN] TT ST [reject] PT OV [LTBKO\]
R PH BL FZ UN [reject] SP HP PP IN [SATPPIN] WT BK SB OV WT FZ BL FT PH BK SB FT SP HP BL PT PH SB HP TT SP SB BK FT WT PP HP IN SP FZ PP MT WT PP BK ST [reject] PH BL FZ FT [PH FZ IN] Note. Stationary (S) objects: Phoenix (PH), speaker (SP), and water (WT). Transportable (T) objects: basket (BK), ball (BL), Frisbee (FZ), hoop (HP), pipe (PP), and surfboard (SB). Relational (R) terms: fetch (FT) and in (IN). Nonrelational actions (A): mouth (MT), over (OV), pec-touch (PT), spit (ST), tail-touch (TT), toss (TS), and under (UN). Modifiers: left (LT) and right (RT). Anomalous sequence is given on left; a rejection or a "divergent" response, if any, is on right, in brackets. Underlining indicates items responded to by dolphin. Example: WT PH BK IN indicates that the basket was placed in the stream of water; SP PH FZ MT indicates that the dolphin placed her mouth about the Frisbee and did not respond to other objects. Divergent responses use objects or actions not referred to in the anomalous sequence (shown in italics). Thus, in response to WT PH PP TT the dolphin touched the Frisbee to her left with her tail (LT FZ TT). "Reject" indicates that the dolphin remained at her station.
was new to Akeakamai's experience, were never rejected. Second, only certain types of anomalies were likely to be rejected, particularly those that contained initial SS subsets, a violation of semantic relations because the subset implies that a nontransportable object be transported. However, if a transportable object were contained in the anomaly, as in SSTR or SSTA sequences, rejections were rare (twice among 13 anomalies). Instead, the T object was frequently used to organize a normal subset, such as STR or TA. The primary basis for rejection was thus inappropriate semantic relations rather than syntactic violations. It appears as if the dolphin examined a sequence for the presence of valid semantic relations, particularly for subsets that preserved normal sequence order without violating semantic relations. If this search failed, Akeakamai rejected the sequence. In the many cases when the dolphin did extract a normal subset embedded within the sequence, the terms of the subset were not necessarily adjacent to one another. The normal ordering had to be preserved, however, regardless of adjacency. For example, TSR sequences were never rearranged to form normal STR sequences, but 10 nonadjacent STR subsets were formed from among 19 SSTR, STTR, and STSR sequences (e.g., S,TR in the SSTR sequences). The dolphin thus maintained the semantic relationships given by word order for relational sequences within her normal gestural language (i.e., the first object gesture refers to the destination of transport and the second
to the item to be transported). TSA and SSA anomalies were characterized both by semantic violations in the TS or SS subsets, assuming they were processed as the beginning of a relational sequence, and by syntactic violations, inasmuch as the sequence actually ended with a nonrelational term. The rejection rates for these sequences (5 of 12 sequences) were only slightly less than those found for the similar TSR and SSR anomalies (7 of 12 sequences). Also, as with these latter two anomalies, the dolphin rarely used any of the referents of the S or T terms in organizing a response to TSA or SSA sequences, despite the availability of normal TA or SA subsets. Instead, the action referred to was applied to an arbitrary or convenient object not referred to in the anomalous sequence. In contrast, STA anomalies, which preserved the normal ST order, resulted in a response to the embedded TA subset in five of six cases (S A was never chosen). Thus, it appears as if the semantic violations in TS or SS subsets (suggesting that a nontransportable object be transported) resulted in a selective rejection of the S or T term or terms. The final item of a sequence, either a relational (R) or nonrelational (A) term, constrained the syntactic evaluation of the anomaly. The data showed that 16 of 18 STTR, STSR, and SSTR sequences resulted in relational responses (the remaining two were rejections). In contrast, none of the 18 anomalies that terminated in an A term rather than the R term (STTA, STSA, and SSTA) yielded a
LANGUAGE-TRAINED DOLPHIN
relational response. Hence, the dolphin discriminated the two different grammatical categories implied by terminal R or A terms, even when the categories of semantic elements preceding these terms were identical. This finding further implies that processing of a sequence continued until all terms were received and the final response was then organized. However, it is emphasized that the final R or A term does not of itself necessarily elicit either a relational or nonrelational response. Instead, rejections of the sequence may occur if the preceding semantic elements are in an inappropriate semantic relation. On the basis of the responses to these various anomalies, we can begin to understand the processing of sequences by the dolphin. First, the language was constructed such that a sequence is anomalous if it references two objects and the second object is not transportable. Suppose that the dolphin used a simple serial-processing strategy to organize the gestures of the sequences. If the second object referenced in a sequence was not transportable, the sequence could be immediately detected as anomalous. Consistent with this strategy is the finding that the dolphin overwhelmingly rejected anomalies of the type SSR and SSRA. However, the anomalous sequence SSTR was rejected only once. Therefore, processing of sequences does not terminate when the second object referenced is not transportable. Furthermore, nonadjacent gestures that form grammatically correct sequences, such as the SiTR subset in the SSTR sequences, were extracted from anomalies. Therefore, the dolphin's processing of sequences is not accurately described by a simple linear model involving serial responses to each sequential gesture. As a further example of nonlinearity, when the dolphin could choose to respond to either the initial gesture or the second gesture as signifying the destination to which some other object must be transported (grammatically, as the indirect object of the sequence), the