Infants’ fear-relevant learning 1 Running Header: INFANTS’ FEAR-RELEVANT LEARNING The origins of snake and spider fear: How infants learn to associate evolutionary fear-relevant stimuli and paired stimuli

Previous research has demonstrated that female infants are capable of learning paired associations between predatory and emotional stimuli that male infants do not learn (Rakison, in review). These findings come in conjunction with evidence pointing towards inherent evolutionary psychological learning mechanisms that allow for the rapid detection of, attending to, and learning about predatory animals that allow for the learning of fear and appropriate fear responses associated with these threats (Rakison & Derringer, 2008, Öhman & Mineka, 2001). Understanding how these learning mechanisms are constrained and develop is important in the path of research eventually leading to treatments and interventions of phobias. In this study, I examined whether female infants demonstrate differences in learning paired associations between predatory and arbitrary stimuli compared to males and whether motor experience would influence infants’ learning paired associations between predatory and emotional stimuli. Infants 11 and 7 to 5 months of age were habituated to these pairings and tested for learning through dishabituation. Infants’ fear-relevant learning 3 The origins of snake and spider fear: How infants learn to associate evolutionary fear-relevant stimuli and paired stimuli The ability to survive is one of the greatest determining factors to whether or not an individual will pass on their genetic information. Naturally, because trial and error in interactions with potentially dangerous predators, such as snakes and spiders, could lead to rather deadly results, innate abilities to detect, orient, and learn about such dangers are extremely plausible and may have resulted from evolutionary selective pressures. In terms of the evolution of survival mechanisms, the ability to recognize recurring threats within the environment and learn to act in an appropriate manner toward them would be a favorable trait that would spread through the population, perhaps via genetics or social learning. A properly functioning mechanism of detection and learning fear for recurrent threats in infancy would serve a great benefit in preventing premature mortality, while over-exaggerated fear of threats could otherwise produce a harmful dysfunction in later life that we term as being a phobia. By determining the predictors and patterns early on that lead to severe phobic anxieties, it may be possible to produce interventions, treatment, and counseling to prevent their emergence. All humans universally experience and express the emotion of fear as a signal of danger during certain situations that may be a potential threat to survival (LeDoux, 1996; Marks, 1987). Humans probably experienced numerous environmental threats throughout evolutionary history and would have benefited from the ability effectively to protect themselves from these experiences. Fear of snakes and spiders, which are both considered to be common threats to survival in early human history, are not thought to be innate characteristics in human and nonhuman primates, learned. Early studies of Watson and Rayner (1920) demonstrated that fear can Infants’ fear-relevant learning 4 indeed be learned through conditioning, but threat relevant stimuli appear to more readily become objects of fear, supported by increasing evidence that fear arises from the presence of evolutionary psychological mechanisms which provide the ability to rapidly detect, attend to, and learn about predators (Rakison & Derringer, 2008, Öhman & Mineka, 2001). Evidence of fear prevalence and response to snakes in non-human primates, comparable to humans, would suggest evolutionarily relevant explanations behind the development of fear perhaps related to genetic variation or differences in learning associations with predatory stimuli Öhman & Mineka, 2003). Rhesus monkeys raised in the wild show strong fear responses to snakes, unlike their captive counterparts. Lab monkeys, found to not show initial fear responses to snakes, were easily able to learn fear of snakes through observations of live and videotaped wild monkeys demonstrating fear responses to not only live, but toy snakes (Cook & Mineka, 1990). However, these monkeys were not capable such substantial fear conditioning for nonthreatening stimuli, like flowers and toy rabbits, though could still be trained to implement both these, as well as the predatory stimuli, as conditioned signals for food. This research supports constrained selective learning of fear with evolutionary threats. Rakison and Derringer (2008) found evidence that human infants may possess evolved spider and snake detection mechanisms, based on perceptual templates, which may have aided in our early ancestors’ abilities to learn about and avoid these predators to ensure survival. In this study, preferential looking and habituation paradigms were used with 5-month-old infants to assess the perceptual template structures for spiders. It was demonstrated that infants showed preference to attending to schematic images of spiders, compared to template spiders with features reconfigured or completely scrambled, but did not show this preference with another biological, but non-threat-relevant stimuli, specifically a flower. It was also found that when Infants’ fear-relevant learning 5 infants were habituated to real colored static images of spiders, they generalized the real spiders to the schematic template but not the reconfigured and scrambled images, indicating that the perceptual preference for the schematic spider was not the product of a simple shape preference. Adult humans and young children appear to possess a greater ability quickly to find evolutionary fear-relevant stimuli, such as snakes and spiders, amid non-fear-relevant stimuli, including flowers, mushrooms, frogs, and caterpillars, than the reverse of non-fear-relevant stimuli mixed with of fear-relevant stimuli (LoBue & DeLoache, 2008; Öhman, Flykt, & Esteves, 2001). Where Öhman, Flykt, and Esteves (2001) primarily studied adults' rapid detection of threatening stimuli hidden among non-threatening