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A global ocean biogeochemical model is used to quantify the sensitivity of marine biogeochemistry and air–sea CO2 exchange to variations in dust deposition over decadal timescales. Estimates of dust deposition generated under four climate states provide a large range in total deposition with spatially realistic patterns; transient ocean model experiments are conducted by applying a step-function change in deposition from a current climate control. Relative to current conditions, higher dust deposition increases diatom and export production, nitrogen fixation and oceanic net CO2 uptake from the atmosphere, while reduced dust deposition has the opposite effects. Over timescales less than a decade, dust modulation of marine productivity and export is dominated by direct effects in high-nutrient, low-chlorophyll regions, where iron is the primary limiting nutrient. On longer timescales, an indirect nitrogen fixation pathway has increased importance, significantly amplifying the ocean biogeochemical response. Because dust iron input decouples carbon cycling from subsurface macronutrient supply, the ratio of the change in net ocean CO2 uptake to change in export flux is large, 0.45–0.6. Decreasing dust deposition and reduced oceanic CO2 uptake over the next century could provide a positive feedback to global warming, distinct from feedbacks associated with changes in stratification and circulation.

In cart-pole balancing, one moves a cart in 1 dimension so as to balance an attached inverted pendulum. We approached perception-action and learning in this task from an ecological perspective. This entailed identifying a space of informational variables that balancers use as they perform the task and demonstrating that they improve by traversing the space to the loci of more useful variables. We presented a novel information space--including fractional derivatives of pendulum angle (e.g., halfway between angle and angular velocity)--as possible information for balancing. Fourteen college students tried to meet a criterion of balancing the pole for 30 s on 3 of 5 successive trials, up to a maximum of 150 attempts. Loci in the fractional derivative space predicted the time series of force production well. Systematic differences were seen in loci as a function of success, and systematic changes in locus were seen with learning. The fractional derivatives were shown to predict pole angles a short time interval into the future, allowing balancers to prospectively control the action and thereby nullify visuomotor delay. In addition to loci in the information space, we analyzed loci in a calibration space, reflecting the gain relating force to information. (Contains 2 tables, 9 figures and 5 footnotes.)

Perceptual systems must learn to explore and to use the resulting information to hone performance. Optimal performance depends on using information available at many time scales, from the near instantaneous values of variables underlying perception (i.e., detection), to longer term information about appropriate scaling (i.e., calibration), to yet longer term information guiding variable use (i.e., attunement). Fractal fluctuations in explorations would entail fluctuation at all time scales, allowing perceptual systems a flexible way to detect information at all time scales. We tested whether perceptual learning in dynamic touch is related to the fractality of wielding behaviors. A reanalysis of wielding behaviors from Arzamarski, Isenhower, Kay, Turvey, and Michaels (2010) revealed that exploratory movements were fractal and that a fractal-scaling exponent predicts individual differences in haptic judgments. (Contains 4 tables and 7 figures.)

The authors attempted to identify perceptual mechanisms that pick up information for initiating a run to catch fly balls and for judging their landing locations. Fly balls have been shown to be tracked with the eyes and head (R. R. D. Oudejans, C. F. Michaels, F. C. Bakker, & K. Davids, 1999). This raised the question of whether constraining eye and head movements of experienced baseball players by having them wear eye-movement-preventing goggles (eye movements would lead to losing sight of the ball) or a head-movement-preventing neck brace, or both, would limit their capacity (a) to start running in the correct direction and (b) to make correct judgments about the balls' landing locations. Restrictions had minimal effects on response accuracy, but response latency was affected. The goggles increased latency of both running and judging. Moreover, the neck brace decreased judgment time, particularly for difficult balls, suggesting that head stability is important for making judgments. High performance levels suggested that the perceptual system was flexible; that is, different parts of the system can perform the same function. The implications of these findings for perceptual mechanisms are discussed.

A dynamic touch paradigm in which participants judged the lengths of rods and pipes was used to test the D. M. Jacobs and C. F. Michaels (2007) theory of perceptual learning. The theory portrays perception as the exploitation of a locus on an information manifold and learning as continuous movement across that manifold to a new locus, as guided by information available in feedback. The information manifold was defined as a 1-dimensional space of inertial variables. To encourage maximal learning, a 2-step procedure was used in each of 2 experiments. Each step comprised a pretest to identify the starting locus on the information manifold, a practice phase in which feedback specifying the optimal locus was given, and a posttest in which the ending locus on the manifold was identified. In the 2nd step, a different feedback variable specified a different optimum. In both experiments, participants, who sometimes began at different loci, showed the predicted movement toward the optimum in each phase. Whereas previous applications of the theory posit the existence of information-for-learning without identifying a candidate variable, such a candidate is identified. (Contains 8 footnotes, 6 figures, and 6 tables.)

