Backpropagation

From Wikipedia, the free encyclopedia

Backpropagation is a method used in artificial neural networks to calculate a gradient that is needed in the calculation of the weights to be used in the network. Backpropagation is shorthand for "the backward propagation of errors," since an error is computed at the output and distributed backwards throughout the network’s layers. It is commonly used to train deep neural networks, a term referring to neural networks with more than one hidden layer.

Backpropagation is a special case of a more general technique called automatic differentiation. In the context of learning, backpropagation is commonly used by the gradient descent optimization algorithm to adjust the weight of neurons by calculating the gradient of the loss function.

Backpropagation requires the derivative of the loss function with respect to the network output to be known, which typically (but not necessarily) means that the desired target value is known. For this reason, it is considered to be a supervised learning method, although it is used in some unsupervised networks such as autoencoders. Backpropagation is also a generalization of the delta rule to multi-layered feedforward networks, made possible by using the chain rule to iteratively compute gradients for each layer. It is closely related to the Gauss–Newton algorithm and is part of continuing research in neural backpropagation. Backpropagation can be used with any gradient-based optimizer, such as L-BFGS or truncated Newton.

History

Backpropagation was derived by multiple researchers in the early 60's and implemented to run on computers much as it is today as early as 1970 by Seppo Linnainmaa Examples of 1960s researchers include Arthur E. Bryson and Yu-Chi Ho in 1969. Paul Werbos was first in the US to propose that it could be used for neural nets after analyzing it in depth in his 1974 PhD Thesis. In 1986 through the work of David E. Rumelhart, Geoffrey E. Hinton, Ronald J. Williams, and James McClelland, backpropagation gained recognition.

Motivation

The goal of any supervised learning algorithm is to find a function that best maps a set of inputs to their correct output. An example would be a classification task, where the input is an image of an animal, and the correct output is the type of animal (e.g.: dog, cat, giraffe, lion, zebra, etc.).

The motivation for backpropagation is to train a multi-layered neural network such that it can learn the appropriate internal representations to allow it to learn any arbitrary mapping of input to output.

Loss function

Sometimes referred to as the cost function or error function (not to be confused with the Gauss error function), the loss function is a function that maps values of one or more variables onto a real number intuitively representing some "cost" associated with those values. For backpropagation, the loss function calculates the difference between the network output and its expected output, after a case propagates through the network.

Assumptions

Two assumptions must be made about the form of the error function. The first is that it can be written as an average ${\textstyle E={\frac {1}{n}}\sum _{x}E_{x}}$ over error functions ${\textstyle E_{x}}$, for ${\textstyle n}$ individual training examples, ${\textstyle x}$. The reason for this assumption is that the backpropagation algorithm calculates the gradient of the error function for a single training example, which needs to be generalized to the overall error function. The second assumption is that it can be written as a function of the outputs from the neural network.

Example loss function

Let ${\displaystyle y,y'}$ be vectors in ${\displaystyle \mathbb {R} ^{n}}$.

Select an error function ${\displaystyle E(y,y')}$ measuring the difference between two outputs. The standard choice is the square of the Euclidean distance between the vectors ${\displaystyle y}$ and ${\displaystyle y'}$:

$${\displaystyle E(y,y')={\tfrac {1}{2}}\lVert y-y'\rVert ^{2}}$$

The error function over ${\textstyle n}$ training examples can then be written as an average of losses over individual examples:

$${\displaystyle E={\frac {1}{2n}}\sum _{x}\lVert (y(x)-y'(x))\rVert ^{2}}$$

Optimization

The optimization algorithm repeats a two phase cycle, propagation and weight update. When an input vector is presented to the network, it is propagated forward through the network, layer by layer, until it reaches the output layer. The output of the network is then compared to the desired output, using a loss function. The resulting error value is calculated for each of the neurons in the output layer. The error values are then propagated from the output back through the network, until each neuron has an associated error value that reflects its contribution to the original output.

Backpropagation uses these error values to calculate the gradient of the loss function. In the second phase, this gradient is fed to the optimization method, which in turn uses it to update the weights, in an attempt to minimize the loss function.

Algorithm

Let ${\displaystyle N}$ be a neural network with ${\displaystyle e}$ connections, ${\displaystyle m}$ inputs, and ${\displaystyle n}$ outputs.

Below, ${\displaystyle x_{1},x_{2},\dots }$ will denote vectors in ${\displaystyle \mathbb {R} ^{m}}$, ${\displaystyle y_{1},y_{2},\dots }$ vectors in ${\displaystyle \mathbb {R} ^{n}}$, and ${\displaystyle w_{0},w_{1},w_{2},\ldots }$ vectors in ${\displaystyle \mathbb {R} ^{e}}$. These are called inputs, outputs and weights respectively.

The neural network corresponds to a function ${\displaystyle y=f_{N}(w,x)}$ which, given a weight ${\displaystyle w}$, maps an input ${\displaystyle x}$ to an output ${\displaystyle y}$.

The optimization takes as input a sequence of training examples ${\displaystyle (x_{1},y_{1}),\dots ,(x_{p},y_{p})}$ and produces a sequence of weights ${\displaystyle w_{0},w_{1},\dots ,w_{p}}$ starting from some initial weight ${\displaystyle w_{0}}$, usually chosen at random.

These weights are computed in turn: first compute ${\displaystyle w_{i}}$ using only ${\displaystyle (x_{i},y_{i},w_{i-1})}$ for ${\displaystyle i=1,\dots ,p}$. The output of the algorithm is then ${\displaystyle w_{p}}$, giving us a new function ${\displaystyle x\mapsto f_{N}(w_{p},x)}$. The computation is the same in each step, hence only the case ${\displaystyle i=1}$ is described.

Calculating ${\displaystyle w_{1}}$ from ${\displaystyle (x_{1},y_{1},w_{0})}$ is done by considering a variable weight ${\displaystyle w}$ and applying gradient descent to the function ${\displaystyle w\mapsto E(f_{N}(w,x_{1}),y_{1})}$ to find a local minimum, starting at ${\displaystyle w=w_{0}}$.
This makes ${\displaystyle w_{1}}$ the minimizing weight found by gradient descent.

Algorithm in code

To implement the algorithm above, explicit formulas are required for the gradient of the function ${\displaystyle w\mapsto E(f_{N}(w,x),y)}$ where the function is ${\displaystyle E(y,y')=|y-y'|^{2}}$.

The learning algorithm can be divided into two phases: propagation and weight update.

Phase 1: propagation

Each propagation involves the following steps:

1. Propagation forward through the network to generate the output value(s)
2. Calculation of the cost (error term)
3. Propagation of the output activations back through the network using the training pattern target to generate the deltas (the difference between the targeted and actual output values) of all output and hidden neurons.

Phase 2: weight update

For each weight, the following steps must be followed:

1. The weight's output delta and input activation are multiplied to find the gradient of the weight.
2. A ratio (percentage) of the weight's gradient is subtracted from the weight.

