The World of Physical Intelligence

As part of the Embodied Intelligence workshop this past week, I saw a presentation by Metin Sitti of the Max Planck Institute for Intelligent Systems on the emerging paradigm of Physical Intelligence. What is Physical Intelligence? It is the intelligent behavior exhibited by motion and takes into account a morphology (embodiment) and action at multiple scales of spatial organization. The talk was wonderful and walked through a number of empirical studies involving both living and non-living systems. I will leave it up to the reader to appreciate all of the points raised in this talk.

Physical Intelligence as an emerging idea.

While Physical Intelligence is not a common paradigm, the general idea is actually not new. Other people have proposed very similar frameworks over the past 15 years or so, including yours truly. Physical Intelligence involves some form of motor or movement behavior, which is generated by an embodied agent, that in turn interacts with the physical environment that can be defined by features such as inertial and gravitational forces, surface textures, and even light energy. 

Physical stimuli for soft robots or other autonomous agents from Figure 1 in Shen et.al, Journal of Materials Chemistry B, 8, 8972-8991 (2020).

At its most human-centric, physical intelligence can be just another word for embodied intelligence, which is where the body shapes and determines what is experienced by the nervous system. In cases where the behaving agent has no nervous system, the body geometry shapes the agent's behavioral output. This is true both in cases of adaptive (intentional) behavior and reactive behavior. In some cases, physical intelligence is identical to Neuromechanics. In other cases, it resembles a range of fields, from Biophysics to Embodied Robotics. The important contribution of the Physical Intelligence paradigm is the principles that guide this diverse topical terrain. Both my talk and Metin's talk provide some of these potential principles, and Scott Grafton's book provides a few more.

One human-centric interpretation of Physical Intelligence (by Scott Grafton).

Metin brings up the example of the Strandbeest, which is a kinetic sculpture with no nervous system or centralized control. This is an example of a purely reactive system that also generates seemingly intelligent behavior. Closer to the human experience is the Passive Dynamic Walker, which produces human-like bipedalism without a central nervous system. This is the essence of the physical: a particular physical configuration can exhibit reactive behavior independently of a central controller.

While serving as part of the peripheral nervous system, and in fact being controlled by a central nervous system, muscles can also play a key role in physical intelligence. While muscle cells can be spontaneously active without being inputs by motor neurons, there is a elaborate coordination between the central nervous system and muscular control. Muscular control can produce both very fast and very slow adaptive movements. In addition, the overall shape of a body in relation to its muscles can constrain the behavior of the agent in question.

The main takeaway is that the brain, body, and environment all work interdependently to shape the behavior that emerges from this complex system. Even in cases where there is no brain (or neural network), the interactions between body and the environment are enough to generate reactive behaviors that appear to be intelligent. This is true for both individual morphologies and the collective behavior of many agents (e.g. swarm intelligence). In fact, the brain can be supplanted by control mechanisms that regulate the conformity and response to physical forces in the environment. Future work should focus on the differences between "neural" and "physical" behavior, as well as the necessity and sufficiency of each component in the triad.

A diagrammatic example of this relationship (with a brain in the feedback loop) from Chiel and Beer, Trends in Neuroscience, 20(12), P553-P557.

In conclusion, DARPA has also engaged in the idea of physical intelligence, and there was a proposer's conference in 2009. This version of Physical Intelligence has a strong cybernetics flavor, particularly in incorporating the EGRT (Every Good Regulator Theorem) into the mix.

Cybernetics of the firm (deemphasizing the role of individual morphology). COURTESY: New World Encyclopedia.

Frontiers in Bioengineering Conference: The Farthest Out in Front

Earlier this month, I attended the Frontiers in Bioengineering conference at the Beckman Institute (UIUC). It was an interesting event with diverse perspectives on the field of Bioengineering. The two-day event featured researchers from all over the world, but focused on the synergies between Engineering and Cell/Molecular Biology.

One way to summarize the proceedings is to discuss the three most interesting (at least to me) technological advances. So here they are, in no particular order:

1) tissue co-cultures: Roger Kamm and Kevin Healey discussed the use of co-cultures to synthetically grow new organs and/or repair scaffolds. Co-cultures [1] are ex vivo systems within which multiple cell types are established and grown in media. The benefit of this artificial system involves the endogenous production of growth factors and a microenvironment. Exogenously-delivered factors apparently do not have the same efficacy for applications such as nerve grafts and cardiac repair. In the case of nerve grafts, supplying a bona-fide microenvironment can increase the distance of nerve innervation across a denervated gap. Co-cultures can also provide target tissues and anterograde cells to better approximate neuronal communication.

