Biomedical subjects

Rob van Lier

Publications and source records attributed to Rob van Lier.

5 recordsLinked to original sources

PubMed2004

No symmetry advantage when object matching involves accidental viewpoints.

The presupposed advantage of symmetrical objects over asymmetrical objects was investigated in an object matching task, using accidental and non-accidental viewpoints. In addition, the accidental views could be symmetric or asymmetric. When two non-accidental views were presented, symmetrical objects were matched faster than asymmetrical objects. When an accidental view was presented first (followed by a non-accidental view), the matching of symmetrical objects was equal to that of asymmetrical objects. When a non-accidental view was presented first (followed by an accidental view), matching was again equal for the symmetrical and asymmetrical objects, although much faster compared with the opposite sequence of presented views. No effects of image symmetry in the accidental viewpoints were found. Apparently, the advantage of symmetrical objects over asymmetrical objects is only present in object matching when 3-D object structures are visible.

Adolescent↗

PubMed2004

Mental rotation depends on the number of objects rather than on the number of image fragments.

It is often intuitively assumed that disconnected image fragments result in a representation of separate objects. When objects are partly occluded, disconnected image fragments can still result in a representation of a single object, based on visual completion. In a simultaneous matching task, displays showing one object, partly occluded objects, or two objects were compared with each other. When only a translation was required to match pairs of displays, one-object displays were matched faster than both occluded-object and two-object displays, which did not differ significantly from each other. When mental rotation and translation were required, the one-object displays were again matched the fastest. In addition, an advantage for occluded-object displays compared with two-object displays was found. We conclude that when the generation of a mental representation is likely, object-based connectedness determines object matching. Mental rotation then seems to depend on the number of objects rather than on the number of image fragments.

Adolescent↗

PubMed2003

Intra- and interocular colour-specific activation during dichoptic suppression.

A new psychophysical method, based on dichoptic suppression, is introduced to study intra- and interocular colour activations. An experiment is performed which shows that activation of a specific colour in one eye may cancel suppression of the same colour in the ipsi-lateral eye or in the contra-lateral eye at non-corresponding retinal locations. A control experiment shows that the effect is not due to an overall response-bias to the activated colour. The colour-specific intra- and interocular activation might play a role in various colour-based percepts known in the literature.

Color Perception↗

PubMed2003

Object-based connectedness facilitates matching.

In two matching tasks, participants had to match two images of object pairs. Image-based (IB) connectedness refers to connectedness between the objects in an image. Object-based (OB) connectedness refers to connectedness between the interpreted objects. In Experiment 1, a monocular depth cue (shadow) was used to distinguish different relation types between object pairs. Three relation types were created: IB/OB-connected objects, IB/OB-disconnected objects, and IB-connected/OB-disconnected objects. It was found that IB/OB-connected objects were matched faster than IB/OB-disconnected objects. Objects that were IB-connected/OB-disconnected were matched equally to IB/OB-disconnected objects. In Experiment 2, stereoscopic presentation was used. With relation types comparable to those in Experiment 1, it was again found that OB connectedness determined speed of matching, rather than IB connectedness. We conclude that matching of projections of three-dimensional objects depends more on OB connectedness than on IB connectedness.

Adult↗

PubMed2003

Differential effects of object orientation on imaginary object/viewer transformations.

Given a specific view of a simple symmetrical object, participants were asked whether a certain imaginary transformation could result in a second viewed image. An experiment was conducted in which the participants had either to mentally rotate an object or to imagine themselves looking at the object from another position (i.e., the object-based condition and the viewer-based condition, respectively). In the experiment, combinations of these imagery tasks (i.e., the combined conditions) were also included. The symmetrical objects could be oriented horizontally or vertically. The performance in the object-based conditions was generally equal to or better than the performance in the viewer-based conditions. In addition, there were more confusions for shapes with a horizontal orientation, especially when viewer-based upside-down rotations were involved, with an apparent mediating role of object rotation in the combined conditions.

Humans↗