Symbolic artificial intelligence Wikipedia
In symbolic AI, discourse representation theory and first-order logic have been used to represent sentence meanings. Latent semantic analysis (LSA) and explicit semantic analysis also provided vector representations of documents. In the latter case, vector components are interpretable as concepts named by Wikipedia articles. For example, language models learn to imitate existing conventions [3], and multi-modal models learn about conventions of denotation, so that they can e.g. produce an image from a description [26]. Proponents of neuro-symbolic models often emphasize these models’ ability to rapidly learn a new concept, from a definition or a few examples [e.g.
Horn clause logic is more restricted than first-order logic and is used in logic programming languages such as Prolog. Extensions to first-order logic include temporal logic, to handle time; epistemic logic, to reason about agent knowledge; modal logic, to handle possibility and necessity; and probabilistic logics to handle logic and probability together. Semantic networks, conceptual graphs, frames, and logic are all approaches to modeling knowledge such as domain knowledge, problem-solving knowledge, and the semantic meaning of language. DOLCE is an example of an upper ontology that can be used for any domain while WordNet is a lexical resource that can also be viewed as an ontology. YAGO incorporates WordNet as part of its ontology, to align facts extracted from Wikipedia with WordNet synsets.
Similar to the problems in handling dynamic domains, common-sense reasoning is also difficult to capture in formal reasoning. Examples of common-sense reasoning include implicit reasoning about how people think or general knowledge of day-to-day events, objects, and living creatures. This kind of knowledge is taken for granted and not viewed as noteworthy. Henry Kautz,[17] Francesca Rossi,[79] and Bart Selman[80] have also argued for a synthesis.
The key AI programming language in the US during the last symbolic AI boom period was LISP. LISP is the second oldest programming language after FORTRAN and was created in 1958 by John McCarthy. LISP provided the first read-eval-print loop to support rapid program development. Program tracing, stepping, and breakpoints were also provided, along with the ability to change values or functions and continue from breakpoints or errors. It had the first self-hosting compiler, meaning that the compiler itself was originally written in LISP and then ran interpretively to compile the compiler code.
In fact, rule-based systems still account for most computer programs today, including those used to create deep learning applications. For other AI programming languages see this list of programming languages for artificial intelligence. Currently, Python, a multi-paradigm programming language, is the most popular programming language, partly due to its extensive package library that supports data science, natural language processing, and deep learning. Python includes a read-eval-print loop, functional elements such as higher-order functions, and object-oriented programming that includes metaclasses. The origin and development of symbolic behaviour in humans suggests a way to make progress towards developing AI that engages with symbols as humans do.
Alain Colmerauer and Philippe Roussel are credited as the inventors of Prolog. Prolog is a form of logic programming, which was invented by Robert Kowalski. Its history was also influenced by Carl Hewitt’s PLANNER, an assertional database with pattern-directed invocation of methods. For more detail see the section on the origins of Prolog in the PLANNER article. Early work covered both applications of formal reasoning emphasizing first-order logic, along with attempts to handle common-sense reasoning in a less formal manner.
For instance, consider computer vision, the science of enabling computers to make sense of the content of images and video. Say you have a picture of your cat and want to create a program that can detect images that contain your cat. You create a rule-based program that takes new images as inputs, compares the pixels to the original cat image, and responds by saying whether your cat is in those images.
Ultimately, it is through the combination of rich, challenging, diverse experiences of human-like socio-cultural interactions and powerful learning-based algorithms that we will develop machines that proficiently use symbols. There are now several efforts to combine neural networks and symbolic AI. One such project is the Neuro-Symbolic Concept Learner (NSCL), a hybrid AI system developed by the MIT-IBM Watson AI Lab.
We argue instead for characterizing behaviourally how a system expresses engagement with symbols. If certain computations or representations are essential, this should be demonstrated through the behavioural competence of a system that includes them when performing rich tasks. Thus, in the next section we draw inspiration from the development of symbolic behaviour in humans to suggest a path towards achieving more human-like symbolic behaviour in artificial intelligence. And unlike symbolic AI, neural networks have no notion of symbols and hierarchical representation of knowledge. This limitation makes it very hard to apply neural networks to tasks that require logic and reasoning, such as science and high-school math.
