powerpoint slides - Gestalt ReVision

Hierarchical Perceptual
Ruth Kimchi
University of Haifa
Leuven, Belgium 2014
Marco Polo describes a bridge, stone by
“But which is the stone that supports the
bridge?” Kublai Khan asks.
“The bridge is not supported by one stone
or another,” Marco answers, “but by the
line of the arch that they form.”
Kublai Kahn remains silent, reflecting.
Then he adds: “Why do you speak to me
of the stones? It is only the arch that
matters to me.”
Polo answers: “Without stones there is no
Invisible Cities by Italo Calvino, 1972/1974, p. 82
Perceptual Relations between Parts and
• Visual objects can be viewed as hierarchical structure of
parts and wholes.
• Structuralist: rooted firmly in British Empiricism,
perceptions are constructed from atoms of elementary,
unrelated local sensations that are unified by
associations due to spatial and temporal contiguity.
• Gestalt: rejected both atomism and associationism.
According to its doctrine of holism, a specific sensory
whole is qualitatively different from the complex that one
might predict by considering only its parts, and the quality
of a part depends upon the whole in which it is
embedded (Köhler, 1930/1971; Wertheimer, 1923/1938).
Some of the modern attempts to grapple
with the issue part-whole relationships in
human perception:
• Global precedence
• Primacy of holistic/configural properties
Global Precedence
• The global precedence hypothesis (Navon, 1977):
 perceptual processing proceeds from the global
structure towards analysis of more local details.
• The framework:
 A visual object can be viewed as a hierarchy of
parts and subparts interrelated by spatial
 The globality of a visual property corresponds to
the place it occupies in the hierarchy: Properties
at the top of the hierarchy are more global than
those at the bottom, which in turn are more local.
 According to the global precedence
hypothesis, global properties of a visual object
are processed first, followed by analysis of
more local properties.
Global-Local Paradigm
RT (msec.)
Hierarchical Condition
After Navon (1977)
• Global advantage: faster identification of the global
letter than the local letter
• Global-to-local interference: disruptive influence
from irrelevant global conflicting information on local
Global advantage: boundary conditions
Overall visual angle (e.g., Kinchla & Wolfe, 1979)
Eccentricity of presentation (e.g., Pomerantz, 1983)
Spatial certainty (e.g., Lamb & Robertson, 1988)
Sparsity of elements (e.g., martin, 1979)
Exposure duration (e.g., Paquet & Merikle, 1984)
Goodness/meaningfulness of elements (e.g.,
Poirel et al., 2006)
• Number & relative size of elements (e.g., Kimchi,
1988, 1998)
The source of global advantage
• Perceptual (e.g., Navon, 1977, 1991)
• A sensory mechanism – faster
processing of low spatial frequencies
than high spatial frequencies (e. g., Shulman &
Wilson, 1987)
• Post-perceptual (e.g., Miller, 1981; Ward, 1982)
Brain localization
• Right hemisphere biased toward global processing
and the left hemisphere biased toward local
processing (e.g., Robertson et al, 1993)
– relation between spatial frequency processing and
global and local perception (e.g., Ivry & Robertson, 1998)
– Saliency of the stimulus: right hemisphere biased toward
more salient objects and left hemisphere biased toward
less salient objects (Mevorach, Humphreys, & Shalev, 2006a,
– Integrating shape and level information: right
hemisphere - binding shapes to the global level, left
hemisphere - binding shapes to the local level (Hubner &
Volberg, 2005)
From a perceptual organization perspective:
• Perceived Hierarchical Structure (Kimchi &
Palmer, 1982)
• Microgenesis of the organization of
hierarchical structure (Kimchi, 1998)
Critical role of number and relative size of
Kimchi &Palmer, 1982
Kimchi &Palmer, 1982
Microgenetic Analysis of Perceptual
Organization of Hierarchical Patterns
• Analysis of the time course of the
development of the percept in adult
• This analysis is important to
understand the processes underlying
organization, rather than just the final
product of these processes.
Primed matching (Beller, 1971):
• A prime is followed by a pair test
of figures.
• Task: Same-different judgment
about the test figures.
• The time to respond correctly to
same pairs is a function of primetest similarity.
• Enables to assess implicitly the
observer’s perceptual
• If we vary the duration of the prime and construct test
figures that are similar to different aspects of the
prime, it enables to probe changes in the
representation over time.
