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Barbara Landau

Publications and source records attributed to Barbara Landau.

10 recordsLinked to original sources
PubMed2005

Object recognition with severe spatial deficits in Williams syndrome: sparing and breakdown.

Williams syndrome (WS) is a rare genetic disorder that results in severe visual-spatial cognitive deficits coupled with relative sparing in language, face recognition, and certain aspects of motion processing. Here, we look for evidence for sparing or impairment in another cognitive system-object recognition. Children with WS, normal mental-age (MA) and chronological age-matched (CA) children, and normal adults viewed pictures of a large range of objects briefly presented under various conditions of degradation, including canonical and unusual orientations, and clear or blurred contours. Objects were shown as either full-color views (Experiment 1) or line drawings (Experiment 2). Across both experiments, WS and MA children performed similarly in all conditions while CA children performed better than both WS group and MA groups with unusual views. This advantage, however, was eliminated when images were also blurred. The error types and relative difficulty of different objects were similar across all participant groups. The results indicate selective sparing of basic mechanisms of object recognition in WS, together with developmental delay or arrest in recognition of objects from unusual viewpoints. These findings are consistent with the growing literature on brain abnormalities in WS which points to selective impairment in the parietal areas of the brain. As a whole, the results lend further support to the growing literature on the functional separability of object recognition mechanisms from other spatial functions, and raise intriguing questions about the link between genetic deficits and cognition.

Adolescent↗
PubMed2005

Motion processing specialization in Williams syndrome.

Williams syndrome (WS) is a rare genetic disorder characterized by severe spatial deficits and relatively spared language. Although initial research suggested that WS entails a generalized motion processing deficit, later work demonstrated intact biological motion perception in people with WS, reflecting a sparing of a specific motion perception system. The present study examined whether this sparing is unique to biological motion, or extends to other motion tasks as well. WS children and adults and normal controls were tested to examine developmental changes across a variety of motion tasks. Results indicated that WS individuals performed at normal levels for motion coherence and biological motion tasks but had elevated thresholds for the 2-D form-from-motion task, a profile that extended into adulthood. These findings provide evidence that a genetic impairment can lead to a selective motion processing deficit and argue against characterizing WS as including a general motion processing impairment. The nature of the motion deficit is considered, including the implications for WS dorsal/ventral processing.

Adolescent↗
PubMed2005

Multiple object tracking in people with Williams syndrome and in normally developing children.

Multiple object tracking is hypothesized to utilize visual indexes, which may provide rapid, parallel access to a limited number of visual objects, thereby supporting a variety of spatial tasks. We examined whether faulty indexing might play a role in the severe visuospatial deficits found in Williams syndrome. We asked observers to track from one to four targets in a display of eight identical objects. Objects remained stationary (static condition) or moved randomly and independently (moving condition) for 6 s, after which observers pointed to the objects they thought were targets. People with Williams syndrome were impaired in the moving condition, but not the static condition, compared with mental-age-matched control participants. Normal children who were younger than the mental-age-matched control children did not show the same profile as individuals with Williams syndrome, which suggests that the difference between the tasks in Williams syndrome did not reflect simple developmental immaturity. Error analysis revealed that all groups had "slippery" indexes, falsely identifying target neighbors, and further suggested that people with Williams syndrome deploy fewer indexes than do people without this disorder.

Adolescent↗
PubMed2004

Starting at the end: the importance of goals in spatial language.

We explored the linguistic encoding of Paths in children between the ages of three and seven, in children with Williams syndrome, and in normal adults, focusing specifically on Source and Goal Paths. The results showed an asymmetry, with Goal Paths regularly and systematically encoded, but Source Paths often omitted. This pattern occurred among all groups and across a broad range of domains including Manner of Motion, Change of Possession, Change of State, and Attachment/Detachment events. It also occurred whether participants spontaneously described events or were asked to use a specific verb that biased them towards a Goal or Source Path (e.g. 'give' vs. 'get'). The results are discussed in terms of non-linguistic foundations of spatial language and the linguistic mapping biases that arise when we describe what we see.

Adolescent↗
PubMed2004

Figure copying in Williams syndrome and normal subjects.

