Mirror-image matching and mental rotation problem solving by baboons (Papio papio): unilateral input enhances performance

Left or right, that is the question: use of egocentric frame of reference and the right-eye advantage for understanding gestural signs in bottlenose dolphins (Tursiops truncatus)

How do bottlenose dolphins visually perceive the space around them? In particular, what cues do they use as a frame of reference for left-right perception? To address this question, we examined the dolphin's responses to various manipulations of the spatial relationship between the dolphin and the trainer by using gestural signs for actions given by the trainer, which have different meanings in the left and right hands. When the dolphins were tested with their backs to the trainer (Experiment 1) or in an inverted position underwater (Experiments 2 and 3), correct responses from the trainer's perspective were maintained for signs related to movement direction instructions. In contrast, reversed responses were frequently observed for signs that required different sounds for the left and right hands. When the movement direction instructions were presented with symmetrical graphic signs such as " × " and "●", accuracy decreased in the inverted posture (Experiment 3). Furthermore, when the signs for sounds were presented from either the left or right side of the dolphin's body, performance was better when the side of the sign movement coincided with the body side on which it was presented than when it was mismatched (Experiment 4). In the final experiment, when one eye was covered with an eyecup, the results showed that, as in the case of body-side presentation, performance was better when the open eye coincided with the side on which the sign movement was presented. These results indicate that dolphins used the egocentric frame for visuospatial cognition. In addition, they showed better performances when the gestural signs were presented to the right eye, suggesting the possibility of a left-hemispheric advantage in the dolphin's visuospatial cognition.

Rhesus monkeys manipulate mental images

Humans form mental images and manipulate them in ways that mirror physical transformations of objects. Studies of nonhuman animals will inform our understanding of the evolution and distribution among species of mental imagery. Across three experiments, we found mostly converging evidence that rhesus monkeys formed and rotated mental images. In Experiment 1, monkeys discriminated rotations of sample images from mirror images, and showed longer response latencies with greater rotation as is characteristic of human mental rotation. In Experiment 2 monkeys used a rotation cue that indicated how far to mentally rotate sample images before tests, indicating a precision of better than 30° in discriminating rotations. Experiment 3 yielded mixed evidence on whether the rotation cue shortened decision times as has been found in humans. These results show that rhesus monkeys manipulate mental images.

Visual Perception of Photographs of Rotated 3D Objects in Goldfish (Carassius auratus)

This study examined goldfishes’ ability to recognize photographs of rotated 3D objects. Six goldfish were presented with color photographs of a plastic model turtle and frog at 0° in a two-alternative forced-choice task. Fish were tested with stimuli at 0°, 90°, 180°, and 270° rotated in the picture plane and two depth planes. All six fish performed significantly above chance at all orientations in the three rotation planes tested. There was no significant difference in performance as a function of aspect angle, which supported viewpoint independence. However, fish were significantly faster at 180° than at +/−90°, so there is also evidence for viewpoint-dependent representations. These fish subjects performed worse overall in the current study with 2D color photographs (M = 88.0%) than they did in our previous study with 3D versions of the same turtle and frog stimuli (M = 92.6%), although they performed significantly better than goldfish in our two past studies presented with black and white 2D stimuli (M = 67.6% and 69.0%). The fish may have relied on color as a salient cue. This study was a first attempt at examining picture-object recognition in fish. More work is needed to determine the conditions under which fish succeed at object constancy tasks, as well as whether they are capable of perceiving photographs as representations of real-world objects.

Recognition of rotated objects and cognitive offloading in dogs

Recognition of rotated images can challenge visual systems. Humans often diminish the load of cognitive tasks employing bodily actions (cognitive offloading). To investigate these phenomena from a comparative perspective, we trained eight dogs (Canis familiaris) to discriminate between bidimensional shapes. We then tested the dogs with rotated versions of the same shapes, while measuring their accuracy and head tilts. Although generalization to rotated stimuli challenged dogs (overall accuracy: 55%), three dogs performed differently from chance level with rotated stimuli. The amplitude of stimulus rotation did not influence dogs’ performance. Interestingly, dogs tilted their head following the direction and amplitude of rotated stimuli. These small head movements did not influence their performance. Hence, we show that dogs might be capable of recognizing rotated 2D objects, but they do not use a cognitive offloading strategy in this task. This work paves the way to further investigation of cognitive offloading in non-human species.

