Males’ superior spatial ability likely is not an evolutionary adaptation

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(Phys.org)—Males and females differ in a lot of traits (besides the obvious ones) and some evolutionary psychologists have proposed hypotheses to explain why. Some argue, for example, that males’ slight, but significant, superiority in spatial navigation over females – a phenomenon demonstrated repeatedly in many species, including humans – is probably “adaptive,” meaning that over the course of evolutionary history the trait gave males an advantage that led them to have more offspring than their peers.

A new analysis published in The Quarterly Review of Biology found no support for this hypothesis. The researchers, led by University of Illinois psychology professor Justin Rhodes, looked at 35 studies that included data about the territorial ranges and spatial abilities of 11 species of animals: cuttlefish, deer mice, horses, humans, laboratory mice, meadow voles, , , rats, rhesus and talastuco-tucos (a type of burrowing rodent). Rhodes and his colleagues found that in eight out of 11 species, demonstrated moderately superior to their female counterparts, regardless of the size of their territories or the extent to which males ranged farther than females of the same species.

The findings lend support to an often-overlooked hypothesis, Rhodes said. The average superiority of males over females in spatial navigation may just be a “side effect” of testosterone, he said. (Previous studies have shown that women who take testosterone tend to see an improvement in their spatial navigation skills, he said.)

Written By: PhysOrg
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20 COMMENTS

  1. And what is testosterone? A non-adaption?

    One, 35 studies implies meta-analysis and all the problems that go with meta-analysis. Two. Why is a psychologist published in a biological journal?

    The alternative hypothesis, testosterone side effect, may be supportable, but one psychologist saying something to other psychologist ( Evolutionary types ) does not impress me. I would rather hear from a scientist. Bias? Yes!!

  2. Oh, I dunno, maybe the brain is part of the human body? Ridiculous right? Whoever heard of such thing.

    Anyway, any quality peer-reviewed journal can appear anywhere as long as the argument is valid & sound. Since when did the discipline of biology becomes a church that rejects any input from other denomination?

  3. In reply to #2 by adiroth:

    Oh, I dunno, maybe the brain is part of the human body? Ridiculous right? Whoever heard of such thing.

    Anyway, any quality peer-reviewed journal can appear anywhere as long as the argument is valid & sound. Since when did the discipline of biology becomes a church that rejects any input from other denomination?

    Since psychology has it’s own organs of publication that biology is rarely, if ever, seen in. One, biology, is a science, one, psychology, is not a science. Aside from the implied meta analysis which is probably never seen in science ( excepting medical ” science ” )

  4. In reply to #1 by Neodarwinian:

    And what is testosterone? A non-adaption?

    I don’t think that is what is being asserted here. If I understand correctly the idea is not that differences in spatial/navigation ability did not evolve at all, but that they were not – as some hypotheses suggest – the feature under strong selection pressure. Instead, Rhodes asserts that selection was more likely acting to increase testosterone levels in males for other well understood reasons, which had the secondary, and not necessarily adaptive, effect of gender differentiation in spatial abilities.

    In essence this research questions whether we have any reason to believe that natural selection should prefer males who are better than females at spatial navigation, rather than just good at it in general.

    Not every trait or sexual dimorphism can be explained because the gender difference itself – in isolation – is adaptive. Neutral or even detrimental traits can evolve by “piggy-backing” on other traits which are under strong positive selection pressure. It is only necessary that the net effect of associated traits be selectively advantageous.

    We have here a case of two conflicting hypotheses which both rely on adaptive explanations, not of an adaptive vs. a non-adaptive explanation.

    One, 35 studies implies meta-analysis and all the problems that go with meta-analysis.

    Good, point. There are lots of problems with meta-analyses for which correction is necessary. I haven’t read the paper in question so I can’t say whether the proper care has been used here, nor would I feel particularly well qualified to make that assessment. I do find the brief explanation of the research in this video persuasive and based on broadly sound principles, however I’d like to hear a vigorous defense of the alternative theory (if anyone is making such) before making up my mind.

    Two. Why is a psychologist published in a biological journal?

    Well, I assume because his research was deemed adequate for publication by the peer review process established by the journal in question. I can’t say whether the particular process of this journal is adequately rigorous. Do you have any reason – other than the fact that they published a paper by a psychologist – to deem it substandard? That would be useful information. In my view however, good peer review focuses on the content of the research in question and is not unduly biased by the specialty of the submitting authors.

