Representation of Object Orientation in Children: Evidence from Mirror-Image Confusions

Interpreting the orientation of objects: A cross-disciplinary review

Is object orientation an inherent aspect of the shape of the object or is it represented separately and bound to the object shape in a similar way to other features, such as colour? This review brings together findings from neuropsychological studies of patients with agnosia for object orientation and experimental studies of object perception in healthy individuals that provide converging evidence of separate processing of object identity and orientation. Individuals with agnosia for object orientation, which typically results from damage to the right parietal lobe, can recognize objects presented in a range of orientations yet are unable to interpret or discriminate the objects' orientation. Healthy individuals tested with briefly presented objects demonstrate a similar dissociation: object identity is extracted rapidly in an orientation-invariant way, whereas processing the object's orientation is slower, requires attention and is influenced by the degree of departure from the canonical orientation. This asymmetry in processing can sometimes lead to incorrect bindings between the identity and orientation of objects presented in close temporal proximity. Overall, the available evidence indicates that object recognition is achieved in a largely orientation-invariant manner and that interpreting the object's orientation requires an additional step of mapping this orientation-invariant representation to a spatial reference frame.

Different reference frames on different axes: Space and language in indigenous Amazonians

Spatial cognition is central to human behavior, but the way people conceptualize space varies within and across groups for unknown reasons. Here, we found that adults from an indigenous Bolivian group used systematically different spatial reference frames on different axes, according to known differences in their discriminability: In both verbal and nonverbal tests, participants preferred allocentric (i.e., environment-based) space on the left-right axis, where spatial discriminations (like "b" versus "d") are notoriously difficult, but the same participants preferred egocentric (i.e., body-based) space on the front-back axis, where spatial discrimination is relatively easy. The results (i) establish a relationship between spontaneous spatial language and memory across axes within a single culture, (ii) challenge the claim that each language group has a predominant spatial reference frame at a given scale, and (iii) suggest that spatial thinking and language may both be shaped by spatial discrimination abilities, as they vary across cultures and contexts.

Developmental differences in children's and adults' use of geometric information in map-reading tasks

Using maps effectively requires the ability to scale distances while preserving angle and orientation, the three properties of Euclidean geometry. The aim of the current study was twofold: first, to examine how the ability to represent and use these Euclidean properties changes with development when scaling maps in object-to-object relationships and, second, to explore the effects on the scaling performance of two variables of the array of objects, type of angular configuration and relative vector length. To this end, we tested seventy-five 4-, 6-, and 8-year-old children, as well as twenty-five adults, in a simple completion task with different linear and triangular configurations of objects. This study revealed important developmental changes between 4 and 6 years of age and between 8 years of age and adulthood for both distance and angle representation, while it also showed that the configuration variables affected younger and older children's performances in different ways when scaling distances and preserving angles and orientation. This study was instrumental in showing that, from an early age, children are able to exploit an intrinsic system of reference to scale geometrical configurations of objects.

Supramodal agnosia for oblique mirror orientation in patients with periventricular leukomalacia

Periventricular leukomalacia (PVL) is characterized by focal necrosis at the level of the periventricular white matter, often observed in preterm infants. PVL is frequently associated with motor impairment and with visual deficits affecting primary stages of visual processes as well as higher visual cognitive abilities. Here we describe six PVL subjects, with normal verbal IQ, showing orientation perception deficits in both the haptic and visual domains. Subjects were asked to compare the orientation of two stimuli presented simultaneously or sequentially, using both a two alternative forced choice (2AFC) orientation-discrimination and a matching procedure. Visual stimuli were oriented gratings or bars or collinear short lines embedded within a random pattern. Haptic stimuli comprised two rotatable wooden sticks. PVL patients performed at chance in discriminating the oblique orientation, both for visual and haptic stimuli. Moreover when asked to reproduce the oblique orientation, they often oriented the stimulus along the symmetric mirror orientation. The deficit generalized to stimuli varying in many low level features, was invariant for spatiotopic object orientation, and also occurred for sequential presentations. The deficit was specific to oblique orientations, and not for horizontal or vertical stimuli. These findings show that PVL can affect a specific network involved with the supramodal perception of mirror symmetry orientation.

Blind readers break mirror invariance as sighted do

Mirror invariance refers to a predisposition of humans, including infants and animals, which urge them to consider mirrored images as corresponding to the same object. Yet in order to learn to read a written system that incorporates mirrored letters (e.g., <b> vs. <d> in the Latin alphabet), humans learn to break this perceptual bias. Here we examined the role visual experience and input modality play in the emergence of this bias. To this end, we tested congenital blind (CB) participants in two same-different tactile comparison tasks including pairs of mirrored and non-mirrored Braille letters as well as embossed unfamiliar geometric shapes and Latin letters, and compared their results to those of age-matched sighted participants involved in similar but visually-presented tasks. Sighted participants showed a classical pattern of results for their material of expertise, Latin letters. CB's results signed for their expertise with the Braille script compared to the other two materials that they processed according to an internal frame of reference. They also evidenced that they automatically break mirror invariance for different materials explored through the tactile modality, including Braille letters. Altogether, these results demonstrate that learning to read Braille through the tactile modality allows breaking mirror invariance in a comparable way to what is observed in sighted individuals for the mirrored letters of the Latin alphabet.

