1.3.1 Basic Principles

A combination of factors produces motivation. For example, a low level of body nutrients tends to increase feeding motivation, as does the presence of tempting food. Such things as food, drugs, and sexual stimuli constitute incentives, and they, together with internal factors, form our focus. Following a period of food deprivation, a rat pressing a lever for food is motivated by the combination of the depleted nutrient state of its body and the incentive available as reward for lever pressing. Conditional stimuli associated with food presentation (e.g. the sound of food being presented) also play a role. The focus of Chapter 4 is on incentives and how their power is modulated by events inside the animal.

The variability of behaviour is one reason that we need a concept of motivation. For example, sometimes we have a strong motivation towards a particular food, but after considerable ingestion of it, the motivation declines to zero. We might even find the prospect of ingesting more of it to be unpleasant. Understanding what causes such changes in reactivity to an incentive forms an important part of the present study.

In, for example, feeding, drinking, and sex, the term appetitive phase of motivation and behaviour is used to describe the behaviour leading to a goal (Salamone & Correa, Reference Salamone and Correa2024). This is in distinction to the consummatory phase of actually eating, drinking, or copulating, that is, after the goal has been reached. For the appetitive phase, Epstein (Reference Epstein and Pfaff1982) uses the term individuation; that is, individuals can exploit a variety of means to achieve their goal. The consummatory phase is usually more stereotyped.

Motivation can arise both internally within the brain and externally in the environment. Imagine that you form a goal in your conscious mind and then pursue it, that is, purposive goal-directed behaviour. For example, you might get a sudden desire to eat chocolate and search for it. Chapter 5 looks at this goal-directed aspect of motivation and links it to the role of incentives.

1.3.2 Distinction with Reflexes and Instincts

To form a contrast with motivation, Epstein (Reference Epstein and Pfaff1982) reminds us of what reflexes are (p. 25):

The pupil light reflex of the eye and the knee-jerk reflex are examples. Epstein asks what the adequate stimuli are to trigger three behaviours seen in rats: sleeping, grooming. and locomotion. He poses two questions and suggests an answer (p. 26):

As Epstein acknowledges, external factors can exert a powerful role in the control of each of these behaviours. However, where it concerns motivation, external stimuli do not simply elicit stereotyped behaviour from a passive nervous system. The animal can also instigate flexible goal-directed behaviour.

At times, external stimuli will take a commanding role in behaviour (e.g. presentation of attractive food to a hungry rat, appearance of a predator), while at other times, internal factors can dominate. Examples of such internal factors include representations of events in the world held in memory and the process underlying apparently spontaneous instigation of behaviour.

When psychologists speak of external factors triggering behaviour, an important complication needs to enter the picture. The action of external factors is determined in part by internal factors. For example, the capacity of food to trigger feeding depends upon:

• the level of body nutrients, as already noted;

• the associations formed with the particular food; for example, an otherwise acceptable food can be devalued if illness following its ingestion is experienced (Chapter 9).

Epstein distinguishes between motivation and instinct. In instincts, an animal is not sensitive to the consequences of its behaviour. It might get stuck into repeating the same unsuccessful motor pattern, while the observer can see that a different motor pattern would have permitted reaching the functional goal. For example, feeding flies were said to employ a rigid pattern of mechanical acts.

Motivation is associated with the two fundamental qualities of (i) expectations of what will appear at the goal and (ii) affect (e.g. human pleasure at reaching the goal).

1.3.3 The Fly as a Simple Model

The blowfly can illustrate some basic properties of motivation, albeit not its flexibility (Dethier, Reference Dethier1966; Moss & Dethier, Reference Moss and Dethier1983). Researchers studied the activity of the fly’s chemoreceptors when presented with a sugar solution. Several characteristics of motivation can be exemplified (Dethier, Reference Dethier1966; Moss & Dethier, Reference Moss and Dethier1983).

• Motivation is based upon internal and external factors.

• There is a variability of responding to nutrients. Following ingestion, the animal’s sensory neurons still respond to the signal set up by the chemoreceptors at the mouth. However, after substantial ingestion, the fly no longer reacts to this signal with feeding.

