Proficient performance of a conjunctive, recursive task by an African gray parrot (Psittacus erithacus).

The comprehension skills of an African gray parrot (Psittacus erithacus), Alex, were tested on a taks that included a conjunctive condition. For each trial, Alex was shown different collections of 7 items, each collection chosen from among 100 objects of various combinations of shapes, colors, and materials, and he was asked to provide (vocally) information about the specific instance of one category of an item that was uniquely defined by the conjunction of two other categories (e.g., "What color is the [object defined by shape and material]?"). Other objects exemplified one, but not both, of these defining categories. Alex responded with an accuracy of 76.5%, which indicated that he understood all the elements in the question, including the conjunctive condition, and that he used these elements to guide his search for the one object in the collection that provided the requested information.     

Number comprehension by a grey parrot (Psittacus erithacus), including a zero-like concept

A Grey parrot (Psittacus erithacus) that was able to quantify 6 item sets (including subsets of heterogeneous groups, e.g., blue blocks within groupings of blue and green blocks and balls) using English labels (I. M. Pepperberg, 1994a) was tested on comprehension of these labels, which is crucial for numerical competence (K. C. Fuson, 1988; see also record 1987-98811-000). He was, without training, asked "What color/object [number]?" for collections of various simultaneously presented quantities (e.g., subsets of 4, 5, and 6 blocks of 3 different colors; subsets of 2, 4, and 6 keys, corks, and sticks). Accuracy was greater than 80% and was unaffected by array quantity, mass, or contour. His results demonstrated numerical comprehension competence comparable to that of chimpanzees and very young children. He also demonstrated knowledge of absence of quantity, using "none" to designate zero.     

Ordinality and inferential abilities of a grey parrot (Psittacus erithacus)

A grey parrot (Psittacus erithacus), able to label the color of the bigger or smaller object in a pair (I. M. Pepperberg & M. V. Brezinsky, 1991), to vocally quantify < or =6 item sets (including heterogeneous subsets; I. M. Pepperberg, 1994), and separately trained to identify Arabic numerals 1-6 with the same vocal English labels but not to associate Arabic numbers with their relevant physical quantities, was shown pairs of Arabic numbers or an Arabic numeral and a set of objects and was asked for the color of the bigger or smaller one. The parrot's success showed he (a) understood number symbols as abstract representations of real-world collections, (b) inferred the relationship between the Arabic number and the quantity via stimulus equivalence, and (c) understood the ordinal relationship of his numbers.     

Postnatal development of lateralized motor preference in the African grey parrot (Psittacus erithacus)

The parrot appears to provide a potentially unique animal model of handedness in humans, but few (if any) observational studies of early postnatal development of postural/motor asymmetries have been published. We studied three African Grey hatchlings, raised without human physical contact, for the first 5 months of life. All three animals failed to show consistent postural and/or motor asymmetries until the end of the 4 postnatal week. These results appear to be comparable to data from prior studies with human infants. Delayed development of lateral motor and/or postural preferences may represent an evolutionarily adaptive strategy for altricial animals.     

Further evidence for addition and numerical competence by a Grey parrot (Psittacus erithacus)

A Grey parrot (Psittacus erithacus), able to quantify sets of eight or fewer items (including heterogeneous subsets), to sum two sequentially presented sets of 0–6 items (up to 6), and to identify and serially order Arabic numerals (1–8), all by using English labels (Pepperberg in J Comp Psychol 108:36–44, 1994; J Comp Psychol 120:1–11, 2006a; J Comp Psychol 120:205–216, 2006b; Pepperberg and Carey submitted), was tested on addition of two Arabic numerals or three sequentially presented collections (e.g., of variously sized jelly beans or nuts). He was, without explicit training and in the absence of the previously viewed addends, asked, “How many total?” and required to answer with a vocal English number label. In a few trials on the Arabic numeral addition, he was also shown variously colored Arabic numerals while the addends were hidden and asked “What color number (is the) total?” Although his death precluded testing on all possible arrays, his accuracy was statistically significant and suggested addition abilities comparable with those of nonhuman primates.     

Grey Parrot (Psittacus erithacus) numerical abilities: addition and further experiments on a zero-like concept

A Grey parrot (Psittacus erithacus), able to quantify 6 or fewer item sets (including heterogeneous subsets) by using English labels (I. M. Pepperberg, 1994), was tested on addition of quantities involving 0-6. He was, without explicit training, asked, "How many total X?" for 2 sequentially presented collections (e.g., of variously sized jelly beans or nuts) and required to answer with a vocal English number label. His accuracy suggested (a) that his addition abilities are comparable to those of nonhuman primates and young children, (b) some limits as to his correlation of "none" and the concept of zero, and (c) a possible counting-like strategy for the quantity 5.     

