Adaptation and repulsion in the figural after-effect

An experiment is reported which shows the effect of inspection of a curved line on the apparent curvature of a curved test line for a range of curvatures of both I and T lines. A second experiment extends the range of I curvatures, using only one T line, a straight line. The experiments showed both adaptation and repulsion components in the FAE.

An experiment by Kohler and Wallach which could not be reconciled with these results was repeated in the relevant part; the results were in agreement with the first experiment here and did not agree with those obtained by Kohler and Wallach.

An argument is presented that both adaptation and repulsion effects could be produced by a cell adaptation mechanism.     

Studies in olfactory acuity. II.: Relative detectability of n-aliphatic alcohols by the rat

The ability of albino and black rats to detect n-aliphatic alcohols in the vapour phase has been investigated and probit analysis used to evaluate the results. At median threshold (= 50 per cent, success level) detectability tends to increase by logarithmic increments as the number of carbon atoms in the molecule is increased. However, a similar but reverse relationship occurs between carbon chain length and the gradient of the probit regression lines; and detectability at the 85 per cent. success level, as estimated by interpolation, shows a trend towards oscillation. It is suggested that this finding can resolve the apparent conflict in the literature concerning the pattern of odour intensity in homologous series, and that it may reflect the influence of low water solubility in limiting response to high concentrations of longer chain alcohols.

When expressed as pressures, median threshold values for alcohols in the rat vary directly with saturated vapour pressures; when expressed as thermodynamic activities intermediate and longer chain alcohols appear to be equally stimulating, whilst short chain alcohols show decreasing activities as the series is ascended. In several of the relations considered the position of methanol and dodecanol appears anomalous.     

Reasoning in the hooded rat

A problem situation was devised to test Deutsch's (1956) theory of reasoning. In this situation various problems can be set the rat and these problems admit of various equally rational solutions. Predictions from the theory were made, not only that the animals would solve the problems, but also which particular solution they would adopt. These predictions are confirmed. The rats were trained to run to two goal-boxes, one near, the other more distant. The near one had two paths of equal length leading to it, the more distant goal only one. After training, the animals chose the near goal-box on the first trial of the day. On the test trials the near goal-box was left empty, or the chosen path blocked, or a mesh placed across the goal-box, with the food accessible via the other short path.