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Dogs have the potential to recognize 2D objects even when these are rotated

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After training, females were more accurate in discriminating upright images

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Dogs tilted their head in the same direction as the images were rotated

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In our setting, dogs did not offload a cognitive process onto their bodies

Developmental origins of cognitive offloading

Many animals manipulate their environments in ways that appear to augment cognitive processing. Adult humans show remarkable flexibility in this domain, typically relying on internal cognitive processing when adequate but turning to external support in situations of high internal demand. We use calendars, calculators, navigational aids and other external means to compensate for our natural cognitive shortcomings and achieve otherwise unattainable feats of intelligence. As yet, however, the developmental origins of this fundamental capacity for cognitive offloading remain largely unknown. In two studies, children aged 4-11 years (n = 258) were given an opportunity to manually rotate a turntable to eliminate the internal demands of mental rotation--to solve the problem in the world rather than in their heads. In study 1, even the youngest children showed a linear relationship between mental rotation demand and likelihood of using the external strategy, paralleling the classic relationship between angle of mental rotation and reaction time. In study 2, children were introduced to a version of the task where manually rotating inverted stimuli was sometimes beneficial to performance and other times redundant. With increasing age, children were significantly more likely to manually rotate the turntable only when it would benefit them. These results show how humans gradually calibrate their cognitive offloading strategies throughout childhood and thereby uncover the developmental origins of this central facet of intelligence.

Visual perception of planar-rotated 2D objects in goldfish (Carassius auratus)

This study examined the ability of goldfish to visually identify 2D objects rotated in the picture plane. This ability would be adaptive for fish since they move in three dimensions and frequently view objects from different orientations. Goldfish performed a two-alternative forced choice task in which they were trained to discriminate between two objects at 0°, then tested with novel aspect angles (+/- 45°, +/- 90°, +/- 135°, 180°). Stimuli consisted of an arrow and half circle (Experiment 1) and line drawings of a turtle and frog (Experiments 2 and 3). In the first two experiments, the S+ and S- were presented at the same aspect angle. Performance in these experiments exceeded chance on four of seven novel aspect angles. Overall accuracy was not significantly different with complex stimuli (animal drawings) vs. simple stimuli (geometric shapes). In Experiment 3, when fish were tested with the S+ at varying aspect angles and the S- always presented at 0°, the fish failed to discriminate among the stimuli at all but one aspect angle. These goldfish viewing planar-rotated 2D objects did not display viewpoint-invariant performance, nor did they show a systematic decrement in performance as a function of aspect angle.

Rotation of Mental Images in Baboons When the Visual Input Is Directed to the Left Cerebral Hemisphere

The mental rotation phenomenon was examined in baboons and humans using a video-formatted mutching-to-sample task. Sample stimuli were presented either centrally or in the right or left visual half-field. Immediately afterward, subjects had to distinguish the previously presented sample stimulus from its mirror image after both had been rotated to the same angular deviation. A mental rotation phenomenon was found in baboons and humans, but in baboons this effect was limited to conditions in which visual input was directed to the right visual half-field. These data represent the first evidence of mental rotation in a nonhuman species.

Male and female guppies differ in speed but not in accuracy in visual discrimination learning

In many species, males and females have different reproductive roles and/or differ in their ecological niche. Since in these cases the two sexes often face different cognitive challenges, selection may promote some degree of cognitive differentiation, an issue that has received relatively little attention so far. We investigated the existence of sex differences in visual discrimination learning in the guppy, Poecilia reticulata, a fish species in which females show complex mate choice based on male colour pattern. We tested males and females for their ability to learn a discrimination between two different shapes (experiment 1) and between two identical figures with a different orientation (experiment 2). In experiment 3, guppies were required to select an object of the odd colour in a group of five objects. Colours changed daily, and therefore, the solution for this task was facilitated by concept learning. We found males' and females' accuracy practically overlapped in the three experiments, suggesting that the two sexes have similar discrimination learning abilities. Yet, males showed faster decision time than females without any evident speed-accuracy trade-off. This result indicates the existence of consistent between-sex differences in decision speed perhaps due to impulsivity rather than speed in information processing. Our results align with previous literature, indicating that sex differences in cognitive abilities are the exception rather than the rule, while sex differences in cognitive style, i.e. the way in which an individual faces a cognitive task, are much more common.

Processing of above/below categorical spatial relations by baboons (Papiopapio)

Three video-formatted experiments investigated the categorization of 'above' and 'below' spatial relations in baboons (Papio papio). Using an identity matching-to-sample task, six baboons correctly matched line-dot stimuli based on the 'above' or 'below' location of the dot relative to the line (Experiment 1). Positive transfer of performance was then observed when the line-dot distance depicted in the sample stimulus differed from that of the two comparison stimuli (Experiment 2). Using a go/nogo procedure, two baboons were further trained to discriminate whether a 'B' character was displayed 'above' or 'below' a '3' character (Experiment 3). After training, a positive transfer of performance was observed with the same type of stimuli depicted in different type fonts. Altogether, these results suggest that baboons may form conceptual representations of 'above' and 'below' spatial relations, and categorize visual forms on that basis.