• Ingestion changes the internal state, switching off feeding behaviour. In this species, inhibition is based upon gut fullness.

• With food deprivation, the fly becomes less discriminating and as satiety approaches it becomes more discriminating (‘finicky’).

1.3.4 Competition for Control

Doing one thing is often incompatible with doing something else. So, there is often competition for the control of behaviour.

Consider first competition within a given motivation. You might have no intention to eat chocolate, even trying to resist it. However, your eyes spot some and you are drawn to this incentive and ingest it. In some cases, such ‘capture’ might well have been instigated at a level below your conscious awareness, so the expression ‘automatic’ would apply (Heatherton & Wagner, Reference Heatherton and Wagner2011). A major task in the study of motivation is how conscious goal-directed behaviour and the ‘magnetic pulling’ of behaviour towards attractive incentives jointly determine behaviour (Chapter 5).

An example of this is the marshmallow effect (Mischel, Reference Mischel2014). Here the competition is between responding to the immediately available incentive of one marshmallow or waiting patiently for the better incentive (e.g. two marshmallows) that is only available after a delay (Chapter 5).

Let us turn now to competition between motivations. The relative strengths of different candidate motivations determine which is expressed in behaviour and which is/are inhibited. For example, a rat might need both food and water but has to go to different locations to obtain them. A low level of body nutrients and/or the availability of attractive food would tend to exert a bias towards expressing feeding motivation. So, there is a process of prioritization and making choices as a feature of the goal-directed nature of motivation.

1.3.5 Sensitization of Responses

As noted, with flexible goal-directed behaviour the nature of the behaviour shown can vary very widely according to circumstances. However, a given motivation can also sensitize particular species-typical responses. These are the relatively stereotyped responses that have proven to be adaptive to the species in its evolutionary history (Gallistel, Reference Gallistel1980; Hinde, Reference Hinde1966). For example, in the presence of a male rat, a sexually receptive (‘motivated’) female rat will show darting movements and ear-wiggling. These are followed by a stereotyped body-arching response, known as the lordosis posture, which facilitates intromission (Beach, Reference Beach1947) (Figure 1.1). In fear, where escape is not possible, a rat will show a species-typical response of freezing (Bolles, Reference Bolles1970).

Figure 1.1

Lordosis response of female rat. Note the arched body posture.

Source: Photograph courtesy of James G. Pfaus.

1.3.6 The Link to Instrumental Behaviour and Reinforcement

The term instrumental conditioning describes a form of conditioning in which behaviour is sensitive to the past consequences of showing the behaviour. The maze can exemplify this. First, a rat is deprived of food for, say, 24 hours, to increase its motivation towards food. The rat is placed at the start of a T-maze, and it runs along the initial arm. As shown in Figure 1.2, if it turns right, it gets food. If it turns left, it gets to an empty dish.Footnote ¹ Over a number of trials, hungry rats reliably come to turn right each time. They also increase their speed of running, indicative of increased motivation towards the goal. The procedure of giving food is said to reinforce the behaviour of turning right.Footnote ² The animal’s behaviour is literally instrumental in determining the outcome.

Figure 1.2

A rat in a T-maze with food in the right arm.

Now consider the Skinner box (Figure 1.3), which has been extensively tested with rats and pigeons. Suppose that, when a hungry animal presses a lever or pecks a key to earn food, the consequence is one of increasing its tendency to repeat this behaviour in the future. Researchers measure the reinforcement value of the food by observing that the frequency of lever pressing or key pecking increases over days. The food would be described as ‘positive reinforcement’, since it is something appetitive that is given conditional upon (often expressed as ‘contingent upon’) the behaviour.

Figure 1.3

Skinner box.

Figure 1.3 Long description

A response lever is shown together with a supply of food pellets. Typically, the situation is arranged so that when the rat presses the lever, a pellet of food falls into a food dispenser. There is a light present in the Skinner box.

Now suppose that the Skinner box is made into a very noisy environment, where a non-hungry rat is placed. The rat learns to lever-press, with each press terminating the noise for just a few seconds. The noise would be described as ‘negative reinforcement’ since behaviour is strengthened by the removal of this aversive stimulus.

