Recognition of line-drawing representations by a chimpanzee (Pan troglodytes)

Parallel developmental changes in children's production and recognition of line drawings of visual concepts

Childhood is marked by the rapid accumulation of knowledge and the prolific production of drawings. We conducted a systematic study of how children create and recognize line drawings of visual concepts. We recruited 2-10-year-olds to draw 48 categories via a kiosk at a children's museum, resulting in >37K drawings. We analyze changes in the category-diagnostic information in these drawings using vision algorithms and annotations of object parts. We find developmental gains in children's inclusion of category-diagnostic information that are not reducible to variation in visuomotor control or effort. Moreover, even unrecognizable drawings contain information about the animacy and size of the category children tried to draw. Using guessing games at the same kiosk, we find that children improve across childhood at recognizing each other's line drawings. This work leverages vision algorithms to characterize developmental changes in children's drawings and suggests that these changes reflect refinements in children's internal representations.

The Development of Object Recognition Requires Experience with the Surface Features of Objects

What role does visual experience play in the development of object recognition? Prior controlled-rearing studies suggest that newborn animals require slow and smooth visual experiences to develop object recognition. Here, we examined whether the development of object recognition also requires experience with the surface features of objects. We raised newborn chicks in automated controlled-rearing chambers that contained a single virtual object, then tested their ability to recognize that object from familiar and novel viewpoints. When chicks were reared with an object that had surface features, the chicks developed view-invariant object recognition. In contrast, when chicks were reared with a line drawing of an object, the chicks failed to develop object recognition. The chicks reared with line drawings performed at chance level, despite acquiring over 100 h of visual experience with the object. These results indicate that the development of object recognition requires experience with the surface features of objects.

The origin of representational drawing: a comparison of human children and chimpanzees

To examine the evolutional origin of representational drawing, two experiments directly compared the drawing behavior of human children and chimpanzees. The first experiment observed free drawing after model presentation, using imitation task. From longitudinal observation of humans (N = 32, 11-31 months), the developmental process of drawing until the emergence of shape imitation was clarified. Adult chimpanzees showed the ability to trace a model, which was difficult for humans who had just started imitation. The second experiment, free drawing on incomplete facial stimuli, revealed the remarkable difference between two species. Humans (N = 57, 6-38 months) tend to complete the missing parts even with immature motor control, whereas chimpanzees never completed the missing parts and instead marked the existing parts or traced the outlines. Cognitive characteristics may affect the emergence of representational drawings.

From colour photographs to black-and-white line drawings: an assessment of chimpanzees' (Pan troglodytes') transfer behaviour

Over two experiments, we investigated the ability of two adolescent and two adult chimpanzees to generalise a learnt, pictorial categorisation to increasingly degraded and abstract stimuli. In Experiment 2, we further assessed the ability of the adolescent chimpanzees to engage in open-ended categorisation of black-and-white line drawings. The current results confirmed and extended previous findings, showing that sub-adult chimpanzees outperform adult chimpanzees in the categorisation of pictorial stimuli, particularly when the stimuli are more degraded and abstract in nature. However, none of the four chimpanzees showed positive transfer of their category learning to a set of black-and-white line drawings, and neither of the adolescent chimpanzees evidenced reliable open-ended categorisation of the black-and-white line drawings. The latter findings suggest that both sub-adult and adult chimpanzees find it difficult to recognise black-and-white line drawings, and that open-ended categorisation of black-and-white line drawings is challenging for chimpanzees.

Social stimuli and social rewards in primate learning and cognition

Many studies have suggested that non-human primates have good individual recognition abilities, that social stimuli can serve as discriminative stimuli in learning tests and that visual access to social objects or events can be a reinforcer for operant behaviour. Intensified research efforts comparing the effectiveness of social and non-social stimuli and rewards across a range of learning and other cognitive tasks would help clarify the extent to which monkeys and apes might be specially predisposed to process information in the social domain. In addition to identity, social interactions and relationships constitute raw material to be mentally represented and processed. Some studies have addressed the individual and evolutionary origins of mechanisms underlying the ability to attribute mental states and intentions to others, for example by looking at the understanding of another's gaze, imitation and the development of tactical deception. The results of some of this research suggest that only some species might be capable of higher-order attribution. Further progress in the study of primate social cognition will require continuing refinement of methods and the development of new techniques to compare primates as behaviourists and mentalists.

Face recognition in primates: a cross-species study

Recognition for human faces, monkey faces, and objects was assessed in both adult humans (Homo sapiens) and monkeys (Macaca mulatta) with a visual paired-comparison task. The results demonstrated that while both species showed strong novelty preference for objects, human participants showed novelty preference for human faces but not for monkey faces, and vice versa for the monkeys. This `species-specific effect' in face recognition is discussed in relation with data on both the `other-race effect' observed in humans and the effects of experience or training on face recognition processes in primates.

What line drawings reveal about the visual brain

Scenes in the real world carry large amounts of information about color, texture, shading, illumination, and occlusion giving rise to our perception of a rich and detailed environment. In contrast, line drawings have only a sparse subset of scene contours. Nevertheless, they also trigger vivid three-dimensional impressions despite having no equivalent in the natural world. Here, we ask why line drawings work. We see that they exploit the underlying neural codes of vision and they also show that artists' intuitions go well beyond the understanding of vision found in current neurosciences and computer vision.

