Building Machines That Learn and Think Like People

Recent progress in artificial intelligence (AI) has renewed interest in building systems that learn and think like people. Many advances have come from using deep neural networks trained end-to-end in tasks such as object recognition, video games, and board games, achieving performance that equals or even beats humans in some respects. Despite their biological inspiration and performance achievements, these systems differ from human intelligence in crucial ways. We review progress in cognitive science suggesting that truly human-like learning and thinking machines will have to reach beyond current engineering trends in both what they learn, and how they learn it. Specifically, we argue that these machines should (a) build causal models of the world that support explanation and understanding, rather than merely solving pattern recognition problems; (b) ground learning in intuitive theories of physics and psychology, to support and enrich the knowledge that is learned; and (c) harness compositionality and learning-to-learn to rapidly acquire and generalize knowledge to new tasks and situations. We suggest concrete challenges and promising routes towards these goals that can combine the strengths of recent neural network advances with more structured cognitive models.Comment: In press at Behavioral and Brain Sciences. Open call for commentary proposals (until Nov. 22, 2016). https://www.cambridge.org/core/journals/behavioral-and-brain-sciences/information/calls-for-commentary/open-calls-for-commentar

Multitasking versus multiplexing: Toward a normative account of limitations in the simultaneous execution of control-demanding behaviors

Why is it that behaviors that rely on control, so striking in their diversity and flexibility, are also subject to such striking limitations? Typically, people cannot engage in more than a few—and usually only a single—control-demanding task at a time. This limitation was a defining element in the earliest conceptualizations of controlled processing; it remains one of the most widely accepted axioms of cognitive psychology, and is even the basis for some laws (e.g., against the use of mobile devices while driving). Remarkably, however, the source of this limitation is still not understood. Here, we examine one potential source of this limitation, in terms of a trade-off between the flexibility and efficiency of representation (“multiplexing”) and the simultaneous engagement of different processing pathways (“multitasking”). We show that even a modest amount of multiplexing rapidly introduces cross-talk among processing pathways, thereby constraining the number that can be productively engaged at once. We propose that, given the large number of advantages of efficient coding, the human brain has favored this over the capacity for multitasking of control-demanding processes.National Science Foundation (U.S.). Graduate Research Fellowship Progra

Active current sheets and hot flow anomalies in Mercury's bow shock

Hot flow anomalies (HFAs) represent a subset of solar wind discontinuities interacting with collisionless bow shocks. They are typically formed when the normal component of motional (convective) electric field points toward the embedded current sheet on at least one of its sides. The core region of an HFA contains hot and highly deflected ion flows and rather low and turbulent magnetic field. In this paper, we report first observations of HFA-like events at Mercury identified over a course of two planetary years. Using data from the orbital phase of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission, we identify a representative ensemble of active current sheets magnetically connected to Mercury's bow shock. We show that some of these events exhibit unambiguous magnetic and particle signatures of HFAs similar to those observed earlier at other planets, and present their key physical characteristics. Our analysis suggests that Mercury's bow shock does not only mediate the flow of supersonic solar wind plasma but also provides conditions for local particle acceleration and heating as predicted by previous numerical simulations. Together with earlier observations of HFA activity at Earth, Venus and Saturn, our results confirm that hot flow anomalies are a common property of planetary bow shocks, and show that the characteristic size of these events is of the order of one planetary radius.Comment: 39 pages, 15 figures, 2 table

Spacecraft observations and analytic theory of crescent-shaped electron distributions in asymmetric magnetic reconnection

Supported by a kinetic simulation, we derive an exclusion energy parameter $\cal{E}_X$ providing a lower kinetic energy bound for an electron to cross from one inflow region to the other during magnetic reconnection. As by a Maxwell Demon, only high energy electrons are permitted to cross the inner reconnection region, setting the electron distribution function observed along the low density side separatrix during asymmetric reconnection. The analytic model accounts for the two distinct flavors of crescent-shaped electron distributions observed by spacecraft in a thin boundary layer along the low density separatrix.Comment: 6 pages, 3 figure

