BJMB
Brazilian Journal of Motor Behavior
Special Issue:
Cognitive and Ecological Approaches to Sports Skills
!
Rodrigues, Gotardi,
Polastri
2020
VOL.14
N.5
141 of 156
Understanding sport skills through the theories of visual perception: Contrasting indirect
and direct approaches
SÉRGIO T. RODRIGUES
1,2
| GISELE C. GOTARDI
1,2,3
| PAULA F. POLASTRI
1,2
1
Laboratory of Information, Vision, and Action (LIVIA), São Paulo State University (UNESP), Bauru, SP, Brazil.
2
Graduate program in Human Movement Science, Department of Physical Education, Faculty of Sciences, São Paulo State University (UNESP), Bauru, SP, Brazil.
3
Faculty of Behavioural and Movement Sciences, Department of Human Movement Sciences, Vrije Universiteit Amsterdam, The Netherlands.
Correspondence to:!Sergio T. Rodrigues, São Paulo State University, Av. Eng. Luiz Edmundo Carrijo Coube, 14-01, Vargem Limpa, Bauru, SP, Brazil, postal code 17033-
360, phone +55 14 31039617.
email: sergio.tosi@unesp.br
https://doi.org/10.20338/bjmb.v14i5.221
ABBREVIATIONS
t optical variable tau
Dideal ideal deceleration
Dmax maximum deceleration
PUBLICATION DATA
Received 13 11 2020
Accepted 30 11 2020
Published 01 12 2020
BACKGROUND: Understanding sport skills through the theories of visual perception brings the debate to the
level of basic and applied components of science, characterizing contributions from the most relevant approaches
in the field of Motor Behavior about the indirect and the direct paradigms.
AIM AND FINDINGS: The first section of this article emphasizes theoretical assumptions of visual perception from
indirect and direct approaches; the notion of the relative utility of these perspectives in explaining vision is
discussed, which includes analysis of the goals of explanation, prediction, and simplicity. The second section is
devoted to demonstrating the critical insufficiencies of indirect perspective. The third and final section focus on the
ecological dynamics account applied to sports, emphasizing the elements of decision-making and motor control.
Ecological dynamics is shown as an interesting alternative to understand sport skills, accounting for involved
complexities of perception, decision-making, and action.
Vision is essential to motor behavior in everyday life and sports contexts. Athletes
are dependent on a constant supply of accurate and reliable information from the environment
while performing complex movements.
1,2
This article describes theoretical assumptions of visual
perception from indirect (i.e., information processing and computational vision) and direct (i.e.,
direct perception, ecological psychology) approaches; then, it is followed by identifying the
relative utility of these perspectives in explaining the visual phenomenon. Secondly, we
compare these representational and dynamical views into the sport context, showing criticisms
of an indirect perspective in sports. As a third and final step, we present the ecological dynamics
account in sports, emphasizing elements of decision-making and motor control. Ecological
dynamics seem an interesting alternative to understanding sport skills, accounting for
perception-action connections, motor action complexities, attunement to the environment, and
cognitive functioning.
MAIN CONCEPTS OF DIRECT AND INDIRECT THEORIES
The terms direct and indirect will be used for clarity of comparison between these
two approaches, although considerable variance can be observed in each point of view. The
following topics were selected to represent relevant theoretical differences. Readers should be
aware that each perspective has its assumptions and logical reasoning, which implies that each
of these comparisons is not trivial or straightforward, as these topics may suggest. However,
they were expected to support the following analysis of relative utility.
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Optic array vs. retinal image
What are the implications of defining the retinal image or the optic array as the
starting point for visual perception? Although the optic array and retinal image concepts may be
interchangeable for many practical reasons, they are associated with distinct approaches.
3
According to the indirect approach, the retinal image is the point of origin for visual perception
studies. As photo-receptors do not map the optic nerve fibers in a one-to-one relationship, the
retinal image itself cannot represent the external world simply and accurately.
4
The retinal
information that leaves the retina to the optic nerve contains only an approximation of light
intensities that initially reaches the retina.
