“Preparing for the Possibility of a North Korean Collapse”, Bennett 2013 (I didn’t know many of those details about how the East German collapse was able to go so smoothly, or that Kim Jong-Il had intimidated his subordinates during the ’90s famines with footage of impoverished East German elites.)
“Assessing Human Error Against a Benchmark of Perfection”, Anderson et al 2016 (Difficulty of a chess endgame position predicts mistakes far better than time constraints or chess ability. Not necessarily surprising—as chess AIs demonstrate, humans only span a fraction of the possible range of objective chess playing ability, so individual human differences in ability won’t matter much.)
The beach is beautiful; and there grow
The sea-tangles swaying,
Lapped by a thousand waves
In the calm of morning,
And by five hundred waves
In the evening calm.
O Suminoe Beach,
Where white-crested waves are racing around!
Could I weary of watching, not only now,
But day in, day out, over and over again,
As those waves break on the shore?
Let me go, with my clothes stained
For remembrance with the yellow clay
Of Suminoe’s shore, which white-crested waves
Visit, ceaselessly lapping!
Zero Escape 3—Zero Time Dilemma (video game with positive review on LW and ANN I instead watched a YouTube 100% walkthrough of, skipping the room-escape puzzles. I watched the first few such puzzles but found them rather tedious-looking, so that’s definitely a reason to prefer watching Zero Time Dilemma to playing it. This way, ZTD can be considered an ultra-low-budget anime done using 3D CGI lasting perhaps 10 hours. The CGI itself is… not great, by any means, but one understands what’s going on, and it’s not quite as tedious as reading a visual novel like Umineko even if Umineko had much better 2D artwork. That leaves the story itself, which is ambitious SF, trying to work together time travel, parallel universes & shifting, the anthropic principle, the Prisoner’s Dilemma, the Sleeping Beauty problem, and amnesia drugs, in the framework of people trapped in a bomb shelter by a psychopathic mastermind. The ‘decisions’ made in each game provide a garden of forking paths the player navigates between to explore the consequences of particular choices, trying to navigate to a good end, where good is relative to the consequences of other possible universes. Eventually the characters themselves start understanding the situation and start shifting as well. Most choices end in death, so the exponential increase doesn’t get out of hand. Some of the plot twists are dramatic and surprised me—for example, the architecture twist surprised me because while I had wondered how they could all have access to the same exit elevator if they were sealed off, I never put the remaining pieces together. Probably I would’ve enjoyed it more if I had watched the previous games to get the backstory, but it was still a fun SF series. That said, I felt some of the story was half-baked and it did not work as well as Steins;gate: the characters do disappointingly little to work around the amnesia despite ample opportunity; I was surprised by the ending because although I had guessed Zero’s motive long before, at the anthropic principle/dice game, some of the events involving x-codes had seemed to specifically disconfirm it and the ultimate product seems kind of trivial compared to Zero’s efforts to obtain it; the availability of both sliding and a space-time teleporter felt inelegant and the possibilities underused; the revelation of who Zero is was a complete asspull which—shades of Umineko—relies on a ‘treachery of images’ trick which simply doesn’t work for both narrative & animation reasons, and worse, was unnecessary; and the narrative pacing is weak as the first part of the game spends what feels like an eternity on the repetitive starting Prisoner’s dilemma game and then rushes through the rest.)
This page is a changelog for Gwern.net: a monthly reverse chronological list of recent major writings/changes/additions.
Following my writing can be a little difficult because it is often so incremental. So every month, in addition to my regular /r/Gwern subreddit submissions, I write up reasonably-interesting changes and send it out to the mailing list in addition to a compilation of links & reviews (archives).
A subreddit for posting links of interest and also for announcing updates to gwern.net (which can be used as a RSS feed). Submissions are categorized similar to the monthly newsletter and typically will be collated there.
Computational complexity theory describes the steep increase in computing power required for many algorithms to solve larger problems; frequently, the increase is large enough to render problems a few times larger totally intractable. Many of these algorithms are used in AI-relevant contexts. It has been argued that this implies that AIs will fundamentally be limited in accomplishing real-world tasks better than humans because they will run into the same computational complexity limit as humans, and so the consequences of developing AI will be small, as it is impossible for there to be any large fast global changes due to human or superhuman-level AIs. I examine the assumptions of this argument and find it neglects the many conditions under which computational complexity theorems are valid and so the argument doesn’t work: problems can be solved more efficiently than complexity classes would imply, large differences in problem solubility between humans and AIs is possible, greater resource consumption is possible, the real-world consequences of small differences on individual tasks can be large on agent impacts, such consequences can compound, and many agents can be created; any of these independent objections being true destroys the argument.
The classical twin study has been a powerful heuristic in biomedical, psychiatric and behavioural research for decades. Twin registries worldwide have collected biological material and longitudinal phenotypic data on tens of thousands of twins, providing a valuable resource for studying complex phenotypes and their underlying biology. In this Review, we consider the continuing value of twin studies in the current era of molecular genetic studies. We conclude that classical twin methods combined with novel technologies represent a powerful approach towards identifying and understanding the molecular pathways that underlie complex traits.
