Impulsivity is a multifaceted construct often characterized by actions taken without forethought. It is typically regarded as a personality trait but can also be observed in various psychiatric conditions.
Psychological models often emphasize the lack of behavioral inhibition as a core component of impulsivity. These models attempt to explain impulsive behavior as a failure to regulate one’s actions according to societal norms or personal long-term goals.
The neurobiological basis of impulsivity involves multiple brain regions, notably the prefrontal cortex, which is crucial for self-control and decision-making processes. The scientific investigation of impulsivity has evolved considerably since early studies that were rooted in philosophical and psychological theories, focusing on impulsive behaviors as moral or ethical failures.
In the 20th century, research began to incorporate biological perspectives, investigating genetic and neurochemical factors. Animal models have been instrumental in understanding the mechanisms underlying impulsivity, providing insights into the brain’s reward systems.
More recent approaches include behavioral models that translate findings from clinical studies to preclinical ones, emphasizing the role of environmental influences.
Throughout the history of personality research, there has been disagreement over where impulsivity stands among other fundamental traits and even whether it is a single factor or a component, or a combination, of factors. One important consequence of this range of viewpoints is that there is no agreement on how to understand the structure of impulsivity or how to appropriately quantify it.
Automatic vs. Controlled Processes
According to dual process theory, mental processes can be classified as either automatic or controlled. In general, automatic processes are experiential in character, do not involve higher levels of cognition, and are based on prior experiences or informal heuristics. Controlled decisions are effortful and largely conscious processes in which an individual weighs alternatives before making a more deliberate decision.
- Automatic Process: Automatic processes have four main features. They occur unintentionally or without a conscious decision, the cost of the decision is very low in mental resources, they cannot be easily stopped, and they occur without conscious thought on the part of the individual making them.
- Controlled Process: Controlled processes also have four main features that are very close to the opposite in spectrum from their automatic counterparts. Controlled processes occur intentionally; they require the expenditure of cognitive resources, the individual making the decision can stop the process voluntarily, and the mental process is a conscious one.
Previously, dual-process theories considered any single action or thought to be either automatic or regulated. However, they are currently viewed as working on a continuum, with most impulsive activities exhibiting both controlled and automatic characteristics. Automatic processes are classified based on whether they are intended to obstruct or facilitate a mental process.
In effect, impulsive decisions can be made as prior information and experiences dictate that one course of action is preferable, whereas careful deliberation would allow the individual to make a more informed and superior choice.
Inhibitory Control
Inhibitory control, commonly thought of as an executive function, is the ability to inhibit or delay a prepotent response. It is hypothesized that impulsive behavior indicates a weakness in the ability to inhibit a response; impulsive persons may find it more difficult to resist action, whereas non-impulsive people may find it simpler.
There is evidence that routinely used behavioral measures of inhibitory control in healthy individuals correspond with standard self-report measures of impulsivity. The prefrontal cortex, caudate nucleus, and subthalamic nucleus are known to regulate inhibitory control cognition. Inhibitory control is impaired in both addiction and attention deficit hyperactivity disorder.
Ego Depletion
According to the ego (or cognitive) depletion model of impulsivity, self-control is the ability to change one’s own responses, particularly to bring them in line with standards such as ideas, values, morality, and societal expectations, as well as to assist the pursuit of long-term objectives. Self-control allows a person to inhibit or override one response, making another response conceivable.
A primary component of the idea is that engaging in acts of self-control depletes a limited “reservoir” of self-control, resulting in reduced capacity for further self-regulation. Self-control is seen as akin to a muscle: just as a muscle takes strength and energy to exert force over time, acts involving high self-control demands require strength and energy to execute.
Similarly, much as muscles fatigue after a period of sustained exertion and have a diminished capacity to exert additional power, self-control can become exhausted when demands are placed on self-control resources over time. Baumeister and colleagues referred to the state of impaired self-control strength as ego depletion (or cognitive depletion).
The model says people can exert self-control despite ego depletion if the stakes are high enough. Offering cash incentives or other motives for good performance counteracts the effects of ego depletion.
This may seem counterintuitive, but it could be quite adaptive. Given the worth and importance of self-control, losing it altogether would be perilous, and as a result, ego depletion may occur when people begin to conserve their residual strength.
The effects of ego depletion do not appear to be a product of mood or arousal. In most studies, mood and arousal has not been found to differ between participants who exerted self-control and those who did not.
Feedback on the success or failure of self-control initiatives does not appear to influence performance. In short, the drop in self-control performance after exerting self-control appears to be directly proportional to the amount of self-control exerted and cannot be simply explained by other well-established psychological processes.
Intertemporal Choice
Intertemporal choice is defined as “decisions with consequences that play out over time”. It is typically measured in the laboratory using a “delayed discounting” paradigm, which measures the process of devaluing rewards and punishments that happen in the future.
In this paradigm, individuals must select between a lesser reward supplied immediately or a greater reward delivered later. Choosing a lesser, sooner reward is deemed impulsive. Indifference points can be estimated by making these decisions several times.
Each participant’s delay discounting curve can be established by charting their indifference points against various incentive levels and time delays. Individual differences in discounting curves are influenced by personality traits such as self-reports of impulsivity and locus of control, personal characteristics such as age, gender, IQ, race, and culture, socioeconomic characteristics such as income and education, and a variety of other factors.
Lesions to the nucleus accumbens core subregion or basolateral amygdala result in a preference for smaller, sooner rewards, implying that these brain regions play a role in the preference for delayed reinforcers. There is additional evidence that the orbitofrontal cortex is implicated in delay discounting, albeit it is still unclear whether lesions in this region cause more or less impulsivity.
Economic theory suggests that optimal discounting involves the exponential discounting of value over time. This model assumes that people and institutions should discount the value of rewards and punishments at a constant rate according to how delayed they are in time.
While economically rational, recent evidence suggests that people and animals do not discount exponentially. Many studies suggest that humans and animals discount future values according to a hyperbolic discounting curve where the discount factor decreases with the length of the delay (for example, waiting from today to tomorrow involves more loss of value than waiting from twenty days to twenty-one days).
Additionally, intertemporal choices differ from economic models because they involve anticipation (which may involve a neurological “reward” even if the reinforcer is delayed), self-control (and the breakdown of it when faced with temptations), and representation (how the choice is framed may influence desirability of the reinforcer).
References:
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