5,6
Because this correspondence is not complete,
indirect perspective researchers argue that pure (i.e., before central processing) information
carried out by the optic nerve needs to be detailed in order to specify objects and events in the
external world. A substantial improvement and mediations into the visual cortex based on
complex computational processes are required in this view.
7,8
Alternatively, Gibson's
9,10
optic array leads to a different conception of the
information available in light to a perceiver.
The optic array may be thought of as a bundle of narrow cones of light with
their apices at the point of observation, each cone having as its base a
distinct environmental texture element and thus being optically differentiable
from its neighbors in terms of the intensity and/or spectral composition of
the light it contains. At each point of observation there is a unique optic array.
It is the passage of the eye through successive points of observation that
gives rise to the optic flow field at the eye (
11
, p. 282).
The ecological concept of information is based on the idea that the richness of
perceptual experience is present in the stimulation itself, and it does not depend on constructive
processes. An accurate specification of the nature of objects, places, and events is available to
the organism at stimulation.
7,12–14
Gibson
10
has criticized the indirect notion of information,
"information that can be extracted from ambient light is not the kind of information transmitted
over a channel. There is no sender outside the head and no receiver inside the head" (p. 64).
In this instance, information, which is the structure that specifies an environment to an
animal,
9,10
is understood as a bi-directional arrow, with one side pointing to the environment and
the other side pointing to the animal. Information-about objects, scenes, events, and
information-for the perceiver are two linked aspects that compose information analysis.
7
The indirect perspective of a mosaic of point-light intensities on the retina describes the input
for a perceiver in the same terms as the input for a single photoreceptor. The input for a receptor
is a stream of photons, but the input for a perceiver is a pattern of light extended over space
and time.
13
Gibson
9,10
described this pattern as gradients and rates of optic texture flow, which
emphasize the changes in the temporal pattern of light.
The indirect view of visual input is not concerned with the environment as perception
is centered on the perceiver.
3,15
The direct approach emphasizes the relationship between the
environment surrounding a perceiver and the optic array that specifies the environment.
10
The
aspect to be discussed in the next section is, in direct view terms, the environment's
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specification by the optic array, or in indirect view terms, the relationship between stimuli and
percept.
Immediate vs. mediate perception
The existence and necessity of cognitive mediation in visual perception is a topic of
intense debate.
13,14,16–20
Indirect perspective researchers have argued that perception requires
inference processes to supplement the supposedly impoverished nature of the flat, static retinal
image.
3,7
Gibson, on the other hand, argued that since the structure of light directly specifies
surface layout, mediating cognitive and/or computational processes are not necessary for
perception.
9,10,21
The indirect approach to visual perception maintains that the objects and surfaces'
world must be reconstructed by piecing together more primitive elements such as edges and
blobs.
22
Knowledge of the world is needed in order to create these reconstructions. Indirect
theories have proposed various kinds of knowledge, for example, the knowledge that natural
objects approximate to general cones.
23
The ecological approach maintains that objects are not
perceived by adding up a set of features and using knowledge of the world. Instead, the
information in higher-order invariants is directly perceived. In this case, it is not necessary or
possible to decompose these processes into more primitive operations or computations.
13,24
Given the assumptions of indirect theories of visual perception, research orientation
has been on the nature of computational stages, types of representations, and storage
necessary for vision. Marr
18
suggested that a consolidated theory of vision should focus on three
levels of explanation and analysis. At the computational level, the most conceptual one, a theory
should specify the task the visual system needs to complete, including a description of the
available sources of pure information to support this task. At the algorithmic level, it is
determined how the information available on the retinal image can be processed to find the
task's computational requirements.!At this point, specific algorithms, processing mechanisms,
and representations should solve the computational task to be discovered and tested. The
implementational level aims to find out possible neural, physiologic mechanisms that put
algorithms to function.
The direct perception perspective only effectively recognizes two levels of vision: an
ecological level (equivalent to Marr’s computational level) and a physiological level (equivalent
to Marr’s implementational level). Usually, the direct perception perspective focus on the
ecological level. The algorithmic level, the level where any representational processes would
exist, is eliminated from the direct perception view.
