AMOUNT OF INDUCED AVOIDANCE BEHAVIOUR TO LIGHT IN THE PROTOZOA TETRAHYMENA AS A FUNCTION OF TIME AFTER TRAINING AND CELL FISSION

B ergström , S. R. Amount of induced avoidance behaviour to light in the Protozoa Tetrahymena as a function of time after training and cell fission. Scand. J. Psychol ., 1969, 10 , 16–20.—Two cultures of Tetrahymena, dividing synchronously after exposure to an alternating heat treatment, were exposed to series of light and electric shocks paired. After 20 and 30 exposures resp. to the stimulus combination, samples of these cultures were drawn every 18 min and placed in a partially lighted chamber. In samples drawn shortly after training, an essentially smaller proportion was found in the light, in comparison with control samples, which had received either shocks or light or neither of the two stimuli. In later samples, this proportion increased until it approached level of control samples. The course of the increase was not influenced by intervening synchronous cell division.     

AVOIDANCE BEHAVIOUR TO LIGHT IN THE PROTOZOA TETRAHYMENA: The effect of a gradual versus an abrupt boundary between dark and light

B ergström , S. R. Avoidance behaviour to light in the Protozoa Tetrahymena. The effect of a gradual versus an abrupt boundary between dark and light. Scand. J. Psychol ., 1969, 10 , 81–88.—Samples of Tetrahymena, trained to avoid light, were placed in the dark part of a partially lighted chamber. The frequency of animals entering the lighted part through a gradual and through an abrupt boundary between dark and light was observed. It was found that a gradual boundary was a much more effective obstacle to the animals than an abrupt one.     

INDUCED AVOIDANCE BEHAVIOUR IN THE PROTOZOA TETRAHYMENA

B ergstrom , S. R. Induced avoidance behaviour in the Protozoa Tetrahymena. Scand.J. Psychol ., 1968, 9, 215–219.—A sample of Tetrahymena, exposed to a series of light and electric shocks paired, was placed in a partially lighted glass chamber. During the first three minutes the number of animals in the lighted parts of the chamber decreased, and an essentially smaller proportion of the sample was then found in the light, in comparison with control samples, which had received either shocks or light or neither of the two stimuli.     

ACQUISITION OF AN AVOIDANCE REACTION TO LIGHT IN THE PROTOZOA TETRAHYMENA

B ergström , S. R. Acquisition of an avoidance reaction to light in the Protozoa Tetrahymena. Scand. J. Psychol ., 1968, 9 , 220–224.—A culture of Tetra-hymena, dividing synchronously after exposure to an alternating heat treatment, was exposed to a series of light and electric shocks paired. Samples of this culture were drawn after 1, 6, 11, 16, 21, 26, and 31 exposures to the stimulus combination and were then placed in a partially lighted chamber. With an increasing number of stimulus presentations, the proportions of the samples found in the lighted parts decreased, while they remained roughly constant in control samples which had received either shocks or light or neither of the two stimuli.     

A PARADOX IN THE PERCEPTION OF LUMINANCE GRADIENTS. III

In the second paper of this series (Bergström, 1967) a psychophysical model of certain contrast phenomena in the perception of luminance gradients was outlined on the basis of empirical findings. From this model two predictions were derived about the appearance of a steplike luminance distribution. These predictions about relations between the brightness of different parts of the distribution have been tested by means of a ranking method and a matching technique. Both predictions were confirmed.     

Distinctness of perceived three-dimensional form induced by modulated illumination: Effects of certain display and modulation conditions

The present study concerns the distinctness of the 3-D shape-induced on flat displays by spacemodulated illumination (“shape from shading”). The displays that we used varied in structure, hue contrast, lightness contrast, and in the number of reflectance edges present. The modulations of the illumination were a square-wave grating, a gradual modulation (a blurred grating), and an “O’Brien modulation,” which combines an edge and a gradient. The displays were compared, using the paired comparison method, as to the distinctness of the perceived 3-D form. The results showed that the structure and chromatic color of the display were important factors facilitating the distinctness of the induced 3-D shape under all the modulation conditions. The results are discussed in relation to the “vector model” for color constancy, proposed in earlier papers.     

Remarks on Penrose’s “New Argument”

It is commonly agreed that the well-known Lucas–Penrose arguments and even Penrose’s ‘new argument’ in [Penrose, R. (1994): Shadows of the Mind, Oxford University Press] are inconclusive. It is, perhaps, less clear exactly why at least the latter is inconclusive. This note continues the discussion in [Lindström, P. (2001): Penrose’s new argument, J. Philos. Logic 30, 241–250; Shapiro, S.(2003): Mechanism, truth, and Penrose’s new argument, J. Philos. Logic 32, 19–42] and elsewhere of this question.     

Egg incubation effects generate positive correlations between size,speed and learning ability in young lizards

Previous studies have suggested that body size and locomotor performance are targets of Darwinian selection in reptiles. However, much of the variation in these traits may derive from phenotypically plastic responses to incubation temperature, rather than from underlying genetic variation. Intriguingly, incubation temperature may also influence cognitive traits such as learning ability. Therefore, we might expect correlations between a reptile’s size, locomotor speed and learning ability either due to selection on all of these traits or due to environmental effects during egg incubation. In the present study, we incubated lizard eggs (Scincidae: Bassiana duperreyi) under ‘hot’ and ‘cold’ thermal regimes and then assessed differences in hatchling body size, running speed and learning ability. We measured learning ability using a Y-maze and a food reward. We found high correlations between size, speed and learning ability, using two different metrics to quantify learning (time to solution, and directness of route), and showed that environmental effects (incubation temperature) cause these correlations. If widespread, such correlations challenge any simple interpretation of fitness advantages due to body size or speed within a population; for example, survivors may be larger and faster than nonsurvivors because of differences in learning ability, not because of their size or speed.