Communication, symbolic communication, and language: reply to Seidenberg and Petitto

Seidenberg and Petitto's (1987) assertion that Kanzi and Mulika's lexigram usage is not representational is evaluated by contrasting their abilities with Nim's. Kanzi and Mulika's data indicate that they (a) comprehend spoken English words; (b) can identify lexigram symbols when they hear these words; (c) can comprehend lexigram usage; (d) can use lexigrams when referents are absent and can, if asked, lead someone to the referent; and (e) that all these skills were acquired through observation, not conditioning. Nim evidenced no comprehension of signs and could not use signs when referents were absent. He was forced to sign and encouraged to imitate his teachers. Seidenberg and Petitto's negative experiences with Nim apparently led them to overgeneralize to all other apes, regardless of species, modality, or training history. Consequently, they unjustifiably disregard important components of Kanzi and Mulika's comprehension data which demonstrate that their lexical knowledge could not have been acquired in an instrumental fashion.     

Chimpanzee responding during matching to sample: control by exclusion

Three chimpanzees performed a computerized matching-to-sample task in which samples were photographs of items and comparison stimuli were geometric symbols called lexigrams. In Experiment 1, samples were either defined (i.e., they represented items that were associated already with a specific lexigram label by the chimpanzees) or undefined (i.e., they did not have an already learned association with a specific lexigram). On each trial, the foil (incorrect) comparison could be either a defined or an undefined lexigram. All 3 chimpanzees selected the correct comparison for undefined samples at a level significantly better than chance only when the foil comparison was defined. In Experiment 2, three comparisons were presented on each trial, and in Experiment 3, four comparisons were presented on each trial. For Experiments 2 and 3, the foil comparisons consisted of either defined or undefined comparisons or a mixture of both. For these two experiments, when the chimpanzees were presented with an undefined sample, they typically made selections of only undefined comparisons. These data indicate that the chimpanzees responded through use of exclusion. A final experiment, however, indicated that, despite the use of exclusion to complete trials with undefined samples correctly, the chimpanzees did not learn new associations between undefined samples and comparisons.     

A dog at the keyboard: using arbitrary signs to communicate requests

As a consequence of domestication, dogs have a special readiness for communication with humans. We here investigate whether a dog might be able to acquire and consistently produce a set of arbitrary signs in her communication with humans, as was demonstrated in “linguistic” individuals of several species. A female mongrel dog was submitted to a training schedule in which, after basic command training and after acquiring the verbal labels of rewarding objects or activities, she learned to ask for such objects or activities by selecting lexigrams and pressing keys on a keyboard. Systematic records taken during spontaneous interaction with one of the experimenters showed that lexigrams were used in an appropriate, intentional way, in accordance with the immediate motivational context. The dog only utilized the keyboard in the experimenter’s presence and gazed to him more frequently after key pressing than before, an indication that lexigram use did have communicative content. Results suggest that dogs may be able to learn a conventional system of signs associated to specific objects and activities, functionally analogous to spontaneous soliciting behaviors and point to the potential fruitfulness of the keyboard/lexigram procedure for studying dog communication and cognition. This is the first report to systematically analyze the learning of arbitrary sign production in dogs. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Spontaneous symbol acquisition and communicative use by pygmy chimpanzees (Pan paniscus)

Two pygmy chimpanzees (Pan paniscus) have spontaneously begun to use symbols to communicate with people. In contrast to common chimpanzees (Pan troglodytes) using the same communicative system, the pygmy chimpanzees did not need explicit training in order to form referential symbol-object associations. Instead, they acquired symbols by observing others use these symbols in daily communications with them. In addition, the pygmy chimpanzees have begun to comprehend spoken English words and can readily identify lexigrams upon hearing the spoken words. By contrast, common chimpanzees who received similar exposure to spoken English are unable to do so. The older pygmy chimpanzee has begun to form requests of the form agent-verb-recipient in which he is neither the agent nor the recipient. By contrast, similarly aged common chimpanzees limited their requests to simple verbs, in which the agent was always presumed to be the addressee and the chimpanzee itself was always the recipient, thus they had no need to indicate a specific agent or recipient. These results suggest that these pygmy chimpanzees exhibit symbolic and auditory perceptual skills that are distinctly different from those of common chimpanzees.     

