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T Caelli

Publications and source records attributed to T Caelli.

9 recordsLinked to original sources
PubMed1979

On the perception of some geometric properties of rotating three dimensional objects.

Various observations and conjectures have been made about how we perceive three dimensional objects under monocular viewing conditions; in particular, when such objects are rotating. In this paper these proposals are reviewed and reinterpreted in the light of geometric properties of objects and their projections. Some results are also presented which support the conclusion that the visual system, in reconstructing the object from its projections, requires a fixed time to establish the objects curvature and torsion parameters. In the perceptual reconstruction process these parameters assume positive or negative values, and this equivocation is related to a form of the adjacency principle involving central projections and "perceptual geodesics".

Form Perception↗
PubMed1979

Frequency, phase, and colour coding in apparent motion.

We present some results which indicate that the known spatiotemporal limits for apparent motion are consistent with the motion being sinusoidal or a result of filtering. Given this we investigated how two such motions interact as a function of their relative temporal phase differences. This was accomplished by inducing two independent motions from complementary coloured event pairs. Results indicated critical phase limits for perceiving the two motions (red and green) which were consistent with the frequency specificity of the effect. The results are discussed within the framework of a filtering process for the perception of apparent motion.

Color Perception↗
PubMed1979

On the limits of Fourier decompostitions in visual texture perception.

Recent discoveries of nonlinear perceptual analyzers in effortless texture discrimination cast serious doubt on the usefulness of Fourier image decompositions to describe suprathreshold visual-texture perception. We now explain the meaning of these results.

Discrimination, Psychological↗
PubMed1979

Frequency, phase, and colour coding in apparent motion: 2.

In an earlier paper, Caelli and Finlay demonstrated that the perception of apparent motion was contingent on critical phase relationships between inducing sources, and their spatio-temporal frequency ranges. In their original stimulus red-green centre-surround sources were used and phase-specific inhibition was found at 60 degrees--90 degreee phase angle differences between the complementarily coloured elements. In this experiment we show that, when centre-surround sources are replaced by vertically-horizontally displaced complementary (or identically coloured) sources, symmetrical phase inhibition effects occur with both motions.

Color Perception↗
PubMed1979

Psychophysical evidence for global feature processing in visual texture discrimination.

By defining texture as a global feature attained by integration over the image domain, we show that texture discrimination can be predicted for a special class of visual textures (composed of paired dots) as a function of such global features. We derive a psychophysical law based on these global features and show that differences in the variance of orientation, but not of dipole length, result in texture discrimination.

Form Perception↗
PubMed1978

Subjective Lorentz transformations and the perception of motion.

It has been known for some 40 years that the perceived velocity of a moving object does not correspond to its physical velocity. It is also known that the perceived length and temporal duration of a moving objects is affected by its physical velocity. In this paper it is argued that such phenomenal distortions can be embedded in a model for motion perception that involves the concepts of moving frames, Lorentz transformations, perceived length contractions, and time dilations. Experimental results support this model and indicate that c, the maximum perceivable velocity of movement, plays a crucial role in determining motion effects.

Humans↗