7,10,13
Bruce and Green
3
put forward an attempt to overcome disagreements from these
two theories. These authors were in line with the direct notion that properties of the world can
be detected without cognitive processes. However, such processes of detection would have to
rely on computation. Bruce and Green used Fodor and Pylyshyn's
16
notions of cognitively
impenetrable processes (which cannot be influenced by beliefs and expectations) and compiled
detectors (which run in an autonomous, data-driven manner) to suggest some common ground
between the two opposite approaches with respect to cognitive mediation.
At a higher level of analysis, compiled detectors can be regarded as
detecting properties of the world directly, but at a lower level of analysis their
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operations can be unpacked. At a behavioral level, it does not matter
whether one argues that
t
[the optical variable that specifies time-to-contact
information (Lee, 1976, 1980)], for example, is perceived directly, or whether
it is computed by compiled detectors. What does matter is that its detection
needs not to rely on inferences of the hypothesis-testing variety (
3
, p. 381).
In summary, the direct approach emphasizes no need for mediation between light
structure and visual perception, while indirect approaches assume information processing of
stimuli features as essential to perception. The subsequent section will focus on the necessity
of mediation at more abstract levels. The meaningfulness of visual information and memory-
related constructs will be discussed.
Affordances vs. representations
The indirect theory also regards perception as a mediated process when discussing
how the world's knowledge is represented in more abstract levels. The term representation is
used in various senses, and it generally refers to any symbolic description of the world.
13,20
Newell, Rosenbloon, and Laird
25
, when describing the functions of the cognitive architecture,
identified memory, symbols, operations, and interpretation as capable of being a symbol system.
However, none of these functions represent the external world; such representation is a function
of the computational system as a whole.
Direct theories of perception reject all such representations. This rejection is based
on the notion that objects and surfaces in the environment are specified by high-level invariant
properties of optic flow patterns. Consequently, there is no need for any processes of
construction or matching representations.
15,26
In addition, the invariants to which the perceiver
is attuned specify the actions that can be performed. Gibson called this relationship affordance.
The affordance of something is the specific combination of its properties of substance with its
surfaces related to the animal.
10,21
It is anything within the environment that contributes to this
kind of interaction.
15,27,28
The fact that affordances are perceived is important because this
provides meaning to perception. To detect affordances of the ambient is to detect meaningful,
available information that is unique, personal, and specific to species.
7,29
Fodor and Pylyshyn
16
strongly disagree with how the gibsonian theory avoids the
use of representation and implies a problem of trivialization.
How do people perceive that something is a shoe? There is a certain
(invariant) property that all and only shoes have - namely, the property of
being a shoe. Perceiving that something is a shoe consists in the pick up of
this property (p. 142).
Fodor and Pylyshyn’s
16
main criticism was that the terms invariant and direct
detection are left so unconstrained that they are meaningless. They defend a “sufficiency
criterion” expressed in the following two constraints: 1) the only thing that can be picked up is a
restricted class of properties of ambient light, and 2) spatio-temporal limits on these properties
are determined by what stimuli turn out to be efficient to cause perceptual judgments. The
consequence of these restrictions is that visual perception must involve inferences based on
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those directly detected light properties. This inference occurs because the causally effective
stimulus for perception usually underdetermines what is seen. For example, one art expert
detecting the fact that Da Vinci executed a painting would rely on inferences because the
sample of light reflected from the painting is not sufficient to cause recognition of it. It is argued
that information about the properties of Da Vinci’s paintings represented in memory is necessary
for such perception.
16
To summarize the concepts discussed above, an example of how a soccer
goalkeeper perceives an approaching ball is illustrative to differentiate the two approaches. Let’s
assume that goalkeepers perceive the remaining time the ball has to arrive and contact their
hands through the variable time-to-contact. The indirect view of perception is based on the idea
that our visual system uses a sequence of static snapshots (retinal images), comparing one to
the next, in order to detect changes and movement, which requires that each image be stored,
represented, and retrieved from a memory system, as well as the participation of higher-order
cognitive processes, such as inference. An “indirect goalkeeper” is expected to mentally
calculate the time-to-contact, dividing the distance to the ball by velocity of the ball
4
or more
complex variations of this type of mental processing.
