Wednesday, February 10, 2021

Zygmunt Pizlo, Philosophizing cannot substitute for experimentation: comment on Hoffman, Singh & Prakash (2014)

 Zygmunt Pizlo:  “I am an “expert” on 3D shape perception, so I will confine my comments about veridicality to shape. Unlike Hoffman et al., I do not have the temerity required to discuss veridicality in vision in general, as well as in smell, taste, touch and hearing in such varied species as humans, bees, and spiders.”

“… Any contemporary use of a Motor Theory of Perception, and this includes Hoffman et al.’s explanation of 3D shape perception, can be viewed as a legacy of psychology’s Dark Age called “Radical Behaviorism”. This is precisely what Hoffman et al. are offering us. As for me, “no, thank you very much.”

Zygmunt Pizlo’s paper does a wonderfully concise job of bringing Hoffman’s “veridicality” challenge back down to Earth and our three dimensional world.  This paper was 1200 words long and I whittled to 500 some odd.  Please visit the complete article for all the details. 

Philosophizing cannot substitute for experimentation: comment on Hoffman, Singh & Prakash (2014)

  • Zygmunt Pizlo, September 18, 2015 

Psychonomic Bulletin & Review

volume 22, pages 1546–1547 (2015)


The perception of a 3D shape must be excluded from Hoffman et al.’s “interface theory” primarily because shape is characterized by its symmetries. When these symmetries are used as a priori constraints, 3D shapes are always recovered from 2D retinal images veridically. 

These facts make it clear that 3D shape perception is completely different from, as well as more important than, all other perceptions because the veridicality of our perception of 3D shapes (and 3D scenes) accounts for our successful adaptation to the natural environment.

… when we talk about veridical 3D perception, we are referring to our natural visual space, that is, a space with natural, symmetrical objects residing, as they naturally do, on a common ground because of gravity. 

The concept of an “empty” visual space, used in laboratories, that contains only a few isolated points of light in total darkness, or a few objects floating in the air, no matter how attractive mathematically, is actually empty from an empirical, as well as from a computational, point of view. …

Note that the concept of a priori constraints is largely ignored by Hoffman et al. Their neglect of such potentially critical factors allows them …

There is absolutely nothing in the literature to justify such a view. Quite the opposite is true: there is overwhelming evidence showing that 3D vision, but not the taste sweetness, is treated as an inverse problem by the perceptual system and is solved as such (Pizlo, 2001; Poggio et al., 1985).

With this said, I will continue my comment by pointing out that the veridicality of visual perception is an empirical question, and visual psychophysics has advanced to the point that we have at hand, and have already used, all of the tools required to answer this question. Speculation about this now is pointless. 

Several relatively sophisticated experiments on how people see 3D shapes have provided a convincing positive answer to the veridicality question (Pizlo et al., 2010). …

Ideally, they would stay away from it completely because continuing to fuss about veridicality can only muddy the waters. 

It would really be a shame to do this now because it took such a long time to separate the wheat from the chaff in the long history of research on shape perception: this took at least 300 years (Pizlo, 2008). 

The fact that we see symmetrical shapes as symmetrical means that we see them veridically, and if an object is not exactly symmetrical, like a chair with a broken leg, we see it as a symmetrical object with one broken part. If this is not veridicality, what is?

I have been presenting such “symmetry” arguments periodically to the authors of the target paper since 2009. 

It was already obvious to me back then that their interface theory does not apply to shape perception, no matter how well it applied elsewhere, but they simply could not put their theory aside. 

They did recognize that shape and symmetry made trouble for it, and the only way they could keep applying their non-veridicality theory to the perception of symmetrical shapes was to claim that it is not our perceptions, but our actions that are symmetrical. 

Any contemporary use of a Motor Theory of Perception, and this includes Hoffman et al.’s explanation of 3D shape perception, can be viewed as a legacy of psychology’s Dark Age called “Radical Behaviorism”. 

This is precisely what Hoffman et al. are offering us. As for me, “no, thank you very much.”



Cc’s Students’ Study Guide for The Case Against Reality

A critical review of, The Case Against Reality:  Why Evolution Hid The Truth From Our Eyes, by Donald Hoffman, ©2019, W.W.Norton Company

I intend to be a witness for a fact based DeepTime, 
Evolutionary perspective on our Human Mind ~ Physical Reality interface.