dolphin generally responded to the initial gesture even though the second gesture was adjacent to the remainder of the grammatically correct subset. Thus, among six STTR sequences, the valid TTR subset, consisting of adjacent items, was formed only once, but the valid STR subset was formed four times. Therefore, simple adjacency of gestures did not compel their use by the dolphin. The preference for the initial gesture in these sequences as the destination object may reflect the rule that the initial gesture in normal STR sequences is always a reference to the destination object. Alternatively, it may have been selected because nontransportable (S) objects are preferred as destinations to transportable (T) objects (possibly because responses to S objects are typically associated with fewer errors, as was shown in Table 1). The preference for SjTR subsets over S2TR subsets in SSTR sequences suggests, however, that a preference for S objects cannot be the complete reason. Instead, the choice of SI over S2 may have been influenced by the dolphin's long experience with relational sequences in which the first-named object is always treated as the destination. The findings on the preference for responding to TA rather than to SA subsets in the nonrelational STA sequences indicates that the initial gesture is not necessarily predominant but is evaluated in relation to the function of the terminal
193
gesture, which identifies uniquely the class of sequence as relational or nonrelational. The decision to respond to the referent of the initial gesture is thus heavily dependent on the class of sequence, a syntactic constraint. These findings, as well as findings on the rejection of both S and T in TSA sequences, argues against the initial item as necessarily dominant or salient, regardless of its semantic value. Thus, it appears that the initial gesture is evaluated together with the remaining gestures, and whether the initial gesture is used to organize a response depends on the overall semantic and syntactic properties of the anomaly. We can conclude from the set of results presented in this study that the dolphin actively processed entire anomalous sequences, apparently searching both backward and forward in the sequence for familiar grammatical structures as well as semantically meaningful relationships. The particular responses taken by the dolphin were generally consistent for a particular anomalous type but varied across types. The particular form of response to an anomalous type thus reflected both the semantic properties of the anomaly and its syntactic structure and the relationship of these to normal sequences in her gestural language. The dolphin's responses were not limited or hampered by the unfamiliarity of the anomalous sentence forms. Instead, the responses made to the anomalies illustrate, first, that the dolphin has implicitly learned the underlying grammatical rules of her imposed artificial language and, second, that she has generalized these rules as applying to the anomalous forms, to the extent that instantiations of the rules can be perceived or extracted within the anomalous structure. Finally, only a limited comparison is possible of this study's findings with the recently reported results of Gisiner and Schusterman (1992) with a sea lion subject. Unlike the current study, these authors did not examine anomalous relational sequences in detail. The only instance of an anomalous sequence terminating with a relational term is a report of the sea lion's responses to each of three exemplars of a TSR sequence. The authors imply that the sea lion did not immediately perceive the TSR anomaly, given that in each case it first swam to the S object and only then discontinued its response. They stated, "Her responses did not present evidence for an expanded semantic relation between the signs and referents (understanding derived from the signs alone, without direct access to the referents themselves)" (p. 86). The dolphin, in contrast, when rejecting TSR sequences or other sequences requesting the transport of an S object (e.g., SSR), simply remained at her station. She never swam toward an S object and then ceased her response. The same was true of the more limited number of tests of TSR or SSR sequences given to Akeakamai 7 years earlier (Herman et al., 1983): Akeakamai never attempted to approach the object referred to by the second S term. It is not only these results, but other results referred to in Herman et al. (1993), that argue strongly for the idea that the gestures (signs) used in Akeakamai's language system have a referential function for her. If we are to accept the interpretation of Gisiner and Schusterman about the meaning of the sea lion's initial approach to a nontransportable object, it would represent a marked
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discontinuity between the sea lion and the dolphin in the understanding of the referential relationship of sign and object. The only other relevant comparison across the two studies occurs with the STA sequences of this study and the TTA sequences of Gisiner and Schusterman (1992). Here, there is an apparent similarity in that both animals responded almost exclusively to the terminal TA subset (i.e.. to TA by the dolphin and to T2A by the sea lion). However, the sea lion was not provided with SSA or TSA anomalies, which, for the dolphin, yielded response patterns very different from those observed with STA sequences. The dolphin, as we noted earlier, rarely used any of the specified object terms when organizing its responses to SSA or TSA anomalies. We interpret this omission as resulting in large part from a rejection of the anomalous semantic relation implied by SS or TS subsets. Gisiner and Schusterman, relying on the more limited data from the TTA sequences alone, reached the conclusion that semantic relations among signs or the semantic properties of signs did not influence the responses of the sea lion. In contrast, the more extensive data relevant to this issue that have been presented in this article clearly show the importance and, at times, the preeminence of semantic relations and semantic properties in determining the responses of the dolphin.
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