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Earlier, to explore the idea of combining physical experiments with algorithms, we introduced a new form of analogue-digital (AD) Turing machine. We examined in detail a case study where an experimental procedure, based on Newtonian kinematics, is used as an oracle with classes of Turing machines. The physical cost of oracle calls was counted and three forms of AD queries were studied, in which physical parameters can be set exactly and approximately. Here, in this sequel, we complete the classification of the computational power of these AD Turing machines and determine precisely what they can compute, using non-uniform complexity classes and probabilities.

Numerous psychological and economic experiments have shown that the exchange of promises greatly enhances cooperative behavior in experimental games. This paper seeks to test two theories to explain this effect. The first posits that individuals have a preference for keeping their word. The second assumes that people dislike letting down others' payoff expectations. According to the latter account, promises affect behavior only indirectly, because they lead to changes in the payoff expectations attributed to others. I conduct an experiment designed to distinguish between and test these alternative explanations. The results demonstrate that the effects of promises cannot be accounted for by changes in payoff expectations. This suggests that people have a preference for promise keeping per se.

We conduct experiments to explore the possibility that subject misconceptions, as opposed to a particular theory of preferences referred to as the \"endowment effect,\" account for reported gaps between willingness to pay (\"WTP\") and willingness to accept (\"WTA\"). The literature reveals two important facts. First, there is no consensus regarding the nature or robustness of WTP-WTA gaps. Second, while experimenters are careful to control for subject misconceptions, there is no consensus about the fundamental properties of misconceptions or how to avoid them. Instead, by implementing different types of experimental controls, experimenters have revealed notions of how misconceptions arise. Experimenters have applied these controls separately or in different combinations. Such controls include ensuring subject anonymity, using incentive-compatible elicitation mechanisms, and providing subjects with practice and training on the elicitation mechanism before employing it to measure valuations. The pattern of results reported in the literature suggests that the widely differing reports of WTP-WTA gaps could be due to an incomplete science regarding subject misconceptions. We implement a \"revealed theory\" methodology to compensate for the lack of a theory of misconceptions. Theories implicit in experimental procedures found in the literature are at the heart of our experimental design. Thus, our approach to addressing subject misconceptions reflects an attempt to control simultaneously for all dimensions of concern over possible subject misconceptions found in the literature. To this end, our procedures modify the Becker-DeGroot-Marschak mechanism used in previous studies to elicit values. In addition, our procedures supplement commonly used procedures by providing extensive training on the elicitation mechanism before subjects provide WTP and WTA responses. Experiments were conducted using both lotteries and mugs, goods frequently used in endowment effect experiments. Using the modified procedures, we observe no gap between WTA and WTP. Therefore, our results call into question the interpretation of observed gaps as evidence of loss aversion or prospect theory. Further evidence is required before convincing interpretations of observed gaps can be advanced.

Unconscious neural activity has been repeatedly shown to precede and potentially even influence subsequent free decisions. However, to date, such findings have been mostly restricted to simple motor choices, and despite considerable debate, there is no evidence that the outcome of more complex free decisions can be predicted from prior brain signals. Here, we show that the outcome of a free decision to either add or subtract numbers can already be decoded from neural activity in medial prefrontal and parietal cortex 4 s before the participant reports they are consciously making their choice. These choice-predictive signals co-occurred with the so-called default mode brain activity pattern that was still dominant at the time when the choice-predictive signals occurred. Our results suggest that unconscious preparation of free choices is not restricted to motor preparation. Instead, decisions at multiple scales of abstraction evolve from the dynamics of preceding brain activity.

Visually impaired individuals often rely on assistive technologies such as white canes for independent navigation. Many electronic enhancements to the traditional white cane have been proposed. However, only a few of these proof-of-concept technologies have been tested with authentic users, as most studies rely on blindfolded non-visually impaired participants or no testing with participants at all. Experiments involving blind users are usually not contrasted with the traditional white cane. This study set out to compare an ultrasound-based electronic cane with a traditional white cane. Moreover, we also compared the performance of a group of visually impaired participants (N = 10) with a group of blindfolded participants without visual impairments (N = 31). The results show that walking speed with the electronic cane is significantly slower compared to the traditional white cane. Moreover, the results show that the performance of the participants without visual impairments is significantly slower than for the visually impaired participants. No significant differences in obstacle detection rates were observed across participant groups and device types for obstacles on the ground, while 79% of the hanging obstacles were detected by the electronic cane. The results of this study thus suggest that electronic canes present only one advantage over the traditional cane, namely in its ability to detect hanging obstacles, at least without prolonged practice. Next, blindfolded participants are insufficient substitutes for blind participants who are expert cane users. The implication of this study is that research into digital white cane enhancements should include blind participants. These participants should be followed over time in longitudinal experiments to document if practice will lead to improvements that surpass the performance achieved with traditional canes.

