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Haste makes waste versus a stitch in time? A reply to Vernon, Nador, and Kantor
INTELI.IGENCE 10, 265--270 (19861
COMMENTARY
Haste Makes Waste versus a Stitch in Time? A Reply to Vernon, Nador, and Kantor ROBERT J. SrERNB~RG Yale Universi O"
Vernon, Nador, and Kantor (1985) conclude from their data that "speed of infi~rmationprocessing was an equally g,.x~ predictor of timed and untimed intelligencetest performance" (p. 357). This conclusiondoes not lc,llow from their data. Rather. their data show that speed-of-informationprocessing better predicts timed than untimcd intelligencetest performance, as one might expect. Vernonet al. also draw several other conclusionsfrom their data that are incorrect.
In their article, "Reaction times and speed-of-processing: Their relationship to timed and untimed measures of intelligence," Vernon, Nador. and Kantor (1985) conclude that "speed of information-processing was an equally go~xt predictor of timed and untimed intelligence test performance" (p. 357). This conclusion does not follow from their data. The data in fact lead to an opposite c o n c l u s i o n - - t h a t speed of information processing is a better predictor of timed than of untimed intelligence test perlbrmance, as one might expect. This reply is divided into two parts. The first part deals with issues of data analysis. The second part deals with conceptual issues regarding the role of speed-of-information processing in intelligence.
D A T A - A N A L Y T I C ISSUES Vernon et al. (1985) used as their psychometric intelligence test the Multidimensional Aptitude Battery (MAB) (Jackson, 1983), and they used a variety of cognitive-task variables, as well. Each subtest of the MAB was first used with a time limit of 5 m per subtest (not the standard time limit). Subjects answered using a colored pencil. When the 5 m were up, subjects switched to a different colored pencil, and then had as long as they wanted to complete the given subtest. The timed score was based on performance during the first 5 m per
Preparation of this paper was supported by Contract N00014-g5-K-0589from the Office of Naval Research and Contract MDAg()3-85-K-0305fi'om the Army Research Institute. Correspondence and requests for reprintsshould be addressed to Robert J. Steinberg,Department of Psychology, Yale University, Box I IA Yale Station. New Haven. CT 06520.
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subtest, whereas the untimed score was based on this performance plus performance during the additional untimed part. Subjects also had a chance to go back and answer problems after they had completed all subtests. Additional items answered went into the untimed score. There is obviously a part-whole relation between timed and untimed score. The investigators used five kinds of cognitive tasks to measure mental speed: (a) a variant of the Sternberg (1966) memory-scanning paradigm: (b) two variants of the Posner, Boies, Eichelman, and Taylor (1969) matching paradigm as modified by Goldberg, Schwartz, and Stewart (1977); (c) two storage-processing tradeoff tasks as developed by Vernon (1983), "'reaction-time" scores and seven "'speed-of-processing" scores were computed from the cognitive-task variables. These various scores are obviously nonindependent. The reaction-time scores are based directly on the original measures, whereas the speed-of-processing scores are derived. If the cognitive-task scores are equally good predictors of timed and untimed psychometric intelligence-test scores, one would expect these cognitive-task scores to correlate more highly with the timed intelligence-test scores about hall" of the time, and more highly with the untimed intelligence-test scores the other half of the time. These simple-correlational data are not presented in the article, but were kindly made available to me by Vernon upon my request. In fact, 1 I of 11 reaction-time scores correlated more highly with the timed MAB than with the untimed MAB, and 6 of 7 speed-of-processing scores correlated more highly with the timed than with the untimed MAB. Vernon et al. also computed 3 factor scores, based upon the speed-of-processing variables and, unsurprisingly, 3 of 3 factor scores correlated more highly with timed than with untimed MAB. Thus, of 21 timed cognitive-task scores, 20 correlated more highly with timed than with untimed psychometric test performance. Ten such higher correlations would have been expected on the null hypothesis of no difference in correlations between cognitive-task scores, on the one hand, and timed and untimed psychometric test scores, on the other. Unfortunately, a sign test is not possible, given the nonindependence of the various cognitive-task scores. However, this pattern of results certainly does not support the conclusion of the authors that "speed of information-processing was an equally good predictor of timed and untimed intelligence test performance" (p. 357)? This pattern of simple correlations is rather astonishing, given the authors' conclusion of no difference. How did the authors arrive at their conclusion in the first place'? They arrived at their conclusion of no difference by comparing 5 shrunken multiple correlations of cognitive-task-based scores with timed versus untimed MAB scores. The authors note that none of the differences in multiple correlations were significant. It will scarcely surprise the reader, by now, that 5 of 5 multiple correlations of cognitive-task scores were higher with timed than with untimed MAB scores, and that 5 of 5 multiple correlations were higher again if g factor scores rather than actual scale scores were used. The authors do
