The Biphasic Response: A Two-Phase Reaction to Stimuli

Life is an unpredictable journey, filled with moments that can shake us to our core. When faced with significant events or losses, we find ourselves caught in the turbulent waves of emotion—an inner storm that rages between agitation and despair. Picture this: one moment you’re grappling with anxiety, your heart racing as the reality of loss sets in; the next, you’re enveloped by a heavy blanket of sadness and disorganization. This dramatic ebb and flow serves not just as a response to trauma but as a powerful testament to our resilience and complexity as human beings.

As we traverse these emotional landscapes, it’s essential to recognize how every wave carries lessons waiting to be uncovered. The initial surge of anxiety often precedes deeper feelings like depression—not merely random phases but rather interconnected chapters in our healing narrative. Gregory M. Buchanan and Martin E. P. Seligman highlight this phenomenon, pointing out that understanding these emotional shifts allows us to navigate grief more effectively (Buchanan & Seligman, 1995).

By exploring the intricate dance between fear and sorrow, we can cultivate greater empathy for ourselves and others while unearthing profound insights about what it means to heal amidst chaos—a journey worth embarking on together!

​Introduction: Our Complex Reaction to Stimuli

A biphasic response is a two phase reaction to a stimulus. For example, scientists and health care workers are noticing that some people are experiencing a biphasic reaction to COVID-19. After first contracting the virus, they  experience one set of symptoms, but later experience a second set of symptoms that linger.

Alcohol consumption has shown to produce a biphasic response. The effects of alcohol on the body has two distinct phases. After consuming alcohol, the body almost immediately responds with a positive affect. The alcohol works as a stimulus. At low blood alcohol levels, the alcohol is associated with pleasurable feelings. However, as the blood alcohol level rises, alcohol begins to have a depressive effect. Alcohol at higher concentrations is associated with negative emotions and feeling ill.

Biphasic responses are not just biological. We often experience psychological biphasic reactions where a reaction to a single event changes from an initial positive response to a later negative reaction. Since a significant source of learning is from biological feedback loop, drawing information from the feeling response of our bodies, biphasic responses confuse the data, creating fuzzy information of confusing positive and negative consequences associated with a single behavior.

An Example of a Psychologic Biphasic Response

A common example of a psychological biphasic response is the presence of guilt following the immediate euphoria of an action. When a teenager engages in sexual activity, they often experience the biological exhilaration in the moment, but, if they have a religious background forbidding the behavior, the joy may quickly be replaced by guilt.

A single behavior that produces both joy and sorrow in distinct phases is a biphasic response.

Why Do We Have a Biphasic Response

Our brains operate in a remarkably intricate manner that often defies our assumptions. When we encounter stimuli, multiple regions of the brain spring into action, each handling information through distinct pathways and mechanisms. For example, when faced with a threat, the amygdala may trigger an immediate fight-flight-freeze response to ensure survival by preparing the body for quick action. This reaction occurs almost instantaneously as a protective measure; however, it is just one aspect of how our brains interpret external events. The initial response prioritizes safety over deliberation and can be viewed as an instinctual safeguard deeply ingrained in our biology.

As we navigate these moments of fear or anxiety, higher-order cognitive functions come into play shortly after the initial response has been activated. Once the more complex cognition kicks in—often involving areas like the prefrontal cortex—we begin reassessing the situation based on context and additional information. This rapid succession of responses illustrates not only how diverse brain functions are but also highlights their varying processing speeds.

While our instincts might drive us towards immediate reactions rooted in survival, it is through this interplay with reflective thought that we can modify our behaviors and make more informed decisions about how to respond to challenges effectively. Understanding this dynamic helps illuminate why human behavior can sometimes appear erratic or contradictory—it embodies both primal instincts and nuanced reasoning working together within us.

Sympathetic Nervous System

The sympathetic nervous system (SNS), a key component of the autonomic nervous system, plays a central role in the body’s initial response to stimuli by inducing excitatory, energy-consuming states (Siegel, 2020). When confronted with a significant or potentially threatening stimulus, the brain’s emotional systems, particularly the amygdala, rapidly activate the SNS, leading to a swift and often unconscious physiological arousal (LeDoux, 2015).