This ratio (percentage) influences the speed and quality of learning; it is called the learning rate. The greater the ratio, the faster the neuron trains, but the lower the ratio, the more accurate the training is. The sign of the gradient of a weight indicates whether the error varies directly with, or inversely to, the weight. Therefore, the weight must be updated in the opposite direction, "descending" the gradient.
Learning is repeated (on new batches) until the network performs adequately.

Pseudocode

The following is pseudocode for a stochastic gradient descent algorithm for training a three-layer network (only one hidden layer):

  initialize network weights (often small random values)
  do
     forEach training example named ex
        prediction = neural-net-output(network, ex)  // forward pass
        actual = teacher-output(ex)
        compute error (prediction - actual) at the output units
        compute ${\displaystyle \Delta w_{h}}$ for all weights from hidden layer to output layer  // backward pass
        compute ${\displaystyle \Delta w_{i}}$ for all weights from input layer to hidden layer   // backward pass continued
        update network weights // input layer not modified by error estimate
  until all examples classified correctly or another stopping criterion satisfied
  return the network

The lines labeled "backward pass" can be implemented using the backpropagation algorithm, which calculates the gradient of the error of the network regarding the network's modifiable weights.

Intuition

Learning as an optimization problem

To understand the mathematical derivation of the backpropagation algorithm, it helps to first develop some intuitions about the relationship between the actual output of a neuron and the correct output for a particular training case. Consider a simple neural network with two input units, one output unit and no hidden units. Each neuron uses a linear output that is the weighted sum of its input.

A simple neural network with two input units and one output unit

Initially, before training, the weights will be set randomly. Then the neuron learns from training examples, which in this case consists of a set of tuples ${\displaystyle (x_{1},x_{2},t)}$ where ${\displaystyle x_{1}}$ and ${\displaystyle x_{2}}$ are the inputs to the network and t is the correct output (the output the network should eventually produce given those inputs). The initial network, given ${\displaystyle x_{1}}$ and ${\displaystyle x_{2}}$, will compute an output y that likely differs from t (given random weights). A common method for measuring the discrepancy between the expected output t and the actual output y is the squared error measure:

${\displaystyle E=(t-y)^{2},}$

where E is the discrepancy or error.

As an example, consider the network on a single training case: ${\displaystyle (1,1,0)}$, thus the input ${\displaystyle x_{1}}$ and ${\displaystyle x_{2}}$ are 1 and 1 respectively and the correct output, t is 0. Now if the actual output y is plotted on the horizontal axis against the error E on the vertical axis, the result is a parabola. The minimum of the parabola corresponds to the output y which minimizes the error E. For a single training case, the minimum also touches the horizontal axis, which means the error will be zero and the network can produce an output y that exactly matches the expected output t. Therefore, the problem of mapping inputs to outputs can be reduced to an optimization problem of finding a function that will produce the minimal error.

Error surface of a linear neuron for a single training case

However, the output of a neuron depends on the weighted sum of all its inputs:

${\displaystyle y=x_{1}w_{1}+x_{2}w_{2},}$

where ${\displaystyle w_{1}}$ and ${\displaystyle w_{2}}$ are the weights on the connection from the input units to the output unit. Therefore, the error also depends on the incoming weights to the neuron, which is ultimately what needs to be changed in the network to enable learning. If each weight is plotted on a separate horizontal axis and the error on the vertical axis, the result is a parabolic bowl. For a neuron with k weights, the same plot would require an elliptic paraboloid of ${\displaystyle k+1}$ dimensions.

Error surface of a linear neuron with two input weights

One commonly used algorithm to find the set of weights that minimizes the error is gradient descent. Backpropagation is then used to calculate the steepest descent direction.

Derivation for a single-layered network

The gradient descent method involves calculating the derivative of the squared error function with respect to the weights of the network. This is normally done using backpropagation. Assuming one output neuron, the squared error function is:

${\displaystyle E={\tfrac {1}{2}}(t-y)^{2},}$

where

${\displaystyle E}$ is the squared error,

${\displaystyle t}$ is the target output for a training sample, and

${\displaystyle y}$ is the actual output of the output neuron.

The factor of ${\displaystyle \textstyle {\frac {1}{2}}}$ is included to cancel the exponent when differentiating. Later, the expression will be multiplied with an arbitrary learning rate, so that it doesn't matter if a constant coefficient is introduced now.

For each neuron ${\displaystyle j}$, its output ${\displaystyle o_{j}}$ is defined as

${\displaystyle o_{j}=\varphi ({\text{net}}_{j})=\varphi \left(\sum _{k=1}^{n}w_{kj}o_{k}\right).}$

The input ${\displaystyle {\text{net}}_{j}}$ to a neuron is the weighted sum of outputs ${\displaystyle o_{k}}$ of previous neurons. If the neuron is in the first layer after the input layer, the ${\displaystyle o_{k}}$ of the input layer are simply the inputs ${\displaystyle x_{k}}$ to the network. The number of input units to the neuron is ${\displaystyle n}$. The variable ${\displaystyle w_{kj}}$ denotes the weight between neurons ${\displaystyle k}$ and ${\displaystyle j}$.

The activation function ${\displaystyle \varphi }$ is non-linear and differentiable. A commonly used activation function is the logistic function:

${\displaystyle \varphi (z)={\frac {1}{1+e^{-z}}}}$

which has a convenient derivative of:

${\displaystyle {\frac {d\varphi }{dz}}(z)=\varphi (z)(1-\varphi (z))}$

Finding the derivative of the error

Calculating the partial derivative of the error with respect to a weight ${\displaystyle w_{ij}}$ is done using the chain rule twice:

${\displaystyle {\frac {\partial E}{\partial w_{ij}}}={\frac {\partial E}{\partial o_{j}}}{\frac {\partial o_{j}}{\partial {\text{net}}_{j}}}{\frac {\partial {\text{net}}_{j}}{\partial w_{ij}}}}$

In the last factor of the right-hand side of the above, only one term in the sum ${\displaystyle {\text{net}}_{j}}$ depends on ${\displaystyle w_{ij}}$, so that

${\displaystyle {\frac {\partial {\text{net}}_{j}}{\partial w_{ij}}}={\frac {\partial }{\partial w_{ij}}}\left(\sum _{k=1}^{n}w_{kj}o_{k}\right)={\frac {\partial }{\partial w_{ij}}}w_{ij}o_{i}=o_{i}.}$

If the neuron is in the first layer after the input layer, ${\displaystyle o_{i}}$ is just ${\displaystyle x_{i}}$.