Cognitive abilities in Malawi cichlids (Pseudotropheus sp.): matching-to-sample and image/mirror-image discriminations

The ability to recognize and distinguish between visual stimuli is fundamental for everyday survival of many species. While diverse aspects of cognition, including complex visual discrimination tasks were previously successfully assessed in fish, it remains unknown if fish can learn a matching-to-sample concept using geometrical shapes and discriminate between images and their mirror-image counterparts. For this purpose a total of nine Malawi cichlids (Pseudotropheus sp.) were trained in two matching-to-sample (MTS) and three two-choice discrimination tasks using geometrical, two-dimensional visual stimuli. Two out of the three discrimination experiments focused on the ability to discriminate between images and their mirror-images, the last was a general discrimination test. All fish showed quick associative learning but were unable to perform successfully in a simultaneous MTS procedure within a period of 40 sessions. Three out of eight fish learned to distinguish between an image and its mirror-image when reflected vertically; however none of the fish mastered the task when the stimulus was reflected horizontally. These results suggest a better discrimination ability of vertical compared to horizontal mirror-images, an observation that is widespread in literature on mirror-image discrimination in animals. All fish performed well in the general visual discrimination task, thereby supporting previous results obtained for this species.

The role of mental rotations in primate-inspired robot navigation

The use of a primate's spatial ability of mental rotation to serve as a basis for robotic navigation has been almost entirely overlooked by the robotics community to date. In this paper, the role of this cognitive capacity is presented as an adjunct to existing robotic control systems, with the underlying approach being derived from studies of primate spatial cognition. Specifically, optical flow is used as a basis for transitory representations (snapshots) that are compared to an a priori visual goal to provide corrective course action for a robot when moving through the world. The underlying architecture and procedures are described.

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.

Rhesus monkeys (Macaca mulatta) immediately generalize the uncertain response

Rhesus monkeys (Macaca mulatta) have learned, like humans, to use an uncertain response adaptively under test conditions that create uncertainty, suggesting a metacognitive process by which human and nonhuman primates may monitor their confidence and alter their behavior accordingly. In this study, 4 rhesus monkeys generalized their use of the uncertain response, without additional training, to 2 familiar tasks (2-choice discrimination learning and mirror-image matching to sample) that predictably and demonstrably produce uncertainty. The monkeys were significantly less likely to use the uncertain response on trials in which the answer might be known. These results indicate that monkeys, like humans, know when they do not know and that they can learn to use a symbol as a generalized means for indicating their uncertainty.

Integrating neuronal coding into cognitive models: predicting reaction time distributions

Neurophysiological studies have examined many aspects of neuronal activity in terms of neuronal codes and postulated roles for these codes in brain processing. There has been relatively little work, however, examining the relationship between different neuronal codes and the behavioural phenomena associated with cognitive processes. Here, predictions about reaction time distributions derived from an accumulator model incorporating known neurophysiological data in temporal lobe visual areas of the macaque are examined. Results from human experimental studies examining the effects of changing stimulus orientation, size and contrast are consistent with the model, including qualitatively different changes in reaction time distributions with different stimulus manipulations. The different changes in reaction time distributions depend on whether the image manipulation changes neuronal response latency or magnitude and can be related to parallel or serial cognitive processes respectively. The results indicate that neuronal coding can be productively incorporated into computational models to provide mechanistic accounts of behavioural results related to cognitive phenomena.

Comparative assessment of distance processing and hemispheric specialization in humans and baboons (Papio papio)

This comparative study explored the ability to process distance and its lateralization in humans and baboons. Using a conditional matching-to-sample procedure in a divided-field format, subjects had to decide whether or not the distance between a line and a dot belonged to a short- or a long-distance category. Experiments 1, 2, and 4 demonstrated the ability of baboons to process and categorize distances. Moreover, humans showed better distance processing for right visual field/left hemisphere presentations than for left visual field/right hemisphere (LVF-RH) displays (Experiments 1-2). The same bias was found in baboons (Experiment 1), but in a weaker way. In Experiment 3, naive human individuals were tested and the difficulty of the discrimination was enhanced. There was a LVF-RH advantage which vanished with practice. Results are discussed by referring to theories (i.e., Kosslyn, 1987) of visuospatial processing for coordinate and categorical judgments.