Prospective memory in a language-trained chimpanzee (Pan troglodytes)

Prospective memory involves the encoding, retention, and implementation of an intended future action. Although humans show many forms of prospective memory, less is known about the future oriented processes of nonhuman animals, or their ability to use prospective memory. In this experiment, a chimpanzee named Panzee, who had learned to associate geometric forms called lexigrams with real-world referents, was given a prospective memory test. Panzee selected between two foods the one she wanted to receive more immediately. That food was scattered in an outdoor yard where she could forage for it. Also outdoors were lexigram tokens, one of which represented the food item that remained indoors throughout a 30 min period, and that could be obtained if Panzee brought in the token that matched that food item. After foraging for the selected food item, Panzee consistently remembered to retrieve and return the correct token when food was available indoors, whereas on control trials involving no indoor food she rarely returned a token. This indicated that Panzee encoded information relevant to the future action of token retrieval after extended delays for one type of food, even when a more immediately preferred food was available.     

Phonological encoding and ideographic reading by the disconnected right hemisphere: Two case studies

The mute disconnected right hemispheres (RHs) of two commissurotomy patients are able to understand spoken words and read printed words by matching them with pictures of the objects named. In this paper we report the results of five experiments. The RH of one patient could “evoke the sound image” of a word to the extent of matching two pictures with homonymous names (experiment 1) or with rhyming names (experiment 2) without being able to name either one. This transformation of picture to covert sound does not depend on orthographic similarity of word ends as a clue to homonymy or rhyme, nor does it improve with short-term learning. Yet neither RH can translate print into sound by matching a spelled word with a picture that has a rhyming name (experiment 3) or by matching two orthographically dissimilar rhymes, be they meaningful (experiment 4) or nonsense words (experiment 5). We suggest that these RHs read “ideographically,” recognizing words directly as visual gestalts without intermediate phonetic recoding or grapheme-to-phoneme translation.     

The development of representational play in chimpanzees and bonobos: Evolutionary implications,pretense, and the role of interspecies communication

This research investigates the development of symbolic or representational play in two species of the genus Pan, bonobos (Pan paniscus) and chimpanzees (Pan troglodytes). The participants varied not only by species, but also as to whether they had become proficient in communicating with humans via a set of arbitrary visual symbols, called lexigrams. Using a developmental sequence of representational play based on McCune, we found every level that children manifest to be constructed by Pan. The most robust and regular ontogenetic sequence for both bonobos and chimpanzee was not McCune's five-level progression, but a three-step ontogenetic sequence: Level 1 (no representation, no pretense) precedes Levels 2–4 (representation but no pretense), which in turn precedes Level 5 (includes pretense as well as representation). A linguistic system for interspecies communication was necessary for Level 5 representational play and “true” pretense. Human scaffolding produced developmental progress within sequences for all the apes, except the bonobo who lacked a system of interspecies communication. This evidence suggests that the potential for representational play and its social stimulation were present in the common ancestor of bonobos, chimpanzees and humans five million years ago.     

Picture Naming Deficits in Developmental Dyslexia: The Phonological Representations Hypothesis

The picture and word naming performance of developmental dyslexics was compared to the picture and word naming performance of non-dyslexic (“garden variety”) poor readers, reading age, and chronological age-matched controls. The stimulus list used for both tasks was systematically manipulated for word length and word frequency. In order to examine picture naming errors in more depth, an object name recognition test assessed each subject's vocabulary knowledge of those names which they were unable to spontaneously label in the picture naming task. Findings indicated that the dyslexic and the garden variety poor readers exhibited a picture naming deficit relative to both chronological and reading age-matched controls. Findings also indicated that both groups of impaired readers obtained superior scores in the word naming task than in the picture naming task, while both groups of controls showed no difference in performance across tasks. The dyslexics' picture naming errors, but not those of the garden variety poor readers, were particularly marked on polysyllabic and/or low frequency words, indicating a possible phonological basis to the picture naming deficit of the dyslexic children. These children also recognized significantly more unnamed target words than all comparison groups, suggesting a particular difficulty inretrievingthe phonological codes of known picture names rather than a vocabulary deficit. Results are discussed in terms of dyslexics' difficulty in encoding full segmental phonological representations of names in long-term memory and/or in processing these representations in order to generate required names on demand.     