First of all, every deep neural net trained by supervised learning combines deep learning and symbolic manipulation, at least in a rudimentary sense. Because symbolic reasoning encodes knowledge in symbols and strings of characters. In supervised learning, those strings of characters are called labels, the categories by which we classify input data using a statistical model. The output of a classifier (let’s say we’re dealing with an image recognition algorithm that tells us whether we’re looking at a pedestrian, a stop sign, a traffic lane line or a moving semi-truck), can trigger business logic that reacts to each classification. Some recent work has begun to pursue directly optimizing natural human-agent interactions at scale.
A change in the lighting conditions or the background of the image will change the pixel value and cause the program to fail. Many of the concepts and tools you find in computer science are the results of these efforts. Symbolic AI programs are based on creating explicit structures and behavior rules. The logic clauses that describe programs are directly interpreted to run the programs specified. No explicit series of actions is required, as is the case with imperative programming languages. A certain set of structural rules are innate to humans, independent of sensory experience.
They have created a revolution in computer vision applications such as facial recognition and cancer detection. Each approach—symbolic, connectionist, and behavior-based—has advantages, but has been criticized by the other approaches. Symbolic AI has been criticized as disembodied, liable to the qualification problem, and poor in handling the perceptual problems where deep learning excels. In turn, connectionist AI has been criticized as poorly suited for deliberative step-by-step problem solving, incorporating knowledge, and handling planning. Finally, Nouvelle AI excels in reactive and real-world robotics domains but has been criticized for difficulties in incorporating learning and knowledge.
“Splitting the task up and letting programs do some of the work is the key to building interpretability into deep learning models,” says Lincoln Laboratory researcher David Mascharka, whose hybrid model, Transparency by Design Network, is benchmarked in the MIT-IBM study. Though statistical, deep learning models are now embedded in daily life, much of their decision process remains hidden from view. This lack of transparency makes it difficult to anticipate where the system is susceptible to manipulation, error, or bias.
Similarly, Allen’s temporal interval algebra is a simplification of reasoning about time and Region Connection Calculus is a simplification of reasoning about spatial relationships. A more flexible kind of problem-solving occurs when reasoning about what to do next occurs, rather than simply choosing one of the available actions. This kind of meta-level reasoning is used in Soar and in the BB1 blackboard architecture.
For example, the discovery of category theory as a unifying perspective on many mathematical research areas fundamentally changed the questions researchers ask [36]. Humans use embodied understanding, e.g. gestures, to help them grasp abstract concepts [37, 38], and domain knowledge aids logical reasoning in Wason Selection Task analogues that frame a logical problem in terms of a social situation [39, 40, 41]. The whole structure of knowledge in which symbols are embedded can, and usually does, affect symbol-use. Their Sum-Product Probabilistic symbolic artificial intelligence Language (SPPL) is a probabilistic programming system. Probabilistic programming is an emerging field at the intersection of programming languages and artificial intelligence that aims to make AI systems much easier to develop, with early successes in computer vision, common-sense data cleaning, and automated data modeling. Probabilistic programming languages make it much easier for programmers to define probabilistic models and carry out probabilistic inference — that is, work backward to infer probable explanations for observed data.
Computer Science > Artificial Intelligence
We expect it to heat and possibly boil over, even though we may not know its temperature, its boiling point, or other details, such as atmospheric pressure. Cognitive architectures such as ACT-R may have additional capabilities, such as the ability to compile frequently used knowledge into higher-level chunks. Japan championed Prolog for its Fifth Generation Project, intending to build special hardware for high performance. Similarly, LISP machines were built to run LISP, but as the second AI boom turned to bust these companies could not compete with new workstations that could now run LISP or Prolog natively at comparable speeds.
” to “How many objects are both right of the green cylinder and have the same material as the small blue ball? ” Once object-level concepts are mastered, the model advances to learning how to relate objects and their properties to each other. For example, we echo others who highlighted the challenges of creating rule-based machine ethics [e.g. Without understanding the meaning behind the rules, such systems would only follow the letter of the law, not the spirit. Consider a rule like “don’t discriminate on the basis of race.” As US history unfortunately illustrates, it’s easy to find a proxy variable for race, like neighborhood, and have essentially the same discriminatory effect [63]. We need a system that behaves in accordance with the meaning behind its principles—a system with judgement [64].