    The alternative hypothesis, testosterone side effect, may be supportable, but one psychologist saying something to other psychologist ( Evolutionary types ) does not impress me.

    I’m not sure what you mean here, but why are you assuming that the first psychologist is not an “Evolutionary type”?

    I would rather hear from a scientist.

    If the journal is reputable – which I can’t speak to with certainty, but have no reason to doubt – then I think we can at least give the guy the benefit of the doubt as to whether he qualifies as a “scientist.” He may of course be wrong, but I don’t think it fair to assume he’s anti-biology because he specializes in another field. Lots of psychologists are very competent in biology. Many others are not. I don’t think we can draw any conclusion from his specialty.

    Bias? Yes!!

    Bias? Bad!!

  5. In reply to #4 by BanJoIvie:

    In reply to #1 by Neodarwinian:

    And what is testosterone? A non-adaption?

    I don’t think that is what is being asserted here. If I understand correctly the idea is not that differences in spatial/navigation ability did not evolve at all, but that they were not – as some hypotheses suggest – the feature under strong selection pressure. Instead, Rhodes asserts that selection was more likely acting to increase testosterone levels in males for other well understood reasons, which had the secondary, and not necessarily adaptive, effect of gender differentiation in spatial abilities.

    In essence this research questions whether we have any reason to believe that natural selection should prefer males who are better than females at spatial navigation, rather than just good at it in general.

    Not every trait or sexual dimorphism can be explained because the gender difference itself – in isolation – is adaptive. Neutral or even detrimental traits can evolve by “piggy-backing” on other traits which are under strong positive selection pressure. It is only necessary that the net effect of associated traits be selectively advantageous.

    We have here a case of two conflicting hypotheses which both rely on adaptive explanations, not of an adaptive vs. a non-adaptive explanation.

    One, 35 studies implies meta-analysis and all the problems that go with meta-analysis.

    Good, point. There are lots of problems with meta-analyses for which correction is necessary. I haven’t read the paper in question so I can’t say whether the proper care has been used here, nor would I feel particularly well qualified to make that assessment. I do find the brief explanation of the research in this video persuasive and based on broadly sound principles, however I’d like to hear a vigorous defense of the alternative theory (if anyone is making such) before making up my mind.

    Two. Why is a psychologist published in a biological journal?

    Well, I assume because his research was deemed adequate for publication by the peer review process established by the journal in question. I can’t say whether the particular process of this journal is adequately rigorous. Do you have any reason – other than the fact that they published a paper by a psychologist – to deem it substandard? That would be useful information. In my view however, good peer review focuses on the content of the research in question and is not unduly biased by the specialty of the submitting authors.

    The alternative hypothesis, testosterone side effect, may be supportable, but one psychologist saying something to other psychologist ( Evolutionary types ) does not impress me.

    I’m not sure what you mean here, but why are you assuming that the first psychologist is not an “Evolutionary type”?

    I would rather hear from a scientist.

    If the journal is reputable – which I can’t speak to with certainty, but have no reason to doubt – then I think we can at least give the guy the benefit of the doubt as to whether he qualifies as a “scientist.” He may of course be wrong, but I don’t think it fair to assume he’s anti-biology because he specializes in another field. Lots of psychologists are very competent in biology. Many others are not. I don’t think we can draw any conclusion from his specialty.

    Bias? Yes!!

    Bias? Bad!!

    And what is testosterone? A non-adaption? You missed the point here. I do not care what is being asserted here as the confusion between ultimate explanations and proximate explanations here is what concerns me. Aside from that, Why is a psychologist published in a biological journal?, is more a rhetorical question designed to elicit caution when dealing with social science.

    ” Bias? Bad!! “

    No. I am biased towards being adequately warm instead of cold, well watered instead of parched and eating the proper nutrients instead of, say, chitin. I am also biased towards science and it’s superior methodology and against social science and it’s incoherent attempts at methodology.

  6. In reply to #5 by Neodarwinian:

    And what is testosterone? A non-adaption? You missed the point here. I do not care what is being asserted here as the confusion between ultimate explanations and proximate explanations here is what concerns me.

    I freely admit I may have missed the point. In fact I still do not understand your objection. The paper seems to be distinguishing between ultimate and proximate, not confusing them. I’d welcome a fuller explanation of the problem as you see it.

    Aside from that, Why is a psychologist published in a biological journal?, is more a rhetorical question designed to elicit caution when dealing with social science.

