Peter Kramer

Most of the energy we get to spend is furnished by mitochondria, minuscule living structures sitting inside our cells or dispatched back and forth within them to where they are needed. Mitochondria produce energy by burning down what remains of our meal after we have digested it, but at the cost of constantly corroding themselves and us. Here we review how our mitochondria evolved from invading bacteria and have retained a small amount of independence from us; how we inherit them only from our mother; and how they are heavily implicated in learning, memory, cognition, and virtually every mental or neurological affliction. We discuss why counteracting mitochondrial corrosion with antioxidant supplements is often unwise, and why our mitochondria, and therefore we ourselves, benefit instead from exercise, meditation, sleep, sunshine, and particular eating habits. Finally, we describe how malfunctioning mitochondria force rats to become socially subordinate to others, how such disparity can be evened off by a vitamin, and why these findings are relevant to us.

Psychologists and psychiatrists tend to be little aware that (a) microbes in our brains and guts are capable of altering our behavior; (b) viral DNA that was incorporated into our DNA millions of years ago is implicated in mental disorders; (c) many of us carry the cells of another human in our brains; and (d) under the regulation of viruslike elements, the paternally inherited and maternally inherited copies of some genes compete for domination in the offspring, on whom they have opposite physical and behavioral effects. This article provides a broad overview, aimed at a wide readership, of the consequences of our coexistence with these selfish entities. The overarching message is that we are not unitary individuals but superorganisms, built out of both human and nonhuman elements; it is their interaction that determines who we are.

Perhaps because gastroenterology, immunology, toxicology, and the nutrition and agricultural sciences are outside of their competence and responsibility, psychologists and psychiatrists typically fail to appreciate the impact that food can have on their patients' condition. Here we attempt to help correct this situation by reviewing, in non-technical, plain English, how cereal grains—the world's most abundant food source—can affect human behavior and mental health. We present the implications for the psychological sciences of the findings that, in all of us, bread (1) makes the gut more permeable and can thus encourage the migration of food particles to sites where they are not expected, prompting the immune system to attack both these particles and brain-relevant substances that resemble them, and (2) releases opioid-like compounds, capable of causing mental derangement if they make it to the brain. A grain-free diet, although difficult to maintain (especially for those that need it the most), could improve the mental health of many and be a complete cure for others.

Natural selection has favored the evolution of behaviors that benefit not only one’s genes, but also their copies in genetically related individuals. These behaviors include optimal outbreeding (choosing a mate that is neither too closely related, nor too distant), nepotism (helping kin), and spite (hurting non-kin at a personal cost), and all require some form of kin detection or kin recognition. Yet, kinship cannot be assessed directly; human kin detection relies on heuristic cues that take into account individuals’ context (whether they were reared by our mother, or grew up in our home, or were given birth by our spouse), appearance (whether they smell or look like us), and ability to arouse certain feelings (whether we feel emotionally close to them). The uncertainties of kin detection, along with its dependence on social information, create ample opportunities for the evolution of deception and self-deception. For example, babies carry no unequivocal stamp of their biological father, but across cultures they are passionately claimed to resemble their mother’s spouse; to the same effect, ‘neutral’ observers are greatly influenced by belief in relatedness when judging resemblance between strangers. Still, paternity uncertainty profoundly shapes human relationships, reducing not only the investment contributed by paternal versus maternal kin, but also prosocial behavior between individuals who are related through one or more males rather than females alone. Because of its relevance to racial discrimination and political preferences, the evolutionary pressure to prefer kin to non-kin has a manifold influence on society at large.

In various versions of the dungeon illusion (P. Bressan, 2001), we show that grouping between targets and contextual disks determines whether remote luminances affect target lightness or not. In the dungeon illusion, target disks surrounded by contextual disks contrast with them rather than with the immediate background. We formally establish the existence of this illusion and show that it reverses when the luminance of the targets is either lower (double decrement) or higher (double increment) than the luminances of both the background and the contextual disks rather than in between them. On the basis of the double-anchoring theory of lightness (P. Bressan, 2006a), we predict and show that grouping gates the effects of remote luminances in such a way that they go in opposite directions in the double-decrement and double-increment inverted-dungeon illusions. Our results support the double-anchoring theory and demonstrate that luminances that are far away from the targets are irrelevant in some conditions but critical in others.

A target gray spot looks darker on a white background than on a black one: the contrast illusion. If the target is embedded in a context consisting of black spots on the white background and white spots on the black background, the effect reverses: the dungeon illusion. Whether the dungeon figure produces contrast or contrast reversal depends on which of its three parts (target, context, and background) is gray, black, or white. In some variants, the effect further depends on whether the figures are themselves surrounded by larger white and black regions, implying that even the illumination and wall color of the laboratory might be critical. Here, the various versions of the dungeon illusion are presented and explained with the help of the double-anchoring theory of lightness—that computes the gray shade of objects by "anchoring" them both to their context and to the brightest region in the scene.

It has been argued that numbers are spatially organized along a ''mental number line'' that facilitates left-hand responses to small numbers, and right-hand responses to large numbers. We hypothesized that whenever the representations of visual and numerical space are concurrently activated, interactions can occur between them, before response selection. A spatial prime is processed faster than a numerical target, and consistent with our hypothesis, we found that such a spatial prime affects non-spatial, verbal responses more when the prime follows a numerical target (backward priming) then when it precedes it (forward priming). This finding emerged both in a number-comparison and a parity judgment task, and cannot be ascribed to a ''Spatial–Numerical Association of Response Codes'' (SNARC). Contrary to some earlier claims, we therefore conclude that visuospatial–numerical interactions do occur, even before response selection.

Interactions between numbers and space have become a major issue in numerical cognition. Neuropsychological studies suggest that the interactions occur, before response selection, at a spatially organized representation of numbers (the mental number line). Reaction time (RT) studies, on the other hand, usually point to associations between response codes that do not necessarily imply a number line. There is only one such study that has found a spationumerical interaction between perception and semantics (SNIPS) effect before response selection. Here, in Experiment 1, we isolated the SNIPS effect from other numerical effects and corroborated the prediction that it can be induced by both left and right spatial cues. In Experiment 2, we isolated the peak of the time course of the SNIPS effect and corroborated the prediction that it occurs when a cue follows a target, and not when both appear simultaneously. The results reconcile neuropsychological and RT studies and support the hypothesis that numbers are represented along a left-to-right spatially organized mental number line.

... Categorical interference and associative priming in picture naming Wid0 La Heij,* Jaap Dirkx and Peter Kramer University of Leiden, Faculty of Social Sciences, Unit of Experimental and Theoretical Psychology, PO. Box 9555, 2300 RB Leiden, The Netherlands ...