MENTAL SPEED
267
not state what test of statistical significance they used nor do they give actual test statistics. A difference o f . 10 points of correlation for the reaction times is at least suggestive, however, especially given the difficulty of getting a difference in a part-whole relationship with substantial overlap. It might be mentioned that the multiple regressions themselves are suspect. Vernon et al. do not present the beta weights for the various multiple regressions, but Vernon kindly provided me with them for the regressions of timed and untimed MAB on the reaction-time and speed-of-processing variables. In the case of the reaction times predicting timed MAB, only I of 11 independent variables (reaction-time measures) had a statistically significant beta weight. In the case of the reaction times predicting untimed MAB. again, only I of 11 independent variables had a statistically significant beta weight. No mention is made in the article that the multiple regressions are based upon large numbers of independent variables, almost all of which have trivial beta weights. Incidentally, the other beta weights were not even close to significance: In both regressions, all other F ' s were less than 1. Two conclusions immediately t611ow. First, the multiple correlations arc likely to be inflated by the inclusion of 10 independent variables per regression, none of which makes a statistically significant contribution to the regression. Second, it is actually just a single variable that is carrying the weight of prediction. One might be curious as to just what this variable is. The single variable is for speed of processing on a synonymsantonyms recognition task. This is obviously a test of high-level mental processing and, because correlations of cognitive tasks with timed or untimed psychometric tests increase with complexity of the cognitive task, such a task would minimize the difference between correlations for timed and untimed tests. In the other multiple regressions with which Vernon supplied me, in each case, at least half of the F ' s for the beta weights of the independent variables were less than I. Incidentally, a problem for all these regressions, as well as for the factor analysis, was that the variables entered were both experimentally and statistically nonindependent. It is generally not considered good form to enter such variables into multivariate techniques. In factor analysis, spurious factors can result (Gotsuch. 1983, p.300). In multiple regression, spuriously high c~)rrelations can result (Cohen & Cohen. 1983, p. 72). 1 alluded before to a problem inherent in Vernon et al.'s data: The timed and untimed MAB scores bear a part--whole relation to each other. The problem is by no means a trivial one: Timed score is 76% of untimed score. In other words, there is a part-whole relation of roughly three-quarters, a relation that would scarcely work against the authors' hypothesis of no difference in correlations of external measures with the timed and untimed MAB measures. Nevertheless, the data, as noted above, do, in fact, support a difference. Given the high degree of artifactual overlap between the two scores, the correlation of .81 between them no longer seems so high. The correlation is based upon only about one-quarter difference in score contributing to timed and untimed measures. The authors note
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STERNBERG
the correlation goes down to .71 when timed MAB is correlated with number of items incrementally completed during the untimed period. Given the use of the same subjects on the same tests during the same testing period, this correlation scarcely suggests that timed and untimed MAB measure the same thing. C O N C E P T U A L ISSUES Vernon and his colleagues propose that "speed-of-processing is a factor underlying intelligence" (p. 370). Of course, they base their claim in part upon the present study, but also a long series of previous studies as well (e.g., Jensen, 1979, 1982; Vernon, 1981, 1983; Vernon & Jensen, 1984). But does any of the evidence that has been adduced really support the claim that speed of processing underlies intelligence? 