Ashley Olivine, Ph.D., presents the SNS activation process in easy to understand language. She explains that, “When the brain senses danger, the amygdala, responsible for interpreting external stimuli, sends a message to the hypothalamus, which is responsible for maintaining our body’s baseline state. Then the brain releases hormones that cause the body to react” (Olivine, 2023).

This process initiates an “initial orienting response,” which serves as a jolt to the system, signaling that something important “is happening here and now” and demanding attention (Siegel, 2020). This prepares the body for immediate action, commonly known as a “fight or flight” response, by mobilizing energy into circulation and increasing physiological signs such as heart rate, respiration, and sweating (Murphy, 2024). This immediate arousal is vital for mental functions like attention and perception, helping to focus cognitive resources on the critical aspects of the situation.

The SNS Prepares the Body for Action

Following this initial wave of SNS-driven arousal, the brain continues with elaborative appraisal processes, assessing the stimulus’s meaning and value to determine whether to approach or withdraw. This dynamic interplay ensures that emotional processing prepares the entire organism for appropriate action. The activation of the SNS triggers the release of stress hormones, like adrenaline and cortisol, which further influence brain activity and body states, with acute effects being adaptive for crisis management but chronic activation potentially leading to pathological consequences (Sapolsky, 2018).

Furthermore, the bodily changes produced by SNS activation generate feedback signals to the brain, influencing the intensity of conscious feelings and contributing to the continuous, “wave-like” evolution of emotional states over time. This intricate feedback loop, involving repeated arousal, appraisal, and physiological adjustments, allows for the refinement and differentiation of primary emotional states into more complex and targeted responses.

See Sympathetic Nervous System for more information on this topic

Prefrontal Cortex

Following an initial sympathetic nervous system (SNS) drive arousal, which mobilizes the body for immediate “fight or flight” responses, the brain’s prefrontal cortex (PFC) becomes critically engaged in more detailed and nuanced cognitions (Sapolsky, 2018). While the amygdala’s rapid, “quick and dirty” processing allows for an immediate, often unconscious, alarm signal to threatening or significant stimuli, the prefrontal cortex, particularly the ventromedial prefrontal cortex (vmPFC) and dorsolateral prefrontal cortex (dlPFC), takes over for “elaborative appraisal processes” (LeDoux, 2015).

This shift allows for a more comprehensive assessment of the stimulus’s meaning and value, moving beyond reflexive reactions to a deliberative consideration of how to approach or withdraw (Siegel, 2020).

The PFC acts as the “governor of mental life,” overseeing attentional selection, vigilance, priority allocation, and working memory, which are crucial for processing larger realities than just the immediate moment. It integrates information from various brain systems, including emotional centers, enabling the organism to move from a raw, immediate reaction to a more refined and appropriate course of action (Sapolsky, 2018).

Executive Functions

The prefrontal cortex’s role in these more detailed cognitions encompasses vital executive functions such as working memory, strategic knowledge organization, gratification postponement, long-term planning, and the regulation of emotions and impulsivity. It is the last brain region to fully mature, extending its development into the mid-twenties, which underlies its capacity for complex, supervisory, and metacognitive functions unique to humans (Donald, 2002).

Instead of merely suppressing emotional responses, the PFC engages in a collaborative relationship with the limbic system, allowing for “as-if” experiments of gut feelings to inform decision-making, which is indispensable for navigating complex personal and social scenarios (Damasio, 2005).

This cortical control over the amygdala and the sympathetic nervous system is crucial for dampening distress and enabling conscious reappraisal of situations, thereby allowing for flexible, adaptive behavioral and cognitive responses that can override initial automatic reactions. The continuous interplay between primary, automatic emotional responses and higher-level, deliberative PFC functions explains the “wave-like” evolution of emotional states and behaviors, leading to a refined and differentiated response over time (Damasio, 2003).