• Prime-test similarity:
Element, configuration,
• Comparing responses to
test pairs at different
prime durations reveals
which structures are
available in earlier and
later representations.
• Prime duration: 40, 90,
130, 390, or 690 ms.
Primed Matching
Test Pairs
Sequence of Events in a Trial
Priming = [RT(ES/Prime)-RT(CS/Prime)] –
Priming > 0
Priming < 0
Priming of Configuration
Priming of Elements
Priming (ms)
• Configuration is primed
at brief exposures.
• Elements are primed at
longer exposures
Prime Duration
Adapted from Kimchi,
• Elements are primed at
brief exposures.
• Configuration is primed
at longer exposures.
Visual Search
Task: Search for diamond
target among square
The target is present at
either the global or the
local level.
Display size: 2, 6, or 10
Main dependent variable:
Search rate -the slop of the
RT function over display
Search time is independent
of number of items
search is efficient and
Search time varies with
number of items
search is inefficient and
effortful (involves focused
Target present trials
• Global configuration is
searched rapidly and
• Local elements are
searched slowly and
• Local elements are
searched rapidly and
efficiently .
• Global configuration is
searched less efficiently.
Kimchi, 1998
Summary: Microgenesis
• Grouping many relatively small elements
into a global configuration differs from
grouping a few relatively large elements:
 Grouping many small elements is rapid and
 Grouping a few relatively large elements
consumes time and is effortful.
• Individuation of elements also differs for
few versus many elements:
 Individuation of few large elements is rapid
and effortless
 Individuation of many small elements consumes time and is effortful.
• Early and rapid grouping of many small
elements and individuation of few large
– are desirable characteristics for a system
whose one of its goals is object
identification and recognition
– because many small elements close to one
another are likely to be texture elements of
a single object, whereas few large
elements are likely to be several discrete
objects or several distinctive parts of a
complex object.
Notwithstanding the critical role of number and
relative size of the elements in the organization
of hierarchical patterns, the “nature” of the
elements also plays an important role (Han,
Humphreys, & Chen, 1999; Kimchi, 1994, 2000)
Interpretation of global advantage:
Issues to be considered
• Overall, global advantage is normally observed with the
typical hierarchical stimuli (i.e., many-element hierarchical
patterns) used in the global–local paradigm to the limits of
visibility and visual acuity.
What does it mean? Two issues to be considered:
• Hierarchical patterns provide an elegant control for many
intervening variables while keeping the hierarchical
structure transparent,
But, the local elements of hierarchical patterns
are not the local properties of the global form
(Kimchi, 1992, 1994; Navon, 2003).
• Global advantage is not an advantage of a global
property of a visual object over its local properties,
but rather, an advantage of properties of higher level
units over the properties of the lower level units
(Kimchi, 1992).
• Global advantage is an advantage of the cluster (or
formation) over its local constituents (Navon, 2003).
• The difference between global and local properties, as
operationally defined in the global/local paradigm, may be
captured in terms of relative size, and relative size alone
may provide a reasonable account for global advantage
with hierarchical patterns.
– Navon (2003, p. 290) argued that it is a fact of nature
that relative size is “an inherent concomitant of part–
whole relationship”.
Yet, if global properties are meant to be properties that
depend on the spatial relationship between components,
then the difference between global properties and
component properties is not captured by their relative size.
To distinguish, for example, squareness from its
component vertical and horizontal lines, or faceness from
its facial components based only on their relative sizes
would miss the point.
A refinement of terminology is called for
• Global properties defined by the level
they occupy within the hierarchical
structure of the stimulus
• Holistic/configural properties that arise
from the interrelations between the
component properties of the stimulus.
The primacy of holistic properties
• Holistic/configural properties: do not inhere in the parts,
and cannot be predicted by considering only the individual
parts or their simple sum.
Arise on the basis of the interrelations and interactions
between the parts (e.g., symmetry, regularity, closure
(Garner, 1978; Kimchi, 1992, 1994; Pomerantz, 1981; Rock, 1986;
Wagemans, 1995, 1997).
• Exist along with, not instead of, component properties, and
are a different aspect of a stimulus (Garner, 1978).
• The hypothesis about the primacy of holistic
properties: holistic properties dominate component
properties in information processing.
