The Stimulus Barrier
As described above, in Freudian theory the initial state of the human being is that of autoerotism and primary narcissism. The stimulus barrier seems to be the mechanism that ensures the preservation of this way of being. Freud (1920/1955a) first described the stimulus barrier as an innate organization that functioned as “a protective shield against stimuli” (p. 27) in the neonate. This protection against noxious, overwhelming stimuli is regarded as a more important function for the vulnerable neonate than the reception of stimuli.
Freud (1920/1955a) has ascribed a biological‐neurological character to this metaphor. He regarded it as a sensory and perceptual threshold for incoming stimuli, an external membrane, under which other, deeper layers exist. The stimulus barrier is the forerunner of an intermediary between the id and the external world, which later came to be called the ego. Therefore, the stimulus barrier is a threshold for internal stimuli too. Tension is reduced and homeostasis is maintained through this barrier.
However, this merging of biological and psychological concepts has led to some confusion about the stimulus barrier (Esman, 1983). Daniel Stern (1985/2000) was critical toward this concept because Freud had placed it in the framework of autoerotism and primary narcissism, a conceptualization that Stern disputed. Other writers from the psychoanalytic field have reformulated the concept. According to Esman (1983), the stimulus barrier is “an innate, selective, maturing screening mechanism” (p. 204), an active mechanism with a dual self‐regulatory function: (i) to accept stimuli of certain kind and intensity and (ii) to ward off other stimuli, according to the degree to which these contribute to the adaptation of the organism. In this regard, the stimulus barrier seeks to preserve optimal stimulation (Esman, 1983; Gediman, 1971). This means that the infant both seeks and avoids stimuli. The avoidance of stimuli is facilitated through this innate, idiosyncratic organization and through the protection provided by the mother, who seems to function as a stimulus barrier herself (Benjamin, 1965; Khan, 1963). Search for stimuli promotes attachment and avoidance of stimuli is the forerunner of defenses and individuation (Shapiro & Stern, 1980) – one could also add here of the capacity to be alone. The stimulus barrier is regarded by many to be present throughout life and to evolve from a more passive mechanism into a complex ego function (Furst, 1978; Gediman, 1971). This means that throughout life the individual is well‐equipped when he/she needs to minimize internal and external distractions and achieve a level of self‐regulation, all of them necessary for being able, on his/her own, to deal with challenges and vicissitudes or engage in various forms of creative activities.
A breach in the stimulus barrier, caused by the penetration of stimuli, may be called trauma. However, trauma can be the result both of overwhelming excitation and of stimulation deprivation. Both situations can be acute or chronic, as well as cumulative. Stimulus infatuation and stimulus hunger are the two sides of the same coin: whereas the individual wishes to reduce the effect of a stimulus, he/she continually searches for new similar stimuli. What is usually avoided is the human relation in favor of other stimuli. Thus, the individual’s inability to feel satisfied, fed, when on his/her own may stem not only from deprivation and from a strong stimulus barrier but also from chronic overload and a weak stimulus barrier (Gediman, 1971). Withdrawal, in the form of a better‐be‐alone‐than tactic, emerges then as a defensive response, and in Freudian terms, may be regarded as an expression of secondary narcissism (discussed above). In light of the aforementioned text, the simultaneous desire and aversion toward stimulation (i.e., craving to escape solitude while struggling to protect it) becomes a less‐puzzling paradox.
Normal Autism and Symbiosis
Inspired by the Freudian views discussed above is the separation‐individuation theory, which was formulated by Margaret Mahler (Mahler et al., 1975). In this theory, two concepts – normal autism and symbiosis – are relevant to the study of beneficial solitude. More specifically, according to this theory, immediately after birth the infant is a profoundly alone and helpless being. In the first two months of life – the normal autistic phase – the infant lives in an autistic shell, which does not lead to disorganization. Instead, the stimulus barrier, the omnipotence stemming from the satisfaction of biological needs, and the hallucinatory wish‐fulfillment protect the infant from the awareness of isolation, which could be overwhelming for his/her immature ego. The controversial claim that this normal developmental phase could be called autistic initiated an intense scientific dialogue. In 1982, Mahler admitted that this is a phase of adaptation in extrauterine life, during which “the newborn has to achieve physiological homeostasis, that is, adequate inner regulation in synchrony with the vocal and gestural rhythms of the caregiver […] each infant is an active partner in the early dialogue” (our emphasis; Bergman, 1999, p. 5). In a personal communication with Stern in 1983, Mahler also suggested that the autistic phase could have been named awakening (Stern, 1985/2000, p. 235), a term very similar to Stern’s emerging sense of self. Pine (1994), Mahler’s collaborator, described a relative autism, which he considered as “primary attunement to internal physiological stimuli” (p. 10).
Following the autistic period, separation‐individuation theory suggests that the infant’s experience is one involving social symbiosis. The infant emerges from the autistic shell and enters a dual unity, that is, an undifferentiated state with mother, with “the delusion of a common boundary” (Mahler et al., 1975, p. 45). Omnipotent symbiotic fusion protects the infant from the awareness of separateness (which is different from separation) and thus from the premature frightening realization of aloneness. In the light of infant research, Pine (1994, 2004) proposed that this phase is critical for the experience of moments of merger (e.g., undifferentiatedness, boundarylessness) that can emerge during nursing (for a discussion of oneness experiences, see succeeding text). It is then that merging becomes highly significant, not only for the infant but for the mother as well, and reaches a kind of resolution, different for each mother–infant dyad.
In a similar line of thought, Thomas Ogden (1994) introduced a primitive infantile state, which he named autistic‐contiguous position. In the beginning of life, the relation to the object is a sensation experience, that is to say, the infant feels the object (mainly the breast) at the skin surface. Ogden adopted the concept autistic shapes and autistic objects introduced by Tustin (1990) for high‐functioning autistic children, but, like Mahler, he did not refer to the psychopathological condition of autism. Rather, he described a realm of personal isolation, an experience of being‐in‐sensation, which serves as a sanctuary in the face of stress inherent in human relationships and is an essential part of aliveness (Ogden was inspired by Winnicott’s theory, which is discussed in the next section). It is as if the infant suspends life in the world of objects by creating an autonomous and insulated realm of nonhuman, machine‐like sensation shapes. Although self‐generated, this position develops only if the mother has the capacity to allow her infant to exist for some moments without her and to wait.
Taken together, the psychoanalytic insights on the solitary self and its origins suggest that solitude plays an important role in protecting the infant from disorganization caused by excessive internal and external excitation, in a time when his/her ego functions, responsible for self‐regulation, are not yet developed. In all these views, there is an implicit recognition that the infant’s solitude is at first a state of primary narcissism and, after the emergence of specific object relations, evolves into secondary narcissism, as Freud conceptualized these states. However, although the infant is described as a rather isolated self‐system,