Language models can discriminate different word senses [51] and exhibit some aspects of pragmatic understanding [52]. These models demonstrate impressive abilities to learn the many subtle constraints that determine language meaning in context, and will likely improve when they are augmented with more human-like faculties and grounded experience [44]. However, it’s less clear whether these models exhibit behaviour that demonstrates that they can, or should, decide to actively shift their understanding of an already known symbol. Any learning-based models will surely alter its understanding of a symbol as it experiences new data. However, this type of malleability is passive, as it depends on researchers to provide the data from which new meaning could be derived. Humans, on the contrary, are malleable with purpose, whether that purpose is to permit more fluid communication, or to come to a deeper understanding of some phenomenon.
Problem solver
The conjecture behind the DSN model is that any type of real world objects sharing enough common features are mapped into human brains as a symbol. Those symbols are connected by links, representing the composition, correlation, causality, or other relationships between them, forming a deep, hierarchical symbolic network structure. Powered by such a structure, the DSN model is expected to learn like humans, because of its unique characteristics. Second, it can learn symbols from the world and construct the deep symbolic networks automatically, by utilizing the fact that real world objects have been naturally separated by singularities. Third, it is symbolic, with the capacity of performing causal deduction and generalization.
In contrast to the US, in Europe the key AI programming language during that same period was Prolog. Prolog provided a built-in store of facts and clauses that could be queried by a read-eval-print loop. The store could act as a knowledge base and the clauses could act as rules or a restricted form of logic. As a subset of first-order logic Prolog was based on Horn clauses with a closed-world assumption—any facts not known were considered false—and a unique name assumption for primitive terms—e.g., the identifier barack_obama was considered to refer to exactly one object.
We suggest that this goal will require pursuing AI that can exhibit symbolic behavior within a holistic, meaningful framework of ethics. Consequently, instead of focusing dichotomously on whether a system (human, animal, or AI) engages with symbols, we focus on characterizing how it engages with symbols; that is, how it exhibits behaviours that implicate meaning-by-convention. This focus offers a set of behavioural criteria that outline the varieties and gradations of symbolic behaviour. These criteria are measurable, which is useful both for assessing current AI, and as a direct target for optimization.
Agents and multi-agent systems
However, performance generally improves when symbols are embedded within a richer, more embodied contexts [43, 44], or even using auxiliary data to learn symbol-symbol relations, as is accomplished with pre-trained word embeddings [45]. These continuous vectors capture complex relationships like analogies [46], providing concrete evidence for the utility of this embedded property (though there are also drawbacks, such as capturing biases in language use [47]). Symbolic artificial intelligence is very convenient for settings where the rules are very clear cut, and you can easily obtain input and transform it into symbols.
Artificial systems mimicking human expertise such as Expert Systems are emerging in a variety of fields that constitute narrow but deep knowledge domains. A perception module of neural networks crunches the pixels in each image and maps the objects. A language module, also made of neural nets, extracts a meaning from the words in each sentence and creates symbolic programs, or instructions, that tell the machine how to answer the question. A third reasoning module runs the symbolic programs on the scene and gives an answer, updating the model when it makes mistakes. It’s not obvious whether any AI system exhibits malleable understanding of symbols as humans do.
Such intentional action motivates techniques that exploit the situated, goal-directed aspects cognition, such as reinforcement learning [53, 54, 55]. Neural networks in particular have strong representational and functional biases toward such behaviour. For example, continuous vector representations are meaningful with respect to the magnitudes and angles of other vectors, and such vector relations are directly shaped by gradient-based learning to be useful for a downstream task, such as classification [42]. For this reason, deep learning models can suffer from poor generalization [6] without sufficient inductive biases, or data from which to learn the interrelationships between symbols.
A second trait of symbolic behaviour is the ability to form new conventions; because meaning is conventional, it can be imposed arbitrarily on top of any substrate. Such an ability can be used to increase the efficiency of communication or reasoning (e.g. by creating a new term for a recurring situation) and for creating new systems of knowledge. Consider, for example, the scientific understanding which followed the introduction of the concept of the “genes” to describe units of heritable variability. The automated theorem provers discussed below can prove theorems in first-order logic.
Their arguments are based on a need to address the two kinds of thinking discussed in Daniel Kahneman’s book, Thinking, Fast and Slow. Kahneman describes human thinking as having two components, System 1 and System 2. System 1 is the kind used for pattern recognition while System 2 is far better suited for planning, deduction, and deliberative thinking. In this view, deep learning best models the first kind of thinking while symbolic reasoning best models the second kind and both are needed.
