The development of adaptive conformity in young children : effects of uncertainty and consensus

Human culture relies on extensive use of social transmission, which must be integrated with independently acquired (i.e. asocial) information for effective decision-making. Formal evolutionary theory predicts that natural selection should favor adaptive learning strategies, including a bias to copy when uncertain, and a bias to disproportionately copy the majority (known as conformist transmission'). Although the function and causation of these evolved strategies has been comparatively well studied, little is known of their development. We experimentally investigated the development of the bias to copy-when-uncertain and conformist transmission in children from the ages of 3 to 7, testing predictions derived from theoretical models. Children first attempted to solve a binary-choice quantity discrimination task themselves using asocial information, but were then given the decisions of informants, and an opportunity to revise their answer. We investigated whether children's revised judgments were adaptively contingent on (i) the difficulty of the trial and (ii) the degree of consensus amongst informants. As predicted, older but not younger children copied others more on more difficult trials than on easier trials, even though older children also showed a tendency to stick with their initial, asocial decision. We also found that older children, like adults, were disproportionately receptive to non-total majorities (i.e. were conformist) whereas younger children were receptive only to total (i.e. unanimous) majorities. We conclude that, whilst the mechanism for incorporating social information into decision-making is initially very blunt, across the course of early childhood it converges on the adaptive learning mechanisms observed in adults and predicted by cultural evolutionary theory. A video abstract of this article can be viewed at http://youtu.be/Qb6JINGYqVkPostprintPeer reviewe

The role of the loss function in the probabilistic function approximation

Generalising results on the time series estimation it is natural to consider function approximation with finite data observations in a probabilistic setting. The function is treated as a stochastic process where for each point in the functions domain the function is a random variable. Equivalently the function can be considered as a single random variable whose range is a space of functions. In this paper two results well known within the context of time series estimation and stochastic control are generalised to probabilistic function approximation problems. Under mild conditions on the space of functions it is shown that the optimal function estimate corresponds for all reasonable symmetrical loss functions to the pointwise conditioned expectation given the observed data. Further in the case where the space of functions belongs to the class of Gaussian process the optimal estimate is the conditional expectation even for asymmetric loss functions

The use of neural networks to characterise problematic arc sounds

Automation of electric arc welding has been at the centre of considerable debate and the subject of much research for several decades. One conclusion drawn from all this effort is that there seems to be no single system that can monitor all of the variables and subsequently, fully control any welding process. To date there has been considerable success in the development of seam tracking systems employing various sensing techniques, good progress has been made in the area of penetration measurement and worthwhile use has been made of the integration of expert systems and modelling software within these control domains. Skilled welders develop their own monitoring and control systems and it has been observed that part of this expertise is the ability to listen subconsciously to the sound of the arc and to alter the electrode position in response to an adverse change in arc noise. Attempts have been made to analyse these sounds using both conventional techniques and more recently expert systems, neither have delivered any usable information. This paper describes a new approach involving the use of neural networks in the identification of sounds which indicate that the welding system is drifting out of control

The management of industrial arc welding by neural networks

New methods of monitoring industrial process variables are constantly being sought with the aim to improve control efficiency. It has been observed that skilled welders subconsciously adapt their manual arc welding technique in response to a variation in the sound produced from the process. This paper proposes an approach to the control of an automated submerged arc welding process using:- 1. Real time monitoring of acoustic emissions 2. The application of neural networks to predict the point of instability of the process variables

The real time analysis of acoustic weld emissions using neural networks

Artificial Neural Networks (ANNs) are becoming an increasingly viable computing tool in control scenarios where human expertise is so often required. The development of software emulations and dedicated VLSI devices is proving successful in real world applications where complex signal analysis, pattern recognition and discrimination are important factors. An established observation is that a skilled welder is able to monitor a manual arc welding process by subconsciously changing the position of the electrode in response to an adverse change in audible process noise. Expert systems applied to the analysis of chaotic acoustic emissions have failed to establish any salient information due to the inabilities of conventional architectures in processing vast quantities of erratic data at real time speeds. This paper describes the application of a hybrid ANN system, utilising a combination of multiple ANN architectures and conventional techniques, to establish system parameter acoustic signatures for subsequent on line control

The application of neural networks for the control of industrial arc welding

The use of automatic closed loop control is well established in all areas of manufacturing industry. New methods for measuring system variables, data processing and process control are being sought to improve system efficiency. Skilled welders are able to subconsciously monitor a manual arc welding process by listening to the sound and repositioning the electrode in response to a change in arc noise. This paper describes the real time monitoring of acoustic emissions from an automated submerged arc welding process and the application of Neural Networks to predict the point of instability of the process variables

The analysis of airborne acoustics of S.A.W. using neural networks

The analysis of acoustic emissions for machine health monitoring has made rapid advances in the last five years due to a revival of interest in the application of Artificial Neural Networks (ANNs). Complex signal analysis, which has often thwarted conventional statistical methods and expert systems, is now more possible with the introduction of 'neural' based computing methods. Acoustic emissions from welding processes are well documented. In particular, it has been established that a manual welder is capable of making intrinsic decisions concerning electrode position based on process noise. The analysis of time / amplitude signals and Fast Fourier Transforms (I-I-1s), within salient frequency bandwidths of the weld acoustic, has yielded erratic, unpredictable and noise polluted data. Extracting a meaningful interpretation from this data is computationally intensive when utilising standard statistical methods and leads to data explosions, especially when an 'on-line' corrective control signal is required. An Artificial Neural Network is 'trained' on examples from acquired data and performs a robust signal recognition task rather than relying on a programmed set of data samples as in the case of an expert system. This technique enables the network to generalise and, as a consequence, allows the input data to be erratic, erroneous and even incomplete. This research defines the development of a hybrid system, utilising high speed date capture and 141-1' computation for the signal pre-processing and a 'self organising' network paradigm to establish weld stability and real time corrective control of the process parameters. The paper describes a successful application of a Neural Network hybrid system to determine weld stability in submerged arc welding (S.A.W) through the interpretation of airborne acoustics

The Role of the Loss Function in Probabilistic Function Approximation

Generalising results on time series estimation, it is natural to consider function approximation with finite data observations in a probabilistic setting. The function is treated as a stochastic process where for each point in the functions domain, the function is a random variable. Equivalently the function can be considered as a single random variable whose range is a space of functions. In this paper, two results, well known within the the context of time series estimation and stochastic control, are generalised to probabilistic function approximation problems. Under mild conditions, on the space of functions, it is shown that the optimal function estimate corresponds, for all reasonable symmetrical loss functions, to the pointwise conditional expectation given the observed data. Further, in the case where the space of functions belongs to the class of Gaussian processes the optimal estimate is the conditional expectation even for asymmetric loss functions

Shifting a Quantum Wire through a Disordered Crystal: Observation of Conductance Fluctuations in Real Space

A quantum wire is spatially displaced by suitable electric fields with respect to the scatterers inside a semiconductor crystal. As a function of the wire position, the low-temperature resistance shows reproducible fluctuations. Their characteristic temperature scale is a few hundred millikelvin, indicating a phase-coherent effect. Each fluctuation corresponds to a single scatterer entering or leaving the wire. This way, scattering centers can be counted one by one.Comment: 4 pages, 3 figure