Contrasting the edge- and surface-based theories of object recognition: behavioral evidence from macaques (Macaca mulatta)

This study assessed the contribution of edge and surface cues on object representation in macaques (Macaca mulatta). In Experiments 1 and 2, 5 macaques were trained to discriminate 4 simple volumetric objects (geons) and were subsequently tested for their ability to recognize line drawings, silhouettes, and light changes of these geons. Performance was above chance in all test conditions and was similarly high for the line drawings and silhouettes of geons, suggesting the use of the outline shape to recognize the original objects. In addition, transfer for the geons seen under new lighting was greater than for the other stimuli, stressing the importance of the shading information. Experiment 3, using geons filled with new textures, showed that a radical change in the surface cues does not prevent object recognition. It is concluded that these findings support a surface-based theory of object recognition in macaques, although it does not exclude the contribution of edge cues, especially when surface details are not available.

Monkeys recognize the faces of group mates in photographs

Nonhuman primates possess a highly developed capacity for face recognition, which resembles the human capacity both cognitively and neurologically. Face recognition is typically tested by having subjects compare facial images, whereas there has been virtually no attention to how they connect these images to reality. Can nonhuman primates recognize familiar individuals in photographs? Such facial identification was examined in brown or tufted capuchin monkeys (Cebus apella), a New World primate, by letting subjects categorize facial images of conspecifics as either belonging to the in-group or out-group. After training on an oddity task with four images on a touch screen, subjects correctly identified one in-group member as odd among three out-group members, and vice versa. They generalized this knowledge to both new images of the same individuals and images of juveniles never presented before, thus suggesting facial identification based on real-life experience with the depicted individuals. This ability was unexplained by potential color cues because the same results were obtained with grayscale images. These tests demonstrate that capuchin monkeys, like humans, recognize whom they see in a picture.

Picture processing in tufted capuchin monkeys (Cebus apella)

Although pictures are frequently used in place of real objects to investigate various aspects of cognition in different non-human species, there is little evidence that animals treat pictorial stimuli as representations of the real objects. In the present study, we carried out four experiments designed to assess picture processing in tufted capuchin monkeys (Cebus apella), using a simultaneous Matching-to-Sample (MTS) task. The results of the first three experiments indicate that capuchins are able to match objects with their colour photographs and vice versa, and that object-picture matching in this New World monkey species is not due to picture-object confusion. The results of the fourth experiment show that capuchins are able to recognize objects in their pictures with a high level of accuracy even when less realistic images, such as black-and-white photographs, silhouettes and line drawings, are employed as bi-dimensional stimuli. Overall, these findings indicate that capuchin monkeys are able to establish a correspondence between the real objects and their pictorial representations.

Concept of uprightness in baboons: assessment with pictures of realistic scenes

How nonhuman primates process pictures of natural scenes or objects remains a matter of debates. This issue was addressed in the current research by questioning the processing of the canonical orientation of pictures in baboons. Two adult guinea baboons were trained to use an interactive key (IK) on a touch-screen to change the orientation of target pictures showing humans or quadruped mammals until upright. In experiment 1, both baboons successfully learned to use the IK when that key induced a 90 degrees rightward rotation of the picture, but post-training transfer of performance did not occur to novel pictures of natural scenes due to potential motor biases. In Experiment 2, a touch on IK randomly displayed the pictures in any of the four cardinal orientations. Baboons successfully learned the task, but transfer to novel pictures could only be demonstrated after they had been exposed to 360-480 pictures in that condition. Experiment 3 confirmed positive transfers to novel pictures, and showed that both the figure and background information controlled the behavior. Our research on baboons therefore demonstrates the development and use of an "upright" concept, and indicates that picture processing modes strongly depend on the subject's past experience with naturalistic pictorial stimuli.

Behavioural responses to photographs by pictorially naïve baboons (Papio anubis), gorillas (Gorilla gorilla) and chimpanzees (Pan troglodytes)

This study assessed how pictorially naïve nonhuman primates understand pictures. Fifty-five baboons with no prior exposure to pictures were trained to grasp a slice of banana presented against a pebble in a two alternative forced choice task. Post-training testing involved three stimulus pairs: (1) real banana slice vs. its picture, (2) the banana picture vs. a real pebble and (3) banana picture vs. a pebble picture which were presented twice. Preliminary data were also collected on naïve gorillas (n=4) and chimpanzees (n=7) using the same procedure. Baboons revealed a preference for the food picture in (2) and (3) and often ate this stimulus, but the food item and its picture were accurately discriminated in (1). These results suggest that baboons mistook the pictorial stimulus and its referent, but processed the banana pictures as poor exemplars of the real banana category. Among apes, only gorillas ate the banana pictures, suggesting that picture-object confusion may also occur in this species. Findings are discussed as pertaining to the general issue of representational abilities in nonhuman primates, and its evolution.

Recognition of pictorial representations by chimpanzees (Pan troglodytes)

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.

Are monkeys aesthetists? Rensch (1957) revisited

Three experiments assessed whether capuchin monkeys (Cebus apella) and squirrel monkeys (Saimiri sciureus) prefer regular and symmetrical visual patterns. Pictorial representations of faces were included in 1 stimulus set. When the monkeys could pick up and manipulate small cards bearing the stimuli, all preferences expressed by capuchins and most of those expressed by squirrel monkeys were for regular stimuli. Symmetry of the patterns was influential but not essential. Some preferences were also found for faces. When images of the patterns were presented on a touch screen, capuchins continued to express preferences especially for regular and symmetrical stimuli, but they showed some avoidance of faces. Squirrel monkeys responded less discriminatingly to the touch screen stimuli. The findings provide support for B. Rensch's (1957) claim that monkeys prefer visual stimuli that humans find aesthetically pleasing.