What is the Meaning of Shape? - Gestalt Theory

GESTALT THEORY, Vol. 33, No.3/4
of one or of the other property is influenced by the vertical/horizontal and
gravitational axis that plays by accentuating the sidedness against the pointedness
in the square and, vice versa, the pointedness against the sidedness in the diamond.
On the basis of these properties, it appears clear why the second order variations
of Fig. 3 are not involved in the square/diamond illusions. In fact, in all the
conditions illustrated sidedness and pointedness are not in contrast but either the
sidedness or the pointedness are attenuated or emphasized, thus weakening only
one of the two effects. This entails that one of the two singularities is weakened,
therefore appearing as a rotation of the other.
The two properties can also account for the reason why we perceive a rotated
square in Fig. 2b. This is due to the strength of the sidedness being higher than
the one of the pointedness.
Similarly, the numerosity illusion of Fig. 5 can be considered as related to the
shape attribute that defines the number of elements in the octagon. We suggest
that this figure, similarly to the other polygons, is mostly defined by the sidedness
and thus by the number of sides. More specifically, to answer a question like
“what polygon is this?” spontaneously we count at a glance the number of sides
but not the number of vertices. The importance of the two properties in defining
the shape appears in fact asymmetrical. Therefore, because in the pointed octagon
of Fig. 5 the sidedness is weakened while the vertices are perceived with a stronger
vividness, the numerosity of the sides is determined taking into account or starting
from the angles or vertices, which induce an increasing of number of sides or a
summation effect due to the numerosity fuzziness of the sides together with the
angles. The calculation at a glance of the number of sides can include also some
vertices that pop out more strongly than the sides.
These phenomenal reports suggest that, all else being equal, the perceived shape
can change or switch from one shape to another by accentuating the sidedness
or the pointedness independently from the vertical/horizontal and gravitational
axes. A demonstration of this expectation is illustrated in Fig. 6, where, despite
the configural orientation effects (i.e. the perception of local spatial orientation
determined by the global spatial orientational structure) studied by Attneave
(1968) and Palmer (1980), rows of figures are perceived as rotated squares or as
diamonds according to the position of the small circle placed near the sides or
near the angles of the figures (see also Pinna, 2010a, 2010b; Pinna & Albertazzi,
2011). While in Figs. 6a and 6c, the geometrical diamonds are phenomenally
perceived as rotated squares, in Figs. 6b and 6d, the geometrical diamonds are
perceived more strongly than in the control (Fig. 6e) as diamonds.
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