Heritability is essential for understanding the biological causes of disease, but requires laborious patient recruitment and phenotype ascertainment. Electronic health records (EHR) passively capture a wide range of clinically relevant data and provide a novel resource for studying the heritability of traits that are not typically accessible. EHRs contain next-of-kin information collected via patient emergency contact forms, but until now, these data have gone unused in research. We mined emergency contact data at three academic medical centers and identified millions of familial relationships while maintaining patient privacy. Identified relationships were consistent with genetically-derived relatedness. We used EHR data to compute heritability estimates for 500 disease phenotypes. Overall, estimates were consistent with literature and between sites. Inconsistencies were indicative of limitations and opportunities unique to EHR research. These analyses provide a novel validation of the use of EHRs for genetics and disease research.
One Sentence Summary
We demonstrate that next-of-kin information can be used to identify familial relationships in the EHR, providing unique opportunities for precision medicine studies.
It is a long standing question as to which genes define the characteristic facial features among different ethnic groups. In this study, we use Uyghurs, an ancient admixed population to query the genetic bases why Europeans and Han Chinese look different. Facial traits were analyzed based on high-dense 3D facial images; numerous biometric spaces were examined for divergent facial features between European and Han Chinese, ranging from inter-landmark distances to dense shape geometrics. Genome-wide association analyses were conducted on a discovery panel of Uyghurs. Six significant loci were identified four of which, rs1868752, rs118078182, rs60159418 at or near UBASH3B, COL23A1, PCDH7 and rs17868256 were replicated in independent cohorts of Uyghurs or Southern Han Chinese. A quantitative model was developed to predict 3D faces based on 277 top GWAS SNPs. In hypothetic forensic scenarios, this model was found to significantly enhance the verification rate, suggesting a practical potential of related research.
The Cagots were a persecuted minority found in the west of France and northern Spain: the Navarrese Pyrenees, Basque provinces, Béarn, Aragón, Gascony and Brittany. Their name differed by province and the local language: Cagots, Gézitains, Gahets, and Gafets in Gascony; Agotes, Argotes, Agotak and Gafos in Basque country; Capots in Anjou and Languedoc; and Cacons, Cahets, Caqueux, and Caquins in Brittany. Evidence of the group exists back as far as AD 1000.
An increasing number of domains are providing us with detailed trace data on human decisions in settings where we can evaluate the quality of these decisions via an algorithm. Motivated by this development, an emerging line of work has begun to consider whether we can characterize and predict the kinds of decisions where people are likely to make errors.
To investigate what a general framework for human error prediction might look like, we focus on a model system with a rich history in the behavioral sciences: the decisions made by chess players as they select moves in a game. We carry out our analysis at a large scale, employing datasets with several million recorded games, and using chess tablebases to acquire a form of ground truth for a subset of chess positions that have been completely solved by computers but remain challenging even for the best players in the world.
We organize our analysis around three categories of features that we argue are present in most settings where the analysis of human error is applicable: the skill of the decision-maker, the time available to make the decision, and the inherent difficulty of the decision. We identify rich structure in all three of these categories of features, and find strong evidence that in our domain, features describing the inherent difficulty of an instance are significantly more powerful than features based on skill or time.
Scholarly peer review is the process of subjecting an author's scholarly work, research, or ideas to the scrutiny of others who are experts in the same field, before a paper describing this work is published in a journal, conference proceedings or as a book. The peer review helps the publisher decide whether the work should be accepted, considered acceptable with revisions, or rejected.
Portia may be about the size of a fat raisin, with eyes no larger than sesame seeds, yet it has a visual acuity that beats a cat or a pigeon. The human eye is better, but only about five times better. So from a safe distance a foot or two away, Portia sits scanning Scytodes, looking to see if it is carrying an egg sac in its fangs… The retinas of its principle eyes have only about a thousand receptors compared to the 200 million or so of the human eyeball. But Portia can swivel these tiny eyes across the scene in systematic fashion, patiently building up an image point by point. Having rejected a few alternatives routes, Portia makes up its mind and disappears from sight. A couple of hours later, the silent assassin is back, dropping straight down on Scytodes from a convenient rock overhang on a silk dragline—looking like something out of the movie, Mission Impossible. Once again, Portia’s guile wins the day.
…Undoubtedly many of Portia’s cognitive abilities are genetic. Laboratory tests carried out by Robert Jackson, chief of Canterbury’s spider unit, have shown that only Portia from the particular area where Scytodes is common can recognise the difference between an egg sac carrying and non-egg sac carrying specimen. And it is a visual skill they are born with. The same species of Portia trapped a few hundred miles away doesn’t show any evidence of seeing the egg sac. But as Jackson points out, this just deepens the mystery. First there is the fact that such a specific mental behaviour as looking for an egg sac could be wired into a spider’s genome. And then there is the realisation that this is a population-specific, not species-specific, trait! It is a bit of locally acquired genetic knowledge. How does any simple hardwiring story account for that?
… “The White Tail can pluck, but only in a programmed, stereotyped, way. It doesn’t bother with tactics, or experimenting, or looking to see which way the other spider is facing. It just charges in and overpowers its prey with its size. Portia is a really weedy little spider and has to spend ages planning a careful attack. But its eyesight and trial and error approach means it can tackle any sort of web spider it comes across, even ones it has never met before in the history of its species,” says Harland. While Portia’s deception skills are impressive, the real admiration is reserved for its ability to plot a path to its victim. For an instinctive animal, out of sight is supposed to be out of mind. But Portia can take several hours to get into the right spot, even if it means losing sight of its prey for long periods.
