Consummatory Behavior

Abstract

Consummatory behavior is a form of animal behavior: the stereotyped, goal-achieving act that completes a motivated sequence—the eating, the drinking, the copulation, the kill—toward which a variable appetitive search is directed. Wallace Craig drew the distinction in 1918, and it has organised the study of motivated behavior ever since: an appetitive phase that is flexible and goal-seeking, and a consummatory phase that is fixed and goal-achieving. This article sets out what the consummatory act is, how it is measured through the taste-reactivity test, and how modern neuroscience separates the hedonic ‘liking’ of consummation from the ‘wanting’ that drives the search. A worked example quantifies satiation as negative feedback; three demonstrations develop drive reduction, palatability, and the liking–wanting dissociation.

Keywords: consummatory behavior, appetitive behavior, taste reactivity

A rat that has been deprived of water is first restless. It moves about the cage, rears, sniffs, and samples surfaces—a flexible, searching activity with no fixed form. The moment its snout meets the spout, the behavior changes character entirely. The searching stops and a rhythmic, stereotyped lick begins, seven times a second, the same in every rat, and it continues until thirst is slaked. The first phase is appetitive; the second, the drinking itself, is consummatory. The two phases look different, are driven differently, and end differently, and telling them apart is the oldest organising idea in the study of motivated behavior.

This article treats the consummatory act as the terminal, goal-achieving component of a motivated sequence. It is the phase that reduces the drive and ends the episode: the swallow that follows the search for food, the copulation that follows courtship, the killing bite that ends a hunt. Because the consummatory act is relatively fixed in form and tied to a specific stimulus, it can be measured precisely—counted, timed, and scored—which has made it the behavioral readout for a century of work on motivation, reward, and the brain systems that generate pleasure.

What Consummatory Behavior Is

Consummatory behavior is the behavior that completes a motivated sequence by achieving its goal: the ingestion of food or water, the act of copulation, the killing and eating of prey. The term was coined by the comparative psychologist Wallace Craig, who separated every instinct into two parts—an appetite, the restless seeking that brings an animal into the right situation, and a consummatory action, the stereotyped act that ends the appetite and, in ending it, brings the sequence to rest (Craig, 1918). The word shares its root with consummate, to complete or bring to fulfilment; a consummatory act is the one that consummates the drive, not merely the one that consumes.

Two features define the consummatory act by contrast with the appetitive search that leads to it. First, it is relatively stereotyped: where the search is variable and shaped to circumstance, the consummatory act takes a fixed form—the lick, the chew, the copulatory pattern—that is much the same across individuals and occasions. Second, it is terminal and drive-reducing: it occurs at the end of the sequence and, by satisfying the need, removes the state that drove the search. Nikolaas Tinbergen built this contrast into his hierarchical model of instinct, casting the consummatory act as the fixed action pattern released at the bottom of a chain of appetitive steps (Tinbergen, 1963). Craig's distinction is thus the parent idea from which both the ethological concept of the fixed action pattern and the modern analysis of reward descend.

Types of Consummatory Behavior

In the Medical Subject Headings vocabulary, consummatory behavior is a child of the broad descriptor animal behavior, and it is itself the parent of three narrower kinds of consummatory act. These are summarised below; the groupings are a classification for indexing the literature, not a claim that the behaviors share a single mechanism, and a given act may be filed under more than one heading.

- Predatory behavior — the capture, killing, and eating of one animal by another; the consummatory act is the kill and the meal that terminate a hunt. - Nesting behavior — the building of a nest or similar structure, the consummatory completion of the drive to prepare a site for eggs or young. - Animal sexual behavior — the copulatory act that consummates a sequence of courtship and mate-seeking.

The three are orthogonal in the sense that an animal's position on one says nothing about its position on another: a skilled predator need not be a diligent nest-builder. They are collected under consummatory behavior because each is a terminal, goal-achieving act rather than because they are produced by one neural system. MeSH classification reflects how the behaviors are indexed in the research literature, and its categories are an aid to retrieval rather than a theory of the behaviors themselves; the boundaries drawn here are looser than the sharp dichotomy the appetitive–consummatory contrast might suggest (Ball & Balthazart, 2008).