External Environments Impact on Reactions

In a biphasic response to a behavior, an internal or external environment change may contribute to a second phase of reaction to a behavior. Often with needs, the drive to fulfill subsides after satisfying the need. Some refer to this as a cathexis of energy. Psychic energy once dedicated to fulfilling the need is diverted to other needs once the original need is satisfied. This presents a change in inner environments.

Drive reduction theory posits that our behaviors are largely motivated by the need to reduce physiological drives, such as hunger, thirst, or discomfort. When we satisfy a primary drive—like eating when we are hungry—we experience a significant shift in priorities and focus. This fulfillment alleviates the immediate biological tension caused by the original need, allowing us to redirect our mental and physical energies toward other goals and pursuits (Murphy, 2024a).

In this sense, satisfying one’s needs acts as a catalyst for personal growth and exploration; once freed from the constraints of an unfulfilled drive, individuals can engage in activities that contribute to their overall well-being.

However, while fulfilling one primary drive may enable us to pursue new objectives, it can also lead to unintended consequences if those subsequent behaviors do not align with our deeper values or long-term aspirations. After experiencing temporary relief from satisfaction, we might realize that some of our actions were misaligned with these secondary goals or ideals. This realization can trigger feelings of regret or guilt as we confront the discrepancy between what we desired at one moment versus what aligns with our broader life ambitions.

Thus, while drive reduction provides invaluable insights into human motivation and behavior management, it also underscores the importance of continuous self-reflection and alignment between immediate desires and enduring values in maintaining emotional balance and psychological health.

Habits and Biphasic Response

A habit can lead to a biphasic response by first triggering an automatic, rapid reaction to a stimulus, deeply ingrained through repeated experience. The brain, evolved in a dangerous world, prioritizes quick and serviceable solutions, often recycling previously successful patterns without conscious awareness to conserve time and energy (DeMoss, 1999).

This automaticity is rooted in implicit memory, where a single, often impactful, episode can form a memory that automatically influences future behavior, surfacing as a strong feeling or motor memory. Sensory information, especially that perceived as significant or threatening, can bypass the cortex via a shortcut directly to the amygdala, initiating a rapid, albeit less accurate, emotional response before conscious cortical processing even begins.

Such pre-programmed or learned reactions, like freezing or an immediate physiological arousal, occur involuntarily and can become so habitual they act like reflexes, with the amygdala playing a key role in learning and expressing vigilance and distrust (Joseph, 1993). This initial automatic reaction, driven by the brain’s lower-level systems, serves as a first, undifferentiated response to a perceived stimulus.

Differentiating the Moment from the Past

Following this initial automatic reaction, a more nuanced cognition emerges, primarily mediated by the prefrontal cortex (PFC), which differentiates the immediate moment from past experiences and enables a different, more adaptive response. While the amygdala provides a “quick and dirty” alarm signal, the PFC engages in “elaborative appraisal processes,” allowing for a comprehensive assessment of the stimulus’s meaning and value (Sapolsky, 2018).

This higher-order processing, involving working memory, executive function, long-term planning, and emotional regulation, allows the individual to integrate factual knowledge and past experiences to consider conflicting options and predict future outcomes (LeDoux, 2003).

The PFC acts as the “governor of mental life,” overseeing attentional selection and allowing for the conscious reappraisal of situations, thereby dampening the amygdala’s and sympathetic nervous system’s immediate arousal and overriding reflexive behaviors (Sapolsky, 2018). This capacity for “response flexibility,” often requiring intentional mental effort, allows the brain to move beyond engrained patterns and generate novel, non-stereotypical responses by processing how the current context differs from past, similar situations (Siegel, 2020).

This continuous interplay between automatic responses and deliberative cortical functions allows for a refined, differentiated, and context-dependent behavioral and cognitive response to stimuli over time.

Dual Process Theory

A biphasic response, characterized by an initial automatic reaction followed by a more nuanced cognitive adjustment, can be effectively understood within the framework of Dual Process Theory. This theory posits that human thinking and decision-making involve two distinct but interconnected cognitive processes: an intuitive system (System 1) and a deliberate and reflective system (System 2) (Murphy, 2023).