The derivative of the output of neuron ${\displaystyle j}$ with respect to its input is simply the partial derivative of the activation function (assuming here that the logistic function is used):

${\displaystyle {\frac {\partial o_{j}}{\partial {\text{net}}_{j}}}={\frac {\partial }{\partial {\text{net}}_{j}}}\varphi ({\text{net}}_{j})=\varphi ({\text{net}}_{j})(1-\varphi ({\text{net}}_{j}))}$

This is the reason why backpropagation requires the activation function to be differentiable. (Nevertheless, the ReLU activation function, which is non-differentiable at 0, has become quite popular recently, e.g. in AlexNet)

The first factor is straightforward to evaluate if the neuron is in the output layer, because then ${\displaystyle o_{j}=y}$ and

${\displaystyle {\frac {\partial E}{\partial o_{j}}}={\frac {\partial E}{\partial y}}={\frac {\partial }{\partial y}}{\frac {1}{2}}(t-y)^{2}=y-t}$

However, if ${\displaystyle j}$ is in an arbitrary inner layer of the network, finding the derivative ${\displaystyle E}$ with respect to ${\displaystyle o_{j}}$ is less obvious.

Considering ${\displaystyle E}$ as a function of the inputs of all neurons ${\displaystyle L={u,v,\dots ,w}}$ receiving input from neuron ${\displaystyle j}$,

${\displaystyle {\frac {\partial E(o_{j})}{\partial o_{j}}}={\frac {\partial E(\mathrm {net} _{u},{\text{net}}_{v},\dots ,\mathrm {net} _{w})}{\partial o_{j}}}}$

and taking the total derivative with respect to ${\displaystyle o_{j}}$, a recursive expression for the derivative is obtained:

${\displaystyle {\frac {\partial E}{\partial o_{j}}}=\sum _{\ell \in L}\left({\frac {\partial E}{\partial {\text{net}}_{\ell }}}{\frac {\partial {\text{net}}_{\ell }}{\partial o_{j}}}\right)=\sum _{\ell \in L}\left({\frac {\partial E}{\partial o_{\ell }}}{\frac {\partial o_{\ell }}{\partial {\text{net}}_{\ell }}}w_{j\ell }\right)}$

Therefore, the derivative with respect to ${\displaystyle o_{j}}$ can be calculated if all the derivatives with respect to the outputs ${\displaystyle o_{\ell }}$ of the next layer – the one closer to the output neuron – are known.
Putting it all together:

${\displaystyle {\frac {\partial E}{\partial w_{ij}}}=\delta _{j}o_{i}}$

with

${\displaystyle \delta _{j}={\frac {\partial E}{\partial o_{j}}}{\frac {\partial o_{j}}{\partial {\text{net}}_{j}}}={\begin{cases}(o_{j}-t_{j})o_{j}(1-o_{j})&{\text{if }}j{\text{ is an output neuron,}}\\(\sum _{\ell \in L}w_{j\ell }\delta _{\ell })o_{j}(1-o_{j})&{\text{if }}j{\text{ is an inner neuron.}}\end{cases}}}$

To update the weight ${\displaystyle w_{ij}}$ using gradient descent, one must choose a learning rate, ${\displaystyle \eta >0}$. The change in weight needs to reflect the impact on ${\displaystyle E}$ of an increase or decrease in ${\displaystyle w_{ij}}$. If ${\displaystyle {\frac {\partial E}{\partial w_{ij}}}>0}$, an increase in ${\displaystyle w_{ij}}$ increases ${\displaystyle E}$; conversely, if ${\displaystyle {\frac {\partial E}{\partial w_{ij}}}<0 annotation="">$, an increase in ${\displaystyle w_{ij}}$ decreases ${\displaystyle E}$. The new ${\displaystyle \Delta w_{ij}}$ is added to the old weight, and the product of the learning rate and the gradient, multiplied by ${\displaystyle -1}$ guarantees that ${\displaystyle w_{ij}}$ changes in a way that always decreases ${\displaystyle E}$. In other words, in the equation immediately below, ${\displaystyle -\eta {\frac {\partial E}{\partial w_{ij}}}}$ always changes ${\displaystyle w_{ij}}$ in such a way that ${\displaystyle E}$ is decreased:

${\displaystyle \Delta w_{ij}=-\eta {\frac {\partial E}{\partial w_{ij}}}=-\eta \delta _{j}o_{i}}$

Extension

The choice of learning rate ${\textstyle \eta }$ is important, since a high value can cause too strong a change, causing the minimum to be missed, while a too low learning rate slows the training unnecessarily.
Optimizations such as Quickprop are primarily aimed at speeding up error minimization; other improvements mainly try to increase reliability.

Adaptive learning rate

In order to avoid oscillation inside the network such as alternating connection weights, and to improve the rate of convergence, refinements of this algorithm use an adaptive learning rate.

Inertia

By using a variable inertia term (Momentum) ${\textstyle \alpha }$ the gradient and the last change can be weighted such that the weight adjustment additionally depends on the previous change. If the Momentum ${\textstyle \alpha }$ is equal to 0, the change depends solely on the gradient, while a value of 1 will only depend on the last change.

Similar to a ball rolling down a mountain, whose current speed is determined not only by the current slope of the mountain but also by its own inertia, inertia can be added:

$${\displaystyle \Delta w_{ij}(t+1)=(1-\alpha )\eta \delta _{j}o_{i}+\alpha \,\Delta w_{ij}(t)}$$

where:

${\textstyle \Delta w_{ij}(t+1)}$ is the change in weight ${\textstyle w_{ij}(t+1)}$ in the connection of neuron ${\textstyle i}$ to neuron ${\textstyle j}$ at time ${\textstyle (t+1),}$

${\textstyle \eta }$ a learning rate (${\textstyle \eta <0 annotation="">$

${\textstyle \delta _{j}}$ the error signal of neuron ${\textstyle j}$ and

${\textstyle o_{i}}$ the output of neuron ${\textstyle i}$, which is also an input of the current neuron (neuron ${\textstyle j}$),

${\textstyle \alpha }$ the influence of the inertial term ${\textstyle \Delta w_{ij}(t)}$ (in ${\textstyle [0,1]}$). This corresponds to the weight change at the previous point in time.

Inertia makes the current weight change ${\textstyle (t+1)}$ depend both on the current gradient of the error function (slope of the mountain, 1st summand), as well as on the weight change from the previous point in time (inertia, 2nd summand).

With inertia, the problems of getting stuck (in steep ravines and flat plateaus) are avoided. Since, for example, the gradient of the error function becomes very small in flat plateaus, a plateau would immediately lead to a "deceleration" of the gradient descent. This deceleration is delayed by the addition of the inertia term so that a flat plateau can be escaped more quickly.

Modes of learning

Two modes of learning are available: stochastic and batch. In stochastic learning, each input creates a weight adjustment. In batch learning weights are adjusted based on a batch of inputs, accumulating errors over the batch. Stochastic learning introduces "noise" into the gradient descent process, using the local gradient calculated from one data point; this reduces the chance of the network getting stuck in local minima. However, batch learning typically yields a faster, more stable descent to a local minimum, since each update is performed in the direction of the average error of the batch. A common compromise choice is to use "mini-batches", meaning small batches and with samples in each batch selected stochastically from the entire data set.

Limitations

Gradient descent can find the local minimum instead of the global minimum.

• Gradient descent with backpropagation is not guaranteed to find the global minimum of the error function, but only a local minimum; also, it has trouble crossing plateaus in the error function landscape. This issue, caused by the non-convexity of error functions in neural networks, was long thought to be a major drawback, but Yann LeCun et al. argue that in many practical problems, it is not.
• Backpropagation learning does not require normalization of input vectors; however, normalization could improve performance.