30
The direct view of perception is based
on the notion that an optic array continuously changing, named optic flow, is visually available
and contains invariant properties of the environment, including the rate of expansion of the ball
image on the retina. A “direct goalkeeper” is expected to directly perceive time-to-contact
information from the optic flow, without the need for mental calculations or representations
31,32
Both of our imaginary indirect and direct goalkeepers are capable of perceiving time-to-contact
of a ball approaching to allow preparation and regulation of arm and body movements.
The arguments presented on the nature of visual input, cognitive mediation, and
representations/affordances briefly described antagonistic aspects of direct and indirect
theories. Many counterarguments from both sides were not mentioned due to the scope of the
present study. In sum, on the indirect view side, the notion of retinal image as the starting point
to visual perception is tightly associated with some computational or cognitive mediation
between stimuli and percept, which includes the necessity of memory-related processes. On
the direct view side, the richness of information present on optic array notion allows a lawful
relation between environment and perceiver, which favors meaningful actions based on optic
flow.
RELATIVE UTILITY OF DIRECT AND INDIRECT THEORIES
An evaluation of the relative utility of these two theories includes an analysis of the
goals of explanation, prediction, and simplicity expected in science. Such inspection requires
the understanding of individual assumptions and contexts of research. Also, practical definitions
of the scientific aims and some criteria normalization are necessary to keep fairness when
comparing distinct theories.
Science attempts to obtain a comprehensive account of the universe and its
contents designating relationships between investigation phenomena.
33–35
Emphases on
aspects of parsimony, explanation, and prediction are cognitively expected in science. The
extent to which different theories succeed in pursuing these aims can be represented by the
degree of utility of these theories. To compare their relative utility, mean parsimony, explanatory
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power, and predictive capability will be used as criteria. The overview elaborated on optic array
topics vs. retinal image, immediate vs. mediate perception, and affordances vs. representations
will support the following comparison.
The first difficulty in this analysis is the difference in the investigation phenomenon
that each theory defines. Although the phenomenon could be simply defined as visual
perception, each theory has a different answer to what visual perception is. Direct perception
theory is basically interested in the ecological level of analysis
9,10,21,
and the research in this
area is directed to describe and explain the ambient-perceiver relationship. The indirect view
includes the work on computational/representational processes as a research topic, as shown
by Marr
18
. As a result, each approach has its own goal. For practical purposes, the direct
perception theory seems as adequate as the indirect theories to explain visual perception.
The conception of parsimony holds that the simplest of a group of theories, which
account for equal adequacy for phenomena, is the most acceptable theory in science, other
aspects being equal. Simplicity refers to the economy in the use of unverified assumptions in
developing explanations. The minimum number of unverified notions and hypothetical
constructs should be used for postulating theories.
34
Bunge
36
defines epistemological simplicity
as the closeness to sense experience and, in particular, to observation.
Regarding parsimony, it seems clear that the notion of direct perception is simpler
than indirect perception. The theory of visual perception, as described by Gibson
9,10
, is more
economical in developing explanations, and it does not use a series of complex abstract
representations, as in the case of the indirect theories. The concepts of optic array and
affordance reduce the number of logical links involved in visual perception.
Also, the notion of mean parsimony asks how close to observation the theories are.
In general, the ecological concepts are based on the light's structure, which seems, in principle,
more verifiable than an abstract mental representation. This does not imply that direct view
concepts are easier to test than indirect view ones. For example, the strongest shreds of
evidence for optic flow were obtained in animal studies, and more investigation in humans could
strengthen the concept.
37
One could correctly argue, in agreement with Bunge
36
, that simplicity,
in this case, does not account for the complex characteristics of the phenomenon if ones’
assumptions include internal representations. Another possible argument is that cognitive
processes are perfectly testable in visual perception, as shown by the enormous amount of
experimental research produced in psychological and physiological studies.
5,6
Bunge
36
defines explanatory power as an epistemological requirement, implying
ambiguity of the demand for simplicity.
Explanatory power = Range X Accuracy: the greater the range of the theory,
the less properties involved; but the greater the accuracy, the more complex
the theory will be…. Consequently the demand for simplicity is ambiguously
relevant to the demand for a large explanatory power (p. 102).