2) SHAPEseq: this an up-and-coming technique that has been used by a number of research groups to sequence the secondary structure of RNA [2]. SHAPEseq, or Selective 2'-hydroxyl acylation analyzed by primer extension, involves several steps that are similar to or go beyond the basic RNAseq technology. These include: preparing a barcoded RNA library, preparing a structure-specific cDNA library, aligning the corresponding reads, and calculating shape reactivities [3]. As with RNAseq, the objective is to build sequence libraries. Unlike with RNAseq, these libraries are structure-dependent. This allows for important structural information (e.g. hairpins, loops) to be estimated from a sample with single-nucleotide resolution.

A graphical summary of the SHAPEseq protocol. COURTESY: protocol description in [3].

3) NiN (nonviral induced neuronal) cells: this is a technique that was presented by Kam Leong at Duke. The idea is to use a non-viral genetic engineering approach (such as CRISPR) to introduce reprogramming factors into a cell. Non-viral factor delivery, as opposed to viral-mediated delivery using polycistronic vectors (genetic elements), is supposedly safer for transplantation and other therapeutic uses [4]. Other non-viral techniques (such as RNA-mediated reprogramming) have been tried with a mixed record of success. But by using the gene editing method [5], a cell population can be reprogrammed to a level of efficiency approximating viral-mediated reprogramming techniques. Despite various issues with estimating reprogramming efficiency and diversity across source cells [6], NiN techniques might be a easy and relatively controllable way to produce highly-specialized types of induced Neurons.

Honorable mention by association: The technology enabling the NiN advance is called CRISPR, or clustered, regularly interspaced, short palindromic repeat technology [7]. By using RNA-guided nucleases such as members of the Cas protein family (Cas9 in particular) [8], CRISPR technology can enable precise targeting of gene regulation. This includes the introduction and control of transgenes, something for which CRISPR has a lot of potential. To be fair, there are other, similar methods such as Transcription Activator-Like Effector Nucleases (TALENs) and Zinc Finger Nucleases (ZFNs) [9]. So congratulations to all of our gene editing technologies as we look to the future.

A diagram of the Cas-mediated CRISPR protocol. COURTESY: James Atmos, Wikipedia.

NOTES:
[1] For examples, please see the following articles:
a) Paschos, N.K., Brown, W.E., Eswaramoorthy, R., Hu, J.C., and Athanasiou, K.A.   Advances in tissue engineering through stem cell-based co-culture. Journal of Tissue Engineering and Regenerative Medicine, doi:10.1002/term.1870 (2014) AND

b) Ma, J., Both, S.K., Yang, F., Cui, F-Z., Pan, J., Meijer, G.J., Jansen, J.A., and van den Beucken, J.J.J.P.   Cell-Based Strategies in Bone Tissue Engineering and Regenerative Medicine. Stem Cells and Translational Medicine, sctm.2013-0126 (2013).

c) Meijer, G.J., de Bruijn, J.D., Koole, R., van Blitterswijk, C.A.   Cell-Based Bone Tissue Engineering. PLoS Medicine, 4(2), e9. doi:10.1371/journal.pmed.0040009 (2007).

[2] For examples, please see the following articles:

a) Lucks, J.B., Mortimer, S.A., Trapnell, C., Luof, S., Aviran, S., Schroth, G.P., Pachter, L., Doudna, J.A., and Arkin, A.P.   Multiplexed RNA structure characterization with selective 2′-hydroxyl acylation analyzed by primer extension sequencing (SHAPE-Seq). PNAS, 108(27), 11063-11068 (2011)

b) Steen, K.A., Malhotra, A., Weeks, K.M.   Selective 2'-hydroxyl acylation analyzed by protection from exoribonuclease. Journal of the American Chemical Society, 132(29), 9940-9943 (2010).

[3] Mortimer, S.A., Trapnell, C., Aviran, C., Pachter, L., and Lucks, J.B.   SHAPE–Seq: High‐Throughput RNA Structure Analysis. Current Protocols in Chemical Biology, 10.1002/
9780470559277.ch120019 (2012).

[4] Park, H.J., Shin, J., Kim, J., and Cho, S.W.   Nonviral delivery for reprogramming to pluripotency and differentiation. Archives of Pharmacology Research, 37(1), 107-119 (2014).