Consider a hungry rat placed in a Skinner box. If the rat presses the lever, a pellet of food drops into the food tray. In principle, over a series of daily trials, one could deprive the rat of food for 23 hours, leave it in the box for an hour each day, and see what happens. The rat might ‘accidentally’ press the lever on occasion and obtain a pellet of food. However, it could take a long time for behaviour to come under the control of the food (‘reinforcement’), and so the process is speeded up by means of shaping.

The term ‘shaping’ derives from an analogy with a potter shaping a vase. An unformed lump of clay is spun on a wheel and the potter gradually shapes it into a well-formed vase. By analogy, the rat is shaped by the careful timing of when food pellets are given, such that an ‘unformed’ (‘naïve’) rat comes to achieve mastery over lever pressing.

First, the rat is given some free rewards. Then receiving a reward is contingent upon the rat’s responses. The rat is shaped by being given a reward each time it is near to the lever. After that, the rat needs to contact the lever, lower the lever, and then make a full press of the lever. At this stage, control is in the hands of the rat.

As with the maze, the Skinner box exemplifies instrumental conditioning. However, it is a special form of instrumental conditioning, known as operant conditioning. Contrast the maze and the Skinner box. With the maze, the experienter needs to place the rat at the start box and lift it out at the goal box. By contrast, following training, the animal in the Skinner box determines its own actions with no intervention by the experimenter.

Teitelbaum (Reference Teitelbaum and Honig1966) wrote:

According to Teitelbaum, the defining requirement underlying a purposive act is the existence of a motivational state. This state determines the strength of the tendency to pursue a particular goal. So, what does this rule out as an example of motivation? Behaviour that is the predictable consequence of a given stimulus. Teitelbaum (Reference Teitelbaum, Honig and Staddon1977) argues:

Teitelbaum uses the combination of operant behaviour and the notion of reinforcement as the criterion for the existence of motivation. According to him, such evidence is obtained when operant behaviour is directed to an appropriate goal object. He claims that this criterion rules out the existence of motivation in the case of feeding in the fly (described in Section 1.3.3).Footnote ³ However, with advances in technology, there are claims that flies can show operant conditioning (Brembs, Reference Brembs2011).

1.3.7 Wanting, Pleasure, and Displeasure

Human motivation is tied closely to notions of wanting, pleasure, and displeasure. There is the wanting phase of motivation and then often pleasure when the goal is attained. Failure to attain a goal can be associated with displeasure. Chapter 6 will discuss such wanting and pleasure/displeasure. It will suggest that with suitable caution these terms can be extrapolated to non-humans. Pleasure comes into focus when we examine how behaviour (e.g. drinking) is controlled and bodily parameters (e.g. level of body fluids) are regulated. The term affect refers to positive states of psychological pleasure or negative states of displeasure (e.g. pain) and will be employed extensively. This is the topic of Chapter 7.

1.5.1 An Ethological Approach

The study of animal behaviour from a zoological perspective is known as ‘ethology’.Footnote ⁴ Within this science, the idea was developed that there are four different types (‘levels’) of explanation that can be brought to a given observation of behaviour (Tinbergen, Reference Tinbergen1963).

1. 1. Causal explanation This describes what causes behaviour in the here-and-now. It is in terms of the causation by events in the environment that impinge upon the animal’s sense organs and events in the body. It is sometimes expressed in terms of the physiology of the brain.

2. 2. Functional explanation This type of explanation is offered to account for how a given behaviour emerged in evolution in terms of the advantage that it conferred on genetic perpetuation.

3. 3. Evolutionary explanation This is in terms of the presence of a particular behaviour in the repertoire of a given species. In which related species is it present or absent?

4. 4. Developmental/learning explanation This concerns the history of behaviour in terms of the life of an individual animal. For example, did the behaviour simply unfold with increasing age or was learning required for it to appear?

In the present study, the emphasis is upon the causal level of explanation. However, in order to gain a more complete picture, occasionally reference will be made to one or more of the other levels.

Two examples illustrate how more than one level can be brought to explain a given phenomenon. First, there is the hypothesis termed evolutionary mismatch. This refers to the fact that evolution happened in an environment very different from the contemporary one. In many respects, our brains reflect what worked in the early environment. For example, we tend to fear snakes and spiders more than cars or guns (Chapter 13).