…As a maze to be worked out from a single viewing—and with no previous experience of such mazes—this would be a tall order even for a rat or monkey. Yet more often than not, Portia could identify the right path. There was nothing quick about it. Portia would sit on top of the dowel for up to an hour, twisting to and fro as it appeared to track its eyes across the various possible routes. Sometimes it couldn’t decide and would just give up. However, once it had a plan, it would clamber down and pick the correct wire, even if this meant at first heading back behind where it had been perched. And walking right past the other wire. Harland says it seems that Portia can see where it has to get to in order to start its journey and ignore distractions along the way. This impression was strengthened by the fact that on trials where Portia made a wrong choice, it often gave up on reaching the first high bend of the wire—even though the bait was not yet in sight. It was as if Portia knew where it should be in the apparatus and could tell straight away when it had made a dumb mistake.
Crazy talk, obviously. There just ain’t room in Portia’s tiny head for anything approaching a plan, an expectation, or any other kind of inner life. The human brain has some 100 billion neurons, or brain cells, and even a mouse has around 70 million. Harland says no one has done a precise count on Portia but it is reckoned to have about 600,000 neurons, putting it midway between the quarter million of a housefly and the one million of a honey bee. Yet in the lab over the past few years, Portia has kept on surprising.
…Rather controversially, Li calls this the forming of a search image. Yet even if this mental priming is reduced to some thoroughly robotic explanation, such as an enhanced sensitivity of certain prey-recognising circuits and a matching damping of others, it still says that there is a general shift in the running state of Portia’s nervous system. Portia is responding in a globally cohesive fashion and is not just a loose bundle of automatic routines.
…Harland says Portia’s eyesight is the place to start. Jumping spiders already have excellent vision and Portia’s is ten times as good, making it sharper than most mammals. However being so small, there is a trade-off in that Portia can only focus its eyes on a tiny spot. It has to build up a picture of the world by scanning almost pixel by pixel across the visual scene. Whatever Portia ends up seeing, the information is accumulated slowly, as if peering through a keyhole, over many minutes. So there might be something a little like visual experience, but nothing like a full and “all at once” experience of a visual field. Harland feels that the serial nature of this scanning vision also makes it easier to imagine how prey recognition and other such decision processes could be controlled by some quite stereotyped genetic programs. When Portia is looking for an egg sac obscuring the face of Scytodes, it wouldn’t need to be representing the scene as a visual whole. Instead it could be checking a template, ticking off critical features in a sequence of fixations. In such a case, the less the eye sees with each fixation, perhaps the better. The human brain has to cope with a flood of information. Much of the work lies in discovering what to ignore about any moment. So the laser-like focus of Portia’s eyes might do much of this filtering by default. Yet while much of Portia’s mental abilities may reduce to the way its carefully designed eyes are coupled to largely reflexive motor patterns, Harland says there is still a disconcerting plasticity in its gene-encoded knowledge of the world. If one population of Portia can recognise an egg-carrying Scytodes but specimens from another region can’t, then this seems something quite new—a level of learning somewhere in-between the brain of an individual and the genome of a species… As Harland says, Portia just doesn’t fit anyone’s theories right at the moment.
Conventional reviews of research on the efficacy of psychological, educational, and behavioral treatments often find considerable variation in outcome among studies and, as a consequence, fail to reach firm conclusions about the overall effectiveness of the interventions in question. In contrast, meta-analysis reviews show a strong, dramatic pattern of positive overall effects that cannot readily be explained as artifacts of meta-analytic technique or generalized placebo effects. Moreover, the effects are not so small that they can be dismissed as lacking practical or clinical significance. Although meta-analysis has limitations, there are good reasons to believe that its results are more credible than those of conventional reviews and to conclude that well-developed psychological, educational, and behavioral treatment is generally efficacious.
Have a nice day is a commonly spoken expression used to conclude a conversation, or end a message by hoping the person to whom it is addressed experiences a pleasant day. Since it is often uttered by service employees to customers at the end of a transaction, particularly in Israel and the United States, its repetitious and dutiful usage has resulted in the phrase developing, according to some journalists and scholars, especially outside of these two countries, a cultural connotation of impersonality, lack of interest, passive–aggressive behavior, or sarcasm. The phrase is generally not used in Europe, as some find it artificial or even offensive. Critics of the phrase characterize it as an imperative, obliging the person to have a nice day. Other critics argue that it is a parting platitude that comes across as pretended. While defenders of the phrase agree that "Have a nice day" can be used insincerely, they consider the phrase to be comforting, in that it improves interactions among people. Others favor the phrase because it does not require a response.
William Harry McRaven is a retired United States Navy four-star admiral who last served as the ninth commander of the United States Special Operations Command from August 8, 2011, to August 28, 2014. From 2015 to 2018, he was the chancellor of The University of Texas System.
Average Is Over: Powering America Beyond the Age of the Great Stagnation is a 2013 book by economist Tyler Cowen laying out his vision for the future trajectory of the global economy. It is a sequel to Cowen's 2011 pamphlet The Great Stagnation, which argued that America had exhausted many of the low-hanging fruit that had powered its growth in the 19th and early 20th century.