The conception of explanatory power considers the relation between the amplitude
and complexity of an explanation. The indirect approach may take advantage of complexity due
to the inclusion of computational/representational mechanisms in their explanations, suggesting
that the indirect view of visual perception is closer to neurophysiology. Findings from this area
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help the statement of possible mechanisms into computational/representational models.
Neurophysiological studies investigate how neurons connect to each other to transmit
information from the eyes to the brain's visual areas and how different areas have different
functions in vision. For example, with the use of sophisticated techniques, it is possible to
explain, within the cognitive framework, how the damage in some areas of the brain may
influence visual attention mechanisms during specific tasks.
38
It is worthy of noting that,
although there is a historical lack of emphasis on nervous systems directly, there are recent
advances available (e.g.,
39
).
Another aspect that can be considered in the discussion of explanatory power is the
ecological validity. Overall, indirect perception studies have a lower ecological validity than
direct perception studies. If it is assumed that low ecological validity negatively affects the range
of explanation and vice-versa, the direct perception approach would have its explanatory power
relatively increased.
The ecological approach seems to face limitations regarding the range of
explanation due to its high specificity of some concepts. Affordance and optic array, for example,
describe relationships specific to the perceivers’ point of observation, specific to objects and
scenes, and specific to the task. Although invariants' notion should represent the system's
metric across aspects of specificity, such invariants are not easily identifiable. On the other hand,
the indirect view approach focuses on understanding the underlying process, which, in principle,
could generically explain a variety of other situations.
The aspect of prediction also represents the utility of a theory. Bunge
36
defines
predictive power (that will be used as synonymous of capability) as follows:
Predictive power = (Range explainable ex post facto + Unexpected range)
X Accuracy: simplicity is ambiguously favorable to predictability not only
because it is incompatible with accuracy and compatible with manifest range,
but also because the unexpected range of a theory … is greater as the
theory is richer (p. 103).
If the relation between ecological validity and explanatory power proposed above is
appropriate, it could be extended to predictability as well. In this case, the predictive capability
of each theory would differ according to the situation. The direct view seems to have a higher
predictive capability in natural situations. For example, visual perception characteristics during
locomotion are well predicted by ecological theories based on the notion of optic flow.
40
Indirect
view, however, could predict properly the situations more dependent on representation, such
as visual illusions
20
or artistic evaluation of paintings.
16
The utility is a topic that emerges when the characteristics of basic and applied types
of science are discussed.
41–43
Theories with higher utility seem to be more indicated to
application. Hoffman and Deffenbacker
42
proposed a more analytical categorization of applied
and basic science including distinct dimensions (validity, relevance, salience,
representativeness) for ecological and epistemological aspects based on characteristics of a
proposed research. They also considered the importance of implications of the experiment’s
results and divided the cognitive notion of generalizability into utility, novelty, and generality.
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The epistemological utility was defined as the extent to which the results lead to refinements in
hypotheses and theories.
42
Comparing the relative utility in terms of mean parsimony, explanatory power, and
predictive capability between direct and indirect views seems constrained by distinct levels of
analyses utilized in each approach. This relative utility analysis does not provide an output of
clear advantage to one of the perspectives (direct or indirect view); the utility comparison's main
conclusion is that indirect and direct approach are similar, according to the referred criteria.
Nevertheless, we argue in favor of the direct approach, suggesting that there are additional
aspects to be considered regarding the context of sports; the developed comparison above was
exclusively based upon the phenomenon of visual perception, which is certainly crucial to
success in sports performance. However, the action itself and intricate perception-action
connections have a central role in motor behavior theories; the ecological dynamics perspective
has been fruitful in the literature, as compared to the indirect view, searching for new
explanations and providing methodological advances to account for complexities and
specificities of sports context. To expand these ideas, we now turn into considering the
difficulties of indirect perspective in explaining visual perception and action during sports.
Particularly, how cognition orchestrate perception and action in the decision-making process
will be focused on in the next section, showing that understanding cognition is certainly not a
privilege of the indirect perspective.