stimuli and showed that those who most fear the threatening stimuli, snakes, found them fastest, resent research has demonstrated that young children are also quite capable of this performing similarly in this task. In studies with children 3 to 5 years of age as well as adults, LoBue and DeLoache (2008) demonstrated that the young children were likewise able to more quickly detect threat-relevant stimuli, snakes, than non-threat-relevant stimuli hidden among the opposite stimuli on a touch screen. For greater support of this rapid detection mechanism, they were able to show that threatrelevant stimuli were more rapidly detected among non-threatening stimuli that were of both differing and similar physical appearance and properties, including flowers, frogs, and caterpillars. In combination with the findings of Rakison and Derringer (2008), the evidence for the existence of predator templates is strong, and be argued to serve as a facilitator learning of fear responses associated with the predator through the initial provision of rapid identification of the potential threat, thus aiding in survival. There is significant variation in the intensity of fear and the methods through which fear leads to responses that provide defense against dangers. The response to fear-relevant stimuli Infants’ fear-relevant learning 6 often varies between individuals not only with each differing situation but also by gender (Fetchenhauer & Buunk, 2005). While men are often more likely to encounter threats to their survival that result in injury and death, women typically report greater fear towards such events. It is proposed that sexual selection created more risk taking tendencies in men, decreasing the extent of their fears, whereas women have favored more cautious strategies. Such caution would not only allow them to provide direct protection for their young, but would furthermore ensure women's survive, thus prolonging their ability to care for their young. As such, risk taking would be of a greater reproductive cost to women than men. The necessity to avoid risks and reasoning behind it could explain why over three times as many women as men list snakes as their object of most extreme fear or phobia (Fredrikson, Annas, Fischer, & Wik, 1996; Agras, Sylvester, & Oliveau, 1969). Recent research suggests that there may indeed be differences in how male and female infants attend to and learn about threatening stimuli, like snakes and spiders (Rakison, under review). In this research with 11-month-old infants, association of facial expressions paired with images of recurrent threats, specifically snakes and spiders, and non-threats, specifically flowers and mushrooms, an often implemented control stimuli by Öhman, Mineka, and others (2001, Cook & Mineka, 1990), was studied. Infants were shown pairings threatening and nonthreatening categories of pictures with stimuli consisting of positive and negative facial expressions. After infants were habituated to a member of either the threatening or nonthreatening category paired with one variation of facial expression, they were then presented with test trials of another member of that category as well as a member of the category to which they were not habituated, paired with the opposite facial expression. It was found that female infants learned the pairing of snakes and spiders with facial expression, but not of flowers and Infants’ fear-relevant learning 7 mushrooms paired with facial expressions, while male infants learned neither of the pairings. It is apparent that infants’ perceptual templates for predatory animals allow for greater associative learning with faces in females than in males of the same age, but it thus specifically questioned whether female infants’ demonstrated stronger paired associative learning with predators are constrained to emotional paired stimuli or if females, who tend to have more phobias then males, simply more apt to learn any associations between predators and stimuli. One goal of the present study was to determine if the learning found in female infants was simply due to the pairings with emotional stimuli or if any and all associations might be learned. Specifically, I examined whether past results will carry over in learning associations of snakes and spiders paired with arbitrary stimuli, shapes, compared to flowers and mushrooms paired with arbitrary stimuli. By 11 months, most infants have become capable of crawling. It is of interest to explore whether infants of similar ages who have reached or have yet to reach this self-locomotion milestone, typically between six to eight months of age, will demonstrate differences in predator learning. Similar effects for self-locomotion have been found for a variety of infant behaviors in which infants learning patterns change with crawling experience (Cicchino & Rakison, 2008; Bertenthal, Campos, & Caplovitz, 1983). Fears for such dangers as heights and drop-offs, as well as fear of strangers and more specifically human males, develop during the same frame of time in which infants gain the ability to crawl (Scarr & Salapatek, 1970, Ainsworth, Blehar, Waters, & Wall, 1960). Theoretically, infants who are capable of crawling are and were more likely to come into contact with potentially dangerous situations as they become more independent of their mothers and have the ability to explore their environment. Those who have reached the milestone of self-locomotion would be in greater need of quickly and efficiently detecting and learning about these recurrent threats. An infant who is capable of autonomously exploring their Infants’ fear-relevant learning 8 surroundings will have a greater likelihood of encountering the threat of a snake or spider than when they remain protected by the guard of their parent. The present study aimed to track if infants’ paired associative learning is dependent on an infant’s crawling status. There is little research indicating whether sex differences will carry over into paired nonemotional, arbitrary stimuli, if learning patterns are found more so in those who are capable of self-locomotion, and whether the results will demonstrate a connection between phobias later in life. Infants of seven to nine months and eleven months of age were tested