Modeling human understanding of complex intentional action with a Bayesian nonparametric subgoal model

Most human behaviors consist of multiple parts, steps, or subtasks. These structures guide our action planning and execution, but when we observe others, the latent structure of their actions is typically unobservable, and must be inferred in order to learn new skills by demonstration, or to assist others in completing their tasks. For example, an assistant who has learned the subgoal structure of a colleague's task can more rapidly recognize and support their actions as they unfold. Here we model how humans infer subgoals from observations of complex action sequences using a nonparametric Bayesian model, which assumes that observed actions are generated by approximately rational planning over unknown subgoal sequences. We test this model with a behavioral experiment in which humans observed different series of goal-directed actions, and inferred both the number and composition of the subgoal sequences associated with each goal. The Bayesian model predicts human subgoal inferences with high accuracy, and significantly better than several alternative models and straightforward heuristics. Motivated by this result, we simulate how learning and inference of subgoals can improve performance in an artificial user assistance task. The Bayesian model learns the correct subgoals from fewer observations, and better assists users by more rapidly and accurately inferring the goal of their actions than alternative approaches

Expression of the tobacco β- 1,3-glucanase gene, PR-2d, following induction of SAR with \u3ci\u3ePeronospora tabacina\u3c/i\u3e

Systemic acquired resistance (SAR) is induced following inoculation of Peronospora tabacina sporangia into the stems of Nicotiana tabacum plants highly susceptible to the pathogen. Previous results have shown that accumulation of acidic P-1,3-glucanases (PR-2\u27s) following induction of SAR by P. tabacina may contribute to resistance to P. tabacina. We showed that up-regulation of the PR-2 gene, PR-2d, following stem inoculation with P. tabacina, is associated with SAR. Studies using plants transformed with GUS constructs containing the full length promoter from PR-2d or promoter deletions, provided evidence that a previously characterized regulatory element that is involved in response to salicylic acid (SA), may be involved in regulation of PR-2d following induction of SAR with P. tabacina. This work provides evidence that regulation of PR-2 genes during P. tabacina-induced SAR may be similar to regulation of these genes during infection of N-gene tobacco by TMV or following exogenous application of SA, and provides further support for the role of SA in regulation of genes during P. tabacina-induced SAR

Expression of the tobacco β- 1,3-glucanase gene, PR-2d, following induction of SAR with \u3ci\u3ePeronospora tabacina\u3c/i\u3e

Systemic acquired resistance (SAR) is induced following inoculation of Peronospora tabacina sporangia into the stems of Nicotiana tabacum plants highly susceptible to the pathogen. Previous results have shown that accumulation of acidic P-1,3-glucanases (PR-2\u27s) following induction of SAR by P. tabacina may contribute to resistance to P. tabacina. We showed that up-regulation of the PR-2 gene, PR-2d, following stem inoculation with P. tabacina, is associated with SAR. Studies using plants transformed with GUS constructs containing the full length promoter from PR-2d or promoter deletions, provided evidence that a previously characterized regulatory element that is involved in response to salicylic acid (SA), may be involved in regulation of PR-2d following induction of SAR with P. tabacina. This work provides evidence that regulation of PR-2 genes during P. tabacina-induced SAR may be similar to regulation of these genes during infection of N-gene tobacco by TMV or following exogenous application of SA, and provides further support for the role of SA in regulation of genes during P. tabacina-induced SAR

Relationship of the North American Monsoon to tropical and North Pacific sea surface temperatures as revealed by observational analyses, The

Includes bibliographical references (pages 43-48).April 2000.The North American Monsoon is a seasonal shift of upper and low level pressure and wind patterns which brings summertime moisture into the Southwest United States and ends the late spring wet period in the Great Plains. The climatology and interannual variability of the North American Monsoon are examined using the NCEP/NCAR Reanalysis (1948-98). The diurnal and seasonal evolution of 500-mb geopotential height, integrated moisture flux, and integrated moisture flux convergence are constructed using a five-day running mean for the months May through September. All of the years are used to calculate an average daily Z-score which removes the diurnal, seasonal, and intraseasonal variability. The average Z-score centered about the date is correlated with three Pacific SST indices associated with the El Niño Southern Oscillation (ENSO) and the North Pacific Oscillation (NPO). These indices are: Niño 3, a North Pacific index, and a North American Monsoon index (M) which combines the previous two. Regional time evolving precipitation indices for the Southwest and Great Plains, which consider the total number of wet or dry stations in a region, are also correlated with the SST indices. The new reanalysis climatology reveals: the time of maximum northward extent of the monsoon is late July, a diurnal cycle in atmospheric moisture which reflects the evolution of summer thunderstorms, the presence of the Baja and Great Plains low level jets, and the seasonal dependence of atmospheric moisture on monsoon ridge position. These results are in agreement with previous, more comprehensive reanalysis climatologies using shorter lengths of record. Pacific SSTs are related to a sequence of teleconnection patterns over North America through the summer. The relationship to the atmospheric circulation is strongest at monsoon onset, when the Pacific Transition pattern controls the large-scale distribution of moisture across the western U.S. A high (low) NPO phase and El Niño (La Nina) conditions favor a trough (ridge) over the northern Rocky Mountains, northern Great Plains. In the Great Plains the spring wet season is lengthened (shortened) and early summer rainfall and integrated moisture flux convergence are above (below) average. In the Southwest monsoon onset is late (early) and early summer rainfall and integrated moisture flux convergence are below (above) average. Relationships with the Pacific SST indices decay in the later part of the monsoon. These idealized climatological responses associated with high and low values of the M index were observed in the Midwest Flood of 1993 and the Drought of 1988, respectively. Tropical and North Pacific SSTs are related to atmospheric moisture and precipitation in the western U.S. to varying degrees depending on location. In the Great Plains, North Pacific SSTs are dominant factor, while in the Southwest tropical and North Pacific SSTs are equally important. Though the M index is the better diagnostic for North American Monsoon, only the time-coincident relationships with atmospheric circulation and moisture are statistically significant. A statistically significant relationship exists between spring Niño- 3 and the atmospheric circulation pattern over North America at monsoon onset

