Piaget's 3-mountains task with impossible options: Sighted, blindfolded, early and late blind participants.

In Piaget's 3-mountains task, 3D objects - a cube, cone and sphere - sit on a square tabletop. They are portrayed in 2D pictures as (projections to the sides) such as one with a square on the left, a triangle in the middle and a circle on the right. Three objects offer six elevations, of which four are possible and two impossible.

Foreshortening increases apparent angles.

The hypothesis that perspective foreshortening leads to errors in the visual perception of angles, was tested in four experiments. An oblique to a z-dimension line was presented (a) on the ground in Experiments 1 and 2, and (b) on a wall in Experiments 3 and 4. Observers judged the acute angle between the oblique and the z-line.

Foreshortening produces errors in the perception of angles pictured as on the ground.

Observers viewed pictures of a simulated ground plane and judged the orientation of lines pictured as lying on the ground. We presented three lines at a time and manipulated three factors: (1) the declination of the lines below the horizon (depicting distance to the target angles), (2) their length, and (3) whether or not they converged to a point on the horizon. Only the first factor had a substantial effect on these errors.

Pointing to azimuths and elevations of targets: blind and blindfolded-sighted.

Three groups of observers pointed to target circles in a path on the ground, in two parallel rows. Participants in one group viewed the circles and then pointed blindfolded. Those in a second group were blindfolded and then touched the circles with a stick while walking past them.

Picture surface illusion: small effects on a major axis.

Perception of 2-D ellipses on a picture surface is inaccurate-if the ellipses depict circles that are tilted in 3-D, receding from the viewer (Hammad, Kennedy, Juricevic, & Rajani, 2008a, Perception, 37, 504-510). Notably, the minor axis of the ellipse is seen as larger than is true. This illusory effect could be due to the simultaneous presence of optical information for the 2-D ellipse and optical information for the 3-D tilted circle.

Elevation easier than plan for sighted and early-blind adults in a perspective-taking task.

Plans show shapes of objects from above, and represent both their left-right order and their order in the z-dimension (the distance of the objects). Elevations show only the vertical shapes of objects arranged from left to right. Plans, having more spatial information, may be more difficult for participants to construct.

Mirror image arm used in monocular, binocular, and blindfolded pointing.

Observers were instructed to point with their right arm to a mirror image of their left shoulder. Instead of pointing to the target with their real arm, they occluded the target with their mirror-imaged finger, and their real finger pointed off to the left side of the target, facts that came as a surprise to them in debriefing. The occlusion by a mirror image finger was not done to avoid double images, since it occurred in monocular conditions.

When age is irrelevant: distractor inhibition and target activation in priming of pop-out.

Objectives: Recent research suggests that inhibition at early stages of visual processing may be age invariant. We test this proposal using a priming of pop-out (PoP) measure developed by Lamy, Antebi, Aviani, and Carmel (2008. Priming of pop-out provides reliable measures of target activation and distractor inhibition in selective attention.

Pivots for pointing: visually-monitored pointing has higher arm elevations than pointing blindfolded.

Observers pointing to a target viewed directly may elevate their fingertip close to the line of sight. However, pointing blindfolded, after viewing the target, they may pivot lower, from the shoulder, aligning the arm with the target as if reaching to the target. Indeed, in Experiment 1 participants elevated their arms more in visually monitored than blindfolded pointing.