Stephanie D. Preston, Ph.D.

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• Preston, S. D.; Muroff, J. R.; Wengrovitz, S. M. (in press). Investigating the mechanisms of hoarding from an experimental perspective. Depression and Anxiety.
  Abstract: Acquiring and discarding objects are routine decision processes for most people. Despite the ubiquitous need to make such decisions, little is known about how they are made and what goes wrong when individuals acquire and fail to discard so many items that many areas of their home become unlivable (i.e., clinical hoarding). We hypothesize that clinical hoarding reflects normal variation in the tendency to acquire and retain objects, just at a more extreme level. To test this hypothesis, we examined 89 nonclinical, undergraduate students' performance on a novel experimental paradigm that measures decisions about acquiring and discarding everyday objects. To test our hypothesis, and validate our task as a possible research tool for studying hoarding, we related decisions on the task to a variety of measures known to correlate with clinical hoarding. The paradigm was sensitive to individual differences, as subjects varied widely in the quantity of objects they chose to acquire and retain under increasing pressure to discard. In addition, we replicated expected relationships from the clinical hoarding literature between acquisition and retention tendencies and self-report measures of hoarding, indecisiveness, and obsessive-compulsive behavior. Our data suggest that decisions about objects, even in a nonclinical undergraduate population, vary widely and are influenced by the same variables that influence clinical hoarding, but to a less extreme degree. Future research with this experimental task can separately investigate the role of acquisition, retention, impulsivity, and sensitivity to constraints in clinical hoarding to inform our understanding of this disorder.
  
  
• Preston, S. D. & Stansfield, R. B. (2008). I know how you feel: Task-irrelevant facial expressions are spontaneously processed at a semantic level. Cognitive, Affective, & Behavioral Neuroscience, 8(1), 54-64.
  Abstract: Previous studies demonstrate that emotions are automatically processed. Even with subliminal presentations, subjects involuntarily mimic specific facial expressions, are influenced by the valence of a preceding emotion during judgments, and exhibit slowed responses to personally-meaningful emotions; these effects are due to reflexive mimicry, unconscious carry-over of valence, and attentional capture, respectively. However, perception-action effects indicate that rapid processing should involve deep, semantic-level representations of emotion (e.g. ÒfearÓ) even in the absence of a clinical emotion disorder. To test this hypothesis, we developed an emotional Stroop task (Emostroop) where participants responded non-verbally to emotion words superimposed over task-irrelevant images of faces displaying congruent or incongruent emotional expressions. Participants reliably responded more slowly to incongruent than congruent stimuli, and this interference was related to trait measures of emotionality. Rapid processing of facial emotions spontaneously activates semantic, content-rich representations at the level of the specific emotion.
  
  
• Preston, S. D.; Bechara, A.; Damasio, H.; Grabowski, T. J.; Stansfield, R. B.; Mehta, S.; Damasio A. R. (2007). The neural substrates of cognitive empathy. Social Neuroscience, 2(3-4), 254-275.
  Abstract: Neuroscientific research has consistently found that the perception of an affective state in another activates the observer's own neural substrates for the corresponding state, which is likely the neural mechanism for "true empathy." However, to date there has not been a brain-imaging investigation of so-called "cognitive empathy," whereby one "actively projects oneself into the shoes of another person," imagining someone's personal, emotional experience as if it were one's own. In order to investigate this process, we conducted a combined psychophysiology and PET and study in which participants imagined: (1) a personal experience of fear or anger from their own past; (2) an equivalent experience from another person as if it were happening to them; and (3) a nonemotional experience from their own past. When participants could relate to the scenario of the other, they produced patterns of psychophysiological and neuroimaging activation equivalent to those of personal emotional imagery, but when they could not relate to the other's story, differences emerged on all measures, e.g., decreased psychophysiological responses and recruitment of a region between the inferior temporal and fusiform gyri. The substrates of cognitive empathy overlap with those of personal feeling states to the extent that one can relate to the state and situation of the other.
  