The Appetitive–Consummatory Sequence

A motivated episode is organised as an ordered sequence that begins with a flexible search and ends with a fixed act. The appetitive phase is governed by the goal that is still to be reached; its form is whatever the situation requires. The consummatory phase is governed by the stimulus now in contact; its form is largely fixed. Barry Everitt's analysis of male sexual behavior made the division concrete and measurable, separating the appetitive responses by which a male works to reach a female from the copulatory, consummatory responses themselves, and showing that the two are driven by distinct neural substrates (Everitt, 1990). The contrast is set out in Table 1.

Table 1. The appetitive and consummatory phases of a motivated sequence contrasted along five properties (Craig, 1918; Everitt, 1990).

The sequence as a whole is shown in Figure 1: a variable appetitive search converges on a fixed consummatory act, which reduces the drive and returns the animal to quiescence until the need next arises.

Satiation and the Negative-Feedback Control of Consummation

The defining property of the consummatory act—that it reduces the drive—is the core of Clark Hull's drive-reduction theory, the most formal of the mid-century learning systems, which held that a response is reinforced to the degree that it reduces a drive (Hull, 1943). On that account the consummatory act does double duty: it terminates the current sequence and, by reducing the drive, stamps in the appetitive behavior that led to it. Drive reduction makes the act self-limiting. As the animal eats, the physiological deficit shrinks; as the deficit shrinks, the rate of consumption falls; and when the rate falls low enough, the behavior stops. This is negative feedback, and it gives satiation a characteristic shape: consumption is fastest at the start, when the deficit is largest, and decelerates smoothly toward a stop. Larry Swanson's synthesis of the forebrain control of motivated behavior places this regulation in concrete anatomy, mapping the hypothalamic and striatal machinery that translates a need state into the motor acts of consummation and reads the feedback that ends them (Swanson, 2000).

The first demonstration makes the feedback explicit. A deprived animal begins with a fixed deficit and consumes at a rate proportional to the deficit remaining; as it consumes, the deficit and the rate both decay exponentially, and the bout ends when the rate drops below a threshold. The sliders set the initial deficit and the feedback rate, and the display traces both the falling rate of consumption and the rising cumulative intake, reporting the time at which consummation stops. The same relationship is quantified in the Worked Example below.

Measuring Palatability: The Taste-Reactivity Test

Because the consummatory reaction is stereotyped, it can be measured as a behavior in its own right, independent of how hard the animal worked to obtain the stimulus. The canonical measure is the taste-reactivity test devised by Harvey Grill and Ralph Norgren, which scores the fixed facial and oral actions a taste releases when it is infused directly into the mouth (Grill & Norgren, 1978a). A palatable taste such as sucrose releases a pattern of ingestive actions—rhythmic tongue protrusions, lateral tongue movements, paw licking—while a bitter taste such as quinine releases a distinct pattern of aversive actions—gapes, chin rubs, headshakes, forelimb flails. The two patterns are separate, graded, and remarkably conserved, appearing in much the same form in rats, in human infants, and in other mammals.

The test's most striking result established that these consummatory reactions are organised below the forebrain. In a companion study, Grill and Norgren showed that a chronically decerebrate rat—one whose forebrain is surgically disconnected from the brainstem—still produces the full ingestive pattern to sucrose and the full aversive pattern to quinine, demonstrating that the motor program for the consummatory reaction is held in the brainstem itself (Grill & Norgren, 1978b). The second demonstration implements the test: a palatability slider runs from strongly aversive to strongly palatable, and the display shows the mix of ingestive and aversive actions a stimulus of that hedonic value releases, reproducing the opposed, graded patterns the test scores.

Liking Versus Wanting

The taste-reactivity reaction turned out to measure something the appetitive search does not, and the discovery reshaped the neuroscience of reward. Kent Berridge and Terry Robinson argued that reward is not one process but at least two: a hedonic reaction, liking, which is the pleasure of the consummatory act and is indexed by the ingestive taste-reactivity pattern; and an incentive-motivational process, wanting, which is the pull toward a reward and belongs to the appetitive phase (Berridge & Robinson, 1998). The two are ordinarily yoked—animals tend to want what they like—but they are produced by different brain systems and can be prised apart. Dopamine, long assumed to be the brain's pleasure signal, proved to govern wanting while leaving liking untouched: depleting it abolishes the pursuit of a reward without blunting the ingestive reaction to its taste (Berridge, 2004).

