Showing papers by "University College London published in 1972"

Psychology of Reasoning: Structure and Content

Abstract: 'Is there any other point to which you would wish to draw my attention?' 'To the curious incident of the dog in the night-time.' 'The dog did nothing in the night-time.' 'That was the curious incident, ' remarked Sherlock Holmes. The quotation from A. Conan Doyle with which this book begins, is a delightfully appropriate summation of the authors' point of view garnered from their fifteen years of experiments on the psychology of reasoning. Dr. Wason and Dr. Johnson-Laird are intrigued by the extent to which most individuals can be considered naturally rational thinkers. They present here the surprising results of their comprehensive investigations of how humans draw explicit conclusions from evidence. Given a set of assertions, the authors write, to what extent can the individual appreciate all that follows from them by virtue of logic alone, and remain unseduced by plausible, but fallacious conclusions? We are not concerned with whether these assertions are true or false, nor with whether the individual holds them among his beliefs, nor with whether they are sane or silly. At the core of the Psychology of Reasoning is a vigorous discussion that incorporates various illustrations--some of them humorous, all of them fascinating--of the use of reason under a wide variety of different conditions. Particular emphasis is placed on the difficulties involved in dealing with negatively marked information that must be combined and used with other information for reaching conclusions. Thorough treatment is given as well to the search for plausible contexts that will render anomalous or ambiguous statements sensible. The authors have strived to isolate the components ofinference, the basic steps of any kind of deductive activity, in order to determine the psychological processes involved in them. What has been the outcome of this research? Dr. Wason and Dr. Johnson-Laird conclude, our research has suggested that the individual's logical competence may be either enhanced or limited by performance variables. And, of these, content has turned out to be vitally important for revealing, or obscuring structure. At best, we can all think like logicians; at worst, logicians all think like us.

Super-resolution aperture scanning microscope.

Abstract: THE classical theory of the resolving power of optical instruments implies a limit to the observation of details in an object if these are significantly smaller than one wavelength, λ0, of the illuminating radiation. This Abee barrier is not entirely impenetrable. Lukosz1,2 has shown how an improvement by a factor of two can be made by the use of complementary spatial filters. Attempts to proceed further in this direction are soon frustrated, however, because the spatial frequencies one is seeking to transfer are such that the waves become evanescent in the direction in which one would like them to propagate. Nassenstein has developed an ingenious scheme3 in which evanescent waves are used to illuminate the object, and a magnified image is obtained using a holographic technique. The resolution capability is determined by the wavelength of the evanescent wave. This is less than λ0, but it is not easy to devise systems where it would be very much smaller.

Extension of covariance selection mathematics

Abstract: This paper gives some extensions of the selection mathematics based on the covariance function published in Price (1970). Application of the mathematics to ‘group selection’ is briefly illustrated. More about applications will be shown in a later paper concerning ‘ Selection in populations with overlapping generations’, which will be submitted to this journal. To facilitate reference in that paper, the equations in this paper are labelled with the letter ‘A. The mathematics given here applies not only to genetical selection but to selection in general. It is intended mainly for use in deriving general relations and constructing theories, and to clarify understanding of selection phenomena, rather than for numerical calculation.

Glass-coated platinum-plated tungsten microelectrodes.

Abstract: Practical methods are described in detail for the construction of tungsten microelectrodes. Straightened 127 μm-diameter tungsten wires are etched to sharp points in KNO2 solution. The sharpened wires are insulated by collapsing borosilicate-glass capillaries onto them in a horizontal pipette puller. A novel technique is described for the removal of insulation from electrode tips by embedding them in a softened bead of solder glass. The bead is then allowed to cool, producing clean fractures of the borosilicate glass at the surface of the bead; the bare, undamaged tip of the electrode is then withdrawn. Electrodes with bare tips from 2 μm to more than 100 μm can be prepared with this method. Finally, the tips are plated with a gold cyanide solution and platinum black. The finished electrodes have tapers of less than 2° and yet are extremely strong. Electrodes with conical plated tips 20 μm long by 6 μm diameter have 1 kHz impedances of less than 1 MΨ.