  
• Preston, S. D.; Buchanan, T. W.; Stansfield, R. B.; Bechara, A. (2007). Effects of anticipatory stress on decision making in a gambling task. Behavioral Neuroscience, 121(2), 257-263.
  Abstract: Recent research has highlighted the fact that emotion that is intrinsic to a task benefits decision making. The authors tested the converse hypothesis, that unrelated emotion disrupts decision making. Participants played the Iowa Gambling Task, during which only experimental participants anticipated giving a public speech (A. Bechara, D. Tranel, & H. Damasio, 2000). Experimental participants who were anticipating the speech learned the contingencies of the choices more slowly, and there was a gender interaction later in the game, with stressed female participants having more explicit knowledge and more advantageous performance and stressed male participants having poorer explicit knowledge and less advantageous performance. Effects of anticipatory stress on decision making are complex and depend on both the nature of the task and the individual.
  
  
• Preston, S. D. (2007). A perception-action model for empathy. In: T.F.D. Farrow & P. Woodruff (Eds.), Empathy in Mental Illness; (pp. 428-447). Cambridge, MA: Cambridge University Press. xxvi, 506 pp.
  Excerpt: This chapter describes and augments the perception-action model (PAM) of empathy, first detailed in Preston and de Waal (2002b). Empathy, ironically, is a term that means different things to different people. It has been difficult to distinguish empathy from sympathy because they both involve the emotional state of one related to the state of another. This problem was compounded by the fact that the mapping of the terms has recently reversed: what is now commonly called empathy was referred to before the middle of the twentieth century as sympathy (see Wispe, 1986 for a full discussion) and some researchers still use the old connotations (e.g. Batson, 1997).
  According to a PAM, empathy is defined as a shared emotional experience occurring when one person (the subject) comes to feel a similar emotion to another (the object) as a result of perceiving the otherÕs state. This process results from the fact that the subjectÕs representations of the emotional state are automatically activated when the subject pays attention to the emotional state of the object. The neural mechanism assumes that brain areas have processing domains based on their cellular composition and connectivity; as such, there is no Ôempathy areaÕ and brain areas are recruited when the relevant domain is required by the task. This definition contains much information, so the model will be detailed in this chapter by deconstructing the definition, focusing on the italicized words.
  
  
• Preston, S. D. & Jacobs, L. F. (2005). Cache decision making: The effects of competition on cache decisions in Merriam's kangaroo rat (Dipodomys merriami). Journal of Comparative Psychology, 119, 187-96.
  Abstract: Caching food is an economic, decision-making process that requires animals to take many factors into account, including the risk of pilferage. However, little is known about how food-storing animals determine the risk of pilferage. In this study, the authors examined the effect of a dominant competitor species on the caching and behavior of Merriam's kangaroo rat (Dipodomys merriami). The authors found that, as with conspecific competitors, kangaroo rats did not alter caching in response to the mere presence of a heterospecific competitor, but moved caches to an unpreferred area when the competitor's presence was paired with pilferage. These data suggest that Merriam's kangaroo rat assesses pilfer risk from actual pilferage by a competitor and adaptively alters cache strategy to minimize future risk.
  
  
• Preston, S. D., (2004). Empathy. Encyclopedia of Animal Behavior, Marc Bekoff, ed., Greenwood Press, Connecticut. Vol. 2, 565-574.
  Excerpt:. Many people believe that animals other than humans do not experience empathy and sympathy. This is primarily because people believe that empathy results from a high-level thinking process where you imagine what it must be like to be in the situation of the other individual, and then you make inferences about how the other individual must feel. If this is how empathy is achieved, then it would be a high-level cognitive process that requires a large information-processing capacity, and many animals may not have such a capacity. When one individual has conscious thoughts about the state of another and makes mental models of the other's feelings and needs, it is called cognitive empathy. Research suggests that cognitive empathy may not exist in creatures other than humans and possibly apes. But most research indicates that the ability to feel the state of another and to try to help the other is an innate and automatic process that does not require conscious thought and exists across species.
  