Liking, instead, is generated in small, anatomically specific hedonic hotspots. Berridge and Morten Kringelbach mapped these sites—in the nucleus accumbens shell, the ventral pallidum, and the brainstem—where opioid or endocannabinoid stimulation amplifies the ingestive taste-reactivity reaction to a sweet taste, enhancing the consummatory pleasure itself rather than the drive to seek it (Berridge & Kringelbach, 2015). The dissociation runs the other way too: sensitising the brain's wanting system can make a reward compulsively wanted without its being any better liked, which Berridge and Robinson developed into an incentive-sensitisation account of addiction (Berridge & Robinson, 2016; Warlow & Berridge, 2021). The third demonstration treats liking and wanting as two independent axes and lets each be set separately, plotting the resulting state and naming the dissociations—ordinary reward, compulsive wanting without liking, and liking without wanting—that the two systems can produce.

Worked Example: A Satiation Curve

The negative-feedback account of satiation can be made quantitative. Let an animal begin a bout with a deficit of C millilitres of water to be replaced, and suppose it drinks at a rate proportional to the deficit still remaining, with rate constant k per minute. If I(t) is the cumulative intake after t minutes, the deficit remaining is C − I(t), and the rate of drinking is

r(t) = k × (C − I(t)).

At the start no water has been taken, so the initial rate is r(0) = k × C. The intake that solves this is a rising exponential approach to the ceiling C,

I(t) = C × (1 − e^{−k t}),

and the drinking rate falls exponentially from its initial value, r(t) = k × C × e^{−k t}. The animal stops when the rate drops to a threshold θ below which it no longer bothers to drink. Setting r(t) = θ and solving gives the stopping time

t\ = (1 / k) × ln(k C* / θ).

Take a deficit of C = 20 mL, a feedback rate of k = 0.2 per minute, and a stopping threshold of θ = 1 mL per minute. The initial rate is r(0) = 0.2 × 20 = 4 mL per minute. The bout ends at t\ = (1 / 0.2) × ln(0.2 × 20 / 1) = 5 × ln(4) = 6.93 minutes. The intake by then is I(t\) = C − θ / k = 20 − 1 / 0.2 = 15 mL—the animal replaces three-quarters of its deficit before the slowing rate crosses the threshold and it stops, leaving a small deficit unfilled. Now raise the deficit to C = 30 mL with k and θ unchanged: the stop moves to t\ = 5 × ln(6) = 8.96 minutes and the intake to 30 − 5 = 25 mL. A larger deficit is consumed longer and more fully, because the rate starts higher and takes longer to decay to the threshold. The DriveReductionDemo above is built on these equations: its deficit and rate sliders set C and k*, and it reports the stopping time and final intake (Swanson, 2000).

Discussion

The appetitive–consummatory distinction has lasted more than a century because it carves motivated behavior at a real joint. The two phases differ in form, in their controlling stimuli, and in their relation to the drive, and—most tellingly—they are separable in the brain: the circuits that drive the appetitive pursuit of a reward can be manipulated without touching the consummatory reaction to it, and the reverse (Everitt, 1990; Berridge & Robinson, 1998). The liking–wanting framework is the distinction's modern descendant, and it has reorganised how reward is understood: the consummatory act carries the hedonic reaction, generated in discrete hotspots, while the appetitive phase carries incentive salience, generated by dopamine, and the two can come apart in ways that matter for conditions from addiction to depression (Berridge, 2019; Morales & Berridge, 2020).

The distinction is not absolute, and its limits are as instructive as its successes. Benjamin Sachs argued that sexual arousal cannot be cleanly partitioned into appetitive and consummatory boxes, because the states that drive approach and those that drive the act overlap and interact (Sachs, 2007). Gregory Ball and Jacques Balthazart pressed the point for neuroendocrine control generally, questioning how useful the dichotomy really is when the same hormones and circuits act across both phases and the boundary between them is often blurred (Ball & Balthazart, 2008). The lesson is that the appetitive–consummatory contrast is a powerful first parse of a motivated sequence—and the right starting point—but not a partition into two sealed compartments. Consummation is best understood as the terminal, drive-reducing pole of a continuum, measurable with unusual precision, rather than as one half of a strict binary.