    Caution is all well and good, but it’s a good idea to distinguish between bias against social science and bias against social scientISTS. The paper is in a biology journal, it should have been vetted by qualified biologists. If this was not done, that is indeed a problem. The fact that the paper’s author specializes in a social science field does not mean he necessarily lacks proficiency in hard science.

    The problem with social sciences is not that the entire fields of study are invalid, but that proper rigor is sometimes lacking in those fields. Shouldn’t we rather seek reform of social scientific fields and encourage those social scientists who engage in hard science and submit their work for the review of hard science professionals rather than write them off by association?

    I am biased towards being adequately warm instead of cold, well watered instead of parched and eating the proper nutrients instead of, say, chitin. I am also biased towards science and it’s superior methodology and against social science and it’s incoherent attempts at methodology.

    I prefer temperate to intemparate weather, hydration to thirst and sustenance to malnutrition because I have good evidence for the desirability of one over the other. Bias is bad when it causes us to assume facts not in evidence. Given that the editors of a science journal saw fit to publish this work after review, I think we have at least enough reason to evaluate the work on its merits before dismissing it. Rhodes may be a social scientist, but that does not mean all his work is social science. Einstein was a patent clerk.

    Good methodology is indeed preferrable to bad, wherever it is found. I would not assume that a scientist had necessarily good methodology just becasue he/she is labeled a biologist, it would be equally unfair to assume bad methodology from a psychologist absent other evidence. I would expect work from both scientists – regardless of their field of expertise – to be subjected to rigorous review.

    If you wish to specifically discredit the methodology of this study, I look forward to hearing it. There may be flaws worth noting which could invalidate the work or require additional research. But ad hominem and an argument from (negative) authority to not amount to a cogent critique.

  7. In reply to #6 by BanJoIvie:

    In reply to #5 by Neodarwinian:

    And what is testosterone? A non-adaption? You missed the point here. I do not care what is being asserted here as the confusion between ultimate explanations and proximate explanations here is what concerns me.

    I freely admit I may have missed the point. In fact I still do not understand your objection. The paper seems to be distinguishing between ultimate and proximate, not confusing them. I’d welcome a fuller explanation of the problem as you see it.

    Aside from that, Why is a psychologist published in a biological journal?, is more a rhetorical question designed to elicit caution when dealing with social science.

    Caution is all well and good, but it’s a good idea to distinguish between bias against social science and bias against social scientISTS. The paper is in a biology journal, it should have been vetted by qualified biologists. If this was not done, that is indeed a problem. The fact that the paper’s author specializes in a social science field does not mean he necessarily lacks proficiency in hard science.

    The problem with social sciences is not that the entire fields of study are invalid, but that proper rigor is sometimes lacking in those fields. Shouldn’t we rather seek reform of social scientific fields and encourage those social scientists who engage in hard science and submit their work for the review of hard science professionals rather than write them off by association?

    I am biased towards being adequately warm instead of cold, well watered instead of parched and eating the proper nutrients instead of, say, chitin. I am also biased towards science and it’s superior methodology and against social science and it’s incoherent attempts at methodology.

    I prefer temperate to intemparate weather, hydration to thirst and sustenance to malnutrition because I have good evidence for the desirability of one over the other. Bias is bad when it causes us to assume facts not in evidence. Given that the editors of a science journal saw fit to publish this work after review, I think we have at least enough reason to evaluate the work on its merits before dismissing it. Rhodes may be a social scientist, but that does not mean all his work is social science. Einstein was a patent clerk.

    Good methodology is indeed preferrable to bad, wherever it is found. I would not assume that a scientist had necessarily good methodology just becasue he/she is labeled a biologist, it would be equally unfair to assume bad methodology from a psychologist absent other evidence. I would expect work from both scientists – regardless of their field of expertise – to be subjected to rigorous review.

    If you wish to specifically discredit the methodology of this study, I look forward to hearing it. There may be flaws worth noting which could invalidate the work or require additional research. But ad hominem and an argument from (negative) authority to not amount to a cogent critique.

    ” I prefer temperate to intemparate weather, hydration to thirst and sustenance to malnutrition because I have good evidence for the desirability of one over the other. “

    No you don’t. Those biases are innate.

    ” If you wish to specifically discredit the methodology of this study, ” ?????? I thought I did when I pointed out the meta analysis implication of 35 studies gone over. Are you actually aware of the problems with meta analysis?

    Regardless, I do not have the time to do this discussion justice as I am studying for a molecular cell biology and astronomy test(s) that will be held tomorrow. I an earlier life I studied for psychology tests and I notice the variance!!