The Pillow Book is a book of observations and musings recorded by Sei Shōnagon during her time as court lady to Empress Consort Teishi during the 990s and early 1000s in Heian Japan. The book was completed in the year 1002.
The Man'yōshū is the oldest extant collection of Japanese waka, compiled sometime after AD 759 during the Nara period. The anthology is one of the most revered of Japan's poetic compilations. The compiler, or the last in a series of compilers, is today widely believed to be Ōtomo no Yakamochi, although numerous other theories have been proposed. The chronologically last datable poem in the collection is from AD 759 (No. 4516). It contains many poems from much earlier, the bulk of the collection represents the period between AD 600 and 759. The precise significance of the title is not known with certainty.
Zero Time Dilemma is an adventure video game developed by Chime. It was released for Nintendo 3DS and PlayStation Vita in June 2016, by Spike Chunsoft in Japan and Aksys Games in North America and Europe. A Microsoft Windows version was released worldwide by Spike Chunsoft in June 2016. A PlayStation 4 version was also released in North America and Japan in August 2017, and in Europe in September 2017. The game is the third entry in the Zero Escape series, following Nine Hours, Nine Persons, Nine Doors (2009) and Virtue's Last Reward (2012).
Escape the room, also known as room escape or escape game, is a subgenre of point-and-click adventure game which requires a player to escape from imprisonment by exploiting their surroundings. The room usually consists of a locked door, objects to manipulate, and hidden clues or secret compartments. The player must use the objects to interact with other items in the room to reveal a way to escape. Escape the room games were born out of freeware browser games created in Adobe Flash, but have since become most popular as mobile games for iOS, and Android. Some examples include Crimson Room, Viridian Room, MOTAS, and Droom. The popularity of these online games has led to the development of real-life escape rooms all around the world.
Up is a 2009 American computer animated comedy-drama adventure film produced by Pixar Animation Studios and released by Walt Disney Pictures. The film centers on an elderly widower named Carl Fredricksen and an earnest boy named Russell ; by tying thousands of balloons to his house, Carl sets out to fulfill his dream to see the wilds of South America and complete a promise made to his late wife, Ellie. The film was directed by Pete Docter and co-directed by Bob Peterson, who also wrote the film's screenplay with Docter, as well as the story with Tom McCarthy. The music was composed by Michael Giacchino, who had also composed music for The Incredibles and Ratatouille.
Yurikuma Arashi is a Japanese yuri anime television series produced by Silver Link and directed by Kunihiko Ikuhara. The series was first announced via a website in August 2012, where it was referred to as the "Kunihiko Ikuhara/Penguinbear Project." The series first aired in Japan between January 5, 2015 and March 30, 2015 and is licensed in North America by Funimation. A manga adaptation illustrated by Akiko Morishima was serialized in Gentosha's Comic Birz magazine between February 2014 and April 2016 and has been licensed in English by Tokyopop under the title Yuri Bear Storm. The name appears to be a reference to Akira Yoshimura's novelization of the Sankebetsu brown bear incident, The Bear Storm, though any more concrete link besides the presence of human-attacking bears is only speculated.
Subscription page for the monthly gwern.net newsletter. There are monthly updates, which will include summaries of projects I’ve worked on that month (the same as the changelog), collations of links or discussions from my subreddit, and book/movie reviews. You can also browse the archives since December 2013.
Newsletter tag: archive of all issues back to 2013 for the gwern.net newsletter (monthly updates, which will include summaries of projects I’ve worked on that month (the same as the changelog), collations of links or discussions from my subreddit, and book/movie reviews.)
Portia is a genus of jumping spider that feeds on other spiders. They are remarkable for their intelligent hunting behaviour, which suggests that they are capable of learning and problem solving, traits normally attributed to much larger animals.
Portia is a behaviourally complex and aberrant salticid genus. The genus is of unusual importance because it is morphologically primitive. Five species were studied in nature (Australia, Kenya, Malaysia, Sri Lanka) and in the laboratory in an effort to clarify the origins of the salticids and of their unique, complex eyes. All the species of Portia studied were both web builders and cursorial.
Portia was also an araneophagic web invader, and it was a highly effective predator on diverse types of alien webs. Portia was an aggressive mimic, using a complex repertoire of vibratory behaviour to deceive the host spiders on which it fed. The venom of Portia was unusually potent to other spiders; its easily autotomised legs may have helped Portia escape if attacked by its frequently dangerous prey. Portia was also kleptoparasitic and oophagic when occupying alien webs. P. fimbriata from Queensland, where cursorial salticids were superabundant, used a unique manner of stalking and capturing other salticids.
The display repertoires used during intraspecific interactions were complex and varied between species. Both visual (typical of other salticids) and vibratory (typical of other web spiders) displays were used. Portia copulated both on and away from webs and frequently with the female hanging from a dragline. Males cohabited with subadult females on webs, mating after the female matured. Adult and subadult females sometimes used specialised predatory attacks against courting or mating males. Sperm induction in Portia was similar to that in other cursorial spiders.
Portia mimicked detritus in shape and colour, and its slow, mechanical locomotion preserved concealment. Portia occasionally used a special defensive behaviour (wild leaping) if disturbed by a potential predator. Two types of webs were spun by all species (Type 1, small resting platforms; Type 2, large prey-capture webs). Two types of egg sacs were made, both of which were highly aberrant for a salticid. Responses of different species and both sexes of Portia were quantitatively compared for different types of prey.
