A core executive function enabling flexible updating of cognitive representations and strategies based on feedback, critical for adapting to novel or changing situations. The opposite is known cognitive rigidity, the tendency to perseverate on a specific pattern of thought or behavior. Not to be confused with: psychological flexibility Not to be confused with: neural flexibility

Convergent thinking: cognition used to arrive at a single, correct solution to a well-defined problem. Involves logical reasoning, analysis, and evaluation to narrow down possibilities to the most appropriate answer. Often measured through traditional intelligence tests.

Divergent thinking: cognition used to generate multiple creative ideas by exploring many possible solutions. Characterized by fluency (many ideas), flexibility (different categories of ideas), originality (unique ideas), and elaboration (developing ideas). Often measured using tasks like the Unusual Uses Task and is strongly associated with creativity.

Not to be confused with: cognitive flexibility
Not to be confused with: psychological flexibility

The ability to generalize study findings to the real world. A subcategory of external validity.

The tendency to interpret others’ behaviors as having malicious intent, even when the behavior is ambiguous or benign. This bias often leads to aggressive responses and is commonly observed in individuals with certain personality disorders or in conflict situations. It’s a key concept in social psychology and conflict resolution studies.

Interoception:
The sensation of internal bodily signals such as heartbeat, hunger, thirst, or breathing. Helps maintain homeostasis by allowing the brain to monitor and regulate internal states. For example, feeling thirsty signals the need for hydration.

Exteroception
The sensation of external stimuli from the environment, such as light, sound, temperature, or touch.

These two sensory systems work together to provide a picture of both internal and external worlds, enabling adaptive responses to physical and environmental changes.

The near-complete paralysis of skeletal muscles during rapid eye movement (REM) sleep. This state, also called REM atonia, is essential for preventing the physical enactment of dreams. While some localized twitching may occur, overall muscle tone is significantly reduced. REM sleep is the only sleep phase requiring all animals to undergo muscle atonia, one feature distinguishing it from non-REM sleep stages. Disorders such as REM behavior disorder and narcolepsy are linked to disruptions in this mechanism

Reflects the brain’s ability to adapt to changing cognitive demands. Represents dynamic changes in synaptic weights within and between brain regions (as measured by functional magnetic resonance imaging (fMRI) signal variation over time). Higher neural flexibility is associated with cognitive flexibility, and reduced neural flexibility is associated with cognitive rigidity, although cognitive and neural flexibility are distinct concepts.

Not to be confused with: neuroplasticity
Not to be confused with: cognitive flexibility
Not to be confused with: psychological flexibility

The process by which new neurons are generated from neural stem cells and progenitor cells. A subcategory of neuroplasticity.

Not to be confused with: neuroplasticity
Not to be confused with: neural flexibility

The brain’s ability to change and reorganize itself by forming new neural connections throughout life, especially in response to learning, experience, or injury. This involves both structural changes, like modifications to synapses and the growth of new connections, and functional changes, altering how brain cells communicate. Key processes include strengthening connections through activity (long-term potentiation) and weakening them when less used (long-term depression). Neuroplasticity is essential for learning, memory, and recovery, and can be influenced by various factors, including training and environmental enrichment.

Not to be confused with: neurogenesis
Not to be confused with: neural flexibility

Also known as a human microdosing study. An optional exploratory trial conducted to speed up the development of promising drugs or imaging agents. It involves administering single subtherapeutic doses of the study drug to a small group of 10-15 subjects to gather preliminary data on the drug’s pharmacokinetics. This phase provides no data on safety or efficacy as the dose is too low to cause any therapeutic effect. The results from this phase help in ranking drug candidates for further development based on their pharmacokinetic parameters in humans.

Source: Wikipedia

Not to be confused with: Preclinical trial
Not to be confused with: Phase I trial

Also known as “first-in-humans” study, is the initial stage of clinical trials. It primarily tests the safety, side effects, optimal dose, and formulation method of a new drug in a small group of 20-100 healthy volunteers. The study includes dose-ranging or dose escalation to find the safest dose and to identify any toxic levels. The trials are usually conducted in clinical trial clinics and are not randomized. The participants are observed until several half-lives of the drug have passed. In some cases, patients with terminal illnesses like cancer or HIV may participate. The study is followed by further phases (II, III, IV) if successful.

