The life-span trajectory of visual perception of 3D objects

Abstract

Deriving a 3D structural representation of an object from its 2D input is one of the great challenges for the visual system and yet, this type of representation is critical for the successful recognition of and interaction with objects. Perhaps reflecting the importance of this computation, infants have some sensitivity to 3D structural information, and this sensitivity is, at least, partially preserved in the elderly population. To map precisely the life-span trajectory of this key visual computation, in a series of experiments, we compared the performance of observers from ages 4 to 86 years on displays of objects that either obey or violate possible 3D structure. The major findings indicate that the ability to derive fine-grained 3D object representations emerges after a prolonged developmental trajectory and is contingent on the explicit processing of depth information even in late childhood. In contrast, the sensitivity to object 3D structure remains stable even through late adulthood despite the overall reduction in perceptual competence. Together, these results uncover the developmental process of an important perceptual skill, revealing that the initial, coarse sensitivity to 3D information is refined, automatized and retained over the lifespan.

Figure 1

Stimuli and experimental design (a) Examples of possible (left panel) and matched impossible objects (right panel). Note that there are minimal physical differences between the two object types, but the perceptual experience in viewing these two object sets is substantially different. (b) Experiment 1: Same-different discrimination of matched objects: Participants performed same/different discriminations on sequentially presented objects, which were physically highly similar even in the ‘different’ trials. (c) Experiment 2: Comparison of depth information: Participants judged which dot is closer in depth - the red or the green dot. (d) Experiment 3: Same-different discrimination of non-matched objects: Participants performed same/different classifications on sequentially presented objects, which were physically different.

Figure 2

Results. (a) Experiment 1: Children and older adults performed poorly overall relative to young adults. While younger and older adults exhibited sensitivity to structural information with better performance for trials in which the first object was a possible object, children did not show this effect. Trial type (same/different) did not interact with first object type and, therefore, the graph is collapsed across this factor. (b) Experiment 2: Children and older adults, performed poorly relative to young adults. In contrast with Experiment 1, all groups were sensitive to structural information with better performance for possible than impossible objects. (c) Children and older adults performed poorly overall relative to young adults. All groups exhibited similar performance for possible and impossible objects. Note that the analyses were conducted on transformed data (see Methods for details) but that, for the sake of clarity, data are presented in raw units. Error bars represent the standard error of the mean for each condition and asterisks indicate significant difference between the two object categories.

Figure 3

Results of the comparison of the two groups of children. (a) Experiment 1: When instructed to process depth information explicitly, and when this experiment was completed as the second experiment, children in the instructed depth group demonstrated sensitivity to structural information. On the other hand, children not instructed to attend to depth were not sensitive to structural information (data repeated from Fig. 2). Note that the overall level of performance was similar between the two groups. Trial type (same/different) did not interact with object type and, therefore, the graph is collapsed across this factor. (b) Experiment 2: The two groups performed equivalently on this task in which depth information is explicitly taken into account. Error bars represent the standard error of the mean for each condition and asterisks indicate significant difference between the two object categories. The key finding is that the instructed depth children who performed Experiment 2 before Experiment 1 now showed the advantage for possible over impossible objects in Experiment 1.

Figure 4

Results of the comparison of younger and older children. (a) Comparison between younger (4–6.5 years old) and older, non-instructed children (7.5–13 years old) in the depth classification task. The data from the older children are based on a subset of the stimuli (first 42 trials). Greater sensitivity to possible than impossible objects was observed only in the older children. (b) Correlation between age and sensitivity to object type. Sensitivity to object type increased as function of age.