Contrast of hand preferences between communicative gestures and non-communicative actions in baboons: Implications for the origins of hemispheric specialization for language

Gestural communication is a modality considered in the literature as a candidate for determining the ancestral prerequisites of the emergence of human language. As reported in captive chimpanzees and human children, a study in captive baboons revealed that a communicative gesture elicits stronger degree of right-hand bias than non-communicative actions. It remains unclear if it is the communicative nature of this manual behavior which induces such patterns of handedness. In the present study, we have measured hand use for two uninvestigated behaviors in a group of captive olive baboons: (1) a non-communicative self-touching behavior (“muzzle wipe” serving as a control behavior), (2) another communicative gesture (a ritualized “food beg”) different from the one previously studied in the literature (a species-specific threat gesture, namely “hand slap”) in the same population of baboons. The hand preferences for the “food beg” gestures revealed a trend toward right-handedness and significantly correlated with the hand preferences previously reported in the hand slap gesture within the same baboons. By contrast, the hand preferences for the self-touching behaviors did not reveal any trend of manual bias at a group-level nor correlation with the hand preferences of any communicative gestures. These findings provide additional support to the hypothesized existence in baboons of a specific communicative system involved in the production of communicative gestures that may tend to a left-hemispheric dominance and that may differ from the system involved in purely motor functions. The hypothetical implications of these collective results are discussed within the theoretical framework about the origins of hemispheric specialization for human language.     

Strategies in landmark use by children, adults, and marmoset monkeys

Common marmosets (Callithrix jacchus jacchus), human children, and human adults learned to find a goal that was located in the center of a square array of four identical landmarks. The location of the landmark array and corresponding goal varied across trials, so the task could not be solved without using the landmark array. In Experiment 1, a matrix of discrete goal locations was presented and the landmarks surrounded and were adjacent to the correct location during training. After training, an expansion test was given in which the distance between landmarks was increased. Marmosets, children (ages 5–9), and adults all readily learned to use the landmarks to search accurately during training. On the expansion test, adults uniformly searched in the center of the array. Monkeys and children concentrated their searching near the landmarks rather than in the center. The monkeys, but not the children, searched more often on the directionally appropriate side of the landmarks than on other sides of the landmarks. In Experiment 2, children (ages 3–5) were trained with a continuous search space and with the goal farther from the landmarks so that a beaconing strategy rule could not be used. Several of the children failed to acquire the training task. Of those who learned to find the goal, three searched in the middle on expansion tests but most searched nearer to the landmarks. The “middle rule” strategy that is uniformly used by adult humans does not appear to be a preferred strategy for children or non-human primates.     

Naming and Exclaiming: Infants' Sensitivity to Naming Contexts

In three experiments, we examined 17-month-olds' acquisition of novel symbols (words and gestures) as names for object categories. Experiment 1 compares infants' extension of novel symbols when they are presented within a familiar naming phrase (e.g., "Look at this [symbol]!") versus presented alone (e.g., "Look! ... [symbol]!") Infants mapped novel gestures successfully in both naming contexts. However, infants mapped novel words only within the context of familiar naming phrases. Thus, although infants can learn both words and gestures, they have divergent expectations about the circumstances under which the 2 symbolic forms name objects. Experiments 2 and 3 test the hypothesis that infants' expectations about the circumstances under which words that name objects are acquired by monitoring how adults indicate their intention to name. By employing a training paradigm, these two experiments demonstrated that infants can infer how an experimenter signals his or her intention to name an object on the basis of a very brief training experience.     