MMS Observations of Plasma Heating Associated With FTE Growth

Upon formation, flux transfer events (FTEs) in the subsolar magnetosheath have been observed to grow in diameter, λ, while convecting along the magnetopause. Plasma pressure has also been found to decrease subâ adiabatically with increasing λ, indicating the presence of internal plasma acceleration and heating processes. Here, the Magnetospheric Multiscale (MMS) fields and plasma measurements are used to determine the relative roles of parallel electric fields, betatron, and Fermi processes in plasma heating inside an ensemble of 55 subsolar FTEs. Plasma heating is shown asymmetric inside FTEs. Parallel electric fields dominate (>75%) ion and electron heating at the leading edge of FTEs. At the trailing edge, betatron and Fermi processes overtake (>50%), resulting in ion cooling and electron heating, respectively. The observed strong net heatings inside FTEs are proportional to λâ 1/2. It is concluded that reconnectionâ driven heating continues inside FTEs far from the subsolar electron and ion diffusion regions.Plain Language SummaryEnergetic charged particles are observed in many space and astrophysical environments, including our solar system. However, the acceleration and heating mechanisms responsible for generating these energetic charged particles remain to be discovered. Simulations and in situ observations have shown that magnetic reconnection, a process through which magnetic field lines â reconnectâ and release magnetic energy, plays a major role in generating energetic charged particles. The primary sites for magnetic energy transfer to charged particle acceleration and heating are the twin exhaust regions that emanate from the reconnection Xâ line. However, the amount of kinetic energy gained by charged particles in the exhaust regions represents only a small fraction of the total energy released by magnetic reconnection. Here, the Magnetospheric Multiscale (MMS) multipoint fields and plasma measurements are used to determine the contributions of acceleration mechanisms operating inside flux transfer events (FTEs), which are formed in the reconnection exhaust regions. We observe that acceleration mechanisms contribute to the charged particles’ energy gain inside FTEs. We further reveal that while acceleration mechanisms are most significant inside smaller FTEs, they continue to accelerate charged particles inside larger FTEs. We conclude that magnetic reconnectionâ driven charged particle acceleration is longâ lasting and can take place far from the exhaust regions.Key PointsThe relative roles of parallel electric fields, betatron, and Fermi processes in plasma heating inside 55 subsolar FTEs are determinedParallel electric fields dominate plasma energization at FTEs’ leading edge. Betatron and Fermi processes overtake at FTEs’ trailing edgeMMS observations reveal strong plasma acceleration inside FTEs that is inversely proportional to the square root of FTE diameterPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152496/1/grl59844_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152496/2/grl59844-sup-0001-2019GL084843-SI.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152496/3/grl59844.pd

MMS Multi-Point Analysis of FTE Evolution: Physical Characteristics and Dynamics

Previous studies have indicated that flux transfer events (FTEs) grow as they convect away from the reconnection site along the magnetopause. This increase in FTE diameter may occur via adiabatic expansion in response to decreasing external pressure away from the subsolar region or due to a continuous supply of magnetic flux and plasma to the FTEs’ outer layers by magnetic reconnection. Here we investigate an ensemble of 55 FTEs at the subsolar magnetopause using Magnetospheric Multiscale (MMS) multi-point measurements. The FTEs are initially modeled as quasi-force-free flux ropes in order to infer their geometry and the spacecraft trajectory relative to their central axis. The MMS observations reveal a radially-inward net force at the outer layers of FTEs which can accelerate plasmas and fields toward the FTE’s core region. Inside the FTEs, near the central axis, plasma density is found to decrease as the axial net force increases. It is interpreted that the axial net force accelerates plasmas along the axis in the region of compressing field lines. Statistical analysis of the MMS observations of the 55 FTEs indicates that plasma pressure, Pth, decreases with increasing FTE diameter, λ, as Pth,obsv - λ-0.24. Assuming that all 55 FTEs started out with similar diameters, this rate of plasma pressure decrease with increasing FTE diameter is at least an order of magnitude slower than the theoretical rate for adiabatic expansion (i.e., Pth,adiab. - λ-3.3), suggesting the presence of efficient plasma heating mechanisms, such as magnetic reconnection, to facilitate FTE growth.Key PointsThe forces inside FTEs observed by MMS suggest plasma acceleration toward and along the FTE’s central axis causing plasma to escapeThe roles of adiabatic expansion and reconnection in FTE growth are explored using MMS observationsThe observed sub-adiabatic decrease of plasma pressure as FTE size increases requires plasma heating mechanisms such as reconnectionPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151362/1/jgra55065_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151362/2/jgra55065.pd