Many of the trends in behaviour within the genus, including quantitative differences in predatory behaviour, seemed to be related to differences in the effectiveness of the cryptic morphology of Portia in concealing the spider in its natural habitat (‘effective crypsis’).
The results of the study supported, in general, Jackson & Blest’s (1982a) hypothesis of salticid evolution which, in part, proposes that salticid ancestors were web builders with poorly developed vision and that acute vision evolved in conjunction with the ancestral spiders becoming proficient as araneophagic invaders of diverse types of webs.
The influence of prey movement on the performance of simple detours by salticids was investigated. Seven species were studied. Two subject species, Portia fimbriata and Portia labiata, are specialized web-invading species that eat other spiders. The other five species investigated (Euryattus sp., Euophrys parvula, Marpissa marina, Trite auricoma and Trite planiceps) are more typical cursorial hunters of insects. We provide evidence that:
salticids will initiate detours toward motionless prey;
salticids are more inclined to initiate detours toward moving than toward motionless prey;
salticids tend to complete detours even when prey that had been moving at the start remains stationary during the detour;
prey movement makes the salticid more likely to stalk and attack when prey is only a few centimetres away and in a position from which it can be reached by a straight-line pursuit;
Portia is more inclined than the other salticids to initiate detours to motionless prey, then to stalk and attack motionless prey when close, than the other salticids are.
Mechanisms that might account for Portia being different from the other salticids are discussed.
Portia is a jumping spider that invades other spiders’ webs, makes vibratory signals that deceive the resident spider (aggressive mimicry), then attacks and eats the spider. Portia exploits a wide range of prey-spider species.
Evidence is provided from observation and experimentation that Portia uses a trial-and-error method as part of its strategy for deriving appropriate signals for different prey. To use this method, Portia first broadcasts an array of different signals, then narrows to particular signals as a consequence of feedback from the prey spider. Feedback can be web vibration or seeing spiders move, or both.
This appears to be an example of deception involving at least a limited form of learning, an uncommon phenomenon in invertebrates.
The terms “reversed-route detours” and “forward-route detours” are introduced to distinguish between detours that require moving away from a goal and those that do not. We provide the first evidence under controlled laboratory conditions that salticids can perform reversed-route detours.
Two species were tested: 1. Portia fimbriata, a web-invading salticid from Queensland, Australia, that normally preys on web-building spiders; 2. Trite planiceps, an insectivorous cursorial salticid from New Zealand.
Although both of these species completed reversed-route detours, Trite planiceps was much more dependent on prey movement than Portia fimbriata. Interspecific differences appear to be related to the different predatory styles of these two salticids.
Portia is a web-invading araneophagic spider that uses aggressive mimicry to deceive its prey. The present paper is a first step toward clarifying experimentally the cues that govern Portia’s decisions of whether to enter a web, whether to make signals once in a web, and whether to persist at signalling once started.
The following conclusions are supported: cues from seeing a web elicit web entry, but volatile chemical cues from webs of prey spiders are not important; seeing a spider in a web increases Portia’s inclination to enter the web; after web entry, cues from webs of prey spiders are sufficient to elicit signalling behaviour, even in the absence of other cues coming directly from the prey spider; seeing a prey spider or detecting vibrations on the web make Portia more prone to signal, but volatile chemical cues from prey spiders are not important; once Portia is on a web and signalling, seeing a moving spider and detecting vibrations on the web encourage Portia to persist in signalling; on the basis of visual cues alone, Portia can distinguish between quiescent spiders, insects and eggsacs.
The stalking behaviour of four species of jumping spiders, Portia fimbriata, P. labiata, P. schultzi and P. africana, was examined to determine whether Portia opportunistically exploits situations in which the prey spider is distracted by environmental disturbances.
Disturbances were created mainly by wind blowing on webs and a magnet shaking webs. All four Portia species moved significantly further during disturbance than during non-disturbance, a behaviour labeled ‘opportunistic smokescreen behaviour’. Portia can discriminate between spiders and other prey such as live insects, wrapped-up insects in the web, and egg sacs, because_Portia_ used opportunistic smokescreen behaviour only against spiders and not against these other types of prey. If the location of disturbances and the location of prey differ, Portia can accurately discriminate between them. Portia’s smokescreen behaviour apparently is a true predatory tactic because Portia attacked prey more often during disturbances than at other times.
Smokescreen behaviour appears to work in part because the disturbances that Portia uses for smokescreens interfere with the prey’s ability to sense_Portia_’s stalking movements.