Modeling human ad hoc coordination

Whether in groups of humans or groups of computer agents, collaboration is most effective between individuals who have the ability to coordinate on a joint strategy for collective action. However, in general a rational actor will only intend to coordinate if that actor believes the other group members have the same intention. This circular dependence makes rational coordination difficult in uncertain environments if communication between actors is unreliable and no prior agreements have been made. An important normative question with regard to coordination in these ad hoc settings is therefore how one can come to believe that other actors will coordinate, and with regard to systems involving humans, an important empirical question is how humans arrive at these expectations. We introduce an exact algorithm for computing the infinitely recursive hierarchy of graded beliefs required for rational coordination in uncertain environments, and we introduce a novel mechanism for multiagent coordination that uses it. Our algorithm is valid in any environment with a finite state space, and extensions to certain countably infinite state spaces are likely possible. We test our mechanism for multiagent coordination as a model for human decisions in a simple coordination game using existing experimental data. We then explore via simulations whether modeling humans in this way may improve human-Agent collaboration

Warm-Dense Molecular Gas in the ISM of Starbursts, LIRGs and ULIRGs

The role of star formation in luminous and ultraluminous infrared galaxies is a hotly debated issue: while it is clear that starbursts play a large role in powering the IR luminosity in these galaxies, the relative importance of possible enshrouded AGNs is unknown. It is therefore important to better understand the role of star forming gas in contributing to the infrared luminosity in IR-bright galaxies. The J=3 level of 12CO lies 33K above ground and has a critical density of ~1.5 X 10^4 cm^-3. The 12CO(J=3-2) line serves as an effective tracer for warm-dense molecular gas heated by active star formation. Here we report on 12CO (J=3-2) observations of 17 starburst spirals, LIRGs and ULIRGs which we obtained with the Heinrich Hertz Submillimeter Telescope on Mt. Graham, Arizona. Our main results are the following: 1. We find a nearly linear relation between the infrared luminosity and warm-dense molecular gas such that the infrared luminosity increases as the warm-dense molecular gas to the power 0.92; We interpret this to be roughly consistent with the recent results of Gao & Solomon (2004a,b). 2. We find L_IR/M_H2 ratios ranging from ~10 to ~128 L_sun/M_sun using a standard CO-H2 conversion factor of 3 X 10^20 cm^-2 (K km s^-1)^-1. If this conversion factor is ~an order of magnitude less, as suggested in a recent statistical survey (Yao et al. 2003), then 2-3 of our objects may have significant contributions to the L_IR by dust-enshrouded AGNs.Comment: 15 Pages, 2 figures, Accepted for Publication in Ap

The mentalistic basis of core social cognition: experiments in preverbal infants and a computational model

Evaluating individuals based on their pro- and anti-social behaviors is fundamental to successful human interaction. Recent research suggests that even preverbal infants engage in social evaluation; however, it remains an open question whether infants' judgments are driven uniquely by an analysis of the mental states that motivate others' helpful and unhelpful actions, or whether non-mentalistic inferences are at play. Here we present evidence from 10-month-olds, motivated and supported by a Bayesian computational model, for mentalistic social evaluation in the first year of life. A video abstract of this article can be viewed at http://youtu.be/rD_Ry5oqCY

Course-based Science Research Promotes Learning in Diverse Students at Diverse Institutions

Course-based research experiences (CREs) are powerful strategies for spreading learning and improving persistence for all students, both science majors and nonscience majors. Here we address the crucial components of CREs (context, discovery, ownership, iteration, communication, presentation) found across a broad range of such courses at a variety of academic institutions. We also address how the design of a CRE should vary according to the background of student participants; no single CRE format is perfect. We provide a framework for implementing CREs across multiple institutional types and several disciplines throughout the typical four years of undergraduate work, designed to a variety of student backgrounds. Our experiences implementing CREs also provide guidance on overcoming barriers to their implementation