Two processes have been hypothesized to underlie improvement in perception: attunement and calibration. These processes were examined in a dynamic touch paradigm in which participants were asked to report the lengths of unseen, wielded rods differing in length, diameter, and material. Two experiments addressed whether feedback informs about the need for reattunement and recalibration. Feedback indicating actual length induced both recalibration and reattunement. Recalibration did not occur when feedback indicated only whether 2 rods were of the same length or of different lengths. Such feedback, however, did induce reattunement. These results suggest that attunement and calibration are dissociable processes and that feedback informs which is needed. The observed change in variable use has implications also for research on what mechanical variables underlie length perception by dynamic touch.

Perceptual systems must learn to explore and to use the resulting information to hone performance. Optimal performance depends on using information available at many time scales, from the near instantaneous values of variables underlying perception (i.e., detection), to longer term information about appropriate scaling (i.e., calibration), to yet longer term information guiding variable use (i.e., attunement). Fractal fluctuations in explorations would entail fluctuation at all time scales, allowing perceptual systems a flexible way to detect information at all time scales. We tested whether perceptual learning in dynamic touch is related to the fractality of wielding behaviors. A reanalysis of wielding behaviors from Arzamarski, Isenhower, Kay, Turvey, and Michael s (2010) revealed that exploratory movements were fractal and that a fractal-scaling exponent predicts individual differences in haptic judgments. Keywords: perceptual learning, dynamic touch, haptic perception, fractal, scaling exponent DOI: 10.1037/a0019219

The authors attempted to identify perceptual mechanisms that pick up information for initiating a run to catch fly balls and for judging their landing locations. Fly balls have been shown to be tracked with the eyes and head (R. R. D. Oudejans, C. F. Michaels, F. C. Bakker, & K. Davids, 1999). This raised the question of whether constraining eye and head movements of experienced baseball players by having them wear eye-movement-preventing goggles (eye movements would lead to losing sight of the ball) or a head-movement-preventing neck brace, or both, would limit their capacity (a) to start running in the correct direction and (b) to make correct judgments about the balls' landing locations. Restrictions had minimal effects on response accuracy, but response latency was affected. The goggles increased latency of both running and judging. Moreover, the neck brace decreased judgment time, particularly for difficult balls, suggesting that head stability is important for making judgments. High performance levels suggested that the perceptual system was flexible; that is, different parts of the system can perform the same function. The implications of these findings for perceptual mechanisms are discussed. Keywords: fly balls, perceptual systems, eye movements, head movements, information pickup

A dynamic touch paradigm in which participants judged the lengths of rods and pipes was used to test the D. M. Jacobs and C. F. Michaels (2007) theory of perceptual learning. The theory portrays perception as the exploitation of a locus on an information manifold and learning as continuous movement across that manifold to a new locus, as guided by information available in feedback. The information manifold was defined as a 1-dimensional space of inertial variables. To encourage maximal learning, a 2-step procedure was used in each of 2 experiments. Each step comprised a pretest to identify the starting locus on the information manifold, a practice phase in which feedback specifying the optimal locus was given, and a posttest in which the ending locus on the manifold was identified. In the 2nd step, a different feedback variable specified a different optimum. In both experiments, participants, who sometimes began at different loci, showed the predicted movement toward the optimum in each phase. Whereas previous applications of the theory posit the existence of information-for-learning without identifying a candidate variable, such a candidate is identified. Keywords: perceptual learning, direct perception, ecological psychology, dynamic touch, haptics

D. M. Jacobs and C. F. Michaels (2006) concluded that aspects of hand movements in lateral catching were predicted by the ratio of lateral optical velocity to expansion velocity. Their conclusions were based partly on a modified version of the required velocity model of catching (C. E. Peper, R. J. Bootsma, D. R. Mestre, & F. C. Bakker, 1994). The present article considers this optical ratio in detail and asks whether it, together with a control law, predicts the (often curious) hand trajectories observed in lateral interception. The optical ratio was used to create a succession of target-position inputs for the vector integration to endpoint model of hand movements (D. Bullock & S. Grossberg, 1988). The model used this succession, initial hand position, and model parameters (fit to 60 trials) to predict hand trajectories on each trial. Predicted trajectories were then compared with observed hand trajectories. Hand movements were predicted accurately, especially in the binocular condition, and were superior to predictions based on lateral ball position, the input variable of the required velocity model. The authors concluded, as did C. E. Peper et al. (1994), that perceivers continuously couple movements to optics. Keywords: interception, perception-action, model, optics

J. J. Gibson (1966, 1979) suggested that improvement in perception and action can be attributed in part to changes in which variable is attended to. Such reattunement has been demonstrated with observers making judgments in response to simulations. The present study sought attunement changes in the perception of real events and in visually guided action. In 3 experiments, adults judged the passing distance of or attempted to catch balls. Discrete measures and the predictions of a modified required velocity model (e.g., R. J. Bootsma, V. Fayt, F. T. J. M. Zaal, & M. Laurent, 1997) were used to reveal which variables were exploited. Participants differed from each other and, to some extent, changed in the optical variables used, in catching as well as judging. Nevertheless, the changes were much smaller than in previous simulation-judgment studies; calibration was also found to underlie the improvements in performance. Keywords: perception-action, interception, learning, calibration

