Shape constancy and slant perception at birth

Two experiments are described the object of which was to investigate whether perception of shape at birth is determined solely by proximal (retinal) stimulation, or whether newborn babies have the ability to perceive objective, real shape across changes in slant. In experiment 1 looking at (ie preference for) one stimulus, a square, when paired with either of two trapeziums, was found to change in a consistent manner with changes in slant, indicating that these changes in stimulation are detected and can cause considerable changes in looking behaviour. In experiment 2 newborns were desensitized to changes in slant during familiarization trials, and subsequently strongly preferred a different shape to the familiarized shape in a new orientation. This suggests that the real shape had been perceived as invariant across the retinal changes caused by the changes in slant, and further suggests that shape constancy is an organizing feature of perception which is present at birth.     

Locus of habituation in the human newborn

There is some controversy concerning the youngest age at which an infant will habituate to a visual stimulus or will prefer a novel to a familiar pattern. One suggestion has been that apparently successful reports of habituation and dishabituation in the newborn baby are attributable to retinal adaptation. This interpretation was tested in two experiments. In both experiments monocular conditions of viewing were used: newborns were habituated with one eye as the 'seeing' eye, and posthabituation novelty preferences investigated with the other eye. Significant preferences were found both for a novel colour (experiment 1) and for a novel shape (experiment 2), which implies that a retinal-adaptation model can be ruled out. It is suggested that the habituation effects and the subsequent novelty preferences found in the experiments are most reasonably interpreted as a function of memory formation, and evidence is presented for the storage of visual experience from birth. The results also demonstrate some form of binocular interaction in the newborn.     

The roles of axes of symmetry in orientation illusions

The lines of a surrounding figure can induce illusory distortion in the apparent orientation of an enclosed line. The axes of symmetry of the figure have been implicated in this distortion. A series of experiments showed generally that the effects are attributable to the axes of bilateral symmetry rather than to less restrictively defined axes of topological symmetry, although those axes may produce other illusory effects. Furthermore, the distortions affect the whole line rather than only parts of it. These results are consistent with interactions of the lines in the orientation rather than position domain. It is suggested that axes of symmetry may play an important role in pattern recognition.     

Incomplete assertions

Fregean logic has difficulty with certain arguments in which there is cross-reference between premises and conclusion. In this paper I describe a method of handling arguments of the troublesome kind: It involves replacing standard quantifiers with explicit existential statements, and turns standard logic into a free one. A validation procedure is provided for the logic.