History

According to various sources, the basics of continuous backpropagation were derived in the context of control theory by Henry J. Kelley in 1960 and by Arthur E. Bryson in 1961. They used principles of dynamic programming. In 1962, Stuart Dreyfus published a simpler derivation based only on the chain rule. Bryson and Ho described it as a multi-stage dynamic system optimization method in 1969.

In 1970 Linnainmaa published the general method for automatic differentiation (AD) of discrete connected networks of nested differentiable functions. This corresponds to backpropagation, which is efficient even for sparse networks.

In 1973 Dreyfus used backpropagation to adapt parameters of controllers in proportion to error gradients. In 1974 Werbos mentioned the possibility of applying this principle to artificial neural networks, and in 1982 he applied Linnainmaa's AD method to neural networks in the way that is used today.

In 1986 Rumelhart, Hinton and Williams showed experimentally that this method can generate useful internal representations of incoming data in hidden layers of neural networks. In 1993, Wan was the first to win an international pattern recognition contest through backpropagation.

During the 2000s it fell out of favour, but returned in the 2010s, benefitting from cheap, powerful GPU-based computing systems. This has been especially so in language structure learning research, where the connectionist models using this algorithm have been able to explain a variety of phenomena related to first and second language learning.

Occupational therapy

From Wikipedia, the free encyclopedia

Occupational therapy
US Navy Occupational therapists providing treatment to outpatients

Occupational therapy (OT) is the use of assessment and intervention to develop, recover, or maintain the meaningful activities, or occupations, of individuals, groups, or communities. It is an allied health profession performed by occupational therapists and Occupational Therapy Assistants. OTs often work with people with mental health problems, disabilities, injuries, or impairments.

The American Occupational Therapy Association defines an occupational therapist as someone who "helps people across the lifespan participate in the things they want and need to do through the therapeutic use of everyday activities (occupations). Common occupational therapy interventions include helping children with disabilities to participate fully in school and social situations, injury rehabilitation, and providing supports for older adults experiencing physical and cognitive changes."

Typically, occupational therapists are university-educated professionals and must pass a licensing exam to practice. Occupational therapists often work closely with professionals in physical therapy, speech therapy, audiology, nursing, social work, clinical psychology, and medicine.

History

Early history

The earliest evidence of using occupations as a method of therapy can be found in ancient times. In c. 100 BCE, Greek physician Asclepiades treated patients with a mental illness humanely using therapeutic baths, massage, exercise, and music. Later, the Roman Celsus prescribed music, travel, conversation and exercise to his patients. However, by medieval times the use of these interventions with people with mental illness was rare, if not nonexistent.

In 18th-century Europe, revolutionaries such as Philippe Pinel and Johann Christian Reil reformed the hospital system. Instead of the use of metal chains and restraints, their institutions used rigorous work and leisure activities in the late 18th century. This was the Moral Treatment era, developed in Europe during the Age of Enlightenment, where the roots of occupational therapy lie. Although it was thriving in Europe, interest in the reform movement fluctuated in the United States throughout the 19th century. It re-emerged in the early decades of the 20th century as Occupational Therapy.

The Arts and Crafts movement that took place between 1860 and 1910 also impacted occupational therapy. In the US, a recently industrialized country, the arts and crafts societies emerged against the monotony and lost autonomy of factory work. Arts and crafts were used as a way of promoting learning through doing, provided a creative outlet, and served as a way to avoid boredom during long hospital stays.

Eleanor Clarke Slagle (1870-1942) is considered to be the “mother” of occupational therapy. Slagle, who was one of the founding members of the National Society for the Promotion of Occupational Therapy (NSPOT), proposed habit training as a primary occupational therapy model of treatment. Based on the philosophy that engagement in meaningful routines shape a person's wellbeing, habit training focused on creating structure and balance between work, rest and leisure. Although habit training was initially developed to treat individuals with mental health conditions, its basic tenets are apparent in modern treatment models that are utilized across a wide scope of client populations.
In 1915 Slagle opened the first occupational therapy training program, the Henry B. Favill School of Occupations, at Hull House in Chicago. Slagle went on to serve as both AOTA president and secretary. In 1954, AOTA created the Eleanor Clarke Slagle Lectureship Award in her honor. Each year, this award recognizes a member of AOTA “who has who has creatively contributed to the development of the body of knowledge of the profession through research, education, and/or clinical practice.”

Development into a health profession

Occupational therapy. Toy making in psychiatric hospital. World War 1 era.

The health profession of occupational therapy was conceived in the early 1910s as a reflection of the Progressive Era. Early professionals merged highly valued ideals, such as having a strong work ethic and the importance of crafting with one's own hands with scientific and medical principles. The National Society for the Promotion of Occupational Therapy (NSPOT), now called the American Occupational Therapy Association (AOTA), was founded in 1917 and the profession of Occupational Therapy was officially named in 1921. William Rush Dunton, one of the founders of NSPOT and visionary figure in the first decades of the profession struggled with "the cumbersomeness of the term occupational therapy", as it lacked the "exactness of meaning which is possessed by scientific terms". Other titles such as "work-cure","ergo therapy"(ergo being the greek root for "work"), and "creative occupations" were discussed as substitutes, but ultimately, none possessed the broad meaning that the practice of occupational therapy demanded in order to capture the many forms of treatment that existed from the beginning.

Occupational therapy during WWI: bedridden wounded are knitting.

The emergence of occupational therapy challenged the views of mainstream scientific medicine. Instead of focusing purely on the medical model, occupational therapists argued that a complex combination of social, economic, and biological reasons cause dysfunction. Principles and techniques were borrowed from many disciplines—including but not limited to physical therapy, nursing, psychiatry, rehabilitation, self-help, orthopedics, and social work—to enrich the profession's scope. Between 1900 and 1930, the founders defined the realm of practice and developed supporting theories. By the early 1930s, AOTA had established educational guidelines and accreditation procedures.

The early twentieth century was a time in which the rising incidence of disability related to industrial accidents, tuberculosis, World War I, and mental illness brought about an increasing social awareness of the issues involved. The entry of the United States into World War I was also a crucial event in the history of the profession. Up until this time, occupational therapy had been concerned primarily with the treatment of people with mental illness. However, U.S. involvement in the Great War and the escalating numbers of injured and disabled soldiers presented a daunting challenge to those in command. The military enlisted the assistance of NSPOT to recruit and train over 1,200 "reconstruction aides" to help with the rehabilitation of those wounded in the war. With entry into World War II and the ensuing skyrocketing demand for occupational therapists to treat those injured in the war, the field of occupational therapy underwent dramatic growth and change. Occupational therapists needed to be skilled not only in the use of constructive activities such as crafts, but also increasingly in the use of activities of daily living.

