Titchener's T in Context Delimited, Discrete Monomotif Patterns

Luminance and contrast in visual perception of time to collision.

AbstractMany animals avoid dark, approaching objects seen against a lighter background but show no or weaker reactions to stimuli with inverted contrast. We investigated whether human observers would respond differently to such stimuli in terms of estimated time-to-arrival. We varied luminances of an approaching, light or dark disk and a plain, grey background, and for several conditions, continuously adjusted calibrations so as to keep contrast and/or overall lightness constant. Since no effects were found, we conclude that humans are able to discard luminance and contrast for the task at hand. Generally, however, performance was affected by different, consecutive regimes of feedback: Init…

Visual discrimination of arrival times: Troublesome effects of stimuli and experimental regime

A Note on the Horizontal-Vertical Illusion - A Reply to Wade (2014).

Like many others before him, Nicholas Wade, in a recent publication in this journal, did not provide the correct title of Adolf Fick's dissertation, approved by the University at Marburg, Germany, in 1851, and Wade also wrongly attributed now famous illusion figures, meant to illustrate the so-called horizontal-vertical illusion (the +, the L, and the inverted T), to this author. After having corrected these errors, I briefly relate Fick’s work to modern work in the field and note that it has been widely neglected.

Age-Correlated Incremental Consideration of Velocity Information in Relative Time-to-Arrival Judgments

International audience; One hundred fifty-one children and 43 adults judged which of 2 cartoon birds would be the first to arrive at a common finish line. Objects moved unidirectionally along parallel trajectories, either at the same or different speeds, and disappeared at different distances from the goal. Overall, 9-10-year-old children performed as well as adults, but 4-5- and 6-8-year-olds erred significantly more often. On trials for which distance to goal at disappearance was a valid cue, 4-5-year-olds scored 80% correct, and no differences were seen between 6-10-year-olds and adults. On the opposite type of trials, where the trailing bird would win the race, only adults retained thei…

Titchener's T with flanks.

Abstract Flanks were added to Titchener's (1901) T-illusion figure to test its susceptibility to context stimuli. The addition of a second divided line yielded H-type figures, and the addition of a second undivided line, +-type figures. The lengths of the Ts' undivided lines was expected to be overestimated relative to the lengths of the divided lines, when all lines were about equally long, and the illusion was expected to become smaller when one or two gaps had been introduced between the lines. Results conformed to the predictions. The amount of illusion was larger for the no-gap H than the T, and was almost annihilated with the two-gaps H, with 3 out of 14 observers showing an inverse r…

Allocentric time-to-contact and the devastating effect of perspective

AbstractWith regard to impending object–object collisions, observers may use different sources of information to judge time to contact (tC). We introduced changes of the observer’s vantage point to test among three sets of hypotheses: (1) Observers may use a distance-divided-by-velocity algorithm or, alternatively, elaborated τ-formulae, all of which give exact tC information; (2) observers may use simple τ-formulae (i.e., formulae of the type: visual angle divided by its own first temporal derivative); (3) observers may capitalize on non-τ variables. Hypotheses (2) and (3) imply specific patterns of errors. We presented animated, impending collisions between a moving object and a stationar…

Titchener's T in context 2 - Symmetric patterns of two Ts.

Abstract Patterns of two Ts, materializing different symmetry groups, were used to explore conditions that would lead to a modulation of the typically observed overestimation of the length of a T's undivided line relative to its divided line. Observers either had to compare the lengths of the lines of one or the other of the Ts in a pattern, or noncorresponding lines between the two Ts. For both tasks alike, the T-illusion was found to be markedly greater with twofold mirror-symmetric 2-T patterns than it usually is with individual Ts. A control experiment suggested that the effect was probably due to the collinearity of the two Ts' undivided lines in these patterns rather than the addition…

The Oppel-Kundt Illusion and Its Relation to Horizontal-Vertical and Oblique Effects.

The Oppel–Kundt illusion consists in the overestimation of the length of filled versus empty extents. Two experiments explored its relation to the horizontal-vertical illusion, which consists in the overestimation of the length of vertical versus horizontal extents, and to the oblique effect, which consists in poorer discriminative sensitivity for obliquely as opposed to horizontally or vertically oriented stimuli. For Experiment 1, Kundt’s (1863) original stimulus was rotated in steps of 45° full circle around 360°. For Experiment 2, one part of the stimulus remained at a horizontal or vertical orientation, whereas the other part was tilted 45° or 90°. The Oppel–Kundt illusion was at its …

The ⊥-Illusion Is Not a T-Illusion

Variants of the capital Latin letter T were prepared with the straight strokes replaced by J-, C-, or S-curves, mimicking handwritten Ts. These were used to test the hypothesis that the overestimation of the length of the T&rsquo

Effects of distance and eye-height on time-to-contact estimates

Les effets de la distance et du point-de-vue sur le jugement du temps de pre-contact Lors de la realisation d’estimations du temps de pre-contact (time-to-contact TTC), les observateurs utilisent parfois des informations erronees dans leurs jugements, privilegiant la rapidite de decision et d’action au detriment de la precision. Dans ce contexte, nous avons etudie le role de la position de l’observateur par rapport a l’approche du mobile. Cinq experiences ont testees les effets de la distance et de la hauteur des yeux de l’observateur. Le sol pouvait avoir une texture reguliere, irreguliere ou absente. En controlant le temps de visibilite, le TTC et la vitesse du mobile, nous avons evite de…

Visual Discrimination of the 17 Plane Symmetry Groups

Within most of the 17 plane symmetry groups, individual symmetry operations act in multiple, nonequivalent ways. This, and the fact that many groups can be realized on the basis of different unit cells and generating regions, poses difficulties for visual discrimination and identification. Because of inherent confounds, only few of the groups can be studied by traditional experimental methodology. The use of an oddity paradigm and specific tiling patterns that camouflage groups in complex textures are recommended as partial remedy to this impasse. In order to prepare readers for an appreciation of the aforementioned issues and to provide a rationale for their investigation, the reporting of…