Reasoning and a sense of reality

Abstract: An experiment was performed to determine whether the use of realistic materials would improve performance in a deceptive reasoning problem. The task involved selecting from a set of envelopes those which, if they were turned over, could violate a given rule. The rule concerned either a realistic relation (‘if a letter is sealed, then it has a 50 lire stamp on it’) or else an arbitrary relation between symbols (‘if a letter has an A on one side, then it has a 3 on the other side’). Twenty-two of the 24 subjects made at least one correct answer with the realistic material but only seven of them did so with the symbolic materials. The verbal formulation of the rule was also varied but yielded only a marginal interaction with the main variable. It is argued that the critical factor is the intrinsic connexion between items rather than their specific nature.

Review Lecture: Adaptive Radiation and Behaviour of the Malagasy Lemurs

Abstract: The systematic distribution of behavioural characters in lemurs can be analysed using the same techniques as for anatomical characters, without considering physiological mechanisms. Behaviour and structure are usually interdependent (functional morphology), so it follows that behavioural features probably evolve hand-in-hand with morphology. Behavioural and morphological characters generally exhibit the same patterns of systematic distribution, though it is not yet clear whether evolution typically operates through selection of inherited behaviour patterns, or through indirect canalization of behaviour which is dependent upon particular structures. The extant Malagasy lemurs and their recent subfossil relatives must be considered together as an integrated lemur fauna, which has undergone great reduction over the last few thousand years. The lemurs appear to form a natural group with the Afro-Asian loris/bush-baby group, certain Miocene lorisoids from East Africa ('Progalago group') and the Eocene Adapinae (Northern Europe) and Notharctinae (North America). This natural group can be referred to as the Strepsirhini. Simpson's classification (1945) implies that these Strepsirhines are closely related to the Tupaiidae (tree-shrews), and to the fossil Anagalidae and Plesiadapidae. Inclusion of these groups in the Order Primates is regarded here as superfluous, and discussion is restricted to the Strepsirhini, as defined above. It is suggested that the Malagasy lemurs and the Afro-Asian bush-babies and lorises had a common origin in Africa (lemur/loris stock), and that this ancestral stock had an earlier common origin with the Adapinae and Notharctinae of the Northern continents. The geographical distribution of the lemurs within Madagascar is examined, and seven basic zones of species distribution are identified. Each of these zones has distinctive climatic and vegetational characteristics which can be expressed on a 'climagramme' incorporating Emberger's pluviothermic quotient. Major physical barriers can be recognized along all of the boundaries between the present distribution zones. A model is suggested, in which climatically and physically demarcated zones of this kind can operate as agents for geographical isolation and speciation. Occasional emigration from zone to zone could produce a dynamic situation in which ecological competition between closely related species would favour a pattern of adaptive radiation with individual species becoming increasingly specialized for distinct ecological niches. In order to discuss the origin of the ancestors of the Malagasy lemurs, the relationship between Madagascar and other land-masses is examined. Although most authors agree that emigration from Africa has provided the main basis for biological invasion of Madagascar, there has been some controversy about the pattern of spatial relationships between Madagascar and Africa over time. Some authors (notably Simpson (1943) and Millot (1952)) have favoured a 'stable continents' hypothesis, and this has led to a concentration of interest on the Northern continents as the seat of Primate evolution. One outcome of this has been the suggestion that lemurs and lorises are separately derived from Northern European Adapinae. New geophysical evidence indicates that the 'stable continents' hypothesis is virtually untenable, and that continental drift theory provides the only coherent explanation of terrestrial evolution. This shifts the emphasis on Primate evolution to the Southern continents (notably Africa), and it seems likely that the lemurs and lorises had a common ancestry in Africa during the early Tertiary (for which no fossil evidence is available). One further consequence of drift theory is the observation that the Mozambique Channel has probably increased in width throughout the Tertiary, and that emigration of mammals to Madagascar from Africa has become increasingly improbable. Having established that Madagascar was probably invaded by a very small number of ancestral lemur species, which subsequently underwent adaptive radiation within the island, the systematic distribution of behavioural characters among living forms is examined. Attention is given to annual and daily patterns of activity, nesting patterns, diet (and some correlated dental features), locomotion (and some skeletal features), reproduction and social behaviour. In each case, it is shown that the Mouse Lemur group (Cheirogaleinae) and the Indri group (Indriidae) are internally cohesive in their characteristic behaviour patterns. The True Lemur group (Lemurinae) exhibits a wide range of behavioural adaptation, which is paralleled by equivalent morphological diversity. Behaviourally, the Aye-aye (Daubentonia) is as distinct as it is in morphological terms. By a process of induction, it is established that the behaviour of the ancestral lemurs was probably quite similar to that now exhibited by some Cheirogaleinae (particularly Microcebus), although living species in this group exhibit a number of probable specializations away from the ancestral condition. This conclusion is not surprising, since the Cheirogaleinae are also the least specialized of the lemurs in morphological terms. However, it is significant that the same ancestral pattern can be deduced for the loris/bush-baby group. Thus, the common ancestor of the Southern Strepsirhini (lemurs + lorises) was probably a small omnivorous form feeding primarily on insects, fruit and sap. The sap would have been gathered with the 'tooth-scraper' in the lower anterior dentition. There was probably a weakly developed spatial system of social organization, with central males of a population nucleus having access to females (a small number to each male), and peripheral males living on the fringe of each population. Competition between males would have provided a basis for selective mating and migration of peripheral males between population nuclei would have ensured exogamy. Extension of Walker's (1967) exemplary study of prosimian locomotion shows that the ancestral lemur/loris probably exhibited hindlimb dominated locomotion based on a grasping function of the extremities (primarily developed in the pes). The ancestral lemur/loris was probably nest-living, giving birth to - and caring for - a small number of well-developed infants after a relatively long period of gestation. There is some evidence that this ancestral form was nocturnal in habits, and it seems likely that the ancestral species which invaded Madagascar would have had a well-developed seasonal pattern of activity. Arboreal adaptation, the attachment to a nest, the small body size, and the ability to survive an adverse period of poor food supply (e.g. on the basis of fat reserves) would have fitted the early lemurs for a period of chance emigration across the Mozambique Channel on natural rafts of vegetation. Such rafts could have been formed from trees and other vegetation torn from forests lining rivers (e.g. the River Zambesi) on the east coast of Africa. Since the common ancestor of the lemurs and lorises was not very far removed from the ancestral Primate stock, many of the characters listed above must have been to some extent developed in the earliest Primates. This provides further evidence for the hypothesis that tree-shrews, anagalids and plesiadapids are quite separately derived from the ancestral Eutherian mammal stock, and that these three groups have no specific relationship to the Order Primates.

