jueves, 17 de febrero de 2011

A philosophy for sensory science

Magni MartensCorresponding Author Contact Information, E-mail The Corresponding Author

The Royal Veterinary and Agricultural University, Rolighedsvej 30, DK-1958 Frederiksberg C, Denmark

Available online 2 June 1999.


A framework for “A philosophy for sensory science” is presented as inquiries into the uniqueness and role of sensory science, the sensory methods and into future issues in the field. The paper is based on an invited lecture to The 3rd Pangborn Sensory Science Symposium “Sense and Sensibility” 1998. Sensory science in the study of food products is in focus, well knowing that sensory science also addresses non-food commodities.

Article Outline

1. Introduction
2. The uniqueness of sensory science
2.1. Sensory science is more than methods—it deals with philosophy
2.2. Sensory science is a relational and interdisciplinary field
2.3. Sensory science is timeless
2.3.1. History of sense perception
2.3.2. Sense perception in psychology
2.4. Sensory science is ‘existential and integrating'
2.5. Sensory science deals with “real world” problems
3. The role of sensory science
3.1. Sensory science in society
3.2. Sensory science in industry
3.3. Sensory science in research
3.4. Some ethical considerations
4. Sensory methods
4.1. Linking goals to methods
4.2. A philosophical perspective
4.3. A multivariate perspective
4.4. Sensory methods are reliable, relevant, robust and rapid (and cheap!)
5. 1999–2000–2001............
5.1. Basic sensory research is needed
5.1.1. Objectivity versus subjectivity
5.1.2. Organoleptic versus sensory
5.2. Teaching in sensory science is needed
6. Conclusions

1. Introduction

Sensory science is a multidisciplinary field comprising measurement, interpretation and understanding of human responses to product properties as perceived by the senses such as sight, smell, taste, touch and hearing. A philosophy for sensory science relies heavily on empirical and theoretical contributions from many professionals such as physiologists, psychologists, philosophers, anthropologists, marketing scientists as well as chemists, technologists and data analysts. One common vision may be to draw more attention towards human beings as respondents to foods, in a rapidly changing world. Understanding stimulus–response interactions between complex biological material and a complex human sensation–perception–cognition system in a cultural context needs more basic research and better platforms for discourses.

The present paper is a tribute to Rose Marie Pangborn in two ways: first, her early insight into the complexity and multidimensional nature of sensory science, and second, her early effort to bring sensory evaluation as an applied field into a recognized scientific discipline. Inspired by her numerous publications, lectures and personal communications, the paper aims at opening for inquiries into “A philosophy for sensory science”.

The unifying theme of the responses given by sensory colleagues worldwide to the concept of “A philosophy for sensory science”, was: I am practising philosophy in my sensory work every day. Personally, I like that answer. “Philosophy” means “love for wisdom”. All of us in the sensory science community have “A philosophy for sensory science” as long as we are enthusiastic and motivated for the work we are doing, searching deeper understanding. “A philosophy for sensory science” deals with why questions. Thus, the title may be used as a framework for inquiries and reflections upon the basis for the field to which we have dedicated our scientific lives.

Rose Marie Pangborn was one of the authors of the famous book Principles of Sensory Evaluation of Food, to be considered as the first and main breakthrough for sensory evaluation as an exciting scientific discipline (Amerine, Pangborn & Roessler, 1965). In the preface to this book is written:

“Food science deals with the multitude of problems involved in providing food for human consumption. It includes the entire process from harvesting to serving............. Our philosophy has been that sound methodology for the sensory analysis of foods rests on a thorough knowledge of sensory physiology and an understanding of the psychology of perception. Essential in addition is careful statistical design and analyses of the data. Finally, new understanding of sensory judgement is to be sought through correlation with physical and chemical data.”