1. Speed is only one dependent variable. The first thing to realize is that maximum speed of performance is only one of many dependent variables along which one can compare people. On the whole, people who think faster may well perform better, on the average, than slower thinkers. But slower thinkers may excel in aspects of mental perlormance, such as depth of thought, or breadth of thinking, that are unrelated, or at best weakly related, to speed. Proponents of speed of processing as underlying intelligence seem preoccupied with speed of processing as a dependent variable in their studies. They seem to act as though speed is the only dependent variable worthy of study, and they are wrong. Measures of response time tell one an important thing about the respective properties of people, but there are many other things to learn about the people. 2. The causal relation between speed of processing and intelligence. In a timed maximum-performance test, a faster person will usually finish more items than a slower person, and thereby get a higher score. The faster person may well be faster because of superior mental abilities. One would not want to conclude, most likely, that the person's superior mental ability is caused by his or her greater speed. Consider two examinees in the laboratory. They are raced against each other in reaction-time tasks, and one subject works almost twice as fast as the other. Are we to conclude hcre that the first subject is more intelligent than the second because she is faster'? Might it not be .just as likely that she is faster because she is more intelligent, as in a car race, where intelligence--power of the brain (engine)--is analogized to power of the car engine'? Depending upon level of explanation, one might attribute both the speed of automobile perlormance and the power of the engine to some third, higher order, factor, such as number or output or design of cylinders. The point, quite simply, is that although one could construct causal explanations for speed underlying intelligence, as Vernon and his colleagues have done, nothing in their tasks actually supports such explanations, anymore than the data from the car race would support an explanation that a German car is more powerful than a Japanese onc because it is faster. Correla-
MENTAL SPEED
269
tion does not imply causation, and researchers on intelligence need to be rather careful not to mislead others or themselves regarding the causal inferences that can be drawn from their data. 3. Maximum versus typical performance. Maximum-performance tests may tell us about performance under conditions that have little to do with real-life demands. How many times have you been a~ked to push little buttons to choose responses as quickly as you can, outside of cognitive-testing situations'? We need to ask ourselves more seriously how well maximum-performance conditions represent performance in everyday life, and whether we are not really as interested, or more interested, in typical performance, something Vernon and his colleagues' reaction-time measures clearly do not measure. 4. The advantages of slowness. I have argued elsewhere that there are tasks and components of task performance in which slowness, rather than speed, of information processing is correlated with greater psychometric intelligence (Mart & Sternberg, in press; Sternberg, 1985). For example, more intelligent individuals seem to spend relatively more time than less intelligent ones in global strategy planning, but relatively less time in local strategy planning (Sternbcrg, 1981). My point in demonstrations such as this one is not that more intelligent people are inherently slower than less intelligent ones, but rather, that the key to their intelligence insofar as speed of processing is concerned is not just that they are fast or slow, but that they know when to be which. Working too fast can result in high error rates, poor decisions, lack of enjoyment of what one is doing and, sometimes, the need to retract impulsive claims. (Premature ejaculation is not limited to sexual encounters?) Whether it is intelligent to be fast or slow depends upon the situation. To conclude, speed of processing is only one of many dependent variables one might and should consider. There is no evidence that speed of information processing is causal of individual differences in intelligence. Speed of processing as measured in maximum-performance situations may not tell us what we want to know about processing in typical situations. And, in some circumstances, it is better to be slow. Sometimes, a stitch in time saves nine. Other times, haste makes waste. The two proverbs contradict each other only it~ they arc applied to the same situations. But they need not be. Which proverb applies depends upon the situation. The same holds true for speed-of-information processing. How useful it is depends upon the situation.
REFERENCES Cohen, J., & Cohen. P. (1983). Applied multiple regression/correlation amdvsi~ h~r the behalioral scien¢'es (2nd ed.L Hillsdale, N J: Erlbaum. Goldberg, R.A., Schwartz; S., & Stewarl, M. 11977). Individual dillercnce~, in cognitive ~rocc,,se~, Journal of Educational Psychology. 69. 9 - 14. Gorsuch, R.L. (1983). Factor anal.v,~is (2nd ed. ). Hillsdale, N J: Erlbaum.