CRITICISMS OF INDIRECT PERSPECTIVE IN SPORTS
Based on the foundations of visual perception according to direct and indirect
approaches, we now advance how visual perception understood in the ecological viewpoint
supports athletes in making decisions and producing movements in sport contexts. We present
some particular criticisms of representational approaches and summarize aspects of the
ecological dynamics account of decision-making in sport.
Sport is an expression of expertise, which strongly relies on perception; athletes see
things differently compared to novices, and such differences and respective knowledge affect
how athletes make decisions, plan their movements, and use their best strategies in sports.
44,45
Based on these assumptions and following the trends in indirect perspective, sports studies
have focused on athletes’ perception and anticipation, attention, memory, and decision-making;
the central role of action and its participation in cognition has been neglected.
46,47
Research on
perception, action, and cognition has been traditionally based on memory enrichment through
representations of various types, such as programs and schemas, which assume stimuli in the
environment is impoverished; internal knowledge structures are responsible for enhancing
meaning and richness of stimuli, allowing interpretation of the environment and movement
programming.
48
Ecological dynamics is an action-based, non-representational approach
grounded on the notion that perception and cognition are embedded and embodied,
emphasizing the performer-environment relationship as an appropriate scale of analysis.
47
The representational approach to human performance assumes that
representations contain the meaning of symbols, which are responsible for connecting an
individual to the world and its own body; representations are considered knowledge structures
able to make these mediations. However, very little is known about how these computational
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processes of symbolic coding, decoding, and the involved rules are biologically implemented.
In a distinct vein, the ecological dynamics approach holds that ambient energy distributions are
necessarily specific to the facts of the environment and of a performer’s actions relative to the
environment
10,28
; information is the basis for keeping contact with the environment since it is
specific to its sources. Using sport context as an example, athletes use different exploratory
actions of their perceptual systems (movements of eyes, head, trunk, and whole-body
locomotion) for perceiving things around. In terms of the ecological dynamics approach,
meaning in perception does not come from any form of mental association but only from
information detected by an observer. Due to practice, athletes are better able to difference
increasing types of information, amplifying the amplitude and economy involved in information
detection; this is perceptual learning, a process of attunement to the environment properties.
These arguments strongly suggest that motor behavior control can be explained without
postulating mental representations.
45,47
ECOLOGICAL DYNAMICS AS THE BASIS OF EXPERT DECISION-MAKING
AND MOTOR CONTROL IN SPORT
The ecological dynamics account applied to sports combines the previously referred
work of Gibson
9,10
with that of Bernstein
49
; these ideas regarding perception and action have
been discussed and amplified by Turvey and colleagues
48
, bringing language and principles
from the dynamical systems approach. A relevant impact was provided by Araujo et al.
46
,
developing an ecological dynamics rationale for decision-making in sports. According to Araujo
et al.
47
, three important assumptions of this approach are the following: First, behavior emerges
from the performer-environment system. So, actions during sports events must be understood
according to the performer’s characteristics and, necessarily, to the performance environment.
For instance, generalization from laboratory or training session context to competition
environment requires rigorous behavioral correspondence between these contexts because
athletes’ motor patterns are generated from the tight coordination emerging between athlete
and sport environment towards a specific goal. Second, perception is of affordances
15,47
;
athletes calibrate informational of their own action capabilities to directly perceive opportunities
to act in the environment.
50
This notion of affordances captures the link between constraints on
each athlete and the environment's characteristics. Decision-making in sport involves selecting
among affordances; once an affordance is perceived, its selection embodies an action mode
(i.e., the action mode is chosen simultaneously), but this action mode can change to other action
modes guided by the information conveyed by the affordance. Importantly, it is understood that
cognition emerges during these continuous interactions between performer and environment,
not from a mental representation of the world.
19,50
Third, action (and therefore cognition)
emerges under constraints. Behavior is understood as resulting from a self-organization
process under constraints.
46
According to this perspective, as constraints have the effect of
reducing the number of configurations available to an athlete at any moment, the task of each
athlete is to exploit physical and informational constraints to stabilize performance.
51
As a sample of research conducted on sports skills such as auto racing and cycling,
we now summarize advances in ecological dynamics on braking and steering to avoid obstacles.
Visually guided actions such as braking and steering are behaviors that involve continuous and