Inspired by these words as a framework for “A philosophy for sensory science” this paper aims at enhancing the consciousness and insight into sensory science in four parts: It starts in a socratic way with “know thyself”, i.e. reflections upon the uniqueness of sensory science as formed through the last 40–50 years, and roughly placing the field in the 2500 years long history of philosophy of sense perception. In the second part the roles of sensory science in society, industry and in research are discussed, embedded in the ethical dimension within philosophy of science. The various roles often call upon different goals which further requires different sensory methodologies and criteria for validity, to be discussed from a philosophical, psychological and multivariate perspective. Lastly, some views on “A philosophy for Sensory Science” for the future are opened for debate addressing ongoing controversies within philosophy of mind as well as within the current International Organization for Standardization for sensory science.

2. The uniqueness of sensory science

2.1. Sensory science is more than methods—it deals with philosophy

What characterizes sensory science and makes it unique? What may constitute a foundation for sensory science? Why isn't the discipline a part of either chemistry or psychology? The many suggestions for a definition throughout the years have heavily relied on the “measurement” or “evaluation” side, e.g. the Institute of Food Technologists definition (Anon., 1975): “Sensory evaluation is a scientific method used to evoke, measure, analyse and interpret reactions to those characteristics of foods and materials as they are perceived by the senses of sight, smell, taste, touch and hearing”. Lawless and Heymann (1998) discuss this definition in more detail in their book, inspiring the reader to enlarge the view of sensory science to include more than just questions about methodology.

This paper does not aim at coming up with a new definition, but rather to throw some philosophical lights upon the field underlying, among others, the sensory methods. In one way we may say that the current practice in sensory science is formed through the last 50 years in a technological and natural scientific context to enhance sensory quality in the food industry. The methods used have been adapted from the 150 years of development in experimental psychology, which again have roots back into the 2500 years long history of philosophy.

Bringing the field to Scandinavia today, we have a more than 20 years tradition in these countries to view sensory science in a broad and visionary way, as here expressed by an International Advisory Board headed by professor Erik von Sydow from Sweden (von Sydow, 1996):

“In food research the most common denominator between projects is sensory science. It is also an obvious link with consumer science and other social sciences bearing on food and food consumption. Internationally, sensory science is often a weak link in any food research programme.”

One keyword for sensory science is “link” due to its nature of bridging two or more entities. Strengthening sensory science as links in a food research programme is of utmost importance for the future, as will be discussed in the following:

Sensory science

• is relational, i.e. links product and person;

• is interdisciplinary, i.e. links professions from chemistry to psychology;

• is timeless, i.e. links past and present inquiries into sense perception;

• is existential, i.e. links sense perception through one human life;

• is integrating, i.e. links the various sense modalities;

• is “real world” science, i.e. links theories to practical problem-solving.

Philosophical topics of relevance to sensory science may address epistemological, linguistic, ethical and metaphysical approaches. Epistemology or theory of knowledge concerns two main questions: first, how do we get knowledge about the world? Is it mainly from external sources (e.g. a product) or internal sources (e.g. a person's image) or a combination? Secondly, how do we justify (legitimate, validate) our knowledge about the world? Can we trust the senses? What is “truth”? Next approach deal with language theories concerning the spoken (or unspoken) expressions of our sense impressions and knowledge about the world. Ethics and value theories concerning motivation and justification of human actions. Metaphysics concerns theories about “reality” (ontology) and limits for scientific knowledge.

In the present paper I shall limit the topics to addressing questions within epistemology and, to a less extent, touching on topics within philosophy of language and ethics. Within epistemology, two philosophical topics are essential to sensory science: First, sense perception including recent views within cognitive and consciousness sciences for understanding the product-person interactive nature and processes; and secondly, psychophysics including recent multivariate approaches for measuring the relevant relationships between stimulus and response.

2.2. Sensory science is a relational and interdisciplinary field

There are two fundamental interfaces linking the broad field of sensory science: first, the product–person interface due to the simple fact that food (product) interacts with human beings (person) upon eating, and second, calling upon various disciplines from molecular chemistry to cognitive psychology; and second, the rational-affective (sense-sensibility) nature of human beings, bridging analytical sensory science in the laboratory to behaviour sciences in the marketplace and eating situation. In Fig. 1 this is illustrated as a continuum with respective focus on the product and the person (or consumer).