Two processes have been hypothesized to underlie improvement in perception: attunement and calibration. These processes were examined in a dynamic touch paradigm in which participants were asked to report the lengths of unseen, wielded rods differing in length, diameter, and material. Two experiments addressed whether feedback informs about the need for reattunement and recalibration. Feedback indicating actual length induced both recalibration and reattunement. Recalibration did not occur when feedback indicated only whether 2 rods were of the same length or of different lengths. Such feedback, however, did induce reattunement. These results suggest that attunement and calibration are dissociable processes and that feedback informs which is needed. The observed change in variable use has implications also for research on what mechanical variables underlie length perception by dynamic touch. Keywords: attunement, calibration, feedback, dynamic touch

ABSTRACT. The authors examined anticipation in tool use, focusing on tool length and tool-use posture. Adults (9 women and 9 men in each experiment) held a rod (length 0.4-0.8 m), [...]

Visually guided action implies the existence of information as well as a control law relating that information to movement. For ball catching, the Chapman Strategy--keeping constant the rate of change of the tangent of the elevation angle (d(tan([alpha]))/dt)--leads a catcher to the right location at the right time to intercept a fly ball. Previous studies showed the ability to detect the information and the consistency of running patterns with the use of the strategy. However, only direct manipulation of information can show its use. Participants were asked to intercept virtual balls in a Cave Automated Virtual Environment (CAVE) or to judge whether balls would pass behind or in front of them. Catchers in the CAVE successfully intercepted virtual balls with their forehead. Furthermore, the timing of judgments was related to the patterns of changing d(tan([alpha]))/dt. The advantages and disadvantages of a CAVE as a tool for studying interceptive action are discussed.

ABSTRACT. Displacing an object with a hand-held rod provided a simple paradigm for studying tool use. The authors asked how reaching was affected by manipulations of rod properties. Adults held [...]

ABSTRACT. In 2 experiments, differences in visual perception of climbing routes (route finding) between 7 expert climbers, 4 novices, and 9 inexperienced participants were studied. In both experiments, participants reproduced [...]

Research indicates that expansion velocity, or looming, is the optical variable an individual uses to begin and guide body movement in hitting a ball, rather than the variable of rate of change of optical expansion. Tests involved seated subjects, whose elbow joint angles were observed for flexion initiation in striking a dropped ball.

Stimulus-response compatibility is demonstrated by improvements in accuracy and reaction times in experiments that preserve the spatial relationships between visual stimuli and response targets. This study utilized a button-pushing response task to measure the effect of changing the distance between the stimulus and response target.

The authors anyalze the results of study comparing the flux and composition of sinking material caught using two different types of upper ocean sediment traps. The traps were deployed in the Sargasso Sea.

Research indicates that carbon budget imbalances in the Bermuda Atlantic Time-series Study may be explained by zooplankton migration in the seasonal absence of deep mixing. Diel migration was found to produce three times as much dissolved organic carbon than diapycnal mixing.

In 3 experiments, participants matched the rotations of a unimanually grasped wheel to a visual oscillation. Two coordination modes were studied: in-phase coordination (no phase difference between stimulus and movement) and anti-phase coordination (180 degrees phase difference). The hand grasped the wheel at either the 12:00 or the 6:00 position. Stimulus frequency, hand placement, phasing, and visibility (whether the hand and wheel were visible) all affected movement amplitude and stability. There were large individual differences especially at the 6:00 position; some participants appeared to couple movements of the wheel to stimulus oscillations, some coupled movements of the hand, and some did both. The results parallel stimulus-response compatibility effects in a similar choice reaction time task and reiterate J. A. S. Kelso's (1995) emphasis on studying intrinsic coupling dynamics at the level of the individual, where apparent differences in strategy can be observed.

The influence of hurricanes on the ocean carbon cycle and exchange of carbon between ocean and atmosphere is not well understood. Observations from the Sargasso Sea are presented, before and after hurricane Felix. A short-lived surface seawater cooling of around 4 degrees C was observed, and a fall in seawater partial pressure of Co(sub2) by about 60 muatm was seen. The efflux of CO(sub2) from ocean to atmosphere was increased by strong winds.

In 7 experiments, undergraduates judged the force exerted by a videotaped standing puller, a computer-generated (stick-figure) puller, or a computer-generated inverted pendulum. Single and stepwise multiple regression analyses determined the kinematic variables exploited by the participants. Results show that (a) judgments correlated highly with force and improved with feedback; (b) judgments correlated more highly with lower order kinematic variables than with force itself; (c) participants differed in the kinematic variables exploited; (d) participants changed over blocks of trials in the variables exploited; (e) some participants used compound kinematic variables; (f) the variables exploited depended on the type of feedback; and (g) judgments to upright pullers, inverted pullers, and simple pendula showed the same qualitative patterns. Implications for theories of direct perception, directed perception, and heuristics are considered.