There was a struggle to keep people in the profession during the post-war years. Emphasis shifted from the altruistic war-time mentality to the financial, professional, and personal satisfaction that comes with being a therapist. To make the profession more appealing, practice was standardized, as was the curriculum. Entry and exit criteria were established, and the American Occupational Therapy Association advocated for steady employment, decent wages, and fair working conditions. Via these methods, occupational therapy sought and obtained medical legitimacy in the 1920s. The 1920s and 1930s were a time of establishing standards of education and laying the foundation of the profession and its organization. Eleanor Clarke Slagle proposed a 12-month course of training in 1922, and these standards were adopted in 1923. Educational standards were expanded to a total training time of 18-months in 1930 to place the requirements for professional entry on par with those of other professions. The first textbook was published in United States for occupational therapy in 1947, edited by Helen S. Willard and Clare S. Spackman. The profession continued to grow and redefine itself in the 1950s. The profession also began to assess the potential for the use of trained assistants in the attempt to address the ongoing shortage of qualified therapists, and educational standards for occupational therapy assistants were implemented in 1960. The 1960s and 1970s were a time of ongoing change and growth for the profession as it struggled to incorporate new knowledge and cope with the recent and rapid growth of the profession in the previous decades. New developments in the areas of neurobehavioral research led to new conceptualizations and new treatment approaches, possibly the most groundbreaking being the sensory integrative approach developed by A. Jean Ayers.

The profession has continued to grow and expand its scope and settings of practice. Occupational science, the study of occupation, was created in 1989 as a tool for providing evidence-based research to support and advance the practice of occupational therapy, as well as offer a basic science to study topics surrounding "occupation". In addition, occupational therapy practitioner's roles have expanded to include political advocacy (from a grassroots base to higher legislation); for example, in 2010 PL 111-148 titled the Patient Protection and Affordable Care Act had a habilitation clause that was passed in large part due to AOTA's political efforts as noted in AOTA's Centennial website (AOTA, 2017) at http://www.otcentennial.org/events/2010. Furthermore, occupational therapy practitioners have been striving personally and professionally toward concepts of occupational justice and other human rights issues that have both local and global impacts. The World Federation of Occupational Therapist's Resource Centre has many position statements on occupational therapy's roles regarding their participation in human rights issues at http://www.wfot.org/ResourceCentre.aspx.

Philosophical underpinnings

The philosophy of occupational therapy has evolved over the history of the profession. The philosophy articulated by the founders owed much to the ideals of romanticism, pragmatism and humanism, which are collectively considered the fundamental ideologies of the past century.

One of the most widely cited early papers about the philosophy of occupational therapy was presented by Adolf Meyer, a psychiatrist who had emigrated to the United States from Switzerland in the late 19th century and who was invited to present his views to a gathering of the new Occupational Therapy Society in 1922. At the time, Dr. Meyer was one of the leading psychiatrists in the United States and head of the new psychiatry department and Phipps Clinic at Johns Hopkins University in Baltimore, Maryland.

William Rush Dunton, a supporter of the National Society for the Promotion of Occupational Therapy, now the American Occupational Therapy Association, sought to promote the ideas that occupation is a basic human need, and that occupation is therapeutic. From his statements came some of the basic assumptions of occupational therapy, which include:

• Occupation has a positive effect on health and well-being.
• Occupation creates structure and organizes time.
• Occupation brings meaning to life, culturally and personally.
• Occupations are individual. People value different occupations.

These assumptions have been developed over time and are the basis of the values that underpin the Codes of Ethics issued by the national associations. The relevance of occupation to health and well-being remains the central theme.

In the 1950s, criticism from medicine and the multitude of disabled World War II veterans resulted in the emergence of a more reductionistic philosophy. While this approach led to developments in technical knowledge about occupational performance, clinicians became increasingly disillusioned and re-considered these beliefs. As a result, client centeredness and occupation have re-emerged as dominant themes in the profession. Over the past century, the underlying philosophy of occupational therapy has evolved from being a diversion from illness, to treatment, to enablement through meaningful occupation.

Three commonly mentioned philosophical precepts of occupational therapy are that occupation is necessary for health, that its theories are based on holism and that its central components are people, their occupations (activities), and the environments in which those activities take place. However, there have been some dissenting voices. Mocellin, in particular, advocated abandoning the notion of health through occupation as he proclaimed it obsolete in the modern world. As well, he questioned the appropriateness of advocating holism when practice rarely supports it. Some values formulated by the American Occupational Therapy Association have been critiqued as being therapist-centric and do not reflect the modern reality of multicultural practice.

In recent times occupational therapy practitioners have challenged themselves to think more broadly about the potential scope of the profession, and expanded it to include working with groups experiencing occupational injustice stemming from sources other than disability. Examples of new and emerging practice areas would include therapists working with refugees, children experiencing obesity, and people experiencing homelessness.

Practice frameworks

An occupational therapist works systematically with a client through a sequence of actions called the occupational therapy process. There are several versions of this process as described by numerous scholars. All practice frameworks include the components of evaluation (or assessment), intervention, and outcomes.This process provides a framework through which occupational therapists assist and contribute to promoting health and ensures structure and consistency among therapists.

The Occupational Therapy Practice Framework (OTPF) is the core competency of occupational therapy in the United States.The OPTF framework is divided into two sections: domain and process. The domain includes environment, client factors, such as the individual's motivation, health status, and status of performing occupational tasks. The domain looks at the contextual picture to help the occupational therapist understand how to diagnose and treat the patient. The process is the actions taken by the therapist to implement a plan and strategy to treat the patient.

The Canadian Model of Client Centered Enablement (CMCE) embraces occupational enablement as the core competency of occupational therapy and the Canadian Practice Process Framework (CPPF) as the core process of occupational enablement in Canada.The Canadian Practice Process Framework (CPPF) has eight action points and three contextual element which are: set the stage, evaluate, agree on objective plan, implement plan, monitor/modify, and evaluate outcome. A central element of this process model is the focus on identifying both client and therapists strengths and resources prior to developing the outcomes and action plan.

Occupations

According to the American Occupational Therapy Association’s (AOTA) Occupational Therapy Practice Framework: Domain and Process, 3rd Edition (OTPF-3), an occupation is defined as any type of meaningful activity in which one engages in order to “occupy” one's time. These occupations can be goal-directed, task-oriented, purposeful, culturally relevant, role specific, individually tailored, and/or community-oriented, depending on one’s values, beliefs, context, and environment. The following are examples of such occupations:

• Activities of daily living (ADLs)
  • o The OTPF-3 defines ADLs as daily activities that are required to take care of one’s self and body, which are instrumental to one’s health, well-being, and social participation.
    • • Examples of ADL’s include: bathing, showering, toileting and toilet hygiene, dressing, swallowing/eating, feeding, functional mobility, personal hygiene and grooming, and sexual activity.
• Instrumental activities of daily living (IADLs)
  • o The OTPF-3 defines IADLs as daily activities that “support daily life within the home and community that often require more complex interactions than those used in ADLs”.
    • • Examples of IADLs include: Care of others, Care of pets, Child rearing, Communication management, Driving and community mobility, Financial management, Health management and maintenance, Home establishment and managements, Meal preparation and cleanup, Medication management, Religious and spiritual activities and expression, Safety and emergency maintenance, Shopping
• Rest and sleep
  • o The OTPF-3 defines rest and sleep as “activities related to obtaining restorative rest and sleep to support healthy, active engagement in other occupations”.
    • • Examples of rest and sleep include: Rest, sleep preparation, and sleep participation
• Education
  • o The OTPF-3 defines education as the activities that are needed to support one's learning, participation, and accessibility within an educational environment.
    • • Examples of education include: formal education participation, informal personal education needs or interests exploration (beyond formal education), and informal personal education participation.
• Work
  • o Employment interests and pursuits
    • • The OTPF-3 cites Mosey (1996, pg. 423) as how an individual selects work opportunities by their likes, dislikes, possible limitations, and assets.
  • o Employment seeking and acquisition
    • • The OTPF-3 defines this aspect of work as the opportunity for one to advocate for oneself along with completing, submitting, and reviewing application materials. The preparation involved for interviews, the act of participating in an interview, as well as following up after an interview. And lastly, the act of participating
  • o Job performance
    • • The OTPF-3 defines this aspect of work as how an individual carries out their job. Examples given are: the way in which a person carries out their job requirements i.e. work skills, work patterns, time management, interactions and relationships with coworkers/managers/customers, supervision, production, initiation, etc.
  • o Retirement preparation and adjustment
    • • The OTPF-3 defines this aspect of work as how an individual adjusts to their new role that includes a vocational interests and opportunities. The opportunity for individuals to develop and enhance interests and skills.
  • o Volunteer exploration
    • • The OTPF-3 defines this aspect of work as the opportunity for an individual to discover community causes, organizations, or opportunities in which they can they can participate without pay that meets their personal interests, skills, location
• Play
  • • Play exploration
    • • The OTPF-3 defines this aspect of work as the opportunity for an individual to discover community causes, organizations, or opportunities in which they can they can participate without pay that meets their personal interests, skills, location
  • o Play participation
    • • The OTPF-3 defines this aspect of play as the individual’s participation in the selected method of play. How an individual is able to balance play with their other occupations. This area also addresses how a person gathers the necessary components for play and uses the equipment appropriately.
• • Leisure
  • o Leisure exploration
    • • The OTPF-3 identifies this aspect of leisure as the individual’s identification of interests, skills, opportunities, and activities that are appropriate.
  • o Leisure participation
    • • The OTPF-3 identifies this aspect of leisure as the individuals activity in planning, and participating in leisure activities that are appropriate. The capacity to maintain a balance between leisure and other occupation as well as using the equipment necessary appropriately.
• • Social participation
  • o Community
    • • The OTPF-3 defines this aspect of social participation as successful interaction through engagement in activities with a group (i.e. neighborhood, workplace, school, religious or spiritual group).
  • o Family
    • • The OTPF-3 cites Mosey (1996 p. 340) and defines this aspect of social participation as successful interaction within a familial role.
  • o Peer, friend
    • • The OTPF-3 defines this aspect of social participation as the distinctive levels of interaction and closeness which can include engagement in desired sexual activity.

Practice settings

According to the 2015 Salary and Workforce Survey by the American Occupational Therapy Association, occupational therapists work in a wide-variety of practice settings including: hospitals (26.6%), schools (19.9%), long term care facilities/skilled nursing facilities (19.2%), free-standing outpatient (10.7%), home health (6.8%), academia (6.1%), early intervention (4.6%), mental health (2.4%), community (2), and other (15%). Recently, there is a trend of OTs moving towards working in the hospital setting and in the long-term care facilities/skilled nursing facilities setting, comprising 46% of the OT workforce.

The Canadian Institute for Health Information (CIHI) found that between 2006-2010 nearly half (45.6%) of occupational therapists worked in hospitals, 31.8% worked in the community, and 11.4% worked in a professional practice.

Areas of practice

The broad spectrum of OT practice makes it difficult to categorize the areas of practice, especially considering the differing health care systems globally. In this section, the categorization from the American Occupational Therapy Association is used.

Children and youth

Platform swing with tire used during occupational therapy with children

In 1951, Joan Erikson became director of activities for the “severely disturbed children and young adults” at the Austen Riggs Center. At that time, “occupational therapy” was used “for keeping patients busy on useless tasks.” Erikson “brought in painters, sculptors, dancers, weavers, potters and others to create a program that provided real therapy.”

Occupational therapists work with infants, toddlers, children, and youth and their families in a variety of settings including schools, clinics, and homes. Occupational therapists assist children and their caregivers to build skills that enable them to participate in meaningful occupations. These occupations may include: feeding, playing, socializing, and attending school.

Occupational therapy with children and youth may take a variety of forms. For example:

• Promoting a wellness program in schools to prevent childhood obesity
• Facilitating handwriting development in school-aged children
• Providing individualized treatment for sensory processing difficulties
• Teaching coping skills to a child with generalized anxiety disorder

Occupational therapists work in the school setting as a related service for children with an Individual Education Plan (IEP). “Related services means transportation and such developmental, corrective, and other supportive services as are required to assist a child with a disability to benefit from special education, and includes speech-language pathology and audiology services, interpreting services, psychological services, physical and occupational therapy, recreation, including therapeutic recreation, early identification and assessment of disabilities in children, counseling services, including rehabilitation counseling, orientation and mobility services, and medical services for diagnostic or evaluation purposes.” As a related service, occupational therapists work with children with varying disabilities to address those skills needed to access the special education program and support academic achievement and social participation throughout the school day (AOTA, n.d.-b). In doing so occupational therapists help children to fulfill their role as students and prepare them to transition to post-secondary education, career and community integration (AOTA, n.d.-b). Occupational therapists have specific knowledge to increase participation in school routines throughout the day, including: • Modification of the school environment to allow physical access for children with disabilities • Provide assistive technology to support student success • Helping to plan instructional activities for implementation in the classroom • Support the needs of students with significant challenges such as helping to determine methods for alternate assessment of learning • Helping students develop the skills necessary to transition to post-high school employment, independent living and/or further education (AOTA, n.d.-a)

Health and wellness

The practice area of Health and Wellness is emerging steadily due to the increasing need for wellness-related services in occupational therapy. A connection between wellness and physical health, as well as mental health, has been found; consequently, helping to improve the physical and mental health of clients can lead to an increase in overall well-being.

As a practice area, health and wellness can include a focus on:

• Prevention of disease and injury
• Prevention of secondary conditions (co-morbidity)
• Promotion of the well-being of those with chronic illnesses
• Reduction of health care disparities or inequalities
• Enhancement of factors that impact quality of life
• Promotion of healthy living practices, social participation, and occupational justice

Occupational therapist conducting a group intervention on interpersonal relationship building

Mental health

Mental health and the moral treatment era have been recognized as the root of occupational therapy. According to the World Health Organization, mental illness is one of the fastest growing forms of disability. OTs focus on prevention and treatment of mental illness in all populations. In the U.S., military personnel and veterans are populations that can benefit from occupational therapy, but currently this is an under served practice area.