(Titles are linked)

(1.01)  The Prelude, Prof Donald Hoffman Playing Basketball In Zero-Gravity

(1.02)  Chapter 10a, Community: Network of Conscious Agents (1/3)

(1.03)  Chapter 10b, Community: Network of Conscious Agents (2/3)

(1.04)  Chapter 10c, Community: Network of Hoffmanian Conscious Agents (3/3)

(1.05)  Chapter 1, Mystery: The Scalpel That Split Consciousness

(1.06)  Chapter 2, Beauty: Siren of the Gene

(1.07)  Chapter 3, Reality: Capers of the Unseen Sun

(1.08)  Chapter 4, Sensory: Fitness beats Truth

(1.09)  Chapter 5, Illusory: The Bluff of the Desktop

(1.10)  Chapter 6, Gravity: Spacetime is Doomed

(1.11)  Chapter 7, Virtuality: Inflating a Holoworld

(1.12)  Chapter 8, Polychromy: Mutations of an Interface

(1.13)  Chapter 9, Scrutiny: You Get What You Need, in Both Life and Business

(1.14)  Appendix,  Precisely: The Right to Be (Foolish)


Hoffman/Prakash’s Objects of ConsciousnessObjections and Replies

Frontiers in Psychology - June 17, 2014

(2.01)  4/4_Hoffman, Objects of Consciousness,  (conclusion)

(2.02)  1/4_Hoffman, Objects of Consciousness, questions + replies (1-12)

(2.03)  2/4_Hoffman, Objects of Consciousness, questions + replies (13-17)

(2.04)  3/4_Hoffman, Objects of Consciousness, questions + replies (18-21)


(3.01)  Diary - But, wait!  There's more.  Ten Learned Responses:

Probing the interface theory of perception: Reply to commentaries, by Donald D. Hoffman, Manish Singh & Chetan Prakash" 

Psychonomic Bulletin & Reviewvolume 22, pages1551–1576(2015)


We propose that selection favors nonveridical perceptions that are tuned to fitness. Current textbooks assert, to the contrary, that perception is useful because, in the normal case, it is veridical. Intuition, both lay and expert, clearly sides with the textbooks. We thus expected that some commentators would reject our proposal and provide counterarguments that could stimulate a productive debate. … (HSP)


(3.02)  Barton Anderson - Where does fitness fit in theories of perception? 


(3.03)  Jonathan Cohen - Perceptual representation, veridicality, and the interface theory of perception. 


(3.04)  Shimon Edelman - Varieties of perceptual truth and their possible evolutionary roots. 


(3.05)  Jacob Feldman - Bayesian inference and “truth”: a comment on Hoffman, Singh, and Prakash. 


(3.06)  Chris Fields -Reverse engineering the world: a commentary on Hoffman, Singh, and Prakash, “The interface theory of perception”. 


(3.07)  Jan Koenderink - Esse est Percipi & Verum est Factum. 


(3.08)  Rainer Mausfeld - Notions such as “truth” or “correspondence to the objective world” play no role in explanatory accounts of perception. 


(3.09)  Brian P. McLaughlin and E. J. Green Are icons sense data


(3.10)  Zygmunt Pizlo - Philosophizing cannot substitute for experimentation: comment on Hoffman, Singh & Prakash. 


(3.11)  Matthew Schlesinger Interface theory of perception leaves me hungry for more. 



Student Resources - Background info:

(4.01)  Rainer Mausfeld: ‘Truth’ has no role in explanatory accounts of perception.

(4.02)  Paul Mealing: considers Hoffman's "Objects of Consciousness.”

(4.03)  The Case For Reality: Because Apparently Someone Needs to Make One

(4.04)  Sabine Hossenfelder: in Defense of Scientific Realism and Physical Reality

(4.05)  "Emergence" - A Handy Summary and Resources

(4.06)  Physical Origins of Mind: Dr. SiegelAllen Institute Brain Science, Tononi, Koch.

(4.07)  Can you trust Frontiers in Psychology research papers?  Student Resource

(4.08)  Critical Thinking Skills - In Defense of Reality - A Student Resource

(4.09)  Philo+Sophia - Love of Wisdom - A Student Resource


(5.01)    Summary, 

explaining why I've pursued this project.


Dr. Mark Solms deftly demystifies Chalmers’ “Hard Problem” of Consciousness, while incidentally highlighting why Hoffman’s “Conscious Agents” are luftgeschäft. 

(6.01)  Dr. Mark Solms demystifies Chalmers' "Hard Problem" of Consciousness.

(6.02)  The Other Side of Mark Solms PhD, farmer, vintner, humanitarian.

(6.03)  Students’ Resource: A representative cross-section of Dr. Mark Solms' scientific publications.


My homemade philosophical underpinnings.

(7.01)    An Alternative Philosophical Perspective - “Earth Centrism

(7.02)   Appreciating the Physical Reality ~ Human Mindscape divide

(7.03)   Being an element in Earth’s Pageant of Evolution

(7.04)   It’s not a “Body-Mind problem” it’s an “Ego-God problem.”

Feel free to copy and share

Email: citizenschallenge  gmail  com



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