Morphogens, such as Decapentaplegic (Dpp) in the fly imaginal discs, form graded concentration profiles that control patterning and growth of developing organs. In the imaginal discs, proliferative growth is homogeneous in space, posing the conundrum of how morphogen concentration gradients could control position-independent growth. To understand the mechanism of proliferation control by the Dpp gradient, we quantified Dpp concentration and signaling levels during wing disc growth. Both Dpp concentration and signaling gradients scale with tissue size during development. On average, cells divide when Dpp signaling levels have increased by 50%. Our observations are consistent with a growth control mechanism based on temporal changes of cellular morphogen signaling levels. For a scaling gradient, this mechanism generates position-independent growth rates.

Membrane fusion within the eukaryotic endomembrane system depends on the initial recognition of Rab GTPase on transport vesicles by multisubunit tethering complexes and subsequent coupling to SNARE-mediated fusion. The conserved vacuolar/lysosomal homotypic fusion and vacuole protein sorting (HOPS) tethering complex combines both activities. Here we present the overall structure of the fusion-active HOPS complex. Our data reveal a flexible ≈30-nm elongated seahorse-like structure, which can adopt contracted and elongated shapes. Surprisingly, both ends of the HOPS complex contain a Rab-binding subunit: Vps41 and Vps39. The large head contains in addition to Vps41 the SNARE-interacting Vps33, whereas Vps39 is found in the bulky tip of its tail. Vps11 and Vps18 connect head and tail. Our data suggest that HOPS bridges Ypt7-positive membranes and chaperones SNAREs at fusion sites.

Plott and Zeiler (2005) report that the willingness-to-pay/willingness-to-accept disparity is absent for mugs in a particular experimental setting, designed to neutralize misconceptions about the procedures used to elicit valuations. This result has received sustained attention in the literature. However, other data from that same study, not published in that paper, exhibit a significant and persistent disparity when the same experimental procedures are applied to lotteries. We report new data confirming both results, thereby suggesting that the presence or absence of a disparity may be a more complex issue than some may have supposed. (JEL C91, D12, D81, D83)

Human information processing is characterized by bottlenecks that constrain throughput. These bottlenecks limit both what we can perceive and what we can act on in multitask settings. Although perceptual and response limitations are often attributed to independent information processing bottlenecks, it has recently been suggested that a common attentional limitation may be responsible for both. To date, however, evidence supporting the existence of such a \"unified\" bottleneck has been mixed. Here, we tested the unified bottleneck hypothesis using time-resolved fMRI. Experiment 1 isolated brain regions involved in the response selection bottleneck that limits speeded dual-task performance. These same brain regions were not only engaged by a perceptual encoding task in Experiment 2, their activity also tracked delays to a speeded decision-making task caused by concurrent perceptual encoding (Experiment 3). We conclude that a unified attentional bottleneck, including the inferior frontal junction, superior medial frontal cortex, and bilateral insula, temporally limits operations as diverse as perceptual encoding and decision-making.

Design activities, when embedded in an inquiry cycle and appropriately scaffolded and supplemented with reflection, can promote the development of the habits of mind (scientific abilities) that are an important part of scientific practice. Through the Investigative Science Learning Environment (ISLE), students construct physics knowledge by engaging in inquiry cycles that replicate the approach used by physicists to construct knowledge. A significant portion of student learning occurs in ISLE instructional labs where students design their own experiments. The labs provide an environment for cognitive apprenticeship enhanced by formative assessment. As a result, students develop interpretive knowing that helps them approach new problems as scientists. This article describes a classroom study in which the students in the ISLE design lab performed equally well on traditional exams as ISLE students who did not engage in design activities. However, the design group significantly outperformed the non-design group while working on novel experimental tasks (in physics and biology), demonstrating the application of scientific abilities to an inquiry task in a novel content domain. This research shows that a learning environment that integrates cognitive apprenticeship and formative assessment in a series of conceptual design tasks provides a rich context for helping students build scientific habits of mind.