  
• Preston, S. D. & de Waal, F. B. M. (2002). Empathy: Its ultimate and proximate bases. Behavior and Brain Sciences, 25, 1-72.
  Abstract: There is disagreement in the literature about the exact nature of the phenomenon of empathy. There are emotional, cognitive, and conditioning views, applying in varying degrees across species. An adequate description of the ultimate and proximate mechanism can integrate these views. Proximately, the perception of an object's state activates the subject's corresponding representations, which in turn activate somatic and autonomic responses. This mechanism supports basic behaviors (e.g., alarm, social facilitation, vicariousness of emotions, mother-infant responsiveness, and the modeling of competitors and predators) that are crucial for the reproductive success of animals living in groups. The Perception-Action Model (PAM), together with an understanding of how representations change with experience, can explain the major empirical effects in the literature (similarity, familiarity, past experience, explicit teaching, and salience). It can also predict a variety of empathy disorders. The interaction between the PAM and prefrontal functioning can also explain different levels of empathy across species and age groups. This view can advance our evolutionary understanding of empathy beyond inclusive fitness and reciprocal altruism and can explain different levels of empathy across individuals, species, stages of development, and situations.
  
  
• Preston, S. D. & de Waal, F. B. M. (2002). The communication of emotions and the possibility of empathy in animals. In: Altruistic love: Science, philosophy, and religion in dialogue, ed. S. Post, L. G. Underwood, J. P. Schloss, & W. B. Hurlburt; pp. 284-308. London: Oxford University Press. xvi, 500 pp.
  Excerpt: The possibility of nonhuman animals having empathy and sympathy has thus far received little attention in behavioral biology. This is due in part to the portrayal of the natural world as a field of combat rather than a place of social connectedness. Some prominent contemporary evolutionists, such as Williams (1989) and Dawkins (1976), still follow T. H. Huxley (1894), seeing no room within the evolutionary realm for morality and kindness. According to Huxley, such tendencies could have come into being only secondarily, as a cultural innovation of the human species. According to many contemporary psychologists and neuroscientists, Òtrue empathyÓ is a cognitive innovation more akin to perspective taking (imagining yourself in the physical or mental place of another) (e.g. Povinelli et al. 1992a and b, Thompson, 1987, Ungerer et al. 1990). This characterization limits Òtrue empathyÓ to those who can pass high level cognitive tests, usually humans above a certain age.
  Interestingly, Darwin (1871) himself expressed in The Descent of Man a much more united view, partly inspired by moral philosophers such as Adam Smith and David Hume. Darwin saw morality, including one of its pillars Ð sympathy Ð as a natural tendency; a viewpoint that is now all but forgotten but highly relevant to the present discussion (Flack & de Waal, 2000). Empirical research on animals supports DarwinÕs view, revealing empathy to be a phylogenetically continuous phenomenon that exists to varying degrees in non-human species.
  
  
• Preston, S. D. (2002). Book Review: George Ainslie (2002) Breakdown of Will. Cambridge: Cambridge University Press. Human Nature Review, 2, 183-186.
  Excerpt: Economic theories of decision making are limited by their emphasis on numbers, graphs, and tangible, linear variables. Evolution has produced nervous systems that use neural representations to mediate between stimuli and responses that develop over time to meet the demands of the environment at hand. Inputs that are tightly linked to their outcome are easy to learn and have a greater impact on behavior. Stimuli that are more present prepare responses to a greater extent. People with different developmental experiences will find different things rewarding. The response that "wins" in this winner-take-all neural battle for response will be the one that is more rewarding to the individual, but reward comes in many different shapes and sizes and is only applicable to the experience of the individuals.
  
  
• Preston, S. D. & Jacobs, L. F. (2001). Conspecific pilferage but not presence affects Merriam's kangaroo rat cache strategy. Behavioral Ecology, 12(5), 517-523.
  Abstract: We investigated the effects of pilferage on caching behavior in the Merriam's kangaroo rat by manipulating two factors associated with pilferage: the presence of a conspecific, and the opportunity for pilferage. In one experiment we assessed animals in either Stealer or Victim roles and measured changes in caching, space use, and behavior after caches were pilfered. Victims shifted from a majority scatter-hoarding to a majority larder-hoarding strategy after their caches were pilfered by the Stealer. In Experiment 2, we measured changes after exposure to a conspecific when there was no pilferage, with or without prior exposure to pilferage from Experiment 1. Merriam's kangaroo rats were vigilant when a conspecific was present, but did not change cache strategy. Prior exposure did not have any major effect on caching or behavior. Food storage is an economic decision that is often made by a solitary forager. Our results suggest that social competition nonetheless influences such economic decisions, even in a nonsocial forager. Key words: anxiety, decision processes, Dipodomys, kangaroo rat, pilferage, scatter hoarding. [Behav Ecol 12:517-523 (2001)]
  