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Figure 1. Sensory science concerns product-person relations in a continuum; i.e. bridging various disciplines from molecular chemistry to cognitive psychology and marketing. Interface 1: product–person relations (e.g. chemical-sensory properties). Interface 2: person–person relations (e.g. descriptive-affective responses).

In the 70s sensory research was mostly concerned with the first interface, relating physicochemical properties of foods to sensory responses. A rough categorization of the contributions to the 3rd Pangborn Symposium in 1998 shows that approximately 15% of the lectures belong to the first interface, while 50% may be placed in the second interface, and the rest (35%) deal with methodology. This is a significant change in the direction of more and more consumer and marketing-oriented research in the 90s. Is this positive or negative?

In my opinion it is important to develop the whole field in a balance of product and person, not being too one-sided on either the technological or the marketing ends. As emphasized by professor Roland Harper from the UK in the 70ties, sensory science concerns the action of the human senses (Harper, 1972). The senses are not passive receivers, but operate in an active and fundamental way for human beings and its relation to the external world. Understanding the product–person relation raises inquiries into the sensation–perception–cognition processing, which from an epistemological point of view, concerns the discovery, by means of the senses, of the existence and properties of the external world. How far can the senses be regarded as a source of knowledge about the world? This is a question dealt with through the history of sense perception.

2.3. Sensory science is timeless

By “timeless” I mean that fundamental issues and controversies raised by the ancient Greeks are relevant topics today. What is the source of knowledge about an apple? Is it the physical measure of sugars or the perceived sweetness or both? Is it the detected sweetness on the tongue or the feeling of happiness when thinking about the apple?

2.3.1. History of sense perception

In broad terms there are two main views on sense perception: realism versus phenomenalism, with a few tendencies to combinations throughout the 2500 year long history of philosophy of science. The following section is for the reader interested in specific philosophical views, here briefly outlined.

In Greek philosophy (not, vert, similar500–300 BC) relevant epistemological questions were discussed: What is the relation between man and the world (cf. person-product interactions)? What is the status of sensing versus thinking? What is “truth”?Democritus, a recognized atomist and realist, claimed that reality is “a stream of atoms moving around in an empty space, reaching the sense organs.... Sight, hearing, smell, taste touch give “bastard” knowledge about the external world, not trueborn”. Protagoras, living in the same period, disagreed with this, and emphasized man as the source of “true” knowledge as expressed through the famous sentence “Man is the measure of all things”. It is common to interpret this expression in an individualistic sense with regard to sense perception (

Copleston, 1985
). For example, if the temperature in a room shows 18°C, some persons feel cold while others feel warm. Both are right, according to Protagoras. “Know thyself” imperative, as guiding the “truth”, would be Socrates” position (according to Plato) focusing on the dialogue between the participants. Plato was inspired by both Protagoras and Socrates, however he never put much emphasize on empirical knowledge as giving any certain and final knowledge about the real world. Plato's argument in the Republic is that sense experience does not give knowledge but only opinion, since knowledge must be certain and cannot be of what is constantly changing—that is, sensations or the sensible world. Wisdom is achieved through thinking, not sensing; thus he somehow introduced the phenomenological view.Aristotle's view against both Protagoras and Plato stressed the element of judgement in perception. Perceptions are acts (energeia) and judgements (krisis). By this view sensing and thinking got a more similar status, both contributing to our knowledge about the world. In De Anima
Aristotle (384–322 BC)
gave a detailed description of perception by means of the five senses:
“Odor and the object of smell are less easily defined than the sensibles already discussed; for the kind of a thing that odor is, is not so clear as that of sound or of color. The cause of this is the fact that the sense which we have of it is not accurate but inferior to that of many animals; for a man smells odors poorly and does not sense object of smell unless it be painful or pleasant, and this indicates that the corresponding sense organ is not accurate.”

Furthermore, he was familiar with the four basic tastes and the “common faculty of sensation” integrating the sensory modalities to a whole. In general, sense perception and the unity of the senses was a central issue to the Greeks (

Emilsson, 1988
).During the Middle Ages (not, vert, similar500–1500) natural science was in