Pauses, clauses, sentences.

Abstract: The tool of pause measurement was applied to the question of the psychological reality of syntactic structures in spontaneous speech. The material investigated covered a wide field of speech productions, of different speakers and different speech tasks. Their analysis showed that the hierarchy of syntactic structures is reflected differentially in the pause structure of spontaneous speech. When readings of the spontaneous texts were compared with the original spontaneous speech it emerged that the reading process modifies the pausing for different syntactic structures differently. Sentences as distinct from clauses are marked by their temporal cohesion in spontaneous speech as well as in reading. This fact is discussed with reference to Wundt's analytical theory of sentence-wholes.

Elicitation of selective T and B lymphocyte responses by cell surface binding ligands.

Abstract: One of the motivating forces in lymphocyte biology is the belief that the behaviour of lymphocytes, and more particularly their response to antigen, provides a unique opportunity to analyse the molecular and cellular events involved in the induction and expression of 'differentiation'. A major advance in the realisation of this potential was the finding (Nowell 1960) that quiescent non-dividing small lymphocytes could be triggered into a derepressed state of active growth and proliferation in vitro by phytohaemagglutinin (PHA). The response observed involves parameters common to many systems in which cell growth and proliferation are occurring, e.g. tissue regeneration and embryogenesis, and includes enhanced glycolysis, lysosomal enzyme activity, enhanced nuclear template activity, histone acetylation, DNA polymerase enzyme activity, etc. More specific changes indicative of 'differentiated' activities of lymphocytes, e.g. immunoglobulin synthesis, may also occur, as will be discussed in this review. Although precise quantitation of the number of responding cells has yet to be reported it is clear that the number of cells reacting to PHA and similar stimulants Is considerably greater than one would expect to observe with a classical 'immunological' response in which antigen recognition by relatively small numbers of cells occurs (i.e. 'cional' selection). The response to PHA and other mitogens (see below) is therefore generally considered to be non-specific, i.e. it is a polyclonal lymphocyte response initiated by