Symbolic artificial intelligence, also known as Good, Old-Fashioned AI (GOFAI), was the dominant paradigm in the AI community from the post-War era until the late 1980s. Deep learning has its discontents, and many of them look to other branches of AI when they hope for the future. Fluent symbol users understand that the conventionality of meaning allows for change. Meaning can be altered by context, by the creation of other symbols (see “embedded”, above) or concepts, or by intentionally redefining the symbol. Newell, Simon, and Peirce therefore agree that a symbol consists of some substrate—a scratch on a page, an air vibration, or an electrical pulse—that is imbued with arbitrary meaning, but Peirce emphasizes the subjectivity of this convention. A substrate is only a symbol with respect to some interpreter(s), making symbols an irreducibly triadic phenomenon whose meanings are neither intrinsic to their substrate, nor objective [16].
Much contemporary artificial intelligence (AI) research strays from GOFAI methods and instead leverages learning-based artificial neural networks [2]. Neural networks have achieved substantial recent success in domains like language [3, 4] and mathematics [5], which were historically thought to require classical symbolic approaches. Despite these successes, some apparent weaknesses of current connectionist-based approaches [6, 7, 8] have lead to calls for a return of classical symbolic methods, possibly in the form of hybrid, neuro-symbolic models [9, 10, 11, 12, 13]. We propose the Neuro-Symbolic Concept Learner (NS-CL), a model that learns visual concepts, words, and semantic parsing of sentences without explicit supervision on any of them; instead, our model learns by simply looking at images and reading paired questions and answers.
Expert systems are monotonic; that is, the more rules you add, the more knowledge is encoded in the system, but additional rules can’t undo old knowledge. Monotonic basically means one direction; i.e. when one thing goes up, another thing goes up. The ability to proficiently use symbols makes it possible to reason about the laws of nature, fly to the moon, write poetry, and evoke thoughts and feelings in the minds of others. Artificial intelligence (AI) pioneers Newell and Simon claimed that “[s]ymbols lie at the root of intelligent action” and should therefore be a central component in the design of artificial intelligence [1]. Their hypothesis drove a decades-long program of Good Old-Fashioned AI (GOFAI) research, which attempted to create intelligent machines by applying the syntactic mechanisms developed in computer science, logic, mathematics, linguistics, and psychology. Deep learning and neural networks excel at exactly the tasks that symbolic AI struggles with.
In this section we elaborate on each dimension, and evaluate the progress of contemporary AI. Using OOP, you can create extensive and complex symbolic AI programs that perform various tasks. The early pioneers of AI believed that “every aspect of learning or any other feature of intelligence can in principle be so precisely described that a machine can be made to simulate it.” Therefore, symbolic AI took center stage and became the focus of research projects. Being able to communicate in symbols is one of the main things that make us intelligent.
They can also be used to describe other symbols (a cat with fluffy ears, a red carpet, etc.). Critiques from outside of the field were primarily from philosophers, on intellectual grounds, but also from funding agencies, especially during the two AI winters. The General Problem Solver (GPS) cast planning as problem-solving used means-ends analysis to create plans. Graphplan takes a least-commitment approach to planning, rather than sequentially choosing actions from an initial state, working forwards, or a goal state if working backwards. Satplan is an approach to planning where a planning problem is reduced to a Boolean satisfiability problem.
For example, AlphaZero [59] uses learned move value estimates as strong heuristics for reducing its search space. However, because AlphaZero’s reasoning process (Monte-Carlo Tree Search) is hand engineered and strictly rule-based, it cannot achieve the second goal. Analogous limitations apply to neuro-symbolic models that use deep learning within a more programmatic reasoning process [e.g. This motivates future research toward systems that can understand their reasoning processes as meaningful, and use that understanding to refine and communicate their reasoning. For organizations looking forward to the day they can interact with AI just like a person, symbolic AI is how it will happen, says tech journalist Surya Maddula.
Further, our method allows easy generalization to new object attributes, compositions, language concepts, scenes and questions, and even new program domains. It also empowers applications including visual question answering and bidirectional image-text retrieval. Classical perspectives on symbols in AI have mostly overlooked the fact that symbols are fundamentally subjective—they depend on an interpreter (or some interpreters) to create a convention of meaning.