270
STERNBERG
Jackson, D.N. (1983). Multidimensional Aptitude Batter?; (MAB). London, Ontario, Canada: Research Psychologists Press. Jensen, AR. (1979). g: Outmoded theory or unconquered frontier? Creative Science and Technology, 2, 16-29. Jensen, A.R. (1982). The chronometry of intelligence. In R.J. Sternberg (Ed.), Advances in the psychology of human intelligence (Vol. I). Hillsdale, N J: Erlbaum. Mart, D.B., & Sternberg, R.J. (in press). The role of mental speed in intelligence: A triarchic perspective. In P.A. Vernon (Ed.), Speed of information processing and intelligence. Norwcx.u.l, NJ: Ablex. Posner, M., Boies, S., Eichelman, W., & Taylor. R. (1969). Retention of visual and name codes of single letters. Journal of Experimental Psychology, 81. I0-15. Sternberg, R.J. (1981). Intelligence and nonentrenchment. Journal of Educational Psychology, 73, 1-16. Sternberg, R.J. (1985). Beyond IQ: A triarchic theory of human intelligence. New York: Cambridge University Press. Sternberg, S. (1966). High-speed memory scanning in human memory. Science, 153, 652-654. Vernon, P.A. (1981). Reaction time and intelligence in the mentally retarded. Intelligence, 5. 345355. Vernon, P.A. (1983). Speed of information processing and general intelligence. Intelligem'e, 7, 5370. Vernon, P.A., & Jensen, A.R. (1984). Individual and group diftercnces in intelligence and speed of information-processing. Personality and Individual Diff~,rences, 5, 411 423. Vernon. P.A., Nador, S., & Kantor, I.. (1985L Reaction times and speed of prtx:essing: Their relationship to timed and untimed measures of intelligence. Intelligence, 9. 357-374.
COMMENTARY
Haste Makes Waste versus a Stitch in Time? A Reply to Vernon, Nador, and Kantor ROBERT J. SrERNB~RG Yale Universi O"
Vernon, Nador, and Kantor (1985) conclude from their data that "speed of infi~rmationprocessing was an equally g,.x~ predictor of timed and untimed intelligencetest performance" (p. 357). This conclusiondoes not lc,llow from their data. Rather. their data show that speed-of-informationprocessing better predicts timed than untimcd intelligencetest performance, as one might expect. Vernonet al. also draw several other conclusionsfrom their data that are incorrect.
In their article, "Reaction times and speed-of-processing: Their relationship to timed and untimed measures of intelligence," Vernon, Nador. and Kantor (1985) conclude that "speed of information-processing was an equally go~xt predictor of timed and untimed intelligence test performance" (p. 357). This conclusion does not follow from their data. The data in fact lead to an opposite c o n c l u s i o n - - t h a t speed of information processing is a better predictor of timed than of untimed intelligence test perlbrmance, as one might expect. This reply is divided into two parts. The first part deals with issues of data analysis. The second part deals with conceptual issues regarding the role of speed-of-information processing in intelligence.
D A T A - A N A L Y T I C ISSUES Vernon et al. (1985) used as their psychometric intelligence test the Multidimensional Aptitude Battery (MAB) (Jackson, 1983), and they used a variety of cognitive-task variables, as well. Each subtest of the MAB was first used with a time limit of 5 m per subtest (not the standard time limit). Subjects answered using a colored pencil. When the 5 m were up, subjects switched to a different colored pencil, and then had as long as they wanted to complete the given subtest. The timed score was based on performance during the first 5 m per
Preparation of this paper was supported by Contract N00014-g5-K-0589from the Office of Naval Research and Contract MDAg()3-85-K-0305fi'om the Army Research Institute. Correspondence and requests for reprintsshould be addressed to Robert J. Steinberg,Department of Psychology, Yale University, Box I IA Yale Station. New Haven. CT 06520.
