Gregory Burton

SELECTIVE PERCEPTION BY DYNAMIC TOUCH

Perceiving the length of a rod by dynamic touch is tied to the inertia tensorIij, a quantification of its resistance to rotational acceleration. Perception of the portion extending in front of the grasp has previously been ascribed to decomposing one component ofIij by attention. The tensorial nature of dynamic touch suggests that this ability must be anchored wholly in the tensor. Three experiments show that perceived partial length is a function of two components of the tensor, one tied primarily to magnitude and the other tied primarily to direction, whereas perceived whole length is a function of a magnitude component alone. Dynamic touch is characterized in terms of a haptic perceptual instrument that softly assembles to exploitIij differently depending on the intention, producing 1:1 maps that are appropriately scaled for each intention.

The role of the sound of tapping for nonvisual judgment of gap crossability

The author investigated the possibility that nonvisual locomotion with a cane depends on the sound of the cane tapping. Blindfolded participants were asked to judge whether a gap in front of them could be crossed by walking. An acoustic analysis suggested that sound could, in theory, distinguish the gaps. Blindfolded sighted participants in Experiments 1 and 2 judged crossability under conditions in which only the sound of tapping was available and in which the sound was minimized; the third and fourth experiments included experienced cane users. Both inexperienced observers and experienced cane users were unaffected by sound reduction and were less able to discriminate gaps when using sound only than when using reduced sound. A fifth experiment indicated that active-passive differences were not responsible for these effects. Results indicate that sound is not necessary or sufficient for judging nonvisible crossability with a probe.

The tenacity of historical misinformation : Titchener did not invent the Titchener illusion

Some well-known psychological facts are actually false, but dispelling them is difficult. One such false fact is that Titchener introduced the illusion depicting a circle ringed by smaller circles, which appears larger than an equivalent circle surrounded by larger circles. A review of contemporary sources indicates that Ebbinghaus probably introduced this illusion in the 1890s, although not in any explicit publication, and Titchener neither had nor asserted any authorship of this figure. There are also 3 other illusions that are sometimes labeled the Ebbinghaus illusion. The modern custom of attributing the surrounded-circles illusion to Titchener, although widespread in the 1960s and 1970s, does not appear before 1957.

Successor states in a four-state ambiguous figure.

The satiation theory of ambiguous figures holds that interpretation shifts are caused by fatigue of neural arrangements responsible for the prevailing interpretation. A four-state multistable figure is introduced, in which two depicted cubes can be seen as connected or unconnected and as facing up or facing down. Observers viewed the figure for 4 min. When descriptive labels were used for the interpretations, shifts to interpretations that shared neither dimension were significantlymore frequent than shifts that conserved orientation or connection/disconnection. However, all types of transitions were equally likely when arbitrary letter codes were used, implying that the putatively fatigued assemblies can be dedicated to whole figures or to their characteristics,depending on observer expectations.

Gap Crossing Decisions in the Sighted and Visually Impaired

Sighted and visually impaired individuals judged whether a gap before them in a raised walkway could be walked across using artificial canes of 3 lengths. Little difference was found between the participant groups in either the number of errors or the typical gap sizes that were judged to be crossable. More errors were committed by participants exploring with the longest probes, but the probe length did not systematically predict judged crossability boundaries. Results imply that some simple aspects of locomotion without vision do not require significant experience.

Parsimony and Affordance: Response to Coss and Moore (2002)

Coss and Moore (2002) reported that young girls, when prompted to indicate where they would hide in a tree if menaced by a lion, pointed to a spot significantly farther from the trunk than did boys of the same age. This pattern was interpreted as evidence that the children retained biases supportive of an ancient sexual dinichism, in which females but not males slept in trees for safety. This article discusses some inherent problems with the concept that an ancestral behavioral pattern can be revealed in modern behavior after generations in which it was not expressed. It is argued that the same pattern can be more parsimoniously interpreted as demonstrating that boys and girls have different affordances for tree climbing and correctly perceive this difference.

How many systems make a global array

Stoffregen & Bardy suggest that the global array provides the specification that is lacking when senses are considered in isolation. This seems to beg the question of the minimum number of senses in a global array. Individuals with sensory loss manage with fewer senses, and humans manage with fewer than electric fish; so specification, if it exists, cannot require all possible senses.