[5] Perez-Pinera, P., Kocak, D.D., Vockley, C.M., Adler, A.F., Kabadi, A.M., Polstein, L.R., Thakore, P.I., Glass, K.A., Ousterout, D.G., Leong, K.W., Guilak, F., Crawford, G.E., Reddy, T.E., and Gersbach, C.A.   RNA-guided gene activation by CRISPR-Cas9–based transcription factors. Nature Methods, 10, 973-976 (2013).

[6] Alicea, B., Murthy, S., Keaton, S.A., Cobbett, P., Cibelli, J.B., and Suhr, S.T.   Defining phenotypic respecification diversity using multiple cell lines and reprogramming regimens. Stem Cells and Development, 22(19), 2641-2654.

[7] Hsu, P.D., Lander, E.S., and Zhang, F.   Development and Applications of CRISPR-Cas9 for Genome Engineering. Cell, 157(6), 1262-1278 (2014).

[8] Sander, J.D. and Joung, J.K.   CRISPR-Cas systems for editing, regulating and targeting genomes. Nature Biotechnology, 32, 347-355 (2014).

[9] Gaj, T., Gersbach, C.A., and Barbas, C.F.   ZFN, TALEN, and CRISPR/Cas-based methods for genome engineering. Trends in Bioengineering, 31(7), 397-405 (2013).

Thought (Memetic) Soup, June edition

Happy middle of summer (in the Northern hemisphere, anyways)! Here are some humorous and puzzling items from my leisure time, cross-posted to Tumbld Thoughts. Also an update on Orthogonal Research, which is turning into quite a productive endeavor. This also marks the return of the Thought Soup series. Bemusement and incredulity abound. 

I. Technological Bemusement (for better and for worse)

Miguel Nicolelis (Neuroscientist of BMI fame) is demoing an EEG-controlled exoskeleton at the World Cup [1]. The exoskeleton is able to engage in soccer-related movements, but is controlled by a human brain. Read the Science News interview for more. And here is the outcome [2], courtesy of Neurogadget.

Contrary to the popular trough of disillusionment, Google Glass is a huge development in the world of Augmented Reality. Soon we will all be wearing glass-mounted displays, even if they are not made by Google. Google is apparently very bad at marketing, but that may not be the whole story [3]. Just know that violent responses to so-called "glassholes" is not entirely new.

25 years ago this month: Star Trek V opens. See William Shatner direct a film. Then see William Shatner rock-climb (poorly) and question God. If God is at the center of our galaxy, then are there gods at the center of all of the other galaxies? And if a god created the Big Bang (as some people claim), then is this God merely a middle manager? These are the types of questions audiences should have been asking, but it was 1989 and we were all fascinated with Spock's levitation boots.

II. Speaking Fee Incredulity

Speaking fee incredulity, courtesy of CREMA [4]. The graph is a sampling of economists on the lecture circuit: the x-axis is their relative internet ubiquity, and the y-axis is their minimum speaker's fee. Notice the red arrow and how it points to a cohort that includes Myron Scholes, Dan Kahneman, and Ben Stein. Funny how the world works sometimes.

III. Spam and Pointless Political Resistance Incredulity

I quit, I give up, Nothing's good enough for anybody else, It seems  -- Circle, Edie Brickell.

The chorus of this song [5] seems to summarize the Democratic Party's 2014 grass-roots fundraising strategy against the conservative Super-PAC fundraising [6]. Do you approve of this message? There are some people (progressive-minded bloggers, no less) who do not [7]. I don't think the Queen (a tory who does not have to worry about being elected) is amused, either. 

Of course, it's only a matter of time before democracy-as-market-economics [8] implodes. Perhaps we are witnessing that implosion right now. In the meantime, enjoy this picture of a jihadist stroking his cat. No, it's not a dirty limerick -- it's some form of PoMo resistance. Is this the height of absurdity, or Dr. Evil, martyrdom edition? Big money and bad religion, it's all highly-offensive performance art to me.

IV. Lack-of-funding Incredulity

My slouch towards intangible forms of enterprise continues. The Orthogonal Research activity report for the second quarter (Q2) of the calendar year (not financial) is now available. Busy quarter, but still without funding (although parties interested in changing that can contact me).

Is placing a value on research necessary but not sufficient? Here's one humorous take. COURTESY: PhD Comics.

NOTES:

[1] Servick, K.   Kickoff looms for demo of brain-controlled machine. Science News, 344(6188), 1069-1070 (2014).