So, in this particular case:

• a causal explanation is in terms of the brain’s mechanisms of processing frightening images and the production of a response;

• an evolutionary explanation is in terms of the kind of environment in which this tendency evolved, and which species exhibit it;

• a functional explanation concerns the advantage served by such a process;

• a developmental/learning explanation is in terms of whether learning is needed for such fears to be expressed.

As the second example, the term taste-aversion learning (the ‘Garcia effect’) refers to the situation where an animal ingests a particular substance, and some minutes or even hours later suffers gastric upset (Garcia & Koelling, Reference Garcia and Koelling1966). Typically, after this experience, the animal will be reluctant to ingest the substance again.

Taste-aversion learning can exemplify the false dichotomy of presenting evolution and learning as competitive explanations (Al-Shawaf, Reference Al-Shawaf2025). The underlying specialized mechanism represents an evolutionary adaptation: that is, something that contributes to the animal’s evolutionary success. However, exactly what is learned depends upon the individual animal’s experience with foods, that is, what made it sick. Given the vast array of different potential toxins associated with food, there is no way that evolutionary processes could yield a solution on exactly what to avoid.

At the level of causation, what was ranked as a positive incentive loses its value, so the substance no longer triggers an approach response. The substance typically acquires aversive properties and triggers rejection. The developmental/learning explanation is in terms of the experience of illness and the formation of an association with taste. There can be a long delay between taste and nausea. Following the experience, the animal’s memory is reorganized. At a functional level, this behaviour serves the advantage that in future the animal avoids ingesting a substance that could prove harmful or even lethal.

At an evolutionary level, consider the very wide range of species that exhibit this phenomenon, including rats and humans. It is also insightful to investigate whether there exist species that do not exhibit taste-aversion learning. One such species is the vampire bat (Ratcliffe et al., Reference Ratcliffe, Fenton and Galef2003), hardly a pleasing choice to meet in Chapter 1 but one that delivers much insight (Figure 1.4).

Figure 1.4

A vampire bat.

Source: Samuel Betkowski/Moment/Getty Images.

How might we make sense of this exception? Vampire bats live by sucking the blood of living animals. Therefore, seen in evolutionary history, it was unlikely that the blood that they ingested had ‘gone bad’. Related species of bat, which live from eating fruit and insects, do exhibit taste-aversion learning.

1.5.2 The Approach Adopted Here

My approach to explanation is something of a hybrid. It is based mainly in terms of observable phenomena: for example, behaviour and brain processes. That is to say, objective terms. However, subjective terms, such as pleasure and mood are also used in the explanations. This allows a more complete picture.

It is possible to develop theories of how motivation works without reference to the physical brain. However, such an approach has shortcomings.

• A theory might be proposed that seems to fit well to the behavioural observations. However, it might be incompatible with an understanding of brain processes. Clearly, it is desirable that so-called psychological models and theories are compatible with what is known about the brain.

• A good psychological theory can provide valuable insights into how brains work.

Hence, the present study will provide links to neural processes.

1.5.3 A Caution

In psychology, one of the most cited articles of all time is that of Maslow (Reference Maslow1943) in which he describes a hierarchy of needs (Figure 1.5). At the bottom of the pyramid (i.e. physiological level) are hunger, thirst, and shelter, all of which are needed for bodily survival. However, sex, which is not needed for bodily survival, is also placed at the bottom. Towards the top is ‘belongingness’, even though some people would place this above sex as a need (Baumeister & Leary, Reference Baumeister and Leary1995). The pyramid seems to confuse causation and function. Sex is needed but for genetic perpetuation not bodily survival.

Figure 1.5

An interpretation of Maslow’s hierarchy of needs.

Figure 1.5 Long description

At the base of the pyramid are physiological needs, bodily needs, example, hunger, thirst, shelter, sex, above the base level are safety needs, needs for security and protection, above this are social needs, belonging, second from top in the pyramid are esteem needs, internal and external esteem. Finally at the top of the pyramid are needs for self-actualization, growth and achieving potential.

