Blue Disk Research Articles

The effects of forebrain lesions on innate and imprinted colour, brightness and shape preferences in domestic chicks

In previous reports we have found that lesions of the lateral forebrain of domestic chicks prevent or destroy imprinted preferential discrimination of objects differing in colour/ brightness and shape. However, there were non-significant departures from random responding and it is possible that some residual learning was interacting with innate colour/ brightness preferences. An initial experiment in the present study showed that visually naive chicks had a significant blue and round shape preference when 1–2 days old. Visually experienced but non-imprinted chicks retained the round shape preference but showed weakened blue choice at 5–6 days of age. Chicks imprinted with a green slab showed a significant green preference at 5–6 days but chose slab and ball shapes equally. Taken together, these findings demonstrate imprinting for both colour and shape. Two further experiments tested lateral-, anterior-, and posterior-lesion and control chicks for retention of imprinted colour/brightness (mid-green) and shape (square) separately. Only the lateral- lesion group failed to choose the stimulus object with the familiar imprinted colour/brightness and instead chose the unfamiliar one (dark blue). No lesion group differed from the controls in the imprinted shape discriminations, all choosing the unfamiliar (round) as often as the familiar one. It appeared that the lateral-lesion chicks were like naive 1-day-olds in their colour/brightness preference but like imprinted birds in their shape preference. The final experiment tested the naive colour/brightness preferences of lateral- and anterior- lesion and control chicks using green and blue coloured discs in two tests with reversal of the brightness values. Both lesion groups behaved like controls in choosing dark blue in preference to light green. With reversed brightness values the controls showed a preference for the darker green discs, the anterior-lesion birds showed a slight tendency to choose the lighter blue disc, and the lateral-lesion birds reponded equally to the two colours. Thus, choices appeared to depend on brightness but in comparison with the controls there was some reduction in the brightness effect in the lateral-lesion birds and especially so in the anterior-lesion chicks. Since anterior lesions did not seriously impair the colour/brightness imprinted preference in the previous experiments, the reversal of the imprinted preference produced by lateral forebrain lesions is probably a true learning /memory loss and is not simply due to a colour or brightness sensory impairment.

The role of test stimuli in matching to compound samples by pigeons

Two pigeons matched to sample in a three-key operant conditioning chamber. In Experiment I, two different kinds of samples were presented on the center key.Element samples were members of one of two sample sets — colors (a red or blue disk) or lines (a vertical or horizontal orientation of a set of white lines). These samples were followed by their respective sample sets on the side keys as comparison stimuli.Compound samples consisted of a set of lines superimposed on a colored disk. Following these samples, either sample set could appear as comparison stimuli. Matching to compound samples was less accurate than matching to element samples. One interpretation is that sharing of attention among elements of a compound sample weakened stimulus control by each element. A different interpretation is that an element sample controlled matching better because it was physically identical to a comparison stimulus whereas a compound sample was not. Experiments II–IV evaluated this “generalization decrement” alternative by testing element- vs. compound sample control with both element and compound comparison stimuli. Irrelevant elements were added to form compound comparison stimuli, some of which were physically identical to a preceding compound sample, but never identical to an element sample. In all experiments, the addition of irrelevant elements of comparison stimuli reduced sample control. However, the generalization decrement hypothesis failed to predict how differences in performance maintained by element and compound samples were affected by different tests of sample control. Matching accuracy appeared to be independently determined by the number of elements in a sample and whether irrelevant elements were present during tests of sample control.

Theory of Dwarf Novae

Recent work on the physical processes resulting from mass transfer between the red and blue components of dwarf nova binaries is reviewed. The optical behaviour of the blue component's accretion disc suggests that it may be the infall, accretion energy which is being liberated during outbursts. Theoretical results which suggest that the red component may suffer quasi-periodic mass transfer instabilities are discussed. The resulting accretion disc properties are considered and compared with the observed optical outburst behaviour for the simplest steady state disc models. The complexity of the interaction between the two stellar components in these systems is emphasized.

Comparison of intra- vs extradimensional transfer of matching by rhesus monkeys

Monkeys were trained to match red, green, and blue disks in a two-choice matching-to-sample paradigm. Once the monkeys’ performance was asymptotic, a novel yellow disk was introduced into the paradigm, with the monkeys showing complete and immediate transfer of matching. However, when a novel triangular form was intr. duced into the paradigm, the same morkevs continued to respond to the familiar lored disks.