Salticids, the largest family of spiders, have unique eyes, acute vision, and elaborate vision-mediated predatory behavior, which is more pronounced than in any other spider group. Diverse predatory strategies have evolved, including araneophagy, aggressive mimicry, myrmicophagy, and prey-specific prey-catching behavior. Salticids are also distinctive for development of behavioral flexibility, including conditional predatory strategies, the use of trial-and-error to solve predatory problems, and the undertaking of detours to reach prey. Predatory behavior of araneophagic salticids has undergone local adaptation to local prey, and there is evidence of predator-prey coevolution. Trade-offs between mating and predatory strategies appear to be important in ant-mimicking and araneophagic species. [Keywords: salticids, salticid eyes, Portia, predatory versatility, aggressive mimicry]
In a laboratory study, 12 different experimental set-ups were used to examine the ability of Portia fimbriata, a web-invading araneophagic jumping spider from Queensland, Australia, to choose between two detour paths, only one of which led to a lure (a dead, dried spider). Regardless of set-up, the spider could see the lure when on the starting platform of the apparatus, but not after leaving the starting platform. The spider consistently chose the ‘correct route’ (the route that led to the lure) more often than the ‘wrong route’ (the route that did not lead to the lure). In these tests, the spider was able to make detours that required walking about 180° away from the lure and walking past where the incorrect route began. There was also a pronounced relationship between time of day when tests were carried out and the spider’s tendency to choose a route. Furthermore, those spiders that chose the wrong route abandoned the detour more frequently than those that chose the correct route, despite both groups being unable to see the lure when the decision was made to abandon the detour.
This chapter illustrates the cognitive abilities of araneophagic jumping spiders. “Portia”, a genus of araneophagic jumping spiders (family Salticidae), appears to have the most versatile and flexible predatory strategy known for an arthropod. A dominant feature of Portia’s predatory strategy is aggressive mimicry, a system in which the predator communicates deceitfully with its prey. Typical salticids do not build webs. Instead, they are hunters that catch their prey in stalk-and-leap sequences guided by vision. Salticids differ from all other spiders by having large anteromedial eyes and acute vision. However, the behavior of Portia is anything but typical for a salticid. Besides hunting its prey cursorily, Portia also builds a prey-catching web. The typical prey of a salticid is insects, but Portia’s preferred prey is other spiders. Portia frequently hunts web-building spiders from other families by invading their webs and deceiving them with aggressive-mimicry signals. While in the other spider’s web, it makes aggressive-mimicry signals by moving legs, palps, abdomen, or some combination of these to make web-borne vibrations. Portia’s typical victim, a web-building spider but not a salticid, typically lacks acute vision and instead perceives the world it lives in by interpreting tension and vibration patterns in its web.
Table of Contents: Introduction · Spiders that eat other spiders · Predator-prey interactions between Portia fimbriata and Euryattus sp. · Detecting Portia’s footsteps · Smokescreen tactics · Flexibly adjusting signals to prey behavior · Making detours and planning ahead · Cognitive levels · Levels of deception · Design options for animal brains
Jumping spiders Portia labiata were tested in the laboratory on three different kinds of detours. In one, both routes led to the lure. In the other variants, one of the routes had a gap, making that route impassable. When tested with only one complete route, Portia chose this route after visually inspecting both routes. An analysis of scanning showed that, at the beginning of the scanning routine, the spiders scanned both the complete and the incomplete route but that, by the end of the scanning routine, they predominantly scanned only the complete route. Two rules seemed to govern their scanning: (1) they would continue turning in one direction when scanning away from the lure along horizontal features of the detour route; and (2) when the end of the horizontal feature being scanned was reached, they would change direction and turn back towards the lure. These rules ‘channeled’ the spiders’ scanning on to the complete route, and they then overwhelmingly chose to head towards the route they had fixated most while scanning.
Portia fimbriata is a web-invading araneophagic jumping spider (Salticidae). The use of signal-generating behaviours is characteristic of how P. fimbriata captures its prey, with three basic categories of signal-generating behaviours being prevalent when the prey spider is in an orb web. The predatory behaviour of P. fimbriata has been referred to as “aggressive mimicry”, but no previous studies have provided details concerning the characteristics of P. fimbriata’s signals.
We attempt to determine the model signals for P. fimbriata’s ‘aggressive mimicry’ signals. Using laser Doppler vibrometer and the orb webs of Zygiella x-notata and Zosis geniculatus, P. fimbriata’s signals are compared with signals from other sources. Each of P. fimbriata’s three categories of behaviour makes a signal that resembles one of three signals from other sources: prey of the web spider (insects) ensnared in the capture zone of the web, prey making faint contact with the periphery of the web and large-scale disturbance of the web (jarring the spider’s cage).
Experimental evidence from testing P. fimbriata with two sizes of lure made from Zosis (dead, mounted in a lifelike posture in standard-size orb web) clarifies P. fimbriata’s signal-use strategy:
when the resident spider is small, begin by simulating signals from an insect ensnared in the capture zone (attempt to lure in the resident spider);
when the resident spider is large, start by simulating signals from an insect brushing against the periphery of the web (keep the resident spider out in the web, but avoid provoking from it a full-scale predatory attack);
when walking in the resident spider’s web, regardless of the resident spider’s size, step toward the spider while making a signal that simulates a large-scale disturbance of the web (mask footsteps with a self-made vibratory smokescreen).
Portia fimbriata from Queensland, Australia, is an araneophagic jumping spider (Salticidae) that includes in its predatory strategy a tactic (cryptic stalking) enabling it to prey effectively on a wide range of salticids from other genera.