265
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STERNBERG
subtest, whereas the untimed score was based on this performance plus performance during the additional untimed part. Subjects also had a chance to go back and answer problems after they had completed all subtests. Additional items answered went into the untimed score. There is obviously a part-whole relation between timed and untimed score. The investigators used five kinds of cognitive tasks to measure mental speed: (a) a variant of the Sternberg (1966) memory-scanning paradigm: (b) two variants of the Posner, Boies, Eichelman, and Taylor (1969) matching paradigm as modified by Goldberg, Schwartz, and Stewart (1977); (c) two storage-processing tradeoff tasks as developed by Vernon (1983), "'reaction-time" scores and seven "'speed-of-processing" scores were computed from the cognitive-task variables. These various scores are obviously nonindependent. The reaction-time scores are based directly on the original measures, whereas the speed-of-processing scores are derived. If the cognitive-task scores are equally good predictors of timed and untimed psychometric intelligence-test scores, one would expect these cognitive-task scores to correlate more highly with the timed intelligence-test scores about hall" of the time, and more highly with the untimed intelligence-test scores the other half of the time. These simple-correlational data are not presented in the article, but were kindly made available to me by Vernon upon my request. In fact, 1 I of 11 reaction-time scores correlated more highly with the timed MAB than with the untimed MAB, and 6 of 7 speed-of-processing scores correlated more highly with the timed than with the untimed MAB. Vernon et al. also computed 3 factor scores, based upon the speed-of-processing variables and, unsurprisingly, 3 of 3 factor scores correlated more highly with timed than with untimed MAB. Thus, of 21 timed cognitive-task scores, 20 correlated more highly with timed than with untimed psychometric test performance. Ten such higher correlations would have been expected on the null hypothesis of no difference in correlations between cognitive-task scores, on the one hand, and timed and untimed psychometric test scores, on the other. Unfortunately, a sign test is not possible, given the nonindependence of the various cognitive-task scores. However, this pattern of results certainly does not support the conclusion of the authors that "speed of information-processing was an equally good predictor of timed and untimed intelligence test performance" (p. 357)? This pattern of simple correlations is rather astonishing, given the authors' conclusion of no difference. How did the authors arrive at their conclusion in the first place'? They arrived at their conclusion of no difference by comparing 5 shrunken multiple correlations of cognitive-task-based scores with timed versus untimed MAB scores. The authors note that none of the differences in multiple correlations were significant. It will scarcely surprise the reader, by now, that 5 of 5 multiple correlations of cognitive-task scores were higher with timed than with untimed MAB scores, and that 5 of 5 multiple correlations were higher again if g factor scores rather than actual scale scores were used. The authors do
MENTAL SPEED
267
not state what test of statistical significance they used nor do they give actual test statistics. A difference o f . 10 points of correlation for the reaction times is at least suggestive, however, especially given the difficulty of getting a difference in a part-whole relationship with substantial overlap. It might be mentioned that the multiple regressions themselves are suspect. Vernon et al. do not present the beta weights for the various multiple regressions, but Vernon kindly provided me with them for the regressions of timed and untimed MAB on the reaction-time and speed-of-processing variables. In the case of the reaction times predicting timed MAB, only I of 11 independent variables (reaction-time measures) had a statistically significant beta weight. In the case of the reaction times predicting untimed MAB. again, only I of 11 independent variables had a statistically significant beta weight. No mention is made in the article that the multiple regressions are based upon large numbers of independent variables, almost all of which have trivial beta weights. Incidentally, the other beta weights were not even close to significance: In both regressions, all other F ' s were less than 1. Two conclusions immediately t611ow. First, the multiple correlations arc likely to be inflated by the inclusion of 10 independent variables per regression, none of which makes a statistically significant contribution to the regression. Second, it is actually