Anatomy of a flash. 2. The 'width' of a temporal edge.

In a previous study it has been found by using the Crawford masking paradigm with spatially coextensive stimuli that the end points of even a weak flash have a strong masking effect on the probe pulse, but no threshold elevation was observed when the probe was 100 ms or longer from flash onset and offset. The relationship between the strength of a temporal edge (eg the amplitude of a sudden increase in field luminance) and the duration of masking has not been systematically investigated. In the present experiments the duration of masking produced by a step of luminance as a function of step size was measured. With steps whose amplitude was between ten and five hundred times detection threshold, the duration of masking was about constant, ie 70 and 50 ms for on-responses and off-responses, respectively. This refractory period defined the 'width' of a temporal edge. Unless two suprathreshold unidirectional luminance changes are separated by an interval exceeding the width of a temporal edge, they are perceived as a single change in brightness. A linear systems analysis led to predictions for ramp stimuli that were confirmed by experiment.     

Extinction of a classically conditioned G.S.R. as a function of awareness

Insight, defined as the ability to verbalize the stimulus-response contingency of acquisition has bsen found to be unrelated to the extinction of an operantly conditioned verbal response. In the present study, the authors classically conditioned a GSR response in thirty Ss without insight, divided them into insight and no-insight groups following acquisition, and ran extinction trials which demonstrated a positive relationship (P< 0.001) under these particular conditions. It was concluded that the role of insight in extinction is a complex function of mode of conditioning (classical vs. operant) and/or mode of response (voluntary vs. involuntary), and that further studies utilizing the classical-voluntary and operant-involuntary combinations will be needed to define that function.     

"把陌生文化当作一面镜子"--访德国汉学家卜松山教授

卜松山 (Ｋ .Ｈ .Ｐｏｈｌ)加拿大多伦多大学哲学博士 ,现任德国特利尔大学汉学系主任 ,资深教授。发表有关中国文化的专著有《与中国进行跨文化对话》 ,论文多篇。问 :卜松山先生 ,近年来您在德国、中国众多学术刊物上发表了许多关于中国文化的文章 ,您为什么这么关注中国文化 ?答 :这得从我求学时代谈起。一次偶然机会 ,我读到一本讲中国禅宗的小册子 ,它向我打开了一个心向往之的神秘世界。我本来是学地球物理的 ,为了进一步了解初窥门径的东方世界 ,决定改学汉学。那是 1 970年 ,当时德国大学政治气氛很浓 ,汉学圈子也不例外。但我置身…     

I.P. Pavlov as a youth

Ivan P. Pavlov's youthful relations with parents and siblings, formal education, and social activities in Riazan' are described. The Pavlovs, a highly achievement-oriented family descending from a lowly serf, improved their social status by serving the Russian Orthodox Church. Pavlov, the son of a priest, studied in the 1860s at the Riazan' Ecclesiastic Seminary for priesthood. The turbulent 1860s' decade was a period of social and political reforms. Western ideas and science were introduced to Russia. The ambitious and idealistic I.P. Pavlov was influenced by popular essays written by the journalist D.I. Pisarev, the works of the German physiologist J. Moleschott, the English writer G.H. Lewes, the German zoologist C. Vogt and the physiologist M.I. Sechenov. Losing his religious faith, Pavlov abandoned the traditional goal of becoming a priest, and, convinced that science was a road to truth and progress, left Riazan' to study natural science at the University of St. Petersburg.     

I.P. Pavlov as a youth

Ivan P. Pavlov’s youthful relations with parents and siblings, formal education, and social activities in Riazan’ are described. The Pavlovs, a highly achievement-oriented family descending from a lowly serf, improved their social status by serving the Russian Orthodox Church. Pavlov, the son of a priest, studied in the 1860s at the Riazan’ Ecclesiastic Seminary for priesthood. The turbulent 1860s’ decade was a period of social and political reforms. Western ideas and science were introduced to Russia. The ambitious and idealistic I.P. Pavlov was influenced by popular essays written by the journalist D.I. Pisarev, the works of the German physiologist J. Moleschott, the English writer G.H. Lewes, the German zoologist C. Vogt and the physiologist M.I. Sechenov. Losing his religious faith, Pavlov abandoned the traditional goal of becoming a priest, and, convinced that science was a road to truth and progress, left Riazan’ to study natural science at the University of St. Petersburg.     

Anatomy of a flash. 1. Two-peak masking and a temporal filling-in

A modified paradigm of Crawford masking was used to link masking to brightness fluctuation, as distinct from flash brightness. Thresholds were measured for a 10 ms incremental pulse (the 'probe') presented before, during, or after a 500 ms pulse (the 'flash'). Both pulses were spatially coextensive with the background field, thus the criterion for probe detection was purely temporal. The flash occurred either in the tested eye, the opposite eye, or in both eyes. In all conditions, masking was strongly bimodal: thresholds peaked near flash onset and flash offset. The flash was perceived as a unitary event. Bimodal masking is attributed to cortical on-and off-effects, as (i) dichoptic masking was strong and (ii) the same incremental probe was masked by either incremental or decremental flashes. Strikingly, monocular probe thresholds were about equally elevated by binocular as by monocular flashes, although the binocular flashes were brighter. Therefore, some monocular features can be preserved in the larger net binocular response. A general conclusion is that masking depends on the same transient neural responses that bring about a brightness fluctuation, whereas the appearance of the flash as a single event, a unitary change of brightness, depends on a different mechanism, perhaps a sustained response that performs a temporal filling-in.     

Timing without a timer.

Inferred-process theories propose various internal timing mechanisms to provide discriminative stimuli for temporal control of behavior. Biobehaviorally informed computer simulations indicate that timing may emerge from the action of reinforcement on neural circuits without the need to postulate timers of any sort.     

Towards a Christian bioethics.

Rather than revealing itself as a single, unified, ecumenical faith, Christianity is sundered with Christians united neither in one communion nor in one baptism. Christian Bioethics seeks to examine the traditional content-full moral commitments which the Christian faiths bring to life, sexuality, suffering, illness and death within the contexts of medicine and health care. Seeking to understand the differences which separate the bioethics of Roman Catholics, Protestants, and the Orthodox, Christian Bioethics explores the manners in which the faiths diverge. The failure of the Enlightenment project to disclose a content-full communality that would bind mankind has left much to be reconsidered by Christians who face new ethical dilemmas in the novel guise of advances in health care technologies.     

E. W. Beth as a philosopher of physics

This paper examines E. W. Beth’s work in the philosophy of physics, both from a historical and a systematic point of view. Beth saw the philosophy of physics first of all as an opportunity to illustrate and promulgate a new and modern general approach to the philosophy of nature and to philosophy tout court: an approach characterized negatively by its rejection of all traditional metaphysics and positively by its firm orientation towards science. Beth was successful in defending this new ideology, and became its leading Dutch representative in the first two decades after the second world war. Beth also contributed importantly to the method of the philosophy of physics in a narrower sense, by proposing and promoting the semantic approach in the formal analysis of physical theories. Finally, he worked on several specific foundational questions; but he was probably too much of a logician to leave his mark in this area.