Source: Wikipedia

Not to be confused with: Phase 0 trial
Not to be confused with: Preclinical trial

The second stage of clinical trials that tests the biological activity or effect of a drug in a larger group of 50-300 individuals. It assesses the drug’s efficacy and continues the safety assessments from Phase I. The trials are often divided into Phase IIa (dose-finding studies) and Phase IIb (proof of concept studies). These trials can be designed as case series or randomized controlled trials. The goal is to determine whether the drug influences the disease and has a broad effect in the patient population. Historically, Phase II studies have the lowest success rate among the development phases (nearly one third).

Source: Wikipedia

A large-scale, randomized controlled multicenter trial designed to assess the effectiveness of a new intervention in comparison with the current ‘gold standard’ treatment. It involves large patient groups (300-3,000 or more) and aims to be the definitive assessment of the drug’s effectiveness. These trials are the most expensive and time-consuming due to their size and duration. They often continue while the regulatory submission is pending, allowing patients to receive potentially lifesaving drugs. The results of successful Phase III trials form the basis of the “regulatory submission” for the drug’s approval. The trials may incorporate adaptive designs to adjust to interim results. The success rate varies depending on the disease and the presence of disease biomarkers.

Source: Wikipedia

Also known as a postmarketing surveillance trial, is conducted after a drug has received regulatory approval. It involves safety surveillance (pharmacovigilance) and ongoing technical support to ensure long-term safety and effectiveness. The trials are designed to detect rare or long-term adverse effects in a larger population and over a longer period than in Phase I-III trials. Findings from Phase IV trials may lead to a drug being withdrawn from the market or its use being restricted.

Source: Wikipedia

A Preclinical study is the stage before clinical trials where a candidate drug, vaccine, medical device, or diagnostic assay is tested extensively. This involves in vitro (test tube or cell culture) and in vivo (animal model) experiments using various doses of the study agent to gather preliminary data on efficacy, toxicity, and pharmacokinetics. These tests help determine if a drug candidate has scientific merit for further development as an investigational new drug.

Source: Wikipedia

Not to be confused with: Phase 0 trial
Not to be confused with: Phase 1 trial

Etymology

Psyche (ψυχή, psykhḗ):
mind, soul, spirit, or animating principle

Delos (δῆλος, dêlos):
to shine, light up, manifest, or reveal

Tropos (τρόπος, trópos):
a way, to turn, to orient or direct

Psychedelotropism (PDT) refers to the potential of psychedelics to help adaptively re-orient their users through functions of the serotonin system as a master homeostatic regulator that integrates mind, body, and world.

Initially conceived in 2018 and first detailed in the preliminary work, “Psychedelotropsim: Serotonergic Origins of Luminous Experience Induced by Classical Psychedelics” (2020), and explored in more depth in the second edition (2024), Fortier draws from foundational work on the serotonin system highlighting its homology with auxin, the primary phototropic growth hormone in plants, to understand psychedelic experience. PDT proposes that acute and enduring effects of classical psychedelics, including its potential for meaning-making, insight, visionary restructuralization, ego dissolution, and tendency to re-orient its users, might be better understood when considered as manifestations of the serotonin system’s roles in managing resources, and integrating the mind, body and world into a cohesive system.

See: Psychedelotropism (book)

“being able to contact the moment as a conscious human being more fully as it is, not as what it says it is, and based on what the situation affords, persisting or changing in behavior in the service of chosen values.”

The design, administration and interpretation of quantitative tests for measuring psychological variables and quantifying constructs. Involves the application of psychological measurement theories to develop reliable and valid instruments (like questionnaires and tests) used in educational settings, hiring processes, and psychological research.

The directional growth or movement responses of organisms to environmental stimuli. The response depends on stimulus direction and can be positive (toward the stimulus) or negative (away). The most typical examples of this phenomenon might be phototropism (growth toward light), gravitropism (growth in response to gravity), and thigmotropism (response to touch). These movements are regulated by signal transduction pathways that guide growth based on external cues. Tropisms play a critical role in optimizing resource acquisition and survival.

Similarly, neurotrophism refers to the growth and guidance of neurons toward specific targets via neurotrophic factors (e.g., nerve growth factor, NGF). Both processes depend on chemical gradients (e.g., auxins in plants, neurotrophins in neurons), enable adaptive responses to environmental cues (resources for plants; synaptic connections for neurons), and involve receptor-mediated signaling to regulate growth trajectories.

The Unusual Uses Task assesses divergent thinking by asking participants to generate as many novel uses as possible for a common object, like a brick or paperclip.