1.6.1 Abnormal Motivation towards an Incentive

Obesity presents a serious problem for many people. Evidence points to the normal motivational processes underlying feeding being stretched abnormally. Interventions (e.g. surgical, pharmacological) can be sought to lower feeding motivation (Chapter 9). To be tolerable to patients, these need to be selective to feeding motivation and not act through some non specific route, such as creating nausea. Conversely, there can be serious problems of undereating as in anorexia nervosa, for which theories based on principles of motivation have been advanced (Loizou et al., Reference Loizou, Panagiotou, Zanos and Paraskevopoulos2024).

Addictions of various sorts present major personal, social, legal, and health problems (Chapters 17 and 18). Addictions reflect aberrations of basic motivational processes that evolved to deal with such things as feeding and sex. Based upon insights into motivation, psychologists understand how such hijacking of basic processes occurs (Felix & Flagel, Reference Felix and Flagel2024; Robinson & Berridge, Reference Robinson and Berridge2024). Treatments can be usefully informed by an understanding of these motivational processes.

1.6.2 Anger and Aggression

Sadly, violence is ever-present both within a society and between nations. Various theories have been proposed to account for this (Chapters 2 and 14). Lorenz (Reference Lorenz1950) argued that the internal contribution to the motivation of aggression can be modelled by the increase in pressure within a tank containing fluid (Chapter 2). This leads to the suggestion that acts of mock violence, for example, punching a pillow or playing violent video games, can lower such pressure and thereby lower the tendency to aggression. This belief is reflected in the folk recommendation to ‘let off steam’. However, modern theories suggest that the pressure model represents a false analogy, and that aggression begets aggression.

1.6.3 Loss of Motivation

Apathy represents a loss of motivation and can be better understood in terms of theories of motivation (Sinha et al., Reference Sinha, Manohar and Husain2013). In cases of severe depression, there might be a near total loss of motivation, not even enough to get the individual out of bed. There is now insight into how this condition arises in terms of loss of motivation and the role of the neurochemical dopamine (DA) (Treadway & Salamone, Reference Treadway, Salamone and Pizzagalli2022).

1.6.4 Incidental Spin-offs

Research into motivation that was based primarily upon drugs and feeding (Robinson & Berridge, Reference Robinson and Berridge1993) has provided some valuable insights into phenomena rarely described before under the heading of ‘motivation’ (Felix & Flagel, Reference Felix and Flagel2024). Some examples include attention (Grignolio et al., Reference Grignolio, Acunzo and Hickey2024) and autism (Kohls et al., Reference Kohls, Chevallier, Troiani and Schultz2012). Other examples are where there is suffering and help is needed, such as pain (Bruneau et al., Reference Bruneau, Frimerman, Verner, Sirois, Fournier, Scott, Perez, Shir and Martel2021), obsessive-compulsive disorder (Albertella et al., Reference Albertella, Le Pelley, Chamberlain, Westbrook, Fontenelle, Segrave, Lee, Pearson and Yücel2019), attention-deficit hyperactivity disorder (Rode et al., Reference Rode, Runnamo, Thunberg and Msghina2023), schizophrenia (Kapur, Reference Kapur2003), and Parkinson’s disease (Politis et al., Reference Politis, Loane, Wu, O’Sullivan, Woodhead, Kiferle, Lawrence, Lees and Piccini2013).

1.6.5 Pain

Pain was once regarded as something simply linked to tissue damage. The greater the tissue damage, the greater the pain; and, if the damage heals, the pain is lifted. Subsequent research has revealed the inadequacy of this explanation (Melzack & Wall, Reference Melzack and Wall1988). Of course, tissue damage is a principal contributor to pain. However, there can be tissue damage but little or no pain and, conversely, there can be serious pain with little evidence of any accompanying tissue damage.

Motivational factors play a role in pain (Chapter 15). Concepts of motivation and reward/ reinforcement are increasingly appearing in the literature on pain (Bolles & Fanselow, Reference Bolles and Fanselow1980; Fields, Reference Fields, Flor, Kalso and Dostrovsky2006; Rizvi et al., Reference Rizvi, Gandhi and Salomons2021).