Furthermore, it can generalize to novel rotations of images that it was not trained for. To give computers the ability to reason more like us, artificial intelligence (AI) researchers are returning to abstract, or symbolic, programming. Popular in the 1950s and 1960s, symbolic AI wires in the rules and logic that allow machines to make comparisons and interpret how objects and entities relate. Symbolic AI uses less data, records the chain of steps it takes to reach a decision, and when combined with the brute processing power of statistical neural networks, it can even beat humans in a complicated image comprehension test.
Newell and Simon define symbols as a set of interrelated “physical patterns” that could “designate any expression whatsoever” [1]. For example, Touretzky and Pomerleau [24] expressed frustration that some researchers render the concept of symbol operationally vacuous by claiming that anything that designates or denotes is a symbol. We’re headed back to NYC on June 5th alongside UiPath to hear from top executive leaders examine how organizations can audit their AI models for bias, performance, and adherence to ethical standards. Join us as we return to NYC on June 5th to engage with top executive leaders, delving into strategies for auditing AI models to ensure fairness, optimal performance, and ethical compliance across diverse organizations. The grandfather of AI, Thomas Hobbes said — Thinking is manipulation of symbols and Reasoning is computation.
Neural networks are almost as old as symbolic AI, but they were largely dismissed because they were inefficient and required compute resources that weren’t available at the time. In the past decade, thanks to the large availability of data and processing power, deep learning has gained popularity and has pushed past symbolic AI systems. During the first AI summer, many people thought that machine intelligence could be achieved in just a few years. By the mid-1960s neither useful natural language translation systems nor autonomous tanks had been created, and a dramatic backlash set in. Although deep learning has historical roots going back decades, neither the term “deep learning” nor the approach was popular just over five years ago, when the field was reignited by papers such as Krizhevsky, Sutskever and Hinton’s now classic (2012) deep network model of Imagenet.
Centers, Labs, & Programs
As soon as you generalize the problem, there will be an explosion of new rules to add (remember the cat detection problem?), which will require more human labor. A key component of the system architecture for all expert systems is the knowledge base, which stores facts and rules for problem-solving.[51]
The simplest approach for an expert system knowledge base is simply a collection or network of production rules. Production rules connect symbols in a relationship similar to an If-Then statement. The expert system processes the rules to make deductions and to determine what additional information it needs, i.e. what questions to ask, using human-readable symbols.
You can foun additiona information about ai customer service and artificial intelligence and NLP. But in recent years, as neural networks, also known as connectionist AI, gained traction, symbolic AI has fallen by the wayside. Symbols also serve to transfer learning in another sense, not from one human to another, but from one situation to another, over the course of a single individual’s life. That is, a symbol offers a level of abstraction above the concrete and granular details of our sensory experience, an abstraction that allows us to transfer what we’ve learned in one place to a problem we may encounter somewhere else.
Typical AI models tend to drift from their original intent as new data influences changes in the algorithm. Scagliarini says the rules of symbolic AI resist drift, so models can be created much faster and with far less data to begin with, and then require less retraining once they enter production environments. The technology actually dates back to the 1950s, says expert.ai’s Luca Scagliarini, but was considered old-fashioned by the 1990s when demand for procedural knowledge of sensory and motor processes was all the rage. Now that AI is tasked with higher-order systems and data management, the capability to engage in logical thinking and knowledge representation is cool again. Insofar as computers suffered from the same chokepoints, their builders relied on all-too-human hacks like symbols to sidestep the limits to processing, storage and I/O. As computational capacities grow, the way we digitize and process our analog reality can also expand, until we are juggling billion-parameter tensors instead of seven-character strings.
Thus, human-like symbolic fluency is not guaranteed simply because a system is equipped with classical “symbolic” machinery. Human socio-cultural situations are perhaps best suited to fulfill this requirement, as they demand the complex coordination of perspectives to agree on arbitrarily-imposed meaning. They can also be collected at scale in conjunction with human feedback, and hence allow the use of powerful contemporary AI tools that mould behaviour. Many recent models have used deep learning to partially address the first point.