The first phase of a biphasic response aligns with System 1 thinking. Keith Stanovich describes that system 1 “is viewed as encompassing primarily the processes of interactional intelligence.” It is “automatic, largely unconscious, and relatively undemanding of computational capacity” Thus, it “conjoins properties of automaticity and heuristic processing” (Stanovich, 1999, p. 144).

For instance, System 1 might trigger an immediate fear response upon seeing a snake-like object, before conscious processing even occurs. This system is highly efficient and relies on mental shortcuts (heuristics) that enable quick decisions based on limited information, having evolved to aid survival in a world full of potential threats. It encompasses automatic and largely unconscious processes, often attributed to more ancient, “reptilian brain” functions, guiding behavior based on primal world beliefs and internal mental maps formed through conditioning, all beneath conscious awareness.

System 2 Thinking

Following this initial, automatic System 1-driven reaction, the second phase of a biphasic response involves a shift to System 2 thinking, which allows for more deliberate, reflective, and analytical processing. System 2 is engaged when faced with complex problems that demand attention, effort, and conscious reasoning. It is the conscious, reasoning self that holds beliefs, makes choices, and decides what to focus on. Daniel Kahneman puts it this way: “System 2 is activated when an event is detected that violates the model of the world that System 1 maintains” (Kahneman, 2013).

This override allows it to monitor, evaluate, and potentially override the initial intuitive responses. This enables a more nuanced cognition that can differentiate the immediate moment from past experiences, allowing for the correction of biases and errors that System 1 might be prone to.

While System 1 relies on past exposures and heuristics, System 2 facilitates a slower, more effortful form of thinking, enabling individuals to recognize when impulsive reactions limit accurate perception and to seek more informed approaches. The wise mind concept in Dialectical Behavior Therapy illustrates the optimal state, where individuals utilize the strengths of both the emotional (System 1) and intellectual (System 2) minds to guide choices. This continuous interplay ensures that responses are not just reactive, but can be refined and adapted to the specific context of the present situation.

Self-Complexity and Biphasic Responses

A biphasic psychological response is often correlated with different and conflicting goals. T. Franklin Murphy wrote:

“Self complexity is the array of multiple aspects underlying our self concept. We are a beautiful mosaic of many pieces. These pieces include social roles, personality traits, histories, psychological habits, preferences, and relationships—to name only a few” (Murphy, 2021).

We are motivated by action from a variety of sources, both biological and psychological—often  some mixture of both. We are not singular, meaning multiple factors push for action simultaneously. In the example of the teenager and sex, the biological drive for sex and the simultaneous drive to follow culturally learned standards for conduct coexist. However, circumstances may strengthen or weaken the strength of the drive.

While sitting in the church pews, or in company of one’s parents, one set of urges may subside, and other desires arise. Environments are key components of behavior.

Examples of Biphasic Reactions

Biphasic Guilt 

Pleasure and guilt cloud the feedback waters. neither pleasure or guilt is inherently wrong, they both provide feedback. When pleasure and guilt are the biphasic reaction to a single behavior, they are signaling an inner conflict of goals.

Leon Festinger referred to this as cognitive dissonance. Several years ago I explained this concept. Basically, we have many priorities and attitudes—seen and unseen. Priorities and attitudes are not constant; they shift with context. Other events push important goals to the back when other events intrude. Recent events prime our mind, we examine the moment with relativistic thoughts and subsequently, we violate commitments, or temporarily adjust priorities. We are constantly at war within ourselves, facing conflicting desires, and incompatible goals (Murphy, 2015).

We are complex beings. Our sanity depends on rectifying some of these conflicts. We will drive ourselves into chaotic insanity, bouncing between poles of pleasure and guilt. Neither pleasure or guilt are sufficient guides. 

