Do environmental similarities explain the similarity in intelligence of identical twins reared apart?

Taylor (1980) claims to show that the similarity in IQ between monozygotic twins reared apart (MZA's) in the three classic studies by Newman, Freeman, and Holzinger (1937), Shields (1962), and Juel-Nielsen (1965) is due to similarity in their environments. A reanalysis, using Taylor's classification of the twins into similar and dissimilar environments on the basis of four different criteria, but using the alternate IQ measure used in two of the studies, shows that his findings do not constructively replicate. Taylor's conclusion that “it seems reasonable to suggest that the IQ correlations characterizing pairs of individuals with absolutely identical genes and absolutely uncorrelated environments would be extremely low” cannot be substantiated from the evidence at hand.     

IQ and social class

A brief overview is given of the nature-nurture debate elicited on the basis of Arthur Jensen's article concerning group differences in IQ test results published in 1969.Sandra Scarr-Salapatek found that the contribution of genetic variance in IQ test results tended to be larger in a more stimulating environment and proportionately smaller in a disadvantaged environment. This finding has been tested on data from a Swedish twin study. A comparison of within-pair similarity for MZ and DZ twins with varying social background has been made. Genetic variance seems to account for a greater proportion of the variance in IQ test scores in social group I and II compared to social group III. This is in accordance with the conclusions drawn by Scarr-Salapatek and thus tend to support the above-mentioned hypothesis. It therefore seems as though the potentially restricting effects of working class conditions for the development of the kind of abilities measured by conventional IQ tests would tend to reduce the degree to which genetic differences are expressed. More stimulating environmental opportunities, on the other hand, tend to allow a greater range of such differences in the middle and higher social classes.     

Eliminating the IQ-RT correlation by eliminating an experimental confound

Three experiments investigated the relation between visual scanning demands, reaction time (RT), and psychometrically defined intelligence (IQ). Prior studies have shown reliable correlations between RT and IQ in the range of −.20 to −.80. However, these studies have confounded the number of possible stimuli (stimulus uncertainty) with the size of the area in which the stimuli may appear (visual angle). Experiment 1 replicated these studies retaining this confound. As the number of stimuli increased from one to eight, the visual angle was permitted to increase as well (from 0° to 30°). The results showed that RT varied in accord with Hick's (1952) law, and a median correlation between IQ and six RT parameters (subjects' mean RTs and standard deviations at three levels of stimulus uncertainty) of −.47 was observed. Experiment 2 removed the confound, varying only stimulus uncertainty, and the median IQ-RT correlation declined to −.02. Experiment 3 held stimulus uncertainty constant at 1 bit (two stimuli) and varied visual angle; a median correlation of −.19 was observed. It was concluded that many of the previously reported correlations may not have hinged on speed of information processing alone, but at least in part on subjects' abilities to scan the display across which the stimuli appeared.     

Familiality estimates from restricted samples

In a recent paper here, Benbow, Zonderman, and Stanley (1983) report that the coefficient of regression of offspring IQ on parental IQ is much lower among the gifted than in the population at large. Thus, Benbow, Stanley, Kirk, and Zonderman conclude in a second paper, the gifted resemble their parents less than do people in general. In this paper, I show that this result is an artifact of the particular estimator of the regression coefficient employed by Bendoq, Zonderman, and Stanley. The leastsquares estimator, which they employ, is severely biased downward, if the sample on the dependent variable is restricted to the upper tail of the distribution, and this is precisely the nature of Benbow et al.'s sample. That is to say, in a bivariate normal distribution with constant regression coefficient, samples restricted to values of the dependent variable (here, child's IQ) above a certain value will always produce a lower regression coefficient than unrestricted samples drawn from the entire but same distribution. I introduce an unbiased estimator that can be calculated from the sample statistics reported in the Benbow, Zonderman, and Stanley article and find that the coefficient of regression of gifted child's IQ on parental IQ is, in fact, higher than the regression coefficients reported in the literature for unrestricted samples. That is, Benbow et al.'s data suggest that the gifted in fact resemble their parents more than do persons in general.     