Optical cues used by P. fimbriata to identify the salticid species on which it most commonly preys, Jacksonoides queenslandicus, were investigated experimentally in the laboratory using odorless lures made from dead prey on which various combinations of features were altered. P. fimbriata adopted cryptic stalking only against intact salticid lures and modified lures on which the large anterior-median eyes were visible. Ordinary stalking was usually adopted when the lure did not have the anterior-median eyes visible. There was no evidence that cues from the legs of prey salticids influence the choice of stalking style of P. fimbriata, but cues from the legs do appear to influence strongly whether a prey is stalked at all. Cues from the cephalothorax and abdomen also influenced the stalking tendency, but to a lesser degree than cues from the legs.
An algorithm to describe the perceptual processes of P. fimbriata when visually discriminating between salticid and non-salticid prey is discussed.
Recent research on the eyes and vision-guided behaviour of jumping spiders (Salticidae) is reviewed. Special attention is given to Portia Karsch. The species in this African, Asian and Australian genus have especially complex predatory strategies. Portia’s preferred prey are other spiders, which are captured through behavioural sequences based on making aggressive-mimicry web signals, problem solving and planning. Recent research has used Portia to study cognitive attributes more often associated with large predatory mammals such as lions and rarely considered in studies on spiders. In salticids, complex behaviour and high-spatial-acuity vision are tightly interrelated. Salticid eyes are unique and complex. How salticid eyes function is reviewed. Size constraints are discussed.
Portia fimbriata, an araneophagic jumping spider (Salticidae), makes undirected leaps (erratic leaping with no particular target being evident) in the presence of chemical cues from Jacksonoides queenslandicus, another salticid and a common prey of P. fimbriata. Whether undirected leaping by P. fimbriata functions as hunting by speculation is investigated experimentally.
Our first hypothesis, that undirected leaps provoke movement by J. queenslandicus, was investigated using living P. fimbriata and three types of lures made from dead, dry arthropods (P. fimbriata, J. queenslandicus, and Musca domestica). When a living P. fimbriata made undirected leaps or a spring-driven device made the lures suddenly move up and down, simulating undirected leaping, J. queenslandicus responded by waving its palps and starting to walk. There was no statistical evidence that the species from which the lure was made influenced J. queenslandicus’ response in these tests.
Our second hypothesis, that J. queenslandicus reveals its location to P. fimbriata by moving, was investigated by recording P. fimbriata’s reaction to J. queenslandicus when J. queenslandicus reacted to lures simulating undirected leaping. In these tests, P. fimbriata responded by turning toward J. queenslandicus and waving its palps.
Portia is a genus of web-invading araneophagic jumping spiders known from earlier studies to derive aggressive-mimicry signals by using a generate-and-test algorithm (trial-and-error tactic). Here P. fimbriata’s use of trial-and-error to solve a confinement problem (how to escape from an island surrounded by water) is investigated. Spiders choose between two potential escape tactics (leap or swim), one of which will fail (bring spider no closer to edge of tray) and the other of which will partially succeed (bring spider closer to edge of tray). The particular choice that will partially succeed is unknown to the spider. Using trial-and-error, P. fimbriata solves the confinement problem both when correct choices are rewarded (i.e. when the spider is moved closer to edge of tray) and when incorrect choices are punished (i.e. when the spider gets no closer to edge of tray).
Three species of Portia (Portia africana from Kenya, Portia fimbriata from Australia and Portia labiata from the Philippines) were tested with flies Drosophila immigrans and Musca domestica and with web-building spiders Badumna longinquus and Pholcus phalangioides. Badumna longinquus has powerful chelicerae, but not especially long legs, whereas Ph. phalangioides has exceptionally long legs, but only small, weak chelicerae. Typically, Portia sighted flies, walked directly towards them and attacked without adjusting orientation. However, Portia‘s attacks on the spiders were aimed primarily at the cephalothorax instead of the legs or abdomen. Portia usually targeted the posterior-dorsal region of B. longinquus’ cephalothorax by attacking this species from above and behind. When the prey was Ph. phalangioides, attack orientation was defined primarily by opportunistic gaps between this species’ long legs (gaps through which Portia could contact the pholcid’s body without contacting one of the pholcid’s legs). Portia’s attack strategy appears to be an adjustment to the different types of risk posed by different types of prey.
Portia is a genus of web-invading araneophagic (spider eating) jumping spiders known from earlier studies to derive aggressive-mimicry signals by using a generate-and-test (trial and error) algorithm. We studied individuals of Portia labiata from two populations (Los Baños and Sagada) in the Philippines that have previously been shown to differ in the level to which they rely on trial-and-error derivation of signals for prey capture (Los Baños relied on trial and error more strongly than Sagada P. labiata).
Here we investigated P. labiata’s use of trial and error in a novel situation (a confinement problem: how to escape from an island surrounded by water) that is unlikely to correspond closely to anything the spider would encounter in nature. During Experiment 1, spiders chose between two potential escape tactics (leap or swim), one of which was set at random to fail (brought spider no closer to edge of tray) and the other of which was set for partially succeeding (brought spider closer to edge of tray). By using trial and error, the Los Baños P. labiata solved the confinement problem significantly more often than the Sagada P. labiata in Experiment 1, both when the correct choices were positively reinforced (i.e., when the spider was moved closer to edge of tray) and when incorrect choices were punished (i.e., when the spider got no closer to edge of tray). In Experiment 2, the test individual’s first choice was always set to fail, and P. labiata was given repeated opportunities to respond to feedback, yet the Sagada P. labiata continued to place little reliance on trial and error for solving the confinement problem.