Function and mechanism of mirror-image ambiguity in bumblebees

This study investigated the function and mechanism underlying a previously documented 'mirror-image ambiguity' (i.e. the mirror image of a pattern is treated as similar to the original stimulus) in foraging bumblebees, Bombus impatiensArtificial flowers were constructed so that the mirror image of a petal configuration was different from the left-right reversal of that configuration. Bees were first trained to discriminate between rewarding and unrewarding artificial flowers that differed only in their configuration of four differently patterned petals. On subsequent choice tests between two empty flowers, the bees chose the rewarding configuration (S+) over the unrewarding one (S-), over the mirror image and over the left-right reversal. In the critical test conditions, the bees failed to choose the mirror image over a novel petal configuration, but they chose the left-right reversal over the novel configuration (78% of the time). A mirror-image mental transformation was ruled out as a mechanism underlying mirror-image ambiguity. The notion that mirror-image ambiguity has general functional significance (e.g. is a by-product of the symmetry of the nervous system) received no support. The results favour a specific mechanism tied to a specific function: a left-right transposition of a floral pattern, which would enable foraging bees to recognize vertically symmetrical flowers that were partially occluded at the time of learning.

Hemispheric specialization for local and global processing of hierarchical visual stimuli in chimpanzees (Pan troglodytes)

This study examined laterality in global and local processing of hierarchical compound stimuli in seven chimpanzees (Pan troglodytes). A divided visual half-field paradigm was used that allowed for unilateral presentation of compound stimuli to either the left or right hemisphere. Comparison stimuli differing on the basis of their global configuration, local elements or both features followed sample stimulus presentation. Subjects were required to accurately discriminate the comparison stimuli on the basis of these features relative to the sample stimulus. No laterality effects were found for accuracy; however, for reaction time, a significant interaction was found between visual field and processing mode. An overall right visual field advantage was found for local processing but no visual field differences for global processing. The overall results are consistent with previous findings in humans and suggests homologous lateralization in chimpanzees and humans.

The effects of visual cortex lesions on the perception of rotated shapes

Monkeys with inferior temporal cortex lesions cannot discriminate between different shapes (e.g., + vs. O) but can discriminate between shapes that differ only in orientation (e.g., 6 vs 9). Lesions of the parietal cortex, on the other hand, impair the discrimination of rotated shapes but spare the ability to discriminate between different shapes. A similar dissociation is found between some visual agnosics who can match but not identify rotated views of objects and other patients who can identify and discriminate objects only if the view is conventional; any change in orientation disrupts performance. In this paper we argue that two mechanisms may be available for the perception of rotated shapes. Which mechanism is used depends on the degree of rotation. It is suggested that the different effects of parietal and temporal lesions reflect the relative contributions of the two areas to the task and disrupt different stages of the two strategies used. A framework for the cortical processing of rotated shapes in the non-human primate is presented.

Eye movements in baboons performing a matching-to-sample task presented in a divided-field format

We examined eye saccades in a baboon solving a video-formatted matching-to-sample (MTS) task. In that task, the animal had to place a cursor by way of joystick manipulation within the boundaries of a fixation point (FP) displayed on a monitor. A sample stimulus was then flashed in either the left or right of FP. Immediately thereafter, two comparison forms were displayed and the animal had to select the comparison form matching the sample. A new video technique requiring no specific head or body constraints was employed to monitor eye movements. Expt. 1 indicated that the gaze was centered on FP during the fixation procedure. However, some goal-directed express saccades, with mean latencies of 100 ms, were observed during sample presentation. Expt. 2 used an overlap procedure in which FP remained visible during sample presentation. Latencies of express saccades increased by approximatively 20 ms. Expt. 3 showed in four baboons that the overlap procedure did not affect scores. It is concluded that the computerized MTS task is a valuable tool for the assessment of hemispheric lateralization in visual processing in intact primates, as long as the sample is not displayed longer than 120 ms.

Hemispheric lateralization in rhesus monkeys can be task-dependent

Two rhesus monkeys with transection of the forebrain commissures were trained on two grating orientation-discrimination tasks. In one task, the simultaneous orientation identification task, monkeys had to decide which of two simultaneously presented gratings was horizontal. In the other task, the temporal same-different task, the monkey had to decide whether or not two successively presented gratings differed in orientation. Both monkeys showed a statistically significant individual asymmetry in the performance on the same-different task with the left hemisphere supporting superior performance compared with the right hemisphere. No such consistent lateralization was found for the identification task. These results show that the demonstration of a behavioral asymmetry depends on the type of discrimination task performed and suggest that the asymmetry is related to interhemispheric differences in higher order stimulus (cognitive) processing and not to a lateralization of early visual processes.