Kant's Expressive Theory of Music

Several prominent philosophers of art have worried about whether Kant has a coherent theory of music on account of two perceived tensions in his view. First, there appears to be a conflict between his formalist and expressive commitments. Second (and even worse), Kant defends seemingly contradictory claims about music being beautiful and merely agreeable, that is, not beautiful. Against these critics, I show that Kant has a consistent view of music that reconciles these tensions. I argue that, for Kant, music can be experienced as either agreeable or beautiful depending on the attitude we take toward it. Although it is tempting to think he argues that we experience music as agreeable when we attend to its expressive qualities and as beautiful when we attend to its formal properties, I demonstrate that he actually claims that we are able to judge music as beautiful only if we are sensitive to the expression of emotion through musical form. With this revised understanding of Kant's theory of music in place, I conclude by sketching a Kantian solution to a central problem in the philosophy of music: given that music is not sentient, how can it express emotion?     

Recency, immediate recognition memory, and reaction time

Four classes of possible mechanisms for short-term item recognition are distinguished: (I) pure list-search, (II) direct-access activation (or trace strength) discrimination, (III) mixtures (of I and II), and (IV) response-association. Manipulations of recency, particularly of negative probe items, provide critical tests between them. Two experiments are reported using Sternberg' s 1966 varied-set reaction time paradigm, coupled with procedures intended to minimize rehearsal and control the recency of probes and memory set items. RT and error rate were greater for negative probe items that had recently been presented than for items less recently presented, and this effect increased with positive set size. In contrast, positive RT was, except for the initial item, a decreasing function of recency (= serial position), and there was no additional effect of set size per se. A brief filled delay between list and probe increased positive RT but not the slope of the set size function. These and other findings appear to reject models of Classes I and IV and, while implying some direct discrimination of an item's recency, require modification of the models of Classes II and III. The implications are discussed with respect to the relation between the two versions of Sternberg's paradigm and also in connection with facilitatory “priming” effects in memory.     

Humphreys's attenuated test of Spearman's hypothesis

Humphreys's test of Spearman's hypothesis (viz., that the size of the standardized black-white differences on various psychometric tests is positively related to the tests' loadings on g, the general intelligence factor) is methodologically weak. It is based on comparison of a fairly representative sample of the black population of U.S. school children with a highly selected sample of the white school population, representing the lowest 15 to 20% of whites in socio-economic status (SES). A fair test of the hypothesis requires that the black and white samples should not be selected on any g-correlated variable, such as SES. Selection attenuates and distorts the relationship between tests' g loadings and the magnitude of the standardized mean black-white differences on the tests. Other unorthodox conditions in Humphreys's study, such as performing factor analysis on the test-score means of various arbitrary demographic groups instead of on individual test scores inflates tests' g loadings and biases the test of Spearman's hypothesis by restriction of reliable variance in g loadings. Humphreys's study cannot be considered a proper replication of Jensen's examination of Spearman's hypothesis in 11 different studies comprising 74 different tests, which consistently bears out Spearman's hypothesis.     

The Euthanasia Debate in Germany - What's the Fuss?

ABSTRACT Both opponents and proponents of Singer's right to speak about euthanasia have concentrated on the tenability of his claims. They have ignored the question of what legitimate grounds there are for suppressing academic discussion, and have failed to take into account the discussion of freedom of speech in recent legal theory. To do this is the aim of my paper. Section I claims that Singer's position is immoral. Section 2 turns to the question of whether it is protected by freedom of speech, irrespective of its merits. I reject two lines of defence for Singer's opponents, that they had no opportunity to present their case, and the Kantian idea of the primacy of practical reason. Section 3 turns to a defence from legal theory. It argues that Singer's views do not pose the kind of threat to other legal and moral values which would license a suspension of his freedom of expression. I conclude that it is illegitimate to silence Singer, since he does not deny the right to live of his disabled opponents, but legitimate to protest against him, since he denies that some of their lives are worth living, in disregard of their own preferences.     

Level I and level II abilities in Asian,white, and black children

All the Asian-American, white, and black children in grades 2 through 6 in a California school district were given a battery of tests including measures of IQ, scholastic achievement, and short-term memory. Factor analysis of the tests yielded two main factors identified as Level I (memory) and Level II (general intelligence) in Jensen's system. The three ethnic groups were compared with one another on uncorrelated Level I and Level II factor scores. At every grade level, bivariate means of the three groups occupy distinctly different quadrants in the factor space. Asians and whites differ on Level I (A < W) but not on Level II. Asians and blacks differ on Level II (A > B) but not on Level I. Whites and blacks differ (W > B) on both Levels I and II, but the white-black difference on Level I is less than one fourth as large as the white-black difference on Level II. A similar pattern of group differences is found for scores on tests of memory and nonverbal IQ. Scholastic achievement shows much smaller correlations with the Level I than with the Level II factor.     