just a single variable that is carrying the weight of prediction. One might be curious as to just what this variable is. The single variable is for speed of processing on a synonymsantonyms recognition task. This is obviously a test of high-level mental processing and, because correlations of cognitive tasks with timed or untimed psychometric tests increase with complexity of the cognitive task, such a task would minimize the difference between correlations for timed and untimed tests. In the other multiple regressions with which Vernon supplied me, in each case, at least half of the F ' s for the beta weights of the independent variables were less than I. Incidentally, a problem for all these regressions, as well as for the factor analysis, was that the variables entered were both experimentally and statistically nonindependent. It is generally not considered good form to enter such variables into multivariate techniques. In factor analysis, spurious factors can result (Gotsuch. 1983, p.300). In multiple regression, spuriously high c~)rrelations can result (Cohen & Cohen. 1983, p. 72). 1 alluded before to a problem inherent in Vernon et al.'s data: The timed and untimed MAB scores bear a part--whole relation to each other. The problem is by no means a trivial one: Timed score is 76% of untimed score. In other words, there is a part-whole relation of roughly three-quarters, a relation that would scarcely work against the authors' hypothesis of no difference in correlations of external measures with the timed and untimed MAB measures. Nevertheless, the data, as noted above, do, in fact, support a difference. Given the high degree of artifactual overlap between the two scores, the correlation of .81 between them no longer seems so high. The correlation is based upon only about one-quarter difference in score contributing to timed and untimed measures. The authors note
268
STERNBERG
the correlation goes down to .71 when timed MAB is correlated with number of items incrementally completed during the untimed period. Given the use of the same subjects on the same tests during the same testing period, this correlation scarcely suggests that timed and untimed MAB measure the same thing. C O N C E P T U A L ISSUES Vernon and his colleagues propose that "speed-of-processing is a factor underlying intelligence" (p. 370). Of course, they base their claim in part upon the present study, but also a long series of previous studies as well (e.g., Jensen, 1979, 1982; Vernon, 1981, 1983; Vernon & Jensen, 1984). But does any of the evidence that has been adduced really support the claim that speed of processing underlies intelligence? 1. Speed is only one dependent variable. The first thing to realize is that maximum speed of performance is only one of many dependent variables along which one can compare people. On the whole, people who think faster may well perform better, on the average, than slower thinkers. But slower thinkers may excel in aspects of mental perlormance, such as depth of thought, or breadth of thinking, that are unrelated, or at best weakly related, to speed. Proponents of speed of processing as underlying intelligence seem preoccupied with speed of processing as a dependent variable in their studies. They seem to act as though speed is the only dependent variable worthy of study, and they are wrong. Measures of response time tell one an important thing about the respective properties of people, but there are many other things to learn about the people. 2. The causal relation between speed of processing and intelligence. In a timed maximum-performance test, a faster person will usually finish more items than a slower person, and thereby get a higher score. The faster person may well be faster because of superior mental abilities. One would not want to conclude, most likely, that the person's superior mental ability is caused by his or her greater speed. Consider two examinees in the laboratory. They are raced against each other in reaction-time tasks, and one subject works almost twice as fast as the other. Are we to conclude hcre that the first subject is more intelligent than the second because she is faster'? Might it not be .just as likely that she is faster because she is more intelligent, as in a car race, where intelligence--power of the brain (engine)--is analogized to power of the car engine'? Depending upon level of explanation, one might attribute both the speed of automobile perlormance and the power of the engine to some third, higher order, factor, such as number or output or design of cylinders. The point, quite simply, is that although one could construct causal explanations for speed underlying intelligence, as Vernon and his colleagues have done, nothing in their tasks actually supports such explanations, anymore than the data from the car race would support an explanation that a German car is more powerful than a Japanese onc because it is faster. Correla-
