Modeling unipolar depression as a chaotic process

This study inspected the deterministic structure of unipolar depression. Two women self-monitored sadness hourly 10 times a day for 6 months. One woman had a recurrent history of unipolar depression, and the other did not. Data were analyzed by visual inspection, examination of the Fourier transforms of the time plots, and the correlation dimension. Results suggested that in addition to a strong periodic component that existed only within the depressed subject's mood time series, a low-dimensional chaotic process might have been operating. In the nondepressed control subject, no such periodicity or process could be identified. The findings support maladaptive deterministic theories of mood disorders and have implications for the assessment of unipolar depression.     

Impulse and Movement Space-Time Variability

In 3 experiments, the authors examined movement space-time variability as a function of the force-time properties of the initial impulse in a movement timing task. In the range of motion and movement time task conditions, peak force, initial rate of force, and force duration were manipulated either independently or in combination across a range of parameter values. The findings showed that (a) impulse variability is predicted well by the elaboration of the isometric force variability scaling functions of L. G. Carlton, K. H. Kim, Y. T. Liu, and K. M. Newell (1993) to movement, and (b) the movement spatial and temporal outcome variability are complementary and well predicted by an equation treating the variance of force and time in Newton's 2nd law as independent random variables. Collectively, the findings suggest that movement outcome variability is the product of a coherent space-time function that is driven by the nonlinear scaling of the force-time properties of the initial impulse.     

Architecture and organizational principles of Broca's region

Identifying cortical areas for language and speech processing is a prerequisite for cognitive neuroscience and clinical research. Although Broca's region is one of the essential nodes in the language network, its anatomical constituents are ill-defined and multiple definitions of Broca's region exist. Sanides' concept of microstructural gradations interpreted Broca's region as developing from neighboring motor, dorsolateral-prefrontal, and insular cortices. Recent mapping approaches based on cytoarchitecture, transmitter receptor distribution, and connectivity revealed a highly differentiated segregation of this region far beyond Brodmann's classical scheme. This novel segregational concept of structural and functional architecture more adequately reflects the various functions of Broca's region in cognitive and/or linguistic processes.     

Automated assembly of optimally spaced and balanced paired comparisons: Controlling order effects

To control order effects in questionnaires containing paired comparisons, Ross (1934) described an optimal ordering of the pairings. The pairs can also be balanced so that every stimulus appears equal numbers of times as the first and the second member of a pair. First, we describe and illustrate the optimally spaced, balanced ordering of pairings. Then we show how the optimally spaced, balanced order can be used to implement a matrix-sampling design or a fully incomplete design when the number of stimuli n is so large that respondents cannot reasonably be expected to judge all n(n - 1)/2 pairs. The algorithm for balancing and optimally spacing the list of pairs is described.     

On the measurement of criterion noise in signal detection theory: the case of recognition memory

Traditional approaches within the framework of signal detection theory (SDT; Green & Swets, 1966), especially in the field of recognition memory, assume that the positioning of response criteria is not a noisy process. Recent work (Benjamin, Diaz, & Wee, 2009; Mueller & Weidemann, 2008) has challenged this assumption, arguing not only for the existence of criterion noise but also for its large magnitude and substantive contribution to individuals' performance. A review of these recent approaches for the measurement of criterion noise in SDT identifies several shortcomings and confoundings. A reanalysis of Benjamin et al.'s (2009) data sets as well as the results from a new experimental method indicate that the different forms of criterion noise proposed in the recognition memory literature are of very low magnitudes, and they do not provide a significant improvement over the account already given by traditional SDT without criterion noise.     

Visual feedback of hand trajectory and the development of infant prehension

The purpose of this longitudinal infant study was to investigate the influence of visual information of the hand trajectory in the development of reaching movements in prehension. Ten infants were observed biweekly from the age of 10 weeks to 28 weeks and 1 yr. The reach kinematics were analyzed at age of reach onset, 6 mo and 1 yr of age. The results showed that infants reached for objects earlier when the visual feedback of the hand trajectory and the object were available. However, visual feedback of the hand trajectory did not change the movement speed and smoothness of the reach component at 6 mo and 1 yr of age. Infants reached for the larger object earlier and with higher velocity than for the smaller object. Visual feedback of the hand facilitates the age of reaching onset, but when the reaching movements become sufficiently stable, infants perform equally well with or without visual trajectory feedback of the hand.     

Self-organized criticality and learning a new coordination task

The purpose of this study was to investigate the hypothesis that a self-organized criticality (SOC) practice condition would have a higher improvement rate in performance outcome than a typical progressive difficulty of practice regimen. The roller ball task was used where participants undergo a phase transition from failure to successful performance after sufficient practice. The findings from two experiments showed that the SOC condition had the fastest rate of improvement and the highest performance success level. The success probability in the SOC practice regime was close to the theoretically predicted value of 50%. It appears that the SOC practice condition - by scaling task difficulty to skill level in a self-controlled adaptive strategy - facilitates the learning of new movement coordination pattern by keeping the participant close to the parameter region of the transition of the movement dynamics.