[2] Paraplegic Man In Mind-Controlled Robotic Suit Kicks Off World Cup 2014. Neurogadget, June 13 (2014) AND Atkins, H.   Human In Robotic Exoskeleton To Kick Off The World Cup. Popular Science, June 6 (2014).

[3] Edwards, J.   Google glass is going to be huge, and its critics are wrong. Business Insider, June 9 (2014).

[4] Center for Research in Economics, Management, and the Arts. Reblogged from The Big Picture blog.

[5] Circle, Edie Brickell and the New Bohemians. YouTube video (1988).

[6] Dear Democrats, please stop spamming me for donations. Weasel Zippers blog, February 28 (2013).

[7] Atrios.   From Bean to Cup, You Fuck Up. Eschaton blog, May 27 (2014) AND Myers, P.Z. Democrats: you suck. Pharyngula blog, May 30 (2014).

[8] Avalon, J. and Keller, M.   The Super PAC Economy. Daily Beast, September 18 (2012) AND Aronsen, G.   Are Super PACs Overhyped? Mother Jones, September 28 (2012).

Increasingly-free Artificial Life and Life-compatible Electronics

Here is yet another opportunity [1] to get A(rtificial) Life. For free. The proceedings of ECAL 2013 (the biennial European Artificial Life conference) is now available from MIT Press.

Now is your chance to learn about the latest advances in adaptive hardware, artificial immune systems, bioinspired robotics/learning, in silico evolution, and much more.....

In semi-related news, check out this video about flexible circuit design (their application is called "imperceptible circuits") from Digitized Information. And in increasingly tangential news, find out more about physically transient electronics [2] that are reabsorbed by the body when no longer needed [3]. 

An electrochemical schematic of a flexible electronic circuitry. Courtesy Figure 1 from [3]. 

NOTES:

[1] The proceedings for the Alife XI, Alife XII, Alife XIII conferences are also available.

[2] A biocompatible and potentially flexible circuitry that could be used for multiple applications in the field of bioelectronics. 

For more information, please see: Hwang et.al A Physically Transient Form of Silicon Electronics.  Science, 337, 1640 (2012).

[3] For more information, listen to this podcast with John Rogers at UIUC. This work is also part of a DARPA initiative in the area of  transparent conducting films. 

Human Augmentation Short Course -- Part III

The next two #human-augmentation flash lectures from my micro-blog, Tumbld Thoughts will feature several potential implementations of Intelligence Augmentation (IA), Augmented Cognition (AugCog), and its integration with smart devices. This includes two topical areas: I (Bio-machine Symbiosis and Allostasis), and II (Augmentation of Touch).

I. Bio-machine Symbiosis and Allostatis

The book "The Symbiotic Man" by Joel DeRosnay can be used to frame a graphical discussion on bio-machine symbiosis (e.g. human-smart home interaction) and the concept of mixed allostatic networks. In this case, the symbiotic relationship is between a biological system and a technical one. While there are fundamentally different dynamics between these two types of systems, the fusion of their interactions are not only possible but essential.

As discussed in previous slides, measurements from a human can be used to provide intelligence to the house (in this case, scheduling and other use information). A mitigation strategy can be used to extract information from the collected data and provides instructions for machine learning.

Measurement of the human can be taken on physiological state (e.g. measurements of brain activity or state monitoring of other organs). This can be done using microelectronics, and the measurements must cross a semi-permeable boundary which is selective with respect to available information. Nevertheless, this network allows us to construct a consensus approximation of the body's homeostatic control mechanisms.

This allows us to construct mixed allostatic networks. A mixed allostatic network includes elements from both the house (e.g. appliances) and the human body (e.g. organs). This has already been done by integrating body area networks and domotic networks.

The key innovation here is to unite the function of both networks under global, allostatic control. When the allostatic load of this network becomes too great, this information can be used to modify the mitigation strategy. This may be done in a manner similar to DeRosnay's Symbionomic Laws of Equilibrium.

II. Applications related to the Augmentation of Touch

In this installment of the #human-augmentation tag, we will discuss an assortment of applications that have the potential to augment the sense of touch and upper body mobility. 

The first technology was recently featured in IEEE Spectrum's startup spotlight. The Italian startup Prensilia [1] is working on a robotic hand called Azzurra. The fully artificial hand mimics human grip by using underactuated movements. Inside the hand, the rotary motion generated by a motor is translated to linear actuation to produce biological (e.g. muscle generated) types of motion.

