How neuroscience interfaces with evolutionary psychology

Given that evolutionary psychology and molecular neuroscience are both relatively recent fields and that both study what is going on in our head, there seems to be fairly little interplay between the two subjects. In their review article, Pankseep et al. attempt to rectify this dearth of collaboration.

The authors concede two crucial points that evolutionary psychology has given to the scientific community: the idea there is a some core human psyche that is a product of our sociobiological evolution, and the correct predictions that it has made in understanding our current mental processes. However, some evolutionary psychologists may go too far in presupposing that our reward system itself is unique, as it was probably co-opted from a shared ancestor of mammals in evolution and adapted to fire to general symbols instead of specific signs. I’m not sure if this is a straw man argument that they are presenting, but if it is not, it deserves serious attention.

Furthermore, many of the social processes regulated by the hypothalamic-pituitary-adrenal axis are seen in other animals as well. For example, consider the “resident-intruder” paradigm common in studies of rats. In these studies, the intruder is almost always the “loser” of the social interaction and very commonly exhibits physiological changes following this defeat. These include loss of weight, testicular regression, and increased fearfulness. The changes are especially evident when the “loser” rat is not placed back in a social housing condition but is instead housed in isolation. It is quite evident that humans are not the only intensely social animals, so why should we limit our study to them?

With this groundwork in play, the authors present what they term the “seven deadly sins of evolutionary psychology”:

1) The assumption that the neocortex is the primary region for human differentiation from other animals may be foolhardy since the system is maintained between mammalian species. Perhaps some of the differentiation emerged epigenitically because of cultural changes?

2) An overemphasis on one species, when others have useful insights to yield as well.

3) They may focus too much on the specifics and miss the general point. What are the general processes that could have evolved that could account our current psychological state?

4) Since the idea of “brain centers” was cast aside a few decades ago, evolutionary psychologists must explain how their ideas fit within an integrated brain.

5) Too often conflating emotions–the will to do something–with reasoning-based decisions. Although they are closely related, there may be a way to distinguish between the two and note where evolutionary adaptations have developed as emotions, and where they have developed as decision making skills.

6) There is no need to ignore the brain, since molecular neuroscience is providing a solid base upon which others can build. They generalize this criticism to all social scientists.

7) Declaring a mental process to be an “algorithm” is silly, because more and more research suggests that the brain does not work with this sort of distinct processes. Although they can be useful as models, ultimately the best models will discuss an integration with the rest of the brain processes. Again, this criticism could be reasonably applied to just about anyone, and probably has more to do with the current system of science than any one researcher’s desire to specialize.

The authors then go on to discuss how some of these “sins” can be resolved through a study of molecular genetics and neuroscience. These demands on evolutionary psychologists are challenging, but if they meet half of the demands of their toughest critics, it will probably be enough for the rest of the scientific community.


Panksepp J, Moskal JR, Panksepp JB, Kroes RA 2002 Comparative approaches in evolutionary psychology: molecular neuroscience meets the mind. Neuroendocrinology Letters 23: 105-115. pii:NEL231002R11.

The Moral Animal book notes

Robert Wright’s The Moral Animal is considered a “popular” introduction to evolutionary psychology. But contrary to expectations based on most “popular” literature, Wright’s foray is balanced, detailed, and funny. Here are some of my notes:

  • The naturalistic fallacy is when people attempt to derive basic moral values from natural selection, or any of nature’s workings. Indeed, just because it is “natural” does not mean that we should adopt it.
  • The watchmaker argument claims that since our current state is so complex, it must be the result of intelligent design. Darwin’s theory of natural selection offered a method by which evolution could function, thus providing a counterargument to intelligent design.
  • “Between us and the australopithecine, which walked upright but had an ape-sized brain, stand a few million years: 100,000 maybe 200,000 generations.” p 26. This means that we only have had a small amount of time to differentiate ourselves from our most recent ancestors.
  • The classic male/female experiment to demonstrate differences between the sexes: “In one experiment, three-fourths of the men approached by an unknown woman on a college campus agreed to have sex with her, whereas none of the women approached by an unknown man were willing.” p 43
  • Bonobos, a close relative of ours, can display homosexual behavior.
  • Women are generally attracted to high social status, men generally to beauty, and therefore youth, and therefore fertility.
  • Women do cheat on their mates: “Blood tests show that in some urban areas more than one fourth of the children may be sired by someone other than the father of record.” p 70
  • Frequency-dependent selection is when “the value of a trait declines as it becomes more common, so that natural selection places a ceiling on its predominance, thus leaving room for the alternative.” p 79
  • A polygynous society is better for women, whereas most men end up worse off. This is counter-intuitive and one of the strongest sections in the book.
  • Human beings are not “fitness maximizers,” they are “adaption executors.” Eliezer has posted upon this previously, it is a tough but crucial point to remember.
  • John Stuart Mill was a utilitarian, and believed in the most happiness for the most people, and happiness of the higher order (not just base pleasure).
  • Kin selection means that you want your shared genes to succeed in life too, not just yourself. It is used to explain a lot of altruistic behavior.
  • A gene for altruism will thrive if c < br, where…
    c = cost to agent organism
    b = benefit to target organism
    r = relatedness of agent and target
  • Poor families will invest in daughters, rich families in sons.
  • Group selectionism is a foolhardy temptation towards which you should not fall. Read about it on Wikipedia, or in the book, where it is given an excellent treatment. It doesn’t stand up empirically.
  • In a sweet iterated prisoner’s dilemma game with repeated trials, the program called “TIT FOR TAT” won, which was designed to essentially treat others how they treat you. This is another empirical explanation for why altruism could have developed.
  • Moulay Ismail the Bloodthirsty sired more children than anybody else according to Guinness world records, 888.
  • We may be biased into deceiving ourselves so as to be more proficient at deceiving others.

You will find many more nuggets if you read the whole book. Neuroscience is fascinating on the cellular and systems level, but in order to consider the brain on a macroscale level, evolutionary psychology must be a part of the equation.

Linking pre-saccadic to post-saccadic stimuli in the visual field

Saccadic eye motion evolved in early vertebrates as an adaptive mechanism to view more areas of a visual scene with the central fovea, and therefore increase overall resolution. Theoretically, it should come at the cost of making it more difficult to link a sequence of objects together, since these saccades would confuse you as to what exactly you are currently looking. However, our visual system compensates for upcoming saccades, resulting in three odd results:

1) Visual fields change their position in shape in real time in order to adjust to the saccade target. For example, in V4, receptive fields generally shift towards the upcoming saccade and modulate their size.

2) Very near to the time that the saccade moves (it’s onset), our perception is that briefly flashed stimuli are closer to the saccade target than they actually are. This is known as peri-saccadic compression, and there ought to be a wikipedia page for it.

3) In experiments that require subjects to both execute a target-directed saccade and discriminate an object (choose it from among a set, I presume), visual discrimation is naturally strongest when the stimuli is located near the target of the saccade.

Their model attempts to explain these distinct phenomena through oculomotor feedback, and show how the brain links the pre-saccadic visual field to the post-saccadic one. Mathematically their model is complex, and they do so not to yield an arbitrarily higher fit, but in order to make it more consistent with the anotomical constraints of visual receptors. Indeed, some of their parameters were so complex that they were forced to estimate their values because of a lack of independently found data to build upon. Nevertheless, their model is fascinating and their predictions robust. Check it out, it’s ungated.


Hamker FH, Zirnsak M, Calow D, Lappe M 2008 The Peri-Saccadic Perception of Objects and Space. PLoS Computational Biology 4(2): e31 doi:10.1371/journal.pcbi.0040031