Challenging Cognitive Control by Mirrored Stimuli in Working Memory Matching

Cognitive conflict has often been investigated by placing automatic processing originating from learned associations in competition with instructed task demands. Here we explore whether mirror generalization as a congenital mechanism can be employed to create cognitive conflict. Past research suggests that the visual system automatically generates an invariant representation of visual objects and their mirrored counterparts (i.e., mirror generalization), and especially so for lateral reversals (e.g., a cup seen from the left side vs. right side). Prior work suggests that mirror generalization can be reduced or even overcome by learning (i.e., for those visual objects for which it is not appropriate, such as letters d and b). We, therefore, minimized prior practice on resolving conflicts involving mirror generalization by using kanji stimuli as non-verbal and unfamiliar material. In a 1-back task, participants had to check a stream of kanji stimuli for identical repetitions and avoid miss-categorizing mirror reversed stimuli as exact repetitions. Consistent with previous work, lateral reversals led to profound slowing of reaction times and lower accuracy in Experiment 1. Yet, different from previous reports suggesting that lateral reversals lead to stronger conflict, similar slowing for vertical and horizontal mirror transformations was observed in Experiment 2. Taken together, the results suggest that transformations of visual stimuli can be employed to challenge cognitive control in the 1-back task.

Neural representation of object orientation: A dissociation between MVPA and Repetition Suppression

How is object orientation represented in the brain? Behavioral error patterns reveal systematic tendencies to confuse certain orientations with one another. Using fMRI, we asked whether more confusable orientations are represented more similarly in object selective cortex (LOC). We compared two widely-used measures of neural similarity: multi-voxel pattern similarity (MVP-similarity) and Repetition Suppression. In LO, we found that multi-voxel pattern similarity was predicted by the confusability of two orientations. By contrast, Repetition Suppression effects in LO were unrelated to the confusability of orientations. To account for these differences between MVP-similarity and Repetition Suppression, we propose that MVP-similarity reflects the topographical distribution of neural populations, whereas Repetition Suppression depends on repeated activation of particular groups of neurons. This hypothesis leads to a unified interpretation of our results and may explain other dissociations between MVPA and Repetition Suppression observed in the literature.

Using the axis of elongation to align shapes: developmental changes between 18 and 24 months of age

An object's axis of elongation serves as an important frame of reference for forming three-dimensional representations of object shape. By several recent accounts, the formation of these representations is also related to experiences of acting on objects. Four experiments examined 18- to 24-month-olds' (N=103) sensitivity to the elongated axis in action tasks that required extracting, comparing, and physically rotating an object so that its major axis was aligned with that of a visual standard. In Experiments 1 and 2, the older toddlers precisely rotated both simple and complexly shaped three-dimensional objects in insertion tasks where the visual standard was the rectangular contour defining the opening in a box. The younger toddlers performed poorly. Experiments 3 and 4 provide evidence on emerging abilities in extracting and using the most extended axis as a frame of reference for shape comparison. Experiment 3 showed that 18-month-olds could rotate an object to align its major axis with the direction of their own hand motion, and Experiment 4 showed that they could align the major axis of one object with that of another object of the exact same three-dimensional shape. The results are discussed in terms of theories of the development of three-dimensional shape representations, visual object recognition, and the role of action in these developments.

Consequences of severe visual-spatial deficits for reading acquisition: evidence from Williams syndrome

To further understand the nature of the visual-spatial representations required for successful acquisition of written language skills, we investigated the written language abilities of two individuals with Williams syndrome (WS) a developmental genetic disorder in which the presence of severe visual-spatial developmental delays and deficits has been well established. Using a case study approach, we examined the relationship between reading achievement and general cognitive ability, phonological skills, and visual-spatial skills for the two individuals. We found that, despite the strong similarity between the two individuals in terms of their verbal and non-verbal cognitive abilities and their phonological abilities (as well as chronological age and educational opportunities), their reading and spelling abilities differed by more than 5 grade levels. We present evidence that the difference in written language performance was likely to be due to differences in the severity and nature of their visual-spatial impairment. Moreover, we show that specific difficulty processing the orientation of visual stimuli is related to the reading difficulties of one of the two individuals. These results underscore the contribution of visual-spatial abilities to the reading acquisition process and identify WS as a potential source of valuable information regarding the role of visual-spatial processing in reading development.