Structures of Physiological Interest in the Frog Heart Ventricle

Abstract: Two structures of physiological interest in frog heart ventricles have been examined in detail: ( a ) the layer of endothelial cells which encloses each bundle of heart fibres, and ( b ) the sarcoplasmic reticulum (SR) inside the heart fibres. Some additional observations on fibre sizes and types have been made. Movement across the endothelial cell layer of molecules (molecular or ionic size ≤ 12.5 nm) occurs through narrow clefts separating each endothelial cell from its neighbour. This conclusion results from experiments made with the extracellular markers ferritin and horseradish peroxidase. A diffusion equation describing the movement of solutes into and out of the fibre bundle has been derived using several geometrical parameters, such as the length and width of the clefts and the size of the extracellular aqueous space inside the bundle, all of which were determined from electron micrographs of the tissue. The theoretical solution for a stepwise change of external calcium concentration gives a halftime of 2.3 s (± 0.8 s, S.D. of 13 bundles) for diffusion equilibrium at the surface of the heart fibres; this value, however, is likely to be an overestimate, by some 20-30 %, on account of several systematic errors which are described. The sarcoplasmic reticulum in heart fibres consists of a network of thin tubules which partially encircle the myofibrils at Z-line level and also form occasional longitudinal connexions. Branches extend to peripheral regions of the cell and terminate in close apposition to the inner surface of the cell membrane. The volume of the SR is estimated to be approximately 0.5% of the myofibrillar volume of the cells. Cross-sectional areas of heart fibres (and also their shapes) vary considerably, from less than 2 to more than 100 µm 2 (average 17.4 µm 2 ).Fibres of large size and small surface/volume ratio contain many fewer myofibrils and more glycogen granules than fibres of the same size but larger surface/volume ratio. Physiological implications of these results are discussed.

Average heterozygosity per locus in man: an estimate based on the incidence of enzyme polymorphisms

Abstract: SUMMARY 1. Data from electrophoretic surveys of enzymes in European populations are reviewed. 2. Out of the seventy-one structural gene loci determining enzyme structure which have been scrutinized electrophoretically, 20 (28 %) were found to show genetic polymorphism. The average heterozygosity per locus for alleles determining electrophoretic variants is estimated at 0·067. 3. These results are compared with data from some other species. 4. For several different reasons, most of which relate to the techniques used and the enzymes and tissues surveyed, it seems likely that the present data considerably underestimate the true incidence of polymorphism and average heterozygosity per locus.

Post-Buckling of Geometrically Imperfect Plates

Abstract: Explicit expressions are derived for the collapse and elastic post-buckling of simply supported, geometrically imperfect plates with stress-free edges. For the purposes of design, such plates can be taken as representative of the stiffened compression elements of thin-walled structural sections. Different generalized geometric imperfection parameters are studied and the effects compared to established test data obtained from cold-formed steel sections subjected to either bending or compression. For these sections a suitable and completely general parameter describing the imperfection amplitude, e\d0t, of a plate of thickness t is shown to be e\d0=0.2σ\dy/σ\Dcr\N in which σ\dy is the yield strength of the plate material; σ\Dcr\N is the theoretical local buckling stress of the equivalent ideal plate and is a direct function of its width to thickness ratio. This parameter is recommended for the design of cold-formed steel sections against local buckling.

On the Nonlinear Response of a Marginally Unstable Plane Parallel Flow to a Two-Dimensional Disturbance

Abstract: The differential equation governing the nonlinear evolution of an initial centred infinitesimal disturbance to a marginally unstable plane parallel flow was obtained by Stewartson & Stuart (1971) and some of its properties elucidated by Hocking, Stewartson & Stuart (1972). Of especial interest is the final localized burst of the solution which occurs when all the coefficients of the equation are real and the first Landau constant is positive. In plane Poiseuille flow, however, the standard example of plane parallel flow, these coefficients are complex and in the present paper an analytic and numerical study is made of the evolution of the solution when they are permitted to take general values. It is found that if the real part $\delta \_{\text{r}}$ of the first Landau constant is positive it is possible to have either a burst or a solution which remains finite for all time depending on the values of the other coefficients. In addition when a burst occurs it can take on two different structures. If $\delta \_{\text{r}}<$< 0 all solutions remain finite but the amplitude of the oscillation does not tend to a limit if the imaginary part $\delta _{\text{i}}$ of the first Landau constant is large enough. For the particular example of plane Poiseuille flow, skewed disturbances burst only if they are inclined to the main stream at an angle exceeding about 56$^{\circ}$.

Alcohol dehydrogenase isozymes in adult human stomach and liver: evidence for activity of the ADH 3 locus.