  8. In reply to #8 by Neodarwinian:

    No you don’t. Those biases are innate.

    Good point. I should have said something more like, “I give credence to these innate biases because they are justified by good evidence.”

    ” If you wish to specifically discredit the methodology of this study, ” ?????? I thought I did when I pointed out the meta analysis implication of 35 studies gone over.

    If you thought that the mere implication that meta analysis may have been used was enough discredit the methodology of a study, then we have very different standards. You arent even sure that this paper was conducted as a formal meta analysis of the 35 studies mentioned in the video, let alone how carefully such a hypothetical analysis may have been nor how narrowly drawn any specific conclusions of such an analysis were.

    Are you actually aware of the problems with meta analysis?

    I already acknowledged that meta analysis is problematic, but it is not universally invalid. Merely raising the specter of “implied” meta analysis is not good critique.

    Regardless, I do not have the time to do this discussion justice as I am studying for a molecular cell biology and astronomy test(s) that will be held tomorrow. I an earlier life I studied for psychology tests and I notice the variance!!

    Best of luck on your exams. I agree that there is significant variance in practice between psychology and the hard sciences. I just think it’s important to be circumspect in what conclusions we do and do not draw from that difference.

  9. In reply to #9 by BanJoIvie:

    Are you actually aware of the problems with meta analysis?

    I already acknowledged that meta analysis is problematic, but it is not universally invalid. Merely raising the specter of “implied” meta analysis is not good critique.

    That’s right. Inferences are judged by their strength, because they are not intended to be valid. And as you would be aware, the work of science are inferences.

  10. In reply to #3 by Neodarwinian:

    In reply to #2 by adiroth:

    Oh, I dunno, maybe the brain is part of the human body? Ridiculous right? Whoever heard of such thing.

    Anyway, any quality peer-reviewed journal can appear anywhere as long as the argument is valid & sound. Since when did the discipline of biology becomes a church that rejects any input from other denomination?

    Since psychology has it’s own organs of publication that biology is rarely, if ever, seen in. One, biology, is a science, one, psychology, is not a science. Aside from the implied meta analysis which is probably never seen in science ( excepting medical ” science ” )

    Wait, that’s just cheap snobbery and turf hugging isn’t it? The beauty about science is that practically everyone can do it as long as the research is done right & passed the peer-review process. So what if the author comes from a different school? If he’s done the job, he deserves the recognition.

    Of course, you are free to debate his claim, because that’s fair game. But based on your post about testosterone, it seems that you are not aware of the way the claim is framed.

  11. ” Lots of psychologists are very competent in biology”

    Biology is required as a main discipline along with math (and that can be only in a scientific area of study) if someone wants to apply to the study of psychology (where I live).

    Well I am not going further with any explanation ……….

    I simply enjoyed the video.

  12. Makes sense. Just because a chemical effect seems subjectively important to us doesn’t mean that natural selection cares about it. Equally, just because something is adaptive doesn’t mean it’s good for us. Aggression, another effect of testosterone, is probably strongly adaptive in males.

  13. In reply to #13 by *guy:

    Neodarwinian,

    Please take a moment to learn about the people you are attacking before you resort to ad hominem. Wikipedia is your friend

    http://en.wikipedia.org/wiki/Justin_Rhodes

    Ad hominem????? No names were mentioned and no attacks against PEOPLES character were made, so I do not know what you are talking about. Do you?

    Studies and work and method are fair game and you need to know this.

  14. In reply to #11 by adiroth:

    In reply to #3 by Neodarwinian:

    In reply to #2 by adiroth:

    Oh, I dunno, maybe the brain is part of the human body? Ridiculous right? Whoever heard of such thing.

    Anyway, any quality peer-reviewed journal can appear anywhere as long as the argument is valid & sound. Since when did the discipline of biology becomes a church that rejects any input from other denomination?

    Since psychology has it’s own organs of publication that biology is rarely, if ever, seen in. One, biology, is a science, one, psychology, is not a science. Aside from the implied meta analysis which is probably never seen in science ( excepting medical ” science ” )

    Wait, that’s just cheap snobbery and turf hugging isn’t it? The beauty about science is that practically everyone can do it as long as the research is done right & passed the peer-review process. So what if the author comes from a different school? If he’s done the job, he deserves the recognition.

    Of course, you are free to debate his claim, because that’s fair game. But based on your post about testosterone, it seems that you are not aware of the way the claim is framed.