There have been several efforts to create complicated symbolic AI systems that encompass the multitudes of rules of certain domains. Called expert systems, these symbolic AI models use hardcoded knowledge and rules to tackle complicated tasks such as medical diagnosis. But they require a huge amount of effort by domain experts and software engineers and only work in very narrow use cases.
As an interpreter’s background, capabilities, and biases vary, so too will their subjective treatment of symbols. This makes it problematic to draw binary distinctions between using and not using symbols. Indeed, as we will explore, symbol use manifests differently over the course of development, as broader cognitive systems and knowledge structures change [cf.
The Disease Ontology is an example of a medical ontology currently being used. The team trained their model on images paired with related questions and answers, part of the CLEVR image Chat PG comprehension test developed at Stanford University. As the model learns, the questions grow progressively harder, from, “What’s the color of the object?
Q&A: Can Neuro-Symbolic AI Solve AI’s Weaknesses? – TDWI
Q&A: Can Neuro-Symbolic AI Solve AI’s Weaknesses?.
Posted: Mon, 08 Apr 2024 07:00:00 GMT [source]
Therefore, symbols have also played a crucial role in the creation of artificial intelligence. When deep learning reemerged in 2012, it was with a kind of take-no-prisoners attitude that has characterized most of the last decade. He gave a talk at an AI workshop at Stanford comparing symbols to aether, one of science’s greatest mistakes. Multiple different approaches to represent knowledge and then reason with those representations have been investigated. Below is a quick overview of approaches to knowledge representation and automated reasoning.
In addition, several artificial intelligence companies, such as Teknowledge and Inference Corporation, were selling expert system shells, training, and consulting to corporations. Expert systems can operate in either a forward chaining – from evidence to conclusions – or backward chaining – from goals to needed data and prerequisites – manner. More advanced knowledge-based systems, such as Soar can also perform meta-level reasoning, that is reasoning about their own reasoning in terms of deciding how to solve problems and monitoring the success of problem-solving strategies. This creates a crucial turning point for the enterprise, says Analytics Week’s Jelani Harper. Data fabric developers like Stardog are working to combine both logical and statistical AI to analyze categorical data; that is, data that has been categorized in order of importance to the enterprise.
- These continuous vectors capture complex relationships like analogies [46], providing concrete evidence for the utility of this embedded property (though there are also drawbacks, such as capturing biases in language use [47]).
- A change in the lighting conditions or the background of the image will change the pixel value and cause the program to fail.
- It’s most commonly used in linguistics models such as natural language processing (NLP) and natural language understanding (NLU), but it is quickly finding its way into ML and other types of AI where it can bring much-needed visibility into algorithmic processes.
- In contrast, a multi-agent system consists of multiple agents that communicate amongst themselves with some inter-agent communication language such as Knowledge Query and Manipulation Language (KQML).
Cyc has attempted to capture useful common-sense knowledge and has “micro-theories” to handle particular kinds of domain-specific reasoning. Forward chaining inference engines are the most common, and are seen in CLIPS and OPS5. Backward chaining occurs in Prolog, where a more limited logical representation is used, Horn Clauses. https://chat.openai.com/ While this may be unnerving to some, it must be remembered that symbolic AI still only works with numbers, just in a different way. By creating a more human-like thinking machine, organizations will be able to democratize the technology across the workforce so it can be applied to the real-world situations we face every day.
- Asked to answer an unfamiliar question like, “What’s the shape of the big yellow thing?
- By the mid-1960s neither useful natural language translation systems nor autonomous tanks had been created, and a dramatic backlash set in.
- In contrast, other probabilistic programming languages such as Gen and Pyro allow users to write down probabilistic programs where the only known ways to do inference are approximate — that is, the results include errors whose nature and magnitude can be hard to characterize.
In [23], humans and agents take control of avatars in a virtual 3D environment called a “Playroom”, comprising objects such as furniture and toys. Setter agents (or humans) pose a task for Solver agents (or humans) using natural language, such as “pick up the blue duck and bring it to the bedroom”. We see this as a promising approach to placing agents in situations requiring conventional, perspectival, and pragmatic interaction with humans. Critically, the authors collected a vast quantity of data—the agents learned from more than 600,000 episodes of human-human interaction in a complex environment. Collecting rich compilations of symbolic behaviours at scale allows for direct optimization towards these competencies. However, further work is needed to create experiences that develop particular aspects of symbolic behaviour, such as constructive and meaningful behaviours.