  
• Preston, S. D. (2001). Effects of stress on decision making in the Merriam's kangaroo rat (Dipodomys merriami). Dissertation in Psychology, University of California at Berkeley.
  Abstract: Kangaroo rats are granivorous animals that live in semi-arid zones where seed production is unpredictable. By caching food when it is available, kangaroo rats can create a predictable supply of food despite the variability in production. Merriam's kangaroo rats are specialized for scatter hoarding (caching seeds in multiple, dispersed locations, each used only once), but they also use larder hoarding (caching all seeds in a single location that is reused). Cache decisions require an animal to take into account many variables, such as the availability of food, the risk of pilferage and the risk of predation. These variables must then be used to determine the optimal proportion of scatter and larder hoarding, the size of each cache, and the location of each cache. Thus, caching in Merriam's kangaroo rats is a cognitive and economic decision that can be used to investigate decision-making processes. Seven laboratory experiments with wild-caught Merriam's kangaroo rats demonstrated the flexibility of cache decisions. Although this species is characterized by its specialization for scatter hoarding, there is great within- and between-individual variation in the actual proportion of scatter and larder hoarding, depending on the external social conditions and the internal state of the animal at the time of caching. Experimental conditions that affected cache strategy included pilferage by a familiar conspecific individual, pilferage by a dominant heterospecific individual, and food deprivation. Food competition from pilferage may be stressful to the animals. Food deprivation is a known physiological stressor that increases circulating levels of glucocorticoid hormones. Thus, a glucocorticoid-based proximate model for cache decision-making was hypothesized and tested. Blood samples from before and after caching, and in response to classical stressors such as food deprivation and physical restraint, were collected and analyzed through radioammunoassay. Results from these experiments are insufficient to support a glucocorticoid-based mechanism for cache decisions. This may be due either to a sampling confound, or to the ecology of this desert-living species.
  
  
• Aureli, F.; Preston, S. D.; de Waal, F. B. M. (1999). Heart rate responses to social interactions in free-moving rhesus macaques (Macaca mulatta): A pilot study.Journal of Comparative Psychology, 113(1), 59-65.
  Abstract: Heart rate telemetry was explored as a means to access animal emotion during social interactions under naturalistic conditions. Heart rates of 2 middle-ranking adult females living in a large group of rhesus macaques (Macaca mulatta) were recorded along with their behavior. Heart rate changes during 2 types of interactions were investigated, while controlling for the effects of posture and activity. The risk of aggression associated with the approach of a dominant individual was expected to provoke anxiety in the approachee. This prediction was supported by the heart rate increase after such an approach. No increase was found when the approacher was a kin or a subordinate individual. The tension-reduction function of allogrooming was also supported. Heart rate decelerated faster during the receipt of grooming than in matched control periods. Keywords: heart rate changes to approach of dominant monkey & tension reduction function of allogrooming, female macaques
  
  
• Insel T. R.; Preston, S. D.; Winslow, J. T. (1995). Mating in the monogamous male: Behavioral consequences. Physiology and Behavior, 57(4), 615-627.
  Abstract:Three experiments explored behavioral changes that follow mating in the male prairie vole. Ss were tested after 24 hr of either mating, social exposure, or no social contact. Exp 1 examined behavioral consequences of mating vs social contact. Exp 2 examined time course of mating effects on aggression. Results demonstrated that mating, but not nonsexual social contact, was associated with an increase in aggression, the formation of a partner preference, and decreased fearfulness. More than 6 hrs of mating was necessary for the increase in aggression. Exp 3 examined behavioral consequences of mating in monogamous males of the closely related montane vole, who did not show increased aggression, partner preference, or alterations in plus maze exploration following 24 hr of mating. Results implicated the mating-induced changes in the prairie vole in the process of pair bonding, because none of these changes were observed in the montane vole, which does not form pair bonds.