Current Directions

The most active work develops the liking–wanting dissociation into a detailed circuit account. The hedonic hotspots that generate the consummatory ‘liking’ reaction have been localised to the nucleus accumbens shell, the ventral pallidum, and brainstem sites, and the current question is how these spatially tiny, opioid- and endocannabinoid-sensitive zones interact to amplify or suppress the pleasure of a consummatory act (Berridge & Kringelbach, 2015). In parallel, the ‘wanting’ system is being traced to specific amygdalar and accumbens circuits whose sensitisation can make a reward compulsively pursued without its being better liked, a mechanism now central to how incentive-sensitisation models explain addiction and relapse (Warlow & Berridge, 2021).

A second front concerns how hedonic reactions are coded at all. The debate is whether affective valence is handled by dedicated, segregated modules—discrete positive and negative circuits—or by distributed modes of activity that can reconfigure the same neurons from generating pleasure to generating disgust, as happens when a hotspot is disturbed (Berridge, 2019). Applied to ingestion, this work is beginning to connect the taste-reactivity reaction to clinical questions about overeating and food reward, asking how the liking and wanting of food diverge in obesity and eating disorders and whether the divergence can be measured and reversed (Morales & Berridge, 2020).

Common Misconceptions

Consummatory means consuming or eating.

The word is from consummate, to complete, not from consume. A consummatory act is the one that completes and ends a drive; eating is only the most familiar example, alongside copulation, the killing bite, and other terminal acts (Craig, 1918).

Liking and wanting are the same thing.

They are separable brain processes. ‘Liking’ is the hedonic reaction of the consummatory act, generated in hedonic hotspots; ‘wanting’ is the incentive pull of the appetitive phase, generated by dopamine. Each can be changed without the other (Berridge & Robinson, 1998; Berridge, 2004).

The pleasure of a reward requires the forebrain.

The stereotyped ingestive and aversive reactions scored by the taste-reactivity test survive in a decerebrate animal, showing that the motor program for the consummatory reaction is organised in the brainstem (Grill & Norgren, 1978b).

The appetitive and consummatory phases are a strict binary.

The distinction is a powerful first parse, not a sealed partition. In sexual and neuroendocrine behavior the same hormones and circuits act across both phases, and the boundary between them is often blurred (Sachs, 2007; Ball & Balthazart, 2008).

Glossary

Appetitive behavior.

The variable, goal-seeking phase of a motivated sequence that brings an animal into the situation where a consummatory act can occur; the search that precedes the act.

Aversive reaction.

The pattern of rejecting consummatory actions—gapes, chin rubs, headshakes, forelimb flails—released by an unpalatable taste in the taste-reactivity test.

Consummatory behavior.

The stereotyped, goal-achieving act that completes a motivated sequence and reduces the drive that produced it, such as eating, drinking, or copulation.

Decerebration.

The surgical disconnection of the forebrain from the brainstem; a chronically decerebrate animal still produces the full consummatory taste-reactivity pattern, localising that program to the brainstem.

Drive.

An internal need state, such as thirst or hunger, that initiates and sustains the appetitive search and is reduced by the consummatory act.

Fixed action pattern.

A stereotyped, innately programmed sequence of movements released by a specific sign stimulus and, once begun, run to completion; the ethological form of the consummatory act.

Hedonic hotspot.

A small, anatomically specific brain site—in the nucleus accumbens shell, ventral pallidum, or brainstem—where opioid or endocannabinoid stimulation amplifies the ‘liking’ reaction to a pleasant taste.

Incentive salience.

The motivational property that makes a reward and its cues attractive and sought after; the ‘wanting’ process of the appetitive phase, generated largely by dopamine.

Ingestive reaction.

The pattern of positive consummatory actions—rhythmic tongue protrusions, lateral tongue movements, paw licking—released by a palatable taste in the taste-reactivity test.

Liking.

The hedonic impact of a consummatory act—the pleasure of a reward as it is consumed—indexed by the ingestive taste-reactivity pattern and distinct from wanting.

Negative feedback.

A regulatory arrangement in which the output of a process reduces the signal that drives it; satiation is negative feedback, the consummatory act reducing the drive it serves.

Palatability.

The hedonic value of a taste, running from strongly aversive to strongly palatable, that sets the balance of ingestive and aversive reactions it releases.

