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The Genesis of the Awareness of Illusion

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Martin (2002) writes, “[I]ntrospection of one’s perceptual experience reveals only the mind-independent objects, qualities and relations that one learns about through perception. Experience is diaphanous or transparent to the objects of perception.”
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The Genesis of the Awareness of Illusion
Ugo Savardi
1
, Michael Kubovy
2
, & Ivana Bianchi
3
Martin (2002) writes:
introspection of one’s perceptual experience reveals only the mind-
independent objects, qualities and relations that one learns about through
perception. Experience is diaphanous or transparent to the objects of
perception….
We agree, and argue that humans are by nature credulous realists; they trust their
senses, even when such trust is unwarranted. We wish to understand the conditions
under which we become aware that we have experienced an illusion, and the
consequences of such an awareness.
Three examples
The rabbit out of the hat. An illusionist pulls a rabbit out of hat, “as if by magic”
(Lamont & Wiseman, 1999; Macknik et al., 2008; Polidoro, 2007). This can happen in
one of three ways: (a) the object was already there but was concealed, (b) the object
was secretly put into position, (c) the object is not there but seems to be. The
illusionist may be using physical misdirection --manipulating what the members of the
audience perceive by controlling where they look, or psychological misdirection --
manipulating what they think by controlling their expectations (Lamont & Wiseman,
1999). Since their manipulations are fragile, illusionists are not inclined to repeat their
tricks; nevertheless all of us have seen such tricks time and time again, and yet we are
forever thrilled by them.
The violin. On one of the internal doors of Chatsworth House, a large country
house in Derbyshire, England, there is a trompe l’œil of a violin and bow (Figure 1.1).
Imagine visiting the house unforwarned about this painting. When the door and the
painting become visible, you might ask yourself “why would anyone have hung a
violin on a door in this opulent house. Could the violin be particularly beautiful or
unusual?” You approach the door and the deceit is revealed. Surprised, you ask
yourself whether the illusion would dissolve in the knowledge of the trick. So you
take a few steps back to test whether you would still see the illusion as powerfully
now that you are aware that this is a trompe l’œil. Charmed, you find that the illusion
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1
!Full professor of General Psychology in the Department of Philosophy, Education and Psychology at
the University of Verona (Italy).!
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!Full professor of Psychology in the Department of Psychology at the University of Virginia (USA).!
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!Associate professor of General Psychology in the Department of Educational Sciences at the
University of Macerata (Italy).!
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is impervious to your knowledge. You file away this little story as an episode to be
shared with friends and savored in the future.
Figure 1.1 - Trompe l’œil of a violin and bow painted on a door of Chatsworth House
(ca. 1723) by Jan van der Vaart
Two unequal lines. Imagine that a psychologist (Ψ) shows you (Φ) the Müller-
Lyer illusion, which you have never seen, on a computer screen (Figure 1.2). The
dialog between you might run like this:
Ψ: “Which line is longer [in Figure 1.2]?”
Φ: “The top one”.
Ψ: “Now I’m going to remove the arrow-heads and draw dashed lines between the
end-points of the lines, like this [Figure 1.3]. Which is longer?”
Φ: “They are the same. May I see the first one again?”
Ψ: “Of course. Here it is.”
Φ: “I can’t make the difference go away.”
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Figure 1.2 - A version of the Müller-Lyer illusion
Figure 1.3 - The Müller-Lyer unmasked by removing the arrow heads and adding
dashed lines
From perception to meta-perception
Our episodes share three phases that are necessary and sufficient for becoming aware
that one has experienced an illusion. To simplify our account, for the moment we
assume that in each of these examples, you are naïve: you don’t know that a magic
trick is about to be performed, that you are about to see a trompe l’œil painting, or that
what you are looking at is an illusion. They are parallel to the story of original sin and
the expulsion of Adam and Eve from Eden (Box 1 and Table 1.1).
1
Box 1 - Genesis, Chapter II
The Lord God planted a garden in Eden; and there He placed the man whom He
had formed….
When the woman saw that the tree was desirable to make one wise, she took from
its fruit and ate; and she gave also to her husband … and he ate.
Then the eyes of both of them were opened, and they knew that they were naked; …
Then the Lord God said, “Behold, the man has become like one of Us, knowing good
and evil … ”
therefore the Lord God sent him out from the garden of Eden.
Table 1.1 - Phases of the loss of innocence
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Magic
Trompe l’œil
Effect
Paradise
“I see an
empty hat”
“I see a violin
on the door”
Naïve
perception
Eat the
fruit
“He pulled a
rabbit out of
the hat”
“It’s a painting”
See the
illusion
Paradise
lost
How was I
fooled?”
“How was I
fooled?”
Meta-
perceptual
experience
Eden: First viewing. You see a pattern or an object (en empty hat, a violin on a
door or one line shorter than the other). If I ask you to describe what you see, you will
say that you see an empty hat or a violin on the door. In the case of the Müller-Lyer, if
I ask you which shaft is longer, you will say the upper. As long as you are naïve, in
none of these cases will your attention be drawn to your perceptual process -- only to
the world in front of you.