That the Los Baños P. labiata relied more strongly on trial-and-error problem solving than the Sagada P. labiata has now been demonstrated across two different tasks.
Our objective was to use expectancy-violation methods for determining whether Portia africana, a salticid spider that specializes in eating other spiders, is proficient at representing exact numbers of prey. In our experiments, we relied on this predator’s known capacity to gain access to prey by following pre-planned detours. After Portia first viewed a scene consisting of a particular number of prey items, it could then take a detour during which the scene went out of view. Upon reaching a tower at the end of the detour, Portia could again view a scene, but now the number of prey items might be different. We found that, compared with control trials in which the number was the same as before, Portia’s behaviour was significantly different in most instances when we made the following changes in number: 1 versus 2, 1 versus 3, 1 versus 4, 2 versus 3, 2 versus 4 or 2 versus 6. These effects were independent of whether the larger number was seen first or second. No significant effects were evident when the number of prey changed between 3 versus 4 or 3 versus 6. When we changed prey size and arrangement while keeping prey number constant, no significant effects were detected. Our findings suggest that Portia represents 1 and 2 as discrete number categories, but categorizes 3 or more as a single category that we call ‘many’.
Most of you probably know about Turing machines: hypothetical gizmos built of paper punch-tape, read-write heads, and imagination, which can—step by laborious step—emulate the operation of any computer. And some of you may be old enough to remember the Sinclair ZX-80— a sad little personal computer so primitive that it couldn’t even run its video display and its keyboard at the same time (typing would cause the screen to go dark). Peer into the darkness between these artifacts, stir in a little DNA, and what do you get? This hairy little spider right here. A pinpoint brain with less than a million neurons, somehow capable of mammalian-level problem-solving. And just maybe, a whole new approach to cognition.
Here’s the thumbnail sketch: we have here a spider who eats other spiders, who changes her foraging strategy on the fly, who resorts to trial and error techniques to lure prey into range. She will brave a full frontal assault against prey carrying an egg sac, but sneak up upon an unencumbered target of the same species…Portia improvises. But it’s not just this flexible behavioral repertoire that’s so amazing. It’s not the fact that somehow, this dumb little spider with its crude compound optics has visual acuity to rival a cat’s (even though a cat’s got orders of magnitude more neurons in one retina than our spider has in her whole damn head). It’s not even the fact that this little beast can figure out a maze which entails recognizing prey, then figuring out an approach path along which that prey is not visible (i.e., the spider can’t just keep her eyes on the ball: she has to develop and remember a search image), then follow her best-laid plans by memory including recognizing when she’s made a wrong turn and retracing her steps, all the while out of sight of her target. No, the really amazing thing is how she does all this with a measly 600,000 neurons— how she pulls off cognitive feats that would challenge a mammal with 70 million or more.
She does it like a Turing Machine, one laborious step at a time. She does it like a Sinclair ZX-80: running one part of the system then another, because she doesn’t have the circuitry to run both at once. She does it all sequentially, by timesharing. She’ll sit there for two fucking hours, just watching. It takes that long to process the image, you see: whereas a cat or a mouse would assimilate the whole hi-res vista in an instant, Portia’s poor underpowered graphics driver can only hold a fraction of the scene at any given time. So she scans, back and forth, back and forth, like some kind of hairy multilimbed Cylon centurion, scanning each little segment of the game board in turn…Portia won’t be deterred by the fact that she only has a few percent of a real brain: she emulates the brain she needs, a few percents at a time.
I wonder what the limits are to Portia’s painstaking intellect. Suppose we protected her from predators, and hooked her up to a teensy spider-sized glucose drip so she wouldn’t starve. It takes her a couple of hours to capture a snapshot; how long will it take the fuzzy-legged little beauty to compose a sonnet? Are we looking at a whole new kind of piecemeal, modular intellect here? And why the hell didn’t I think of it first? [Watts would reuse this idea in his 2014 SF novel Echopraxia.]
Peter Watts is a Canadian science fiction author. He specializes in hard science fiction. He earned a Ph.D from the University of British Columbia in Vancouver, British Columbia in 1991, from the Department of Zoology and Resource Ecology. He went on to hold several academic research and teaching positions, and worked as a marine-mammal biologist. He began publishing fiction around the time he finished graduate school.
Jumping spiders or the Salticidae are a family of spiders. As of 2019, it contained over 600 described genera and over 6000 described species, making it the largest family of spiders at 13% of all species. Jumping spiders have some of the best vision among arthropods and use it in courtship, hunting, and navigation. Although they normally move unobtrusively and fairly slowly, most species are capable of very agile jumps, notably when hunting, but sometimes in response to sudden threats or crossing long gaps. Both their book lungs and tracheal system are well-developed, and they use both systems. Jumping spiders are generally recognized by their eye pattern. All jumping spiders have four pairs of eyes, with the anterior median pair being particularly large.
Echopraxia is a hard science fiction novel by Canadian writer Peter Watts. It is a "sidequel" to his 2006 novel Blindsight. It follows the story of a biologist who gets caught up in a voyage into the heart of the Solar System among members of a transcendentalist monastic order and allies to investigate a mysterious signal seemingly coming from the mission sent to initiate first contact in Watts' previous novel.