THE EFFECTS OF KNOWN-ITEM INTERSPERSAL ON ACQUISITION AND RETENTION OF SPELLING AND SIGHTREADING WORDS1

The use of well-documented procedures such as shaping, differential reinforcement, and fading may not be the most practical for teaching certain academic behaviors. An alternative procedure of interspersing trials on previously trained items with trials on unknown items has been suggested, but its effects on acquisition and retention have not been systematically examined. This study investigated the effects of interspersing known items during training on new tasks. Six mentally retarded adolescents were given pretests on spelling and sightreading words, which were divided into pools of learned and unlearned items. Training and baseline conditions were implemented concurrently, using a multi-element design. During interspersal training sessions, 10 known words from the pretest were alternately presented with each of 10 test words that were incorrect on the pretest. The ratio of previously mastered words to test words was gradually reduced. During baseline sessions, 10 different test words were presented without alternation of previously known words. During this condition, a procedure involving high-density social reinforcement contingent on task-related behaviors, but not necessarily correct responses, was later introduced, followed by a return to the original noninterspersal baseline. During all conditions, test words were deleted and replaced after meeting a mastery criterion of three consecutive correct trials. Retention tests were administered over learned test words for all conditions, at specified intervals. Results showed that both acquisition and retention of spelling and sightreading words were facilitated by the interspersal procedure. All subjects acquired more words during the interspersal condition than either the high-density or baseline conditions. The effectiveness of the procedure may possibly be attributed to better maintenance of attending behavior to unknown items as a function of the inclusion of known items, which directly increase the amount of reinforcement for correct responses during the early stages of skill acquisition.     

Recognition of pictorial representations by chimpanzees (<Emphasis Type="Italic">Pan troglodytes</Emphasis>)

In this study, I investigated chimpanzees' ability to recognize pictorial representations. Four adults and three juvenile chimpanzees were trained to choose images of photographs of flowers among 12 items belonging to four categories on a touch-sensitive monitor. As a generalization test, the following five types of images were presented: (1) novel photographs, (2) colored sketches (more realistic), (3) a colored clip art (cartoon-like images), (4) black-and-white line drawings, and (5) Kanji characters (as the control images). One adult and all three juvenile chimpanzees were able to choose any style of the nonphotographic images of flowers significantly above the chance level, whereas none could choose the correct Kanji characters corresponding to a flower significantly above the chance level. The other three adult chimpanzees' performance level did not exceed the chance level in terms of choosing nonphotographic images although they showed good transfer skills to novel photographs. The results revealed that not all chimpanzees could recognize pictures used by humans without training. The results also suggest "critical period" in acquisition of skill in recognizing pictures in chimpanzees. Only one adult chimpanzee, who had acquired skill in recognizing visual symbols, also recognized pictures aside from the juvenile chimpanzees. Her learning history might have aided her in acquiring this skill. The results of this study suggest a relationship between pictorial competence and symbolic one.     

A bird is a bird is a bird: Making reference within and without superordinate categories

Adults with localized cerebral insult often err in their use of a word to refer to an object or an idea. It is important to assess, then, the patients' appreciation of what a word can refer to, and the way in which they may violate the borders around a referential field. Nonfluent aphasics, fluent aphasics, and nonaphasic patients with insult to the right hemisphere were asked to provide names of items which could be referred to by familiar superordinate terms like “bird.” The principal results revealed that the nonfluent aphasics are anchored to the central portions of a superordinate's referential field (naming items like “robin” and “sparrow,” for instance). While fluent aphasics often violate the borders around a referential field (e.g., providing “beaver” in response to “birds”), it was nevertheless possible to characterize some limits to their choice of a superordinate's referents. These findings were independent both of the absolute number of responses provided and the frequency of occurrence of the response. Further, the patients with insult to the left hemisphere produce few consecutive items whose referents hold attributes in common. When these clusters are produced by aphasics, they consist primarily of subordinates whose referents exhibit many overlapping features (e.g., “bald eagle, black eagle, golden eagle” in response to “bird”). The right-hemisphere-damaged subjects, in contrast, produce many clusters of related items. These consist of less central, basic object level words whose referents hold less obvious features in common (e.g., “albatross, crane, gull” in response to “bird”). Aphasics, then, may be limited in their ability to analyze referents for critical features. Taken together, these data contribute to a more precise characterization of the nonfluent aphasics' and the fluent aphasics' referential deficits, and lend support specifically to the notion that neither group of aphasics relies on definition-like features to determine what a word can refer to.     