To eat the fruit: Second viewing. You carry out, or are confronted with, a second
observation. The magician pulls a rabbit out of the hat you just a moment ago saw to
be empty. You happen to approach the door on which the violin hangs and -- by touch
or by sight -- discover that the musical instrument you just a moment ago saw hanging
on the door is painted. The experimenter modifies the display to reveal the illusion, or
offers you a ruler to measure the lines, which you now realize are equal.
Shame: Awareness or doubt. Having had both experiences draws your attention
to your perception. Was the magician’s hat really empty? If it wasn’t, how could I
have not seen that it concealed saw a large live animal as a rabbit? If it was empty,
how would I have not seen the moment when a rabbit was put into it? Did the trompe
l’œil violin really look solid from a distance, and if it did, can I see it that way when
I’m close up? Did the parallel lines of the Müller-Lyer really look different when the
arrow-heads were present, and if they did, can I make myself see them correctly?
Knowledge: Illusion. You experience having undergone an illusion because you
cannot reconcile two experiences. This contradiction leaves you puzzled, a bit shaken,
but perhaps also entertained.
Analysis
You will not experience having undergone an illusion unless you believe that the
property of the object about which you were mistaken is unchanged between the first
observation and the second.
In the case of the rabbit and the hat, you mistook a hat with a rabbit in it for an
empty hat. Unless you experienced the hat as being the same hat inexplicably both
empty and full, you would not think that you had experienced an illusion.
In the case of the painted violin, you mistook flatness for solidity. To realize
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that you have experienced an illusion, you must believe that the violin is painted on a
surface when you are far away and when you are close up, rather than solid when you
are far away and painted on a surface when you are close.
In the case of the Müller-Lyer, you mistook equality of length for a difference
in length. To realize that you have experienced an illusion, you must believe that the
experimenter is not changing the length of the shafts when she removes the
arrowheads and fins, and that approaching the pattern with a ruler does not cause the
lengths of the shafts to become equal.
For the sake of developing our argument we assumed that the first observation
was naïve or uninformed. However, I look forward to seeing magic, to revisiting
Chatsworth house, and to be fooled by illusions, even though I may not be naïve any
more.
We also said that in order to have the experience of having undergone an
illusion “you must believe X”. We are not saying that you necessarily reported to
yourself (or someone else) that X was the case. Rather, we mean that if someone had
asked you whether you think that the violin had been painted on the door all along,
you would have said Yes. Indeed, the most likely cause of such a belief is that (a) you
did not see any of the changes that you would expect had the object of the illusion
changed, and that (b) you believe that you would have seen these changes had the
object of the illusion changed. It is precisely under these conditions that the
assumption of object permanence (Paterson, Heim, Thomas Friedman, Choudhury, &
Benasich, 2006) is triggered.
Shame and Paradise Lost: The recognition of epistemological vulnerability
When you first experience having undergone an illusion you are beset by a concern
brought about by a failure of your senses. This concern has an object (as do all
emotions) -- your own perception; it is meta-perceptual. This meta-perceptual concern
may trigger a decision to test the limits of your perceptual system in this setting. That
is, you ask yourself whether you can overcome the illusion.
If you were taken in by the trompe l’œil violin, you might back off to the point where
the cues to the object’s flatness are minimal. You try to see if you could have avoided
falling prey to the error. Likewise, if you just saw the Müller-Lyer for the first time,
you might look carefully at the drawing to see if by an effort of the will you could see
the equality of two lines. These are meta-perceptual activities. In both cases you are
likely to be impressed by the robustness of the illusion, a meta-perceptual conclusion.
To be sure, the concern produced by your recognition of your epistemological
vulnerability is mild. This should not surprise us: you have encountered many
illusions in the past, and you have come to realize that your vulnerability in such
situations is insuperable, but of little consequence. The more ingrained this realization,
the weaker the emotional response to a new illusion.
This analysis suggests an account of the widespread interest in trompe l’œil and
optical illusions
2
they are a mild form of thrill-seeking, an epistemological roller-
coaster, as it were (Apter, 1992; Elias & Dunning, 1986).
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Precursors
Four authors have anticipated our proposal that experiences of illusion are triggered
by an inconsistency of two perceptions.
Kubovy (1986) proposed that the essence of experiencing an illusion involves a
perceptual paradox.
Take, for instance, the vertical-horizontal illusion [Figure 1.4]. The
vertical looks longer than the horizontal…. But it is only when you are
put in a position to experience a perceptual dilemma -- such as being told
to rotate the drawing slowly and becoming aware of the changes in the
relative lengths of the two lines, while realizing that the drawing is
invariant, that you experience an illusion. This is a metaperceptual
experience: the visual system does not try to reconcile the two
experiences, and that non-reconciliation gives rise to the experience of
illusion” (1986, p. 84).