The second technology features the DARPA initiative to create better prosthetic arms. In this video from IEEE Spectrum, the work of Dean Kamen and his group at DEKA Research is profiled. This type of prosthetic arm uses bioelectric signals from chest muscles in combination with servo motors to enable both fine motor and ballistic movements.

The third technology is simulated touch, which unlike the last two does not explicitly involve artifacts. Touch is a physical phenomenon, as contemplated in this Minute Physics video. However, touch also involves human perception, as discussed previously on Tumbld Thoughts. A thourough understanding of this sense allows us to build better ways to interact with virtual environments and robots using touch [2]. 

COURTESY: Chapter 4 from [2b].

NOTES:

[1] Cipriani, C.   Startup Spotlight: Prensilla developing robot hands for research, prosthetics. IEEE Spectrum, July 18 (2013).

[2] The second image from bottom is a LilyPad Arduino project. For more information on the engineering of touch, please see these two books:

a) McLaughlin, M.L., Hespanha, J.P., and Sukhatme, G.S.   Touch in Virtual Environments: haptics and the design of interactive systems. Prentice-Hall, Upper Saddle River, NJ (2002).

b) Bicchi, A., Buss, M., Ernst, M.O., and Peer, A.   The Sense of Touch and its Rendering. Springer, Berlin (2008).

Human Augmentation Short Course -- Part II

I have been continuing to introduce an area of science and engineering called human augmentation to a broader audience using the "flash lecture" format discussed a few posts back. I have using my micro-blog Tumbld Thoughts as a test site for posting these lectures, and the social networking function of Tumblr (e.g. Tumblr radar) has garnered some sporadic direct interest (in the form of likes and re-posts). 

In this portion of the course (four lectures), we move beyond the basics and towards both more detailed phenomena related to augmentation and practical implementations of the technology.

I. Extending the Phenotype

In previous #human-augmentation posts, I briefly touched on the potential role of augmentation (e.g. wearing a prosthetic limb or see-though, head-mounted display) on physiological regulation. This may leave some readers puzzled, because often times these technologies do not directly interface with the nervous system. Nevertheless, once a technology provides a stand-in (or enhancer) of something the body does, it becomes incorporated into the body's physiology and representation of the world [1].

While technologies from rakes to nests have been found to represent an extended phenotype, an intelligent technology (one that includes an adaptive mitigation strategy) can actually serve to enhance or work in concert with an individual's ability for environmental adaptation [2]. Much like the diet and exercise regimen that helps a person lose weight, this ability exhibits great variation across individuals, which may be explained by pre-existing phenotypic or even genotypic differences.

The extent to which the technology participates in the physiological millieu depends of course on how much the augmentation assists in or takes over function. To understand this better, we can turn to the ergonomics definition of symbiosis, which defines "ergonomy" as the degree of coupling between human and mechanical device [3]. This ranges from tightly-coupled systems (implants that are seamlessly integrated into normal function) to ill-fitting systems (poorly-designed interfaces or computer mice).

II. Instrumented Motorcycle Helmet

Here is an example of performance augmentation in the form of an intelligent, see-through, and heads up display integrated into a motorcycle helmet. Brought to you by a start-up called LiveMap. The information presented in the field of view enables the wearer to improve their navigation ability and improve their riding experience. 

The first article (from Mashable - [4]) highlights the components of the helmet, which includes ambient information from multiple types of sensor (e.g. light sensor, microphone, GPS). This information is then fused and presented in a single location (in this case, the helmet) [5].

II. Wired Science Live Chat on Bionic Augmentation

Last week, I attended a live chat called "Our Cyborg Future", hosted by Wired Science. This was a live chat with two scientists in the field: John Rogers from UIUC and Michael McAlpine from Princeton [6]. These researchers work in a field called "bionics", where biological systems are augmented with electronics or other technology to either restore function or provide new sensory or performance capabilities.

The talk featured a number of visions for the future of bionic technologies and technologies for human augmentation. Fundamentally, the major challenge is to merge the language of electronics (e.g. electrons, phonons, and heat) with the language of biology (e.g. ions, proteins, and enzymes). While John Rogers is working towards electronically-augmented organs [7], Michael McAlpine is working towards using piezoelectric materials to harvest energy from biological motion and print 3-D structures such as tissue scaffolds. 

Three of the most interesting ideas [8] discussed during the talk:

* advances such as flexible [7] and bio-compatible electronics might be used to infuse a biological system with distributed electronics at the cellular and subcellular scale. This could include a range of components from silicon diodes to LEDs.