Vocal learning in the Grey parrot (Psittacus erithacus): effects of species identity and number of trainers

Grey parrots (Psittacus erithacus) learn referential English labels when they view and interact with 2 humans who model vocal labeling and who demonstrate referentiality and functionality of a label (I.M. Pepperberg, 1990a). To test if both trainers are necessary, the authors contrasted 2-trainer modeling with training by 1 human who presented targeted labels to a bird in concert with appropriate items, who asked questions, and who would reward attempts at the label with the item. The bird was also tutored by either 1 or 2 interactive humans in conjunction with a conspecific who already used referential labels. Referential labels were learned from multiple live tutors but not a single trainer. Presence of a conspecific enhanced learning compared with single-trainer sessions but did not affect acquisition in 2-human sessions. Specific aspects of paired tutoring seem critical for acquiring referential vocal labels.     

Simultaneous development of vocal and physical object combinations by a Grey parrot (Psittacus erithacus): bottle caps, lids, and labels

On the basis of primarily behavioral data, researchers (e.g., P. M. Greenfield, 1991) have argued (a) that parallel development of communicative and physical object (manual) combinatorial abilities exists in young children; (b) that these abilities initially have a common neural substrate; (c) that a homologous substrate in great apes allows for similar, if limited, parallel development of these 2 abilities; and (d) that such abilities thus may indicate a shared evolutionary history for both communicative and physical behavior (J. Johnson-Pynn, D. M. Fragaszy, E. M. Hirsh, K. E. Brakke, & P. M. Greenfield, 1999). The authors of the present study found a comparable, if limited, parallel combinatorial development in a Grey parrot (Psittacus erithacus). Given the evolutionary distance between parrots and primates, the authors suggest that the search for and arguments concerning responsible substrates and common behavior should be approached with care and should not be restricted to the primate line.     

The discrimination of discrete and continuous amounts in African grey parrots (Psittacus erithacus)

A wealth of research in infants and animals demonstrates discrimination of quantities, in some cases nonverbal numerical perception, and even elementary calculation capacities. We investigated the ability of three African grey parrots (Psittacus erithacus) to select the largest amount of food between two sets, either discrete food items (experiment 1) or as volume of a food substance (experiment 2). The two amounts were presented simultaneously and were visible at the time of choice. Parrots were tested several times for all possible combinations between 1 and 5 seeds or 0.2 and 1 ml of food substance. In both conditions, subjects performed above chance for almost all combinations. Accuracy was negatively correlated with the ratio, that is performance improved with greater differences between amounts. Therefore, these results with both individual items and volume discrimination suggest that parrots use an analogue of magnitude, rather than object-file mechanisms to quantify items and substances.     

Comprehension of "absence" by an African Grey parrot: Learning with respect to questions of same/different

An African Grey parrot, Alex, learned to report on the absence or presence of similarity and difference between two objects. Alex was shown pairs of objects that were (a) totally dissimilar, (b) identical, or (c) similar or different with respect to one of three attributes (color, shape, or material). In the first two cases, he responded to the respective queries of “What's same?” or “What's different?” with the vocalization “none,” and in the third case he responded with the appropriate category label (“color,” “shape,” or “mah-mah” [matter]). His accuracy was 80.9% to 83.9% for pairs of familiar objects not used in training and 72.5% to 78.4% for pairs whose colors, shapes, and materials were unfamiliar. The data provide evidence that this parrot's abilities are comparable to those of mammals that have been trained to report on the presence or absence of objects or features of objects.     

Successive reversal of concurrent discriminations by macaques (Macaca mulatta): proactive interference effects

Rhesus monkeys received concurrent within-session training on eight, two-choice object pairs and then underwent successive reversals of these problems. Initially, reversals required about six times more training than acquisition with no improvement over seven successive reversals. Surprisingly, performance on these eight problems was unimpaired if they were embedded in different eight-problem tasks, thereby indicating a release from proactive interference. When the original eight problems again underwent successive reversal, no improvement was seen over seven reversals, although there was significantly less error-per-reversal than in the initial test. Subsequently, monkeys appeared to be developing a learning set for successive reversal because performance on successive reversal of eight novel problems was not different from that seen with the old familiar task. Set acquisition was confirmed when proficient reversal was eventually achieved on both old and new concurrent tasks. Thus, concurrent reversal set did develop, but it required arduous training to overcome proactive interference effects on memory. The ubiquitous influence of measurement context on organization of monkey memory was noted.     