We evaluated the copying abilities of ten subjects with Williams syndrome (WS; age 6-14 years) and ten normally developing children (age 3-6 years) matched for mental age using the matrices component of the Kaufman Brief Intelligence Test (mKBIT). Each subject copied six figures, including line drawings of closed and open geometrical shapes (alone and in combination), crossed lines, and geometrical shapes made of distinct small, filled circles. Qualitatively, subjects of both groups made comparable copies, although several subjects with WS drew a continuous line when copying figures composed of distinct circles. Quantitatively, the goodness of the copies was assessed by three human observers who rated on an analog scale the similarity of each copy to its visual template. Ratings were converted to a scale from zero (completely different) to 100 (the same) for statistical analyses. We found the following. First, the overall goodness of copies of the templates was very similar between the WS and control groups (WS: mean=46.7, range=0.89-95.4; control: mean=54.5, range=0.89-98.2). Second, there were systematic differences in the goodness of copies between the two groups, depending on the features of the figures. Specifically, the goodness of copies of control subjects was almost the same as that of WS subjects for simple line figures, but was consistently better for composite line figures, and even better for figures in which the shape was made of small, filled circles. Third, there was a significant relation between the goodness of copies (dependent variable) and mental age (mKBIT, independent variable) in both groups, although it was stronger and more highly statistically significant in the control than the WS group. These findings indicate that the principles guiding copying are similar in the two groups and suggest that WS is a case of developmental rather than deviance disorder.

Adolescent↗
PubMed2003

Spatial breakdown in spatial construction: evidence from eye fixations in children with Williams syndrome.

We investigated the role of executive and spatial representational processes in impaired performance of block construction tasks by children with Williams syndrome (WS), a rare genetic defect that results in severely impaired spatial cognition. In Experiment 1, we examined performance in two kinds of block construction tasks, Simple Puzzles, in which block faces contained a single color, and Complex, in which some block faces contained an arrangement of two colors. WS and control children were comparable in their ability to solve simple puzzles, and showed similar eye-fixation patterns, suggesting that basic executive processes were intact. However, WS children were severely impaired in their ability to solve complex puzzles. In these puzzles, WS children fixated the complex puzzle models and checked their partial solutions less often than normal children, but they were comparable in their ability to detect errors in their copies and almost exclusively made repairs to copies that were, in fact, incorrect. We conjecture that the abnormal fixation patterns were a consequence of impoverished spatial representations, rather than a cause of it. This conjecture was tested in Experiment 2, where we examined children's capacity to match and place individual blocks without engaging the complex executive processes required to carry out a complete puzzle solution. We found serious deficiency among WS children in both aspects of spatial representation. Moreover, estimates of the errors in representing the identity and location of model blocks derived from Experiment 2 provided a good account of the observed errors in the block construction task of Experiment 1.

Adolescent↗
PubMed2003

Objects, motions, and paths: spatial language in children with Williams syndrome.

The acquisition of spatial language is often assumed to be built upon an early- emerging system of nonlinguistic spatial knowledge. We tested this relationship by examining spatial language in children with Williams syndrome (WS), a rare genetic disorder that gives rise to severe nonlinguistic spatial de deficits together with relatively spared language. Twelve children with WS, 12 normally developing mental-age matched children, and 12 normal adults described 80 videotaped motion events. Children with WS showed substantial control over key linguistic components of the motion event, including appropriate semantic and syntactic encoding of Figure and Ground objects, Manner of Motion, and Path. The expression of Path, although surprisingly spared, was more fragile among children with WS in contexts plausibly related to their nonlinguistic spatial deficit. The results show strong preservation of the formal aspects of spatial linguistic knowledge and suggest that the nonlinguistic spatial deficits shown by children with WS have, at most, limited effects on their spatial language. These findings have implications for the relationship between spatial language and other aspects of spatial cognition.

Adult↗
PubMed2002

Object name learning provides on-the-job training for attention.

By the age of 3, children easily learn to name new objects, extending new names for unfamiliar objects by similarity in shape. Two experiments tested the proposal that experience in learning object names tunes children's attention to the properties relevant for naming--in the present case, to the property of shape--and thus facilitates the learning of more object names. In Experiment 1, a 9-week longitudinal study, 17-month-old children who repeatedly played with and heard names for members of unfamiliar object categories well organized by shapeformed the generalization that only objects with ith similar shapes have the same name. Trained children also showed a dramatic increase in acquisition of new object names outside of the laboratory during the course of the study. Experiment 2 replicated these findings and showed that they depended on children's learning both a coherent category structure and object names. Thus, children who learn specific names for specific things in categories with a common organizing property--in this case, shape--also learn to attend to just the right property--in this case, shape--for learning more object names.

Attention↗
PubMed2002

Intact perception of biological motion in the face of profound spatial deficits: Williams syndrome.

Williams syndrome (WS) is a rare genetic disorder that results in profound spatial cognitive deficits. We examined whether individuals with WS have intact perception of biological motion, which requires global spatial integration of local motion signals into a unitary percept of a human form. Children with WS, normal mental-age-matched children, and normal adults viewed point-light-walker (PLW) displays portraying a human figure walking to the left or right. Children with WS were as good as or better than control children in their ability to judge the walker's direction, even when it was masked with dynamic noise that mimicked the local motion of the PLW lights. These results show that mechanisms underlying the perception of at least some kinds of biological motion are unimpaired in children with WS. They provide the first evidence of selective sparing of a specialized spatial system in individuals with a known genetic impairment.

Adolescent↗