* the increases in brain-machine interface bandwidth due to flexible, laminated skin-like devices.

* the development of emerging technologies such as stretchable batteries, glucose fuel cells, implantable micro-heaters, and mechanical energy harvesting.

IV. The Role of Attention, Training, and critical Meta-Analysis

In a previous #human-augmentation post, I pointed to one experimental paradigm (environmental switching) that may serve as a natural (e.g. non-computational) filter for eliminating (e.g. mitigating) non-optimal performance due to environmental stresses or other challenges. This case is illustrative for two reasons: 

1) in cases where performance response curves are very complex and cannot be characterized by a simple mathematical function (e.g. a "U" shaped curve), a mitigation strategy involving physical chaos (rather than computational control) or other environmental manipulations may be more effective. In the first image (top), the potential dynamic effects of perturbation on attentional shifts during an episode of "Star Trek" is used as an example.

2) fully understanding the effects of mitigation may require more systematic experimental evaluation. One example of this involves the claim that long-term expertise with action video games improves cognitive abilities [9]. A meta-analysis of such studies [10] questions this assumption on several grounds, particularly with respect to the magnitude of improvement (e.g. effect size).

In this case of action video game expertise, two types of effect have been reported [10, 11]. The first involves relative expertise based on cross-sectional comparisons, which evaluate differences between gamers and non-gamers. The second involves acquired expertise (training in action video game play) as having numerous cognitive benefits.

The second type of effect is partially due to an effect called transfer of training (see image, lower left), in which skills acquired in one context can be transferred to another context. This effect also plays a role in human augmentation, and may exhibit a large degree of individual variation. However, there are three caveats raised in [10] that must be kept in mind not only for future action video game studies, but human augmentation studies as well:

* in studies that evaluate the effects of training, an adequate baseline for untrained performance must be used. 

* results should be generalizable to different settings and population (e.g. exhibit a high degree of experimental reproducibility).

* while there may be several improvements to performance/cognition attributable to prior training or experience with the activity in question, there may be many more outcomes that are unaffected by the treatment (action video games) or mitigation (human augmentation). 

NOTES:

[1] A few examples of this extension of the phenotype includes examples from humans (i), social insects (ii, iii), and animals (iv):

(i) Maravita, A. and Iriki, A.   Tools for the body (schema). Trends in Cognitive Science, 8(2), 79-86 (2004).

(ii) Turner, J.S.   The Extended Organism: The Physiology of Animal-Built Structures. Harvard University Press, Cambridge, MA (2002).

(iii) Turner, J.S.   Extended Phenotypes and Extended Organisms. Biology and Philosophy, 19, 327–352 (2004).

(iv) Schaedelin, F.C. and Taborsky, M.   Extended phenotypes as signals. Biological Reviews of the Cambridge Philosophical Society, 84(2), 293-313 (2009). 

[2] This ability, or adaptability, can be characterized using a parametric landscape as shown in a previous post.

[3] Licklider, J.C.R.   Man-Computer Symbiosis. IRE Transactions on Human Factors in Electronics, HFE-1, 4-11 (1960).

[4] Murphy, S.   A Motorcyclist's Dream: Google Glass in helmet form. Mashable, June 17 (2013).

[5] Mike E. New motorcycle helmet with augmented reality and navigation technology built in. VR-Zone, June 17 (2013).

[6] A transcript of the talk can be found here. Also see the McAlpine Research YouTube channel.

[7] For more on flexible robotics, please see this: Zheng, Y., He, Z., Gao, Y., and Liu, J.   Direct Desktop Printed-Circuits-on-Paper Flexible Electronics. Scientific Reports, 3, 1786 (2013).

[8] For more interesting ideas related to cyborgs and bio-inspired robotics, see these:

Rowe, A.   Top 10 Cyborg Videos. Wired Science, November 15 (2009)

When Animals Learn to Control Robots, You Know We’re in Trouble. Wired Science, March 21 (2013).

[9] Green, C. and Bavelier, D.   Learning, Attentional Control, and Action Video Games. Current Biology, 22(6), R197-R206.

[10] Boot, W.R., Blakley, D.P., Simons, D.J.   Do action video games improve perception and cognition? Frontiers in Psychology, 2, 226 (2011).

[11] Simons, D.   Think video games make you smarter? Not so fast..... Daniel Simons blog, December 30 (2012).