Abstract: Ann. Hum. Genet., Lond. (1972), 35, 243 Pyinted in Great Britain Alcohol dehydrogenase isozymes in adult human stomach and liver : evidence for activity of the ADH3 locus BY MOYRA SMITH, D. A. HOPKINSON AND HARRY HARRIS M.R.C. Human Biochemical Genetics Unit, Galton Laboratory, University College London I n a previous paper (Smith, Hopkinson & Harris, 1971) we put forward a genetical hypothesis to explain the isozyme patterns of human alcohol dehydrogenase in various tissues and at different times in development. It was suggested that there are three loci each coding for a structurally distinct type of polypeptide chain; that the isozymes are dimers; and that any particular isozyme may be made up of two identical subunits coded by a specific allele at one of the loci, or of two non-identical subunits coded by alleles at two separate loci, or of two non-identical subunits coded by different alleles at the same locus. The loci were called ADH,, ADH, and ADH, and the corresponding polypeptide subunits a, /3 and y . At each of the ADH, and ADH, loci the evidence indicated that two different common alleles occur, coding for structurally distinct forms of the corresponding polypeptide. According to the hypothesis, the isozymes in the cells of a particular tissue at a given time in development depend on the relative activities of the three loci. Thus in liver, a polypeptides determined by ADH, appear to predominate in early foetal life, but in the course of foetal develop- ment /3 polypeptides determined by ADH, appear in increasing amounts, so that while in the early foetus the main isozyme observed is aa, as development proceeds the isozymes a/3 and /3/3 appear in increasing quantities. I n adult liver ADH, activity exceeds ADH, activity. In lung, kidney and the gastro-intestinal tract the total alcohol dehydrogenase activity is very much less than in liver, and the contributions made by the different loci to the total activity show striking differences. I n lung, polypeptides determined by ADH, appear to predominate both in foetal life and in the adult. I n kidney y polypeptides determined by ADH, predominate throughout foetal life but diminish after birth, and in the adult the ADH activity that can be detected appears to be mainly derived from ADH,. I n the gastro-intestinal tract y polypeptides determined by ADH, are found as in the kidney to predominate throughout foetal life. But because of lack of suitable material the situation in adult gastro-intestinal tract was not established in our earlier work. The findings reported in the present paper are concerned with two aspects of the problem. The first concerns the ADH isozymes in the adult gastro-intestinal tract. I n our previous studies we had attempted to examine this question using material from the intestine obtained at autopsy. However, sufficiently clear and consistent isozyme patterns were not obtained. We have now found, however, that adult stomach samples from autopsy give clearly defined isozyme patterns and these correspond to those previously observed in foetal kidney and foetal intestine. Thus it appears that most of the ADH activity in adult stomach is derived from the ADH, locus. The second topic we consider here concerns certain isozymes which had previously been observed in adult liver, but which at that time could not be easily accounted for in terms of the three-locus hypothesis. These isozymes occur in addition to the aa, a/3 and /3/3 isozymes of liver, and it had been noted that they show marked variations from individual to individual in their

The isolation and properties of a clonal tissue culture strain of pluripotent mouse teratoma cells.

Abstract: SUMMARY A clonal tissue culture strain of pluripotent cells has been isolated from a transplantable teratoma of inbred strain of mice 129 Sv-Sl 3 CP. This cell strain S1KR when re-inoculated into mice produces teratomas containing at least ten types of tissue. Sub-clones have been isolated and two types distinguished. (1) 'C-type' with a densely-piled in vitro growth. These are tumourigenetic and pluripotent displaying a comparable range of differentiation to the original SIKR. (2) 'E-type' spreading, often epithelioid growth. These grow to a lower density in culture than 'C-type'. Mostly non-tumourigenetic; in those cases where a tumour has been obtained it did not display multiple differentiations. The results are interpreted as demonstrating that the culture consists of equivalently pluripotent cells which may become determined and differentiate spontaneously in vitro into slower growing cell types which are continuously overgrown by the culture.

Segmentation of input in simultaneous translation.

Abstract: This paper examines the events of the simultaneous translation situation. Parallel visual records of the input speech and of the interpreter's speech were used to investigate what is the length and nature of the segment which the interpreter needs to monitor before he can start encoding. The results suggest that lexical and grammatical aspects of the text, as well as the interpreter's subjective organization of the material, interplayed in a systematic fashion.