Figure 1.4 - The vertical-horizontal illusion
Furthermore, Kubovy shows that the experience of the eyes of a portrait “following”
us is a rare instance of an object spontaneously giving rise to the experience of an
illusion. It is here that he introduced the notion of a double dilemma (Figure 1.5).
On the one hand, even though we are walking past a picture, we perceive
the spatial layout of the represented scene as if it remains unchanged.
This is what we have called the robustness of perspective …. On the
other hand, even though the spatial layout of the scene remains
unchanged, we perceive our own motion in space as we walk past the
picture. The experience of a rotation of the painting is one way to resolve
this dilemma: To perceive the scene as being invariant while we are
walking past it, we must perceive the picture to be rotating [dilemma
1]…. (1986, p. 84)
But that solution to the dilemma is, so to speak, shortsighted, because it
gives rise to another dilemma: If the picture is turning, how is it that it
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looks so well attached to the wall? Why does its relation to the room not
change? The experience of illusion stems from the visual system’s
inability to resolve this dilemma within a dilemma. (1986, p. 86)
Figure 1.5 - The double dilemma of picture perception that leads to the experience that
the turning of the picture, as we walk past it, is illusory
Reynolds (1988) had a similar view, although he did not deal with subtleties of picture
perception:
The psychological concept of illusion is defined as a process involving an
interaction of logical and empirical considerations. Common usage
suggests that an illusion is a discrepancy between one’s awareness and
some stimulus. (1988, p. 217)
After proposing and rejecting five definitions of illusion based on this usage, he
redefines illusion
without reference to truth or falsity, but relative to the functioning of a
given perceptual system under different conditions[:] ‘a discrepancy
between one’s perceptions of an object or event observed under different
conditions.’ Conditions may differ in terms of stimulus exposure, stimulus
as I walk
past the
picture,
my vantage
point is
changing
because of the
robustness
of perspective,
the scene
isn't
changing
the picture
is rotating
to follow me
the picture
is rotating
to follow me
but, from
other evidence
therefore,
I experience
perceptual
paradox
I call it an
illusion
DILEMMA 1
DILEMMA 2
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context, or experiential context.” (1988, p. 217)
Da Pos (1996, 1997, 2008) distinguishes between two kinds of perceptual
illusions:
1. Psychophysical: “there are discrepancies between what we perceive (for example,
redness) and the physical, not perceivable variables (for example, wavelength) which
are known to be correlated.” (1997, p. 37).
2. Phenomenological: there are discrepancies within the phenomenal world, as,
for instance, when the same perceived object appears now with some and now with
contrasting characteristics. Phenomenal illusions always keep their illusory
characteristics as far as the same event appears (in perceptual sense) under contrasting
aspects. Therefore the more direct is the connection of contrasting aspects with the
same event, the stronger is the evidence of an illusion.” (1997, p. 37).
Savardi & Bianchi (1998, 1999) agree with the preceding authors that illusions
involve a dilemma. They however emphasize that, whatever the specific contents of
the dilemma, it should be understood in a more general framework of analysis of
errors in the experimental phenomenology of perception. According to the traditional
view, the so-called “stimulus error” involves substituting a description of the
geometry or physical characteristics of the stimulus for a description of what one sees.
Savardi and Bianchi show that the error is better understood as substituting the
description of what is experienced by the subject here and now (that is, what he sees)
with a description of “the same stimulus” experienced under different conditions (that
is, the two lines after having removed the arrowheads, reporting a measurement
instead of the naked eye, touching a stimulus instead of looking at it, and so on).
According to them, a crucial component of the phenomenology of having
undergone an illusion, in addition to the experience of a discrepancy between the two
descriptions, is that observers must believe that what they have seen in two different
ways has not changed -- in other words, what is crucial is experiencing that two
contrary perceptions apply to the same configuration.
What is new
In this article we presented a tripartite phenomenological analysis of the experience of
having undergone an illusion. The first two components have been proposed before.
The third is new. The first necessary component is the presence of two perception-
based beliefs, one that the observer believes is true and the other the observer believes
is false. The second necessary component is the observer’s belief that no change has
occurred in the source of the illusion. The third component is the observer’s
recognition of having been let down by his or her perceptual system, since it suggests
two equally valid descriptions for the same object. This differs from what happens the
rest of the time when he or she experiences a stable and consistent world. This
recognition inevitably gives rise to a succession of two responses: (a) a concern; (b) a
test of the robustness of the illusion in an attempt to learn more about the fallibility of
one’s encounter with reality.
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... Both perspectives presuppose the idea of veridicality. The third stance, which is suggested by the author, is a phenomenological one (e.g., Zavagno et al. 2015;Savardi et al. 2012). According to this stance, perspective illusions are not considered to be errors. ...
... This work reports my concept of illusion, in particular in relation to visual perception. I believe that it fits well within the tradition of experimental phenomenology, and it may find some resonance in other studies on the same topic (for example: Da Pos 2021; Mausfeld 2015;Savardi et al. 2012;Schwartz 2012). The arguments advanced here are a development of positions that I have already expressed in other works (for instance, Zavagno 2021; Zavagno et al. 2015). ...
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