• Examining the relative dominance of component and
holistic properties by testing whether the
discriminability of the components predicts the
discrimination of their configurations.
• If holistic properties dominate information processing,
then, irrespective of the discriminability of the
 Discrimination between stimuli that have dissimilar
holistic properties should always be easier than
discrimination between stimuli that have similar
holistic properties
 Classification by holistic properties should be
easier than classification by the components.
Summary of Results
• The pattern of performance with the configurations
was not predicted by the discriminability of the
• When both holistic and component properties are
present in the stimuli and can be used for the task at
hand, performance is dominated by holistic
properties, regardless of the discriminability of the
component properties.
• When holistic properties are not effective for the task
at hand, discrimination and classification can be
based on component properties, but there is a
significant cost.
Kimchi, 2000
Kimchi, 2000
• Studies using primed matching, showed that
shapes grouped by closure and/or by
collinearity were primed at very short
exposure durations
closure and collinearity were effective
already early in the perceptual processing
(Kimchi, 2000; Hadad & Kimchi, 2008).
• Holistic properties were also found to be
accessible to rapid search (e.g., Hadad & Kimchi,
2006; Rensink & Enns, 1995).
Global versus holistic/configural properties
• To examine whether the distinction between
global and holistic properties has
psychological reality, we must dissociate level
of globality (global vs. local) from type of
property (configural vs. nonconfigural).
• With hierarchical stimuli, it is possible to
construct stimuli in which different types of
properties are present at the global and the
local levels.
• Relative global or local advantage for manyelement hierarchical patterns depends on
whether discrimination at each level involves
configural or nonconfigural properties.
• When local discrimination involves a
configural property like closure, the global
advantage markedly decreases or even
disappears relative to the case in which
discrimination at that level involves a
nonconfigural property like orientation (Kimchi,
1994; Han et al., 1999)
• Holistic/configural dominance can arise:
– Temporal precedence of the global level of
structure, as when the global configuration
of a many-element pattern is represented
before the elements are individuated
(global precedence)
– Dominance in information processing, as
when holistic properties such as closure,
dominate component properties in
discrimination and classification of visual
forms (primacy of holistic properties)
• In light of this evidence, a view that
holds that the whole is perceived just by
assembling components is hardly
• Positing holistic dominance as a rigid
perceptual law is hardly tenable either
– Stimulus factors
– Relevance to the task at hand
• Different kinds of wholes with different kinds
of parts and part-whole relationships (e.g.,
a face with its eyes, nose, mouth, and a
wall of bricks).
• There are weak or strong wholes, mere
aggregation of elements or configuration
that preempt the components
• A distinction between global versus local in
terms of relative size and levels of
representation in a hierarchical structure
and between holistic/configural versus
component properties.
• Global precedence characterizes the
course of processing of some wholes
but not of others;
• The processing of some wholes but not
of others is dominated by holistic
• The processing of some wholes (e.g.,
faces) is characterized by the integrality
of holistic and component properties.
• Holistic dominance and the logical relations
between parts and wholes, or between
components and configurations:
 Components are logically prior:
• components can exist without a global
configuration, but a configuration cannot exist
without components.
• holistic/configural properties do not reside in the
component properties but emerge from the
interrelations among components.
• The logical structure of the stimulus does not
necessarily predict processing consequences at
all levels of processing (Garner, 1983; Kimchi, 1992; Kimchi
& Palmer, 1985)
• Holistic dominance is also not easily reconciled
with the classical view of visual hierarchy in the
spirit of Hubel and Wiesel
• The anatomical, structural aspects of the
hierarchy of the visual system can be
distinguished from the temporal, functional
aspects of itnto account the extended connection
within cortical areas and the massive feedback
pathways (e.g., Maunsell & Essen, 1983).
Rama Amishav
Orit Baruch
Marlene Behrmann
Tomer Carmel
Aliza Cohen-Savransky
Batsheva Hadad
Steve Palmer
Yossi Pirkner
Irene Razpurker-Apfeld
Einat Rashal
Suzy Scherf
Guy Sha’ashua
Sarah Shomstein
Branka Spehar
Johan Wagemans
Yaffa Yeshurun
• Max Wertheimer Minerva Center for Cognitive
Processes and Human Performance, U. of Haifa
Thank You !!!
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