Acquisition of navigation by chimpanzees (Pan troglodytes) in an automated fingermaze task

These experiments investigated how chimpanzees learn to navigate visual fingermazes presented on a touch monitor. The aim was to determine whether training the subjects to solve several different mazes would establish a generalized map-reading skill such that they would solve new mazes correctly on the first presentation. In experiment 1, two captive adult female chimpanzees were trained to move a visual object (a ball) with a finger over the monitor surface toward a target through a grid of obstacles that formed a maze. The task was fully automated with storage of movement paths on individual trials. Training progressed from very simple mazes with one obstacle to complex mazes with several obstacles. The subjects learned to move the ball to the target in a curved path so as to avoid obstacles and blind alleys. After training on several mazes, both subjects developed a high level of efficiency in moving the ball to the target in a path that closely approached the ideal shortest path. New mazes were then presented to determine whether the subjects had acquired a more generalized maze-solving performance. The subjects solved 65–100% of the new mazes the first time they were presented by moving the ball around obstacles to the target without making detours into blind alleys. In experiment 2, one of the chimpanzees was trained using mazes with two routes to the target. One of the routes was blocked at one of many possible locations. After training to avoid the blind alley in different mazes, new mazes were presented that also had one route blocked. The subject correctly solved 90.7% of the novel mazes. When the mazes had one short and one long open route to the target the subject preferred the shorter route. When the short route was blocked, the subject solved only 53.3% of the mazes because of the preference for the shorter route even when blocked. The overall results suggest that with the training methods used the subjects learned to solve specific mazes with a trial-and-error method. Although both subjects were able to solve many of the novel mazes they did not fully develop a more general "map-reading" skill. Accepted after revision: 30 July 2001 Electronic Publication     

Acquisition of a same-different discrimination task by pigeons (Columba livia)

Four homing pigeons were trained to discriminate two figures simultaneously presented on an LCD screen. The figure was either a rectangle (A) or a square (B), and four combinations of the two figures, AA, AB, BA, BB, appeared in a pseudo-randomized order. The pigeons' task was to peck one of these figures based upon whether the two figures were identical or not. One pigeon successfully learned this discrimination, with proportions of correct responses above 90% in two consecutive sessions. Of the other birds, two performed above chance level but had difficulty meeting a learning criterion of above 80% in two consecutive sessions. All birds achieved this criterion when the combinations of figures presented were reduced to two. Results suggested that learning the present same-different discrimination is within the capacity of pigeons to a certain extent, although there exists considerable individual variation in the pigeons' skills to acquire complex discrimination.     

Acquisition of expertise on a difficult perceptual-motor task by an amnesic patient

While numerous studies have reported learning of perceptual-motor skills by amnesic patients, few if any have documented the eventual acquisition of expertise on a given task. This paper recounts the learning of the computer game Tetris by a hippocampal amnesic, whose acquisition of the task in a formal evaluation was somewhat slower than that of a comparison group, but who after many hours of self-paced practice achieved expert-level play.     

Towards defining a unified concept for the acceptability of Intelligent Transport Systems (ITS): A conceptual analysis based on the case of Intelligent Speed Adaptation (ISA)

A key success factor in the future implementation of new in-vehicle technologies is in understanding how users will experience and respond to these devices. Although it is recognized that acceptance, acceptability and/or support is important, consistency in the definition of acceptability, and how it can be measured, is absent. In this paper we conceptualize acceptance as the attitudes towards a new device after its introduction and acceptability as the attitudes to it before its introduction. It is our goal to describe and conceptualize the most common and relevant socio-psychological factors that can influence acceptance and acceptability of Intelligent Speed Adaptation (ISA). By analysing the different theories and methods used in ISA trials we arrived at the 14 most potential indicators that could influence the definition of acceptability and acceptance. A test survey was conducted to determine if these indicators are relevant and if they affect acceptability. The use of a factor analysis helped to single out those questions that were deemed relevant in doing our conceptual acceptability analysis, and to allocate correlations between the different items. We conclude that we have found a concept with some main possible indicators that directly influence the acceptability of ISA.