MENTAL SPEED
269
tion does not imply causation, and researchers on intelligence need to be rather careful not to mislead others or themselves regarding the causal inferences that can be drawn from their data. 3. Maximum versus typical performance. Maximum-performance tests may tell us about performance under conditions that have little to do with real-life demands. How many times have you been a~ked to push little buttons to choose responses as quickly as you can, outside of cognitive-testing situations'? We need to ask ourselves more seriously how well maximum-performance conditions represent performance in everyday life, and whether we are not really as interested, or more interested, in typical performance, something Vernon and his colleagues' reaction-time measures clearly do not measure. 4. The advantages of slowness. I have argued elsewhere that there are tasks and components of task performance in which slowness, rather than speed, of information processing is correlated with greater psychometric intelligence (Mart & Sternberg, in press; Sternberg, 1985). For example, more intelligent individuals seem to spend relatively more time than less intelligent ones in global strategy planning, but relatively less time in local strategy planning (Sternbcrg, 1981). My point in demonstrations such as this one is not that more intelligent people are inherently slower than less intelligent ones, but rather, that the key to their intelligence insofar as speed of processing is concerned is not just that they are fast or slow, but that they know when to be which. Working too fast can result in high error rates, poor decisions, lack of enjoyment of what one is doing and, sometimes, the need to retract impulsive claims. (Premature ejaculation is not limited to sexual encounters?) Whether it is intelligent to be fast or slow depends upon the situation. To conclude, speed of processing is only one of many dependent variables one might and should consider. There is no evidence that speed of information processing is causal of individual differences in intelligence. Speed of processing as measured in maximum-performance situations may not tell us what we want to know about processing in typical situations. And, in some circumstances, it is better to be slow. Sometimes, a stitch in time saves nine. Other times, haste makes waste. The two proverbs contradict each other only it~ they arc applied to the same situations. But they need not be. Which proverb applies depends upon the situation. The same holds true for speed-of-information processing. How useful it is depends upon the situation.
REFERENCES Cohen, J., & Cohen. P. (1983). Applied multiple regression/correlation amdvsi~ h~r the behalioral scien¢'es (2nd ed.L Hillsdale, N J: Erlbaum. Goldberg, R.A., Schwartz; S., & Stewarl, M. 11977). Individual dillercnce~, in cognitive ~rocc,,se~, Journal of Educational Psychology. 69. 9 - 14. Gorsuch, R.L. (1983). Factor anal.v,~is (2nd ed. ). Hillsdale, N J: Erlbaum.
270
STERNBERG
Jackson, D.N. (1983). Multidimensional Aptitude Batter?; (MAB). London, Ontario, Canada: Research Psychologists Press. Jensen, AR. (1979). g: Outmoded theory or unconquered frontier? Creative Science and Technology, 2, 16-29. Jensen, A.R. (1982). The chronometry of intelligence. In R.J. Sternberg (Ed.), Advances in the psychology of human intelligence (Vol. I). Hillsdale, N J: Erlbaum. Mart, D.B., & Sternberg, R.J. (in press). The role of mental speed in intelligence: A triarchic perspective. In P.A. Vernon (Ed.), Speed of information processing and intelligence. Norwcx.u.l, NJ: Ablex. Posner, M., Boies, S., Eichelman, W., & Taylor. R. (1969). Retention of visual and name codes of single letters. Journal of Experimental Psychology, 81. I0-15. Sternberg, R.J. (1981). Intelligence and nonentrenchment. Journal of Educational Psychology, 73, 1-16. Sternberg, R.J. (1985). Beyond IQ: A triarchic theory of human intelligence. New York: Cambridge University Press. Sternberg, S. (1966). High-speed memory scanning in human memory. Science, 153, 652-654. Vernon, P.A. (1981). Reaction time and intelligence in the mentally retarded. Intelligence, 5. 345355. Vernon, P.A. (1983). Speed of information processing and general intelligence. Intelligem'e, 7, 5370. Vernon, P.A., & Jensen, A.R. (1984). Individual and group diftercnces in intelligence and speed of information-processing. Personality and Individual Diff~,rences, 5, 411 423. Vernon. P.A., Nador, S., & Kantor, I.. (1985L Reaction times and speed of prtx:essing: Their relationship to timed and untimed measures of intelligence. Intelligence, 9. 357-374.