The gestures of a gorilla: language acquisition in another pongid

A female lowland gorilla, Koko, has been engaged in an ongoing language program since July 1972 when she was 1 year old. During the first 30 months of training she acquired a vocabulary of 100 words in American Sign Language which she spontaneously combined into meaningful and often novel statements of up to 11 signs in length. The gorilla is using a rapidly expanding vocabulary of signs to express semantic and possibly grammatical relations similar to those expressed by human children in the early stages of language acquisition. Patterns of generalization, gradual increase in mean length of utterance, and innovative use of gestural language are discussed in relation to data available on children and chimpanzees.     

Moray revisited: High-priority affective stimuli and visual search

Previous research offers conflicting suggestions about whether “high-priority” verbal stimuli such as an individual's own name or emotionally charged words automatically grab attention and/or can be detected without the usual capacity limitations. Nine experiments investigated this issue, using visual search through displays of words. In speeded search tasks, the subject's own name was detected more quickly than other targets, but in no case were search slopes flat enough to suggest parallel search or “pop-out”. Further, names were not found to be unusually potent distractors. Emotionally charged words were neither more readily detected as targets nor more potent as distractors than neutral words. Acomparison of observers' accuracy in searching briefly exposed simultaneous vs. successive displays provided further evidence that search for “high-priority” word targets is subject to the same severe capacity limitations as those that are found with search for neutral words.     

Selective attention to words and colours

In the Stroop test it is found that the presence of words interferes with the task of naming colours. The usual account of this phenomenon is that the names of words are more readily obtained than are the names of colours and that the production of the latter is interfered with by the spontaneous occurrence of the former. Treisman and Fearnley (1969) have suggested a modification of the usual account such that stress is laid on the correspondence between the nature of the response (“verbal”) and that feature of a stimulus which will dominate. The present experiments seem to demonstrate that the data which Treisman and Fearnley use in support of their claim can be attributed to the strategy which their subjects adopted in their task. Some further observations are made concerning the different levels at which comparisons can be made between two stimuli.     

Contingent associations and the double-function,verbal-discrimination task

Three experiments examined the role of contingent associations in learning double-function, verbal-discrimination lists. Some 15-pair lists of category instances were constructed in such a way that the learning of three contingent associations based on category names would mediate correct performance for all 15 pairs. The first experiment gave no evidence that the three contingencies aided learning. The second experiment showed that subjects could be taught the three contingent associations in isolation and that they could then apply them successfully to the double-function list. To make the contingencies more apparent to the subjects, the category names were used during feedback in the third experiment. The learning was not facilitated by such feedback. It was concluded that the learning observed for the usual double-function list does not involve contingent associations.     

Tracking Multiple Statistics: Simultaneous Learning of Object Names and Categories in English and Mandarin Speakers

Two experiments were conducted to examine adult learners' ability to extract multiple statistics in simultaneously presented visual and auditory input. Experiment 1 used a cross‐situational learning paradigm to test whether English speakers were able to use co‐occurrences to learn word‐to‐object mappings and concurrently form object categories based on the commonalities across training stimuli. Experiment 2 replicated the first experiment and further examined whether speakers of Mandarin, a language in which final syllables of object names are more predictive of category membership than English, were able to learn words and form object categories when trained with the same type of structures. The results indicate that both groups of learners successfully extracted multiple levels of co‐occurrence and used them to learn words and object categories simultaneously. However, marked individual differences in performance were also found, suggesting possible interference and competition in processing the two concurrent streams of regularities.     

Mode-relations in language learning by language-deficient retarded subjects

The relationship between language comprehension and production was examined with two severely language-deficient retarded subjects who were taught the plural form /z/. Comprehension and production were trained concurrently with different words in each mode until correct plural use occurred in the untrained mode for each word. Subsequent training of reversed plural use in comprehension for one subject and production for the other failed to result in reversed plural use in the untrained modes for those words. This mode-independence contrasted with interdependence displayed by normal children in earlier study using similar procedures. The results are discussed in relation to the normal developmental process and the possible deviation from it.