Jensen's reaction-time studies: A reply to Longstreth

Longstreth's (1984) critique of Jensen's research on the relationship of IQ to individual differences in visual reaction time (RT), measured in the Hick paradigm, is found to have numerous errors of fact and interpretation, some trivial and some of theoretical importance. Longstreth's narrowly focused and conjectural style of criticism, which peculiarly strains to favor the null hypothesis, unfortunately obscures the essential findings of Jensen's (and others') studies of the RT-IQ relationship. The two main negative verdicts of Longstreth's critique concerning the RT-IQ relationship are refuted by meta-analyses of presently available data. First, not only do individual differences in RT show a significant negative correlation with IQ, but individual differences in the slope of the regression of RT on stimulus set size scaled in bits (i.e., the binary logarithm of the number of potential reaction stimuli) also show a fully significant, albeit low, negative correlation with IQ. Contrary to Longstreth's second negative surmise, meta-analysis also shows that the magnitude of the RT-IQ correlation itself is a linearly increasing (negative) function of stimulus set-size scaled in bits.     

Peirce on Education: Discussion of Peirce’s Definition of a University

I write this short essay in response to Peirce, as a feminist, pragmatist, and cultural studies scholar, in the hope that it will help to bring feminism and pragmatism together. I suggest that Peirce offers marginalized and colonized people a way to argue for the importance of their input, with his theory of fallibilism, even if he still claims a position of privilege. He also offers assistance through his concept of “a community of inquirers.” It is curious that Peirce’s definition of a university argues for a split between theory and practice that his earlier work sought to heal. Peirce opened a door to help diverse scholars be able to enter the university, and find a way to address issues of power, with his youthful connecting of theory to practice, that his more senior position draws our attention away from and seeks to hold off. Fortunately, it is too late. Peirce’s youthful pragmatism has been developed in important ways by other scholars and now serves as an example of a way to do philosophy that does connect theory to practice and does seek to address real problems in diverse peoples lives, and help to find solutions that effect change.     

Myth and reality: A response to Lynn on the determinants of Italy's North-South imbalances

In his article “In Italy, North-South differences in IQ predict differences in income, education, infant mortality, stature, and literacy,” Richard Lynn claims to have found the reason causing the divergence between the Northern and the Southern regions of Italy. This article identifies the four main hypotheses formulated in his paper and presents significant evidence against each one of them. We claim that the evidence presented by the author is not sufficient to say that the IQ of Southern Italians is lower than the one of Northern Italians; that his analysis does not prove that there is any causal link between what he defines as IQ and any of the variables mentioned; that there is no evidence that the alleged differences in IQ are persistent in time and, therefore, attributable to genetic factors.     

Modularity and attention: Is the binding problem real?

Abstract

Van der Heijden rejects the feature integration theory of visual attention (Treisman, 1988, 1993; Treisman & Gelade, 1980) and proposes instead a theory relating modularity in the visual system to selection for action. His positive proposals about the relations between visual processing, intention, and selection for action are interesting, but I do not believe they are incompatible with my theory. In this paper I will focus on and question his arguments about the binding problem and the role of attention in visual perception. Van der Heijden attacks two claims that are fundamental to my theory: (1) the idea that modularity gives rise to a “binding problem” (the need to specify which of the features present characterize any particular object), and (2) the more general idea that there are limits to capacity at the level of perceptual processing. I will argue that he is wrong to reject the two claims, that the binding problem is a real one, for his model as for others, and that his account is more similar to mine than he appears to realize.     

RAWLS AND THE STATUS OF POLITICAL LIBERTY

Abstract:  In his late work, Rawls makes strong claims about the status of political liberty. These claims, if accepted, would have significant implications for the content of "justice as fairness." I discuss the nature of these claims, clarifying Rawls's fair value guarantee of the political liberties and critically discussing the arguments that he and others have given for assigning special importance to the political liberties. I conclude that justice as fairness, properly understood, is not a deeply democratic conception of justice.     

What Dennett can't imagine and why

Woven into Dennett's account of consciousness is his belief that certain possibilities are not conceivable. This is manifested in his view that we are not conscious in any sense in which we can imagine that philosophers’ ‘zombies’ might not be conscious, and also in his claims about ‘Hindsight’, and what possibilities this can coherently suggest to us. If the possibilities Dennett denies none the less seem conceivable to us, then if he does not give us reason to think they are actually incoherent, we ought to reject his theory, since it denies the intelligibility of the very notion we should want a theory of consciousness to discuss. I argue that Dennett does not provide us with convincing reasons of the relevant sort, and I suggest that his difficulty with the concept of consciousness is rooted in questionable epistemological assumptions which he fails to justify.     