Satiation.

The progressive reduction and eventual cessation of a consummatory act as the drive it serves is satisfied; the behavioral expression of negative feedback.

Taste-reactivity test.

A behavioral assay, devised by Grill and Norgren, that scores the fixed ingestive and aversive oral actions a taste releases when infused into the mouth, giving an objective measure of the consummatory reaction.

Wanting.

The incentive-motivational pull toward a reward, belonging to the appetitive phase and generated by dopamine; separable from the liking of the consummatory act.

Key Researchers

Kent C. Berridge

(University of Michigan). Affective neuroscientist whose dissociation of ‘liking’—the hedonic impact of the consummatory act—from ‘wanting’ reorganised the neuroscience of reward, and whose hedonic-hotspot work localised where the brain generates consummatory pleasure. ORCID

Wallace Craig

(University of Maine; Harvard University). Comparative psychologist whose 1918 paper introduced the term consummatory action, defining it as the stereotyped, goal-achieving act that terminates the variable appetitive search. Wikipedia · Wikidata

Barry J. Everitt

(University of Cambridge). Behavioural neuroscientist whose analysis of copulatory responses dissected the circuitry executing the consummatory act of mating, separating it from the appetitive pursuit that precedes it. ORCID

Morten L. Kringelbach

(University of Oxford and Aarhus University). Neuroscientist whose mapping of the brain's pleasure systems and hedonic hotspots characterised the consummatory, ‘liking’ phase that completes a motivated sequence. ORCID

Terry E. Robinson

(University of Michigan). Behavioural neuroscientist who, with Berridge, established that mesolimbic dopamine drives ‘wanting’ rather than the ‘liking’ of consummation, clarifying which neural signal belongs to which phase of a motivated sequence. ORCID

Nikolaas Tinbergen

(University of Oxford). Dutch-British ethologist and Nobel laureate whose hierarchical model of instinct cast the consummatory act as the fixed action pattern released at the end of an appetitive sequence. Wikipedia

Frequently Asked Questions

What is consummatory behavior?

Consummatory behavior is the stereotyped, goal-achieving act that completes a motivated sequence and reduces the drive behind it—eating, drinking, copulation, the killing bite. It is defined by contrast with the variable appetitive search that leads up to it (Craig, 1918).

Does consummatory mean consuming?

No. The word comes from consummate, to complete or fulfil, not from consume. A consummatory act is the one that consummates a drive by achieving its goal; eating is only the most familiar case (Craig, 1918).

How is consummatory behavior different from appetitive behavior?

The appetitive phase is a variable, goal-seeking search governed by a distant goal; the consummatory phase is a fixed, goal-achieving act governed by the goal in direct contact. The appetitive phase sustains the drive, the consummatory phase reduces it (Everitt, 1990).

What is the taste-reactivity test?

It is a behavioral assay, devised by Harvey Grill and Ralph Norgren, that scores the fixed oral actions a taste releases when infused into the mouth: ingestive actions to a palatable taste, aversive actions to an unpalatable one. It gives an objective measure of the consummatory reaction (Grill & Norgren, 1978a).

What is the difference between liking and wanting?

‘Liking’ is the hedonic pleasure of the consummatory act, indexed by the ingestive taste-reactivity pattern and generated in hedonic hotspots. ‘Wanting’ is the incentive pull of the appetitive phase, generated by dopamine. The two are separable and can be changed independently (Berridge & Robinson, 1998; Berridge, 2004).

Why does consummatory behavior stop?

Because it reduces the drive that produced it. As the deficit shrinks the rate of consumption falls, and when the rate drops below a threshold the behavior ends—satiation as negative feedback (Swanson, 2000).

Is the consummatory reaction controlled by the forebrain?

The basic motor program is not. A decerebrate rat still produces the full ingestive reaction to sucrose and the full aversive reaction to quinine, showing the consummatory reaction is organised in the brainstem (Grill & Norgren, 1978b).

Is the appetitive–consummatory distinction still accepted?

It remains the standard first parse of a motivated sequence, but its limits are recognised: in sexual and neuroendocrine behavior the two phases overlap and share circuits, so the distinction is a continuum rather than a strict binary (Sachs, 2007; Ball & Balthazart, 2008).

References