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One of the earliest and best replicated findings resulting from the experimental investigation of animal learning is that conflict can produce disordered behaviour (Pavlov, 1927). These conflicts vary in kind, ranging from a conflict, as in the circle and ellipse discrimination experiments, between responding and not responding, to a conflict between approach and avoidance as in the pairing of electric shock with food. As Kimmel (1971) points out, whether or not a conflict produces disordered behaviour is a function of the animal's previous history. An ellipse has already to be clearly associated with ‘no food’ and a circle with food for disorder to be produced by presenting a circle and ellipse which are very similar to each other. Similarly, special conditions of training can be found which enable a dog to salivate and wag his tail in response to an injury severe enough to draw blood.

The dynamics of the COVID-19 epidemic vary due to local population density and policy measures. When making decisions, policy makers consider an estimate of the effective reproduction number R_t which is the expected number of secondary infections by a single infected individual. We propose a simple method for estimating the time-varying infection rate and reproduction number R_t using a sliding window approach applied to a Susceptible-Infectious-Removed model. The infection rate is estimated using the reported cases for a seven-day window to obtain continuous estimation of R_t. We demonstrate that the proposed adaptive SIR (aSIR) model can quickly adapt to an increase in the number of tests and associated increase in the reported cases of infections. Our results also suggest that intensive testing may be one of the effective methods of reducing R_t. The aSIR model was applied to data at the state and county levels.

There are two methods of measuring rotation: ( i ) taking direction into account (directional rotation) and ( ii ) not doing so ( total rotation). Because the latter has been repeatedly found to be related to specific visual conditions, John's proposal (John, 1964) to call ic "error" seems inappropriate; the word "error" is usually applied co undetermined variation.John's results indicate that directional rotation is affected to a lesser degree, and in somewhat different ways, by the same visual conditions affecting total rotation. W e cannot at present account for these findings or for the effects of horizontal vs vertical table-grain, which he also investigated. An explanation might be arrived at on the basis of ( i ) an examination of the current theory (Shapiro, 1953) with its known but limited predictive efficiency and ( i i ) study of directional rotation and its visual conditions.The present theory of rotation makes two assumptions. T h e first is that two separate visual situations are involved in the reproduction of designs: the "target" sinlation, i.e., the copied model in its own visual context, and the "reproduction" situation, S's reprod~iction of the model, again in its own visual context. The second assumption is that differences between model and reproduction may be due to differences between the two sinintions in percepn~al properties, especially in relation to the "constancies." Direction of rotation cannot be predicted by this theory, though the writers have been able to predict the following characteristics of drawn reproductions: ( i ) Shape-the relatively fore-shortened projection of the more distant model upon the retina results in squares being reproduced as oblongs. (ii) Internal Proportioas-when parts of each model are coloured either yellow or blue, yellow tends to be seen as larger than blue; therefore. S would draw, on white paper, the yellow parts larger than the blue. (iii) S i z e t h e relatively small visual angle subtended by more distant models compared with a reproduction of the same size would result in drawings being smaller than their models. Predicted results (smallest N = 9 7 ) were obtained for shape and internal proportions, and directly opposite results for size (Beech, 1957).