This book is intended for a popular audience. It is low on technical detail, rhetorically selective in its presentation of research findings and light-hearted in tone: but none of this should deter either the lay or professional psychologist reader.
Robert Kurzban has used his view of evolutionary psychology to pursue the concept of "self" at the heart of both the discipline of psychology and the everyday understanding of human behaviour - which surely is of interest to everyone.
Kurzban adheres to the massive modularity hypothesis, which holds that our cognition is partitioned into functionally specific computational packages or modules. Modules are a consequence of natural selection and our minds are the result of many instances of selection adding modules to the collection. Modules carry out their selected functions without the need to interact with each other and, as a consequence, it is entirely possible for a person to present contradictory beliefs and behaviours, thus appearing hypocritical. For example, we can know that eating sweet, fatty foods is bad for our health and yet choose to eat them when we are hungry.
The basic conceit is that we are a species with an evolutionary history of periodic starvation. In our ancestral past it would have made good sense to eat as much as we possibly could of sweet, fatty foods when we encountered them to lay down energy stores against future shortages. As modern humans, we have learned that such storage is detrimental to long-term health. However, the modules that enable us to learn about health and the modules that enable consumption are not connected and, under certain conditions, the cues to consume win out over those that cause us to consider our future morbidity. Indeed, Kurzban reminds us not to go to the supermarket when hungry for precisely this reason.
It is difficult to think of a truly domain-general device. Any tool that you may care to name will have been designed specifically for hammering, levering, drilling, etc. That you might be able to use the handle of a screwdriver to bang home a nail is not evidence for the domain-generality of a screwdriver. First, it functions superbly well when dealing with screws, but requires a large amount of force to push a nail through a plank. Hammers are better, as designers have selected the weight-to-swing ratio for this purpose.
Second, even if a particular screwdriver turned out to be an excellent hammer, it would not be much use as a drill, so its utility would still have limits. Kurzban makes this point but also does an excellent job of showing the key benefits of modularity. With modular devices pursuing their own ends, the overall organism will not get bogged down in lengthy sequential calculations, but instead will be able to deliver behaviours in parallel. From an evolutionary perspective this is a much better design than a relatively general computational device trying to prioritise tasks, access appropriate stored knowledge and then act, not least because time is a significant limiting factor. Moreover, multiple modules for multiple tasks introduce great flexibility, which enables the organism to use a broader range of ecologies.
On occasions, however, organisms appear inconsistent. There is no oversight mechanism weighing up which modular response to favour; instead, the organism is at the mercy of the cues it encounters. This is a pandemonium model of the mind, which means that under certain circumstances some modules will be more impatient than others, which is presumably why fast food outlets remain open after pub closing hours.
It is this latter argument that Kurzban recruits to do away with the self. Self-esteem, self-deception, stable preferences and moral dispositions are all interrogated as versions of a claim to an executive, domain-general mechanism. Moreover, if there were to be a "self" module, this would serve a specific function and, in keeping with massive modularity, would have no contact with other modules.
None of its arguments is new, but the book itself is fresh. Kurzban's style is to take traditional questions and apparently reasonable positions and then demonstrate that reasonableness is actually only so under a set of assumptions - and that if they do not conform to the modularity hypothesis then we ought to rethink.
Early in the book, economist Steven Landsburg's second mystery of the universe - why people lock the refrigerator door at night - is cited. The intuition is that locking the fridge seems odd when humans could exert self-control after rationally thinking through the costs of eating between meals. This rational actor view of human cognition is a domain-general view.
But if we concede that there can be no domain-general reasoning and selection has not built our minds this way, then various cues might act to make the modules in charge of snacking more impatient than those that think about health, to the detriment of the individual.
To Kurzban the mystery is not mysterious, and Landsburg's assumptions are awry.
Why Everyone (Else) is a Hypocrite: Evolution and the Modular Mind
By Robert Kurzban. Princeton University Press. 288pp, £19.95. ISBN 9780691146744. Published 2 February 2011