Dual-task interference as a function of cognitive processing load

Sixteen subjects from the Naval Submarine Medical Research Laboratory participated in a dual-task study designed to measure processing requirements of a choice reaction time (RT) task. Two levels of choice RT stimulus-response (S-R)compatibility were tested with each of two tracking tasks to provide different levels of dual-task loading. In one tracking task, the target's temporal-spatial pattern was fixed; in the other, the target's path was a function of the subject's performance. In the choice RT task, compatibility was treated as a between-subjects factor, while the number of alternatives (set size) within a sequence was a within-subjects variable. Choice RT results indicated that compatibility and set size interacted; the increase in response latency as a function of set size was much greater when compatibility was low. An increase in choice RT response latency occurred when the secondary tracking task was added. Within a given compatibility level, this dual-task decrement was constant for all levels of set size; however, the magnitude of the dual-task decrement varied as a function of S-R compatibility, being greater when compatibility was low than when it was high. For these data, a model like Sternberg's (1969) stages model is seen to have more explanatory value than a pooled processing capacity model (e.g., Norman and Bobrow 1975).     

Is Putnam's Causal Theory of Meaning Compatible with Internal Realism?

Putnam originally developed his causal theory of meaning in order to support scientific realism and reject the notion of incommensurability. Later he gave up this position and adopted instead what he called ‘internal realism’, but apparently without changing his mind on topics related to his former philosophy of language. The question must arise whether internal realism, which actually is a species of antirealism, is compatible with the causal theory of meaning. In giving an answer I begin with an analysis of the content and metaphysical background of scientific realism. I show that it presupposes metaphysical realism and that Putnam's philosophical conversion is due to his becoming aware of the latter's incoherence. After giving a brief sketch of internal realism I conclude by arguing that within this new theoretical framework the causal theory of meaning loses its force as a weapon against incommensurability. This revised version was published online in August 2006 with corrections to the Cover Date.     

Quine’s Behaviorism and Linguistic Meaning: Why Quine’s Behaviorism is not Illicit

Some of Quine’s critics charge that he arrives at a behavioristic account of linguistic meaning by starting from inappropriately behavioristic assumptions (Kripke 1982, 14; Searle 1987, 123). Quine has even written that this account of linguistic meaning is a consequence of his behaviorism (Quine 1992, 37). I take it that the above charges amount to the assertion that Quine assumes the denial of one or more of the following claims: (1) Language-users associate mental ideas with their linguistic expressions. (2) A language-user can have a private theory of linguistic meaning which guides his or her use of language. (3) Language learning relies on innate mechanisms. Call an antecedent denial of one or more of these claims illicit behaviorism. In this paper I show that Quine is prepared to grant, if only for the sake of argument, all three of the above claims. I argue that his claim that “there is nothing in linguistic meaning beyond what is to be gleaned from overt behavior in observable circumstances” is unscathed by these allowances (Quine 1992, 38). And I show that the behaviorism which Quine does assume should be viewed as a largely uncontroversial aspect of his evidential empiricism. I conclude that if one sets out to dismiss Quine’s arguments for internal-meaning skepticism, this dismissal should not be motivated by the charge that his conclusions rely on the illicitly behavioristic assumptions that some have suggested that they do.     

Evading conceptual self-annihilation: Some implications of Albert Bandura's theory of the self-system for the status of psychology

There are two cognitive revolutions occuring in psychology. The first in the fields of perception, memory, language and thought uses information processing and computer models of cognition. The second in learning theory and behavioral therapy uses folk psychological concepts of cognition. To test the philosophical compatibility of these cognitive revolutions I examine the implications of Albert Bandura's theory of the self-system for the disputed question of the status of folk psychology. I argue that if the theory of the self-system is correct, then strong eliminative materialist claims about the falsity of folk psychology are disconfirmed, functionalist homunculi hypotheses need modification, and certain constraints are imposed on neurophysiological accounts of the self. Thus I conclude that the cognitive revolution in learning theory and behavior therapy is making its own distinctive contribution to the new philosophical psychology emerging from the cognitive revolution in psychology as a whole.