    You seem not aware of the fact the author did no study but evaluated others work. We are not arguing anything here, ” If he’s done the job, he deserves the recognition.. “

    ” University of Illinois psychology professor Justin Rhodes, looked at 35 studies that included data …”

    Who did the job?

  15. In reply to #9 by BanJoIvie:

    In reply to #8 by Neodarwinian:

    No you don’t. Those biases are innate.

    Good point. I should have said something more like, “I give credence to these innate biases because they are justified by good evidence.”

    ” If you wish to specifically discredit the methodology of this study, ” ?????? I thought I did when I pointed out the meta analysis implication of 35 studies gone over.

    If you thought that the mere implication that meta analysis may have been used was enough discredit the methodology of a study, then we have very different standards. You arent even sure that this paper was conducted as a formal meta analysis of the 35 studies mentioned in the video, let alone how carefully such a hypothetical analysis may have been nor how narrowly drawn any specific conclusions of such an analysis were.

    Are you actually aware of the problems with meta analysis?

    I already acknowledged that meta analysis is problematic, but it is not universally invalid. Merely raising the specter of “implied” meta analysis is not good critique.

    Regardless, I do not have the time to do this discussion justice as I am studying for a molecular cell biology and astronomy test(s) that will be held tomorrow. I an earlier life I studied for psychology tests and I notice the variance!!

    Best of luck on your exams. I agree that there is significant variance in practice between psychology and the hard sciences. I just think it’s important to be circumspect in what conclusions we do and do not draw from that difference.

    ” f you thought that the mere implication that meta analysis may have been used was enough discredit the methodology of a study, then we have very different standards. You arent even sure that this paper was conducted as a formal meta analysis of the 35 studies mentioned in the video, let alone how carefully such a hypothetical analysis may have been nor how narrowly drawn any specific conclusions of such an analysis were. “

    Fair enough, but I guess I can not really question the methodology of this particular work as the work was only a review of other work as is clearly stated in the article.

  16. In reply to #15 by Neodarwinian:

    In reply to #13 by guy:*

    Neodarwinian,

    Please take a moment to learn about the people you are attacking before you resort to ad hominem. Wikipedia is your friend

    http://en.wikipedia.org/wiki/Justin_Rhodes

    Ad hominem????? No names were mentioned and no attacks against PEOPLES character were made, so I do not know what you are talking about. Do you?

    Studies and work and method are fair game and you need to know this.

    Yes, and if you had actually criticized the study or the work or the method, then your criticism wouldn’t have been ad hominem. But you didn’t. Your argument was only to assert that he was a psychologist and therefore is somehow unworthy of publishing in Biology journals. AKA attacking the individual, and not the work. You confess yourself that you didn’t even look at the publication… so how could you possibly be judging it on its merits? You went on to basically imply that meta-analysis is hard, and that therefore those dumb psychology people couldn’t possible have done it. again… ad hominem.

    You haven’t made any argument at all. You are just callously disregarding someones work based on your preconceived idea about what the person is like. However, I suspect after reading Prof Rhodes wikipedia page that he is more than qualified to perform meta analysis.

  17. How unattractive to see an alleged proponent of science and reason dismissing an entire academic discipline from the ranks of science because of a difference in content and methodology. Since we are all members of a site designed in part to teach the difference between science and non-science, we might all do well to be able to distinguish what science is.

    Coincidentally, the factors that make psychology a “soft” science apply to evolutionary biology in the same sense. If one concludes the former to be unscientific, one must conclude the same for the latter. Luckily, there are many different valid ways to do science. Kudos on the academically mature replies to Neodarwinian.

  18. In reply to #1 by Neodarwinian:

    And what is testosterone? A non-adaption?

    One, 35 studies implies meta-analysis and all the problems that go with meta-analysis. Two. Why is a psychologist published in a biological journal?

    The alternative hypothesis, testosterone side effect, may be supportable, but one psychologist saying something to other psychologist ( Evolutionary types ) does not impress me. I would rather hear from a scientist. Bias? Yes!!

    Hi there. I’m the lead author of the paper. My paper is not a meta-analysis and nowhere is that implied. This paper is biopsychology. It is concerned with evolution and the behavior of animals. That’s actually perfect material for a biology journal. Also, Justin Rhodes, the who is seen in the video, has a background in biology (PhD in zoology, not psychology) though he chooses to work in biopsych. I can assure you that he is a “scientist”, and so am I.

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