Complexity challenges our understanding of the drives creating the pleasure and guilt. Instead of constantly chasing pleasure and suffering from guilt, or sacrificing every pleasure to appease guilt, we may need to take a deeper look into our souls. Perhaps, adjusting beliefs creating guilt in some cases; and foregoing some pleasures that significantly conflict with some honorable goals. Finding this balance is not a one time self-exploration, but a lifetime challenge of complex beings, such as ourselves.

Biphasic Response to Loss

Significant events and losses often propel us through a labyrinth of emotional phases, revealing the intricate nature of our healing processes. When we encounter distressing situations such as bereavement or personal failure, our reactions can fluctuate dramatically over time. Initially, we may experience heightened states of agitation and anxiety as we grapple with the reality of our circumstances. This early response serves as a protective mechanism that alerts us to potential threats in our environment. It is during this phase that feelings of uncertainty and fear can overwhelm our thinking, making it challenging to find clarity amidst the chaos.

As time progresses and we begin to process these initial emotions, there tends to be a transition towards deeper emotional responses such as depression, disorganization, and despair (Buchanan & Seligman, 1995). The shift from anxiety to depressive symptoms signifies not only an adaptation process but also underscores the complexity inherent in human emotion. During this latter stage, individuals may confront feelings of hopelessness or isolation as they navigate their grief or loss more profoundly.

Understanding this biphasic pattern highlights how emotional responses are not linear; instead, they unfold like layers that require acknowledgment for true healing to occur. By recognizing these transitions within ourselves or others experiencing significant life changes, we cultivate empathy and support essential for navigating the tumultuous waters of human emotion effectively.

Associated Concepts

• Evolutionary Theory: Suggests that emotions have developed as adaptive responses to environmental stimuli, which can be immediate or evolve over multiple phases as the situation unfolds.
• James-Lange Theory: Proposes that physiological arousal precedes the experience of emotion, which could involve initial and subsequent emotional phases following a stimulus.
• Maslow’s Hierarchy of Needs: Maslow’s theory proposes that humans have a hierarchy of needs ranging from basic physiological needs to self-actualization. While drive reduction theory focuses on physiological needs, Maslow’s theory encompasses a broader spectrum of motivations.
• Cannon-Bard Theory: Argues that physiological arousal and emotional experience occur simultaneously, not sequentially, which can lead to complex, multi-layered emotional responses.
• Schachter-Singer Theory (Two-Factor Theory): Emphasizes that both physiological arousal and cognitive interpretation are essential for an emotional response, allowing for varied emotional phases depending on how the stimulus is appraised over time¹.
• Cognitive Appraisal Theory: Focuses on the individual’s interpretation of a situation, which can lead to different emotional phases as the appraisal process evolves.
• Facial-Feedback Theory: Suggests that the physical act of forming a facial expression can influence the emotional experience, potentially leading to a biphasic response where the initial emotion is modified by the feedback from the facial expression.

A Few Words by Psychology Fanatic

Just as pleasure and pain may provide a feedback loop, so does a biphasic responses. Biphasic responses signal conflicting goals. We can ignore this feedback, reliving the pain or pause, investigate, and grow.

In conclusion, the intricate tapestry of human emotion unfolds in a complex choreography of responses to stimuli. The biphasic and multiple phase models offer a window into the nuanced interplay between immediate reactions and the subsequent waves of feelings that can ripple through our consciousness. Like a stone cast into a pond, a single event can generate emotional ripples that touch distant shores within our psyche, each wave a distinct phase of understanding and adaptation.

As we navigate the ebb and flow of these emotional tides, we are remin

ded of the profound depth of the human experience. Our emotions are not simply binary states but are rich, layered, and dynamic responses that reflect the multifaceted nature of our interactions with the world. They serve as a compass, guiding us through the complexities of life and allowing us to emerge with greater insight and resilience.

The study of these emotional phases is not just an academic pursuit but a journey into the heart of what it means to be human. It challenges us to consider not only how we respond to the world around us but also how we evolve and grow from each experience. May this exploration of our emotional landscape inspire a deeper appreciation for the intricate dance of feelings that animate our lives and shape our shared humanity.

Last Update: January 28, 2026

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