Mental health illnesses that may require occupational therapy include schizophrenia and other psychotic disorders, depressive disorders, anxiety disorders, eating disorders, trauma- and stressor-related disorders (e.g. post traumatic stress disorder or acute stress disorder), obsessive-compulsive and related disorders such as hoarding, and neurodevelopmental disorders such as autism spectrum disorder, attention deficit/hyperactivity disorder and learning disorders.

Productive aging

Occupational therapists work with older adults to maintain independence, participate in meaningful activities, and live fulfilling lives. Some examples of areas that occupational therapists address with older adults are driving, aging in place, low vision, and dementia or Alzheimer's Disease (AD). When addressing driving, driver evaluations are administered to determine if drivers are safe behind the wheel. To enable independence of older adults at home, occupational therapists perform falls risk assessments, assess clients functioning in their homes, and recommend specific home modifications. When addressing low vision, occupational therapists modify tasks and the environment. While working with individuals with AD, occupational therapists focus on maintaining quality of life, ensuring safety, and promoting independence.

Visual Impairment

Visual impairment is one of the top 10 disabilities among American adults. Occupational therapists work with other professions, such as optometrists, ophthalmologists, and certified low vision therapists, to maximize the independence of persons with a visual impairment by using their remaining vision as efficiently as possible. AOTA’s promotional goal of “Living Life to Its Fullest” speaks to who people are and learning about what they want to do, particularly when promoting the participation in meaningful activities, regardless of a visual impairment. Populations that may benefit from occupational therapy includes older adults, persons with traumatic brain injury, adults with potential to return to driving, and children with visual impairments. Visual impairments addressed by occupational therapists may be characterized into 2 types including low vision or a neurological visual impairment. An example of a neurological impairment is a cortical visual impairment (CVI) which is defined as “...abnormal or inefficient vision resulting from a problem or disorder affecting the parts of brain that provide sight”. The following section will discuss the role of occupational therapy when working with the visually impaired. Occupational therapy for older adults with low vision includes task analysis, environmental evaluation, and modification of tasks or the environment as needed. Many occupational therapy practitioners work closely with optometrists and ophthalmologists to address visual deficits in acuity, visual field, and eye movement in people with traumatic brain injury, including providing education on compensatory strategies to complete daily tasks safely and efficiently. Adults with a stable visual impairment may benefit from occupational therapy for the provision of a driving assessment and an evaluation of the potential to return to driving. Lastly, occupational therapy practitioners enable children with visual impairments to complete self care tasks and participate in classroom activities using compensatory strategies.

Adult Rehabilitation

Occupational therapists address the need for rehabilitation following an injury or impairment. When planning treatment, occupational therapists address the physical, cognitive, psychosocial, and environmental needs involved in adult populations across a variety of settings.
Occupational therapy in adult rehabilitation may take a variety of forms:

• Working with adults with autism at day rehabilitation programs to promote successful relationships and community participation through instruction on social skills
• Increasing the quality of life for an individual with cancer by engaging them in occupations that are meaningful, providing anxiety and stress reduction methods, and suggesting fatigue management strategies
• Coaching individuals with hand amputations how to put on and take off a myoelectrically controlled limb as well as training for functional use of the limb
• As for paraplegics, there are such things as sitting cushion and pressure sore prevention. Prescription of these aids is the common job for paraplegics.
• Using and implementing new technology such as speech to text software and Nintendo Wii video games
• Communicating via telehealth methods as a service delivery model for clients who live in rural areas
• Working with adults who have had a stroke to regain strength, endurance, and range of motion on their affected side.

Travel occupational therapy

Because of the rising need for occupational therapists in the U.S., many facilities are opting for travel occupational therapists—who are willing to travel, often out of state, to work temporarily in a facility. Assignments can range from 8 weeks to 9 months, but typically last 13–26 weeks in length. Most commonly (43%), travel occupational therapists enter the industry between the ages of 21–30.

Work and industry

Occupational therapists work with clients who have had an injury and are returning to work. OTs perform assessments to simulate work tasks in order to determine best matches for work, accommodations needed at work, or the level of disability. Work conditioning and work hardening are interventions used to restore job skills that may have changed due to an illness or injury. Occupational therapists can also prevent work related injuries through ergonomics and on site work evaluations.

Occupational Justice

The practice area of occupational justice relates to the “benefits, privileges and harms associated with participation in occupations” and the effects related to access or denial of opportunities to participate in occupations. This theory brings attention to the relationship between occupations and health. The skills of an occupational therapist enable them to serve as advocates for systemic change, impacting institutions, policy, and entire populations. Examples of populations that experience occupational injustice include:

• Refugees
• Prisoners
• Homeless persons
• Survivors of natural disasters

For example, the role of an occupational therapist working with refugees could include:

• addressing developmental delays and psychological trauma of children through participation in the occupation of play
• training workers at refugee camps who work with children on common issues associated with child forced migration and strategies to address these issues through occupation
• educating and lobbying politicians and the public on the effects of forced migration on children and what can be done

Community Based therapy

Community-Based Practice

As occupational therapy (OT) has grown and developed, community based practice has blossomed from an emerging area of practice to a fundamental part of occupational therapy practice (Scaffa & Reitz, 2013). Community based practice allows for OTs to work with clients and other stakeholders such as families, schools, employers, agencies, service providers, stores, day treatment and day care and others who may influence the degree of success the client will have in participating. It also allows the therapist to see what is actually happening in the context and design interventions relevant to what might support the client in participating and what is impeding her or him from participating. Community-based practice crosses all of the categories within which OTs practice from physical to cognitive, mental health to spiritual, all types of clients may be seen in community based settings. The role of the OT also may vary, from advocate to consultant, direct care provider to program designer, adjunctive services to therapeutic leader.

Occupational Injustice

In contrast, occupational injustice relates to conditions wherein people are deprived, excluded or denied of opportunities that are meaningful to them. Types of occupational injustices and examples within the OT practice include:

• Occupational deprivation: The exclusion from meaningful occupations due to external factors that are beyond the person’s control. As an example, a person who has difficulties with functional mobility may find it challenging to reintegrate into the community due to transportation barriers.
• Occupational apartheid: The exclusion of a person in chosen occupations due to personal characteristics such as age, gender, race, nationality or socioeconomic status. An example can be seen in children with developmental disabilities from low socioeconomic backgrounds whose families would opt out from therapy due to financial constraints.
• Occupational marginalization: Relates to how implicit norms of behavior or societal expectations prevents a person from engaging in a chosen occupation. As an example, a child with physical impairments may only be offered table-top leisure activities instead of sports as an extracurricular activity due to the functional limitations caused by his physical impairments.
• Occupational imbalance: The limited participation in a meaningful occupation brought about by another role in a different occupation. This can be seen in the situation of a caregiver of a person with disability who also has to fulfill other roles such as being a parent to other children, a student or a worker.
• Occupational alienation: The imposition of an occupation which does not hold meaning for that person. In the OT profession, this manifests in the provision of rote activities which does not really relate to the goals or the interest of the client.

Within occupational therapy practice, injustice may ensue in situations wherein professional dominance, standardized treatments, laws and political conditions create a negative impact on the occupational engagement of our clients. Awareness of these injustices will enable the therapist to reflect on his own practice and think of ways in approaching their client’s problems while promoting occupational justice.

Education

Worldwide, there is a range of qualifications required to practice occupational therapy. Requirements can range from a bachelor’s degree (e.g. Australia), a master’s degree (e.g. Canada) and more recently an Occupational therapy doctorate (OTD) is becoming more common (e.g. United states). Additionally, in the United States, there is also an option to become a certified occupational therapy assistant (COTA), which can be achieved from completing an associates degree from an accredited educational program. It can be noted that the educational requirement to have a doctoral degree for practice in occupational therapy is not required until 2027 in the United States, and practitioners with a lesser degree achieved before 2027 will be grandfathered into practice. In conjunction with the educational component of occupational therapy education, there exists a fieldwork component for all educational programs which is a requirement to achieve a degree in OT. All OT education program include periods of clinical education and fieldwork practicing with evaluation and treatment of clients in various clinical settings. Some examples of fieldwork experience include but are not limited to working with stroke patients in rehabilitation hospitals, developmental treatment with children in the community, working with olders adults with dementia in skilled nursing homes, and mental health settings. The profession of occupational therapy is based on a wide theoretical and evidence based background. The OT curriculum focuses on the theoretical basis of occupation through multiple facets of science, including occupational science, anatomy, physiology, biomechanics, and neurology. In addition, this scientific foundation is integrated with knowledge from psychology, sociology and more. All of the educational programmes around the world need to meet the minimum standard of the World Federation of Occupational Therapy (WFOT). The WFOT concerns that occupational therapists will have access to further professional education, higher degrees and post professional training. Occupational therapists are also participating in research in various areas of practice. In the United States, Canada and other countries around the world, there is a licensure requirement. In order to obtain OT license, the Occupational therapists need to graduate from an accredited OT educational program, complete their fieldwork requirements and to apply and pass national certification examination.

Theoretical frameworks

Occupational therapists use theoretical frameworks to frame their practice. Note that terminology differs between scholars. An incomplete list of theoretical bases for framing a human and their occupations include the following:

Generic Models

Generic models are the overarching title given to a collation of compatible knowledge, research and theories that form conceptual practice. More generally they are defined as "those aspects which influence our perceptions, decisions and practice".

Person Environment Occupation Performance Model

• The Person Environment Occupation Performance model (PEOP) was originally published in 1991 (Charles Christiansen & M. Carolyn Baum) and describes an individual's performance based on four elements including: environment, person, performance and occupation. The model focuses on the interplay of these components and how this interaction works to inhibit or promote successful engagement in occupation.

Occupation-Focused Practice Models

• Occupational Therapy Intervention Process Model (OTIPM) (Anne Fisher and others)
• Occupational Performance Process Model (OPPM)
• Model of Human Occupation (MOHO) (Gary Kielhofner and others)
  • MOHO was first published in 1980. It explains how people select, organise and undertake occupations within their environment. The model is supported with evidence generated over thirty years and has been successfully applied throughout the world.
• Canadian Model of Occupational Performance and Engagement (CMOP-E)
• Occupational Performances Model – Australia (OPM-A) (Chris Chapparo & Judy Ranka)
  • The OPM(A) was conceptualized in 1986 with its current form launched in 2006. The OPM(A) illustrates the complexity of occupational performance, the scope of occupational therapy practice, and provides a framework for occupational therapy education.
• Kawa (River) Model (Michael Iwama)

Frames of Reference

Frames of Reference are so called as they are an additional knowledge base for the Occupational Therapist to develop their treatment and/or assessment of a patient or client group. Though there are Conceptual Models (listed above) that allow the Therapist to conceptualise the Occupational Roles of the patient, it is often important to use further reference to embed Clinical Reasoning. Therefore, many Occupational Therapists (OTs) will use additional Frames of Reference to both assess and then develop therapy goals for their patients and/or service users.

Biomechanical Frame of Reference

• The Biomechanical Frame of Reference is primarily concerned with motion during occupation. It is used with individuals who experience limitations in movement, inadequate muscle strength or loss of endurance in occupations. The Frame of Reference was not originally compiled by Occupational Therapists, and therapists should translate it to the Occupational Therapy perspective, to avoid the risk of movement or exercise becoming the main focus.

Rehabilitative (compensatory)

Neurofunctional (Gordon Muir Giles and Clark-Wilson)

Dynamic Systems Theory

Client-Centered Frame of Reference

• This Frame of Reference is developed from the work of Carl Rogers. It views the client as the center of all therapeutic activity, and the client's needs and goals direct the delivery of the Occupational Therapy Process.

Cognitive-Behavioural Frame of Reference
 
Ecology of Human Performance Model

The Recovery Model
 
Sensory Integration: Sensory integration

• Sensory integration framework is commonly implemented in clinical, community, and school-based occupational therapy practice. It is most frequently used with children with developmental delays and developmental disabilities such as autism spectrum disorder and dyspraxia. Core features of sensory integration in treatment include providing opportunities for the client to experience and integrate feedback using multiple sensory systems, providing therapeutic challenges to the client’s skills, integrating the client’s interests into therapy, organizing of the environment to support the client’s engagement, facilitating a physically safe and emotionally supportive environment, modifying activities to support the client’s strengths and weaknesses, and creating sensory opportunities within the context of play to develop intrinsic motivation. While sensory integration is traditionally implemented in pediatric practice, there is emerging evidence for the benefits of sensory integration strategies for adults.

ICF

The International Classification of Functioning, Disability and Health (ICF) is a framework to measure health and ability by illustrating how these components impact one's function. This relates very closely to the Occupational Therapy Practice Framework, as it is stated that "the profession's core beliefs are in the positive relationship between occupation and health and its view of people as occupational beings". The ICF is built into the 2nd edition of the practice framework. Activities and participation examples from the ICF overlap Areas of Occupation, Performance Skills, and Performance Patterns in the framework. The ICF also includes contextual factors (environmental and personal factors) that relate to the framework's context. In addition, body functions and structures classified within the ICF help describe the client factors described in the Occupational Therapy Practice Framework. Further exploration of the relationship between occupational therapy and the components of the ICIDH-2 (revision of the original International Classification of Impairments, Disabilities, and Handicaps (ICIDH), which later became the ICF) was conducted by McLaughlin Gray.

It is noted in the literature that occupational therapists should use specific occupational therapy vocabulary along with the ICF in order to ensure correct communication about specific concepts. The ICF might lack certain categories to describe what occupational therapists need to communicate to clients and colleagues. It also may not be possible to exactly match the connotations of the ICF categories to occupational therapy terms. The ICF is not an assessment and specialized occupational therapy terminology should not be replaced with ICF terminology. The ICF is an overarching framework for current therapy practices.