Because of the important role which the ‘autocatalytic’ or ‘logistic’ equation has played in determining the direction of a good deal of research both in demography and in the study of individual growth phenomena, a critical and comparative evaluation of those leading ideas inRobertson's book which pertain to this equation and of some of the criticisms levelled against it seemed to be of interest. The present paper shows that, contrary to common belief,Robertson did not really assume that the autocatalytic reactions (...) to which he compared growth processes, took place in closed systems . On the other hand, he does not seem to have found a satisfactory representation of how the growth phenomena of the individual cells in an organism might interact to yield the overall growth of the organism as a whole. Nor is the manner in which he made his equation account for the openness of the individual cells free from possible criticism. An alternative equation is here proposed, which will be discussed in another paper. The properties of the solutions of this equation are such that the autocatalytic theory might never have gained a foothold if this, more realistic, equation would have been the object of the initial studies. (shrink)

This note is viewing survival data of a natural cohort as being generated by a possibly nonlinear, nonhomogeneous death process. It proves that the usual conditional distributions of the number of survivors at a certain age are binomial if and only if the death process is linear. Thus the customary statistical methods for the analysis of life table data are, strictly speaking, invalid whenever the underlying death process is nonlinear. For example, if a contagious disease is the cause of some (...) or all of the deaths, the deaths will not be independent and the death process, not linear. One should then base the statistical analysis on a model for the spread of the disease rather than the routine binomial model. (shrink)

Evolutionary psychology is put forward by its defenders as an extension of evolutionary biology, bringing psychology within the integrated causal chain of the hard sciences. It is extolled as a new paradigm for integrating psychology with the rest of science. We argue that such claims misrepresent the methods and explanations of evolutionary biology, and present a distorted view of the consequences that might be drawn from evolutionary biology for views of human nature. General theses about adaptation in biology are empty (...) schemata, not laws of nature allowing the subsumption of mind under biology. Functional thinking is an indispensable tool for psychology, mostly of value in abstractive unification and as a heuristic, but it gains little from association with evolutionary notions of selection. Thus, we argue, the cherished integrative causal model evaporates, and evolutionary phraseology serves no more than rhetorical purposes. Moreover, the universality of human nature and the evolutionary irrelevance of individual variation are presented as biological truths that psychologists should respect in their approach to mind. On closer inspection, this turns out to be rather dubious biology. Psychology might conceivably be better off as a continuation of biology by different means, but evolutionary psychology does not provide the conceptual integration leading to such a happy union. (shrink)

A commonly used experimental procedure for the study of granulocyte kinetics involves the labelling and subsequent tracing of granulocyte DNA. Following the introduction of a label into the system, observations are made periodically on the concentration of label in the DNA of granulocytes taken from the circulating blood. A mathematical model for the expected value of this concentration has been derived, studied, and related to experimental observations from studies using P32 as a label. Insofar as the derivation of the model (...) accurately incorporates the relevant aspects of granulocyte kinetics, the model will be useful in the interpretation of the experimental observations in terms of these kinetics.Among other things, study of the model indicates that the assumption of “flash” labelling made with respect to some labels is quite crucial and needs to be examined critically. It has also been necessary to make adjustments to allow for the observed emergence of labelled cells from the marrow soon after label introduction. In addition, despite a high degree of confounding of parameter effects it has been possible to suggest bounds on some of the parameters of the model for some species. The bounds will be refined as the model is improved and more data become available. Study and development of the model continues with particular interest in generalizations to include the diseased state chronic granulocytic leukemia. (shrink)

Although euthanasia and assisted suicide in people with psychiatric disorders is relatively rare, the increasing incidence of EAS requests has given rise to public and political debate. This study aimed to explore support of the public and physicians for euthanasia and assisted suicide in people with psychiatric disorders and examine factors associated with acceptance and conceivability of performing EAS in these patients. A survey was distributed amongst a random sample of Dutch 2641 citizens and 3000 physicians. Acceptance and conceivability of (...) performing EAS, demographics, health status and professional characteristics were measured. Multivariable logistic regression analyses were performed. Of the general public 53% were of the opinion that people with psychiatric disorders should be eligible for EAS, 15% was opposed to this, and 32% remained neutral. Higher educational level, Dutch ethnicity, and higher urbanization level were associated with higher acceptability of EAS whilst a religious life stance and good health were associated with lower acceptability. The percentage of physicians who considered performing EAS in people with psychiatric disorders conceivable ranged between 20% amongst medical specialists and 47% amongst general practitioners. Having received EAS requests from psychiatric patients before was associated with considering performing EAS conceivable. Being female, religious, medical specialist, or psychiatrist were associated with lower conceivability. The majority of the psychiatrists were of the opinion that it is possible to establish whether a psychiatric patient’s suffering is unbearable and without prospect and whether the request is well-considered. The general public shows more support than opposition as to whether patients suffering from a psychiatric disorder should be eligible for EAS, even though one third of the respondents remained neutral. Physicians’ support depends on their specialization; 39% of psychiatrists considered performing EAS in psychiatric patients conceivable. The relatively low conceivability is possibly explained by psychiatric patients often not meeting the eligibility criteria. (shrink)

Colour has been shown to facilitate the recognition of scene images, but only when these images contain natural scenes, for which colour is ‘diagnostic’. Here we investigate whether colour can also facilitate memory for scene images, and whether this would hold for natural scenes in particular. In the first experiment participants first studied a set of colour and greyscale natural and man-made scene images. Next, the same images were presented, randomly mixed with a different set. Participants were asked to indicate (...) whether they had seen the images during the study phase. Surprisingly, performance was better for greyscale than for coloured images, and this difference is due to the higher false alarm rate for both natural and man-made coloured scenes. We hypothesized that this increase in false alarm rate was due to a shift from scrutinizing details of the image to recognition of the gist of the image. A second experiment, utilizing images without a nameable gist, confirmed this hypothesis as participants now performed equally on greyscale and coloured images. In the final experiment we specifically targeted the more detail-based perception and recognition for greyscale images versus the more gist-based perception and recognition for coloured images with a change detection paradigm. The results show that changes to images are detected faster when image-pairs were presented in greyscale than in colour. This counterintuitive result held for both natural and man-made scenes and thus corroborates the shift from more detailed processing of images in greyscale to more gist-based processing of coloured images. (shrink)

Transcranial direct current stimulation over the contralateral primary motor cortex of the target muscle has been described to enhance corticospinal excitability, as measured with transcranial magnetic stimulation. Recently, tDCS targeting the brain regions functionally connected to the contralateral primary motor cortex was reported to enhance corticospinal excitability more than conventional tDCS. We compared the effects of motor network tDCS, 2 mA conventional tDCS, and sham tDCS on corticospinal excitability in 21 healthy participants in a randomized, single-blind within-subject study design. We (...) applied tDCS for 12 min and measured corticospinal excitability with TMS before tDCS and at 0, 15, 30, 45, and 60 min after tDCS. Statistical analysis showed that neither motor network tDCS nor conventional tDCS significantly increased corticospinal excitability relative to sham stimulation. Furthermore, the results did not provide evidence for superiority of motor network tDCS over conventional tDCS. Motor network tDCS seems equally susceptible to the sources of intersubject and intrasubject variability previously observed in response to conventional tDCS. (shrink)

The explanatory gap refers to the lack of concepts for understanding “how it is that . . . a state of consciousness comes about as a result of irritating nervous tissue.” By assuming that there are colours in the outside world, Block needlessly widens this gap and Lycan and Kitcher simply fail to see the gap. When such assumptions are abandoned, an unnecessary and incomprehensible constraint disappears. It then becomes clear that the brain can use its own neural language for (...) representing aspects of the outside world. While this may not close the gap, it becomes clearer where we need new concepts. (shrink)

This contribution is a gentle introduction to so-called dynamic epistemic logics, that can describe how agents change their knowledge and beliefs. We start with a concise introduction to epistemic logic, through the example of one, two and finally three players holding cards; and, mainly for the purpose of motivating the dynamics, we also very summarily introduce the concepts of general and common knowledge. We then pay ample attention to the logic of public announcements, wherein agents change their knowledge as the (...) result of public announcements. One crucial topic in that setting is that of unsuccessful updates: formulas that become false when announced. The Moore-sentences that were already extensively discussed at the conception of epistemic logic in Hintikka’s ‘Knowledge and Belief’ give rise to such unsuccessful updates. After that, we present a few examples of more complex epistemic updates. Our closing observations are on recent developments that link the ‘standard’ topic of belief revision, as in ‘On the Logic of Theory Change: partial meet contraction and revision functions’, by Alchourron et al. , to the dynamic epistemic logics introduced here. (shrink)