Love: What Is It, Why Does It Matter, and How Does It Operate?

ABSTRACT— Love is a perennial topic of fascination for scholars and laypersons alike. Whereas psychological science was slow to develop active interest in love, the past few decades have seen considerable growth in research on the subject, to the point where a uniquely psychological perspective on love can be identified. This article describes some of the more central and well-established findings from psychologically informed research on love and its influence in adult human relationships. We discuss research on how love is defined, the significance of love for human activity and well-being, and evidence about the mechanisms by which love is believed to operate. We conclude by describing several key questions and potentially important new directions for the next wave of psychological science.     

Opposing actions of chronic Delta9-tetrahydrocannabinol and cannabinoid antagonists on hippocampal long-term potentiation

Memory deficits produced by marijuana arise partly via interaction of the psychoactive component, Delta(9)-tetrahydrocannabinol (Delta(9)-THC), with cannabinoid receptors in the hippocampus. Although cannabinoids acutely reduce glutamate release and block hippocampal long-term potentiation (LTP), a potential substrate for learning and memory, the consequences of prolonged exposure to Delta(9)-THC for hippocampal function are poorly understood. Rats were injected with Delta(9)-THC (10 mg/kg, i.p., q.d.) for 1, 3, or 7 d, and electrophysiological recordings were performed in hippocampal slices 1d after the final injection. At this time, Delta(9)-THC was undetectable in hippocampus using liquid chromatography-mass spectrometry (LC-MS). Hippocampal LTP generated using high-frequency (HFS) or theta burst stimulation was not observed in brain slices from the 7-d Delta(9)-THC-treated animals. Delta(9)-THC also blocked HFS-LTP after 3 d, but not 1 d of treatment. The complete blockade of LTP persisted for 3 d after the last Delta(9)-THC injection, and full reversal of the LTP deficit was not observed up to 14 d following Delta(9)-THC withdrawal. The cannabinoid antagonist AM251 (2 mg/kg), administered before each Delta(9)-THC injection prevented the blockade of LTP, and 7-d treatment with AM251 alone significantly increased the level of LTP. Chronic Delta(9)-THC also produced tolerance to the inhibition of synaptic GABA, but not glutamate release by the agonist WIN55,212-2. These data define consequences of repeated Delta(9)-THC exposure for synaptic plasticity in the hippocampus that may help explain memory impairments in humans following chronic marijuana use.     

Evidence for a neuroendocrinological foundation of human affiliation: plasma oxytocin levels across pregnancy and the postpartum period predict mother-infant bonding

Although research on the neurobiological foundation of social affiliation has implicated the neuropeptide oxytocin in processes of maternal bonding in mammals, there is little evidence to support such links in humans. Plasma oxytocin and cortisol of 62 pregnant women were sampled during the first trimester, last trimester, and first postpartum month. Oxytocin was assayed using enzyme immunoassay, and free cortisol was calculated. After the infants were born, their interactions with their mothers were observed, and the mothers were interviewed regarding their infant-related thoughts and behaviors. Oxytocin was stable across time, and oxytocin levels at early pregnancy and the postpartum period were related to a clearly defined set of maternal bonding behaviors, including gaze, vocalizations, positive affect, and affectionate touch; to attachment-related thoughts; and to frequent checking of the infant. Across pregnancy and the postpartum period, oxytocin may play a role in the emergence of behaviors and mental representations typical of bonding in the human mother.     

Empirical Support for an Evolutionary Model of Self‐Destructive Motivation

We tested predictions generated from an evolutionary account of self‐destructive motivation in two survey studies of 18–24‐year‐old university students. As hypothesized, hierarchical regressions showed that the positive relationship between perceived burden to family and suicide ideation was amplified for participants with low measured health and romantic relationship satisfaction, and for participants with relatively young mothers. The moderating effect of maternal age was also observed in logistic regressions of suicide attempts. These effects occurred independently of depression, hopelessness, and other relevant extraneous variables. Results have implications for understanding self‐destructive motivation, assessing suicide risk, and preventing suicidal thinking and behavior.     

Do computer simulations support the Argument from Disagreement?

According to the Argument from Disagreement (AD) widespread and persistent disagreement on ethical issues indicates that our moral opinions are not influenced by moral facts, either because there are no such facts or because there are such facts but they fail to influence our moral opinions. In an innovative paper, Gustafsson and Peterson (Synthese, published online 16 October, 2010) study the argument by means of computer simulation of opinion dynamics, relying on the well-known model of Hegselmann and Krause (J Artif Soc Soc Simul 5(3):1–33, 2002; J Artif Soc Soc Simul 9(3):1–28, 2006). Their simulations indicate that if our moral opinions were influenced at least slightly by moral facts, we would quickly have reached consensus, even if our moral opinions were also affected by additional factors such as false authorities, external political shifts and random processes. Gustafsson and Peterson conclude that since no such consensus has been reached in real life, the simulation gives us increased reason to take seriously the AD. Our main claim in this paper is that these results are not as robust as Gustafsson and Peterson seem to think they are. If we run similar simulations in the alternative Laputa simulation environment developed by Angere and Olsson (Angere, Synthese, forthcoming and Olsson, Episteme 8(2):127–143, 2011) considerably less support for the AD is forthcoming.     

“Was It Good for You?”: Reply to Commentaries

In many ways, psychoanalysis revolutionized attitudes about sexuality. Yet by undertheorizing female erotic passion and downplaying the role of the clitoris, psychoanalysis perpetuated a long historical tradition of denying essential aspects of women's sexual experience. Psychoanalysis has at times contributed to women perceiving their own bodily erotic excitement as frightening, dangerous, and out of control. In this reply to the commentaries, the authors continue to explore the ways in which women and women's experience, especially their embodied sexual experience, are so often rendered invisible.     

Conditioned enhancement of human's liking for flavor by pairing with sweetness

This paper reports a procedure, like classical conditioning, that produces enhancement of liking for flavors by humans. The procedure is “pairing” of a relatively neutral flavor with sugar (a hedonically positive taste). Specifically, subjects drank 24 small samples of flavor A sweetened and 24 small samples of flavor B unsweetened. They were then tested for their liking for flavors A and B, both sweetened and unsweetened. In three different studies, varying in a number of aspects of stimulus presentations and context, a relative enhancement in liking for flavor A appeared both on the day of exposure and 1 week later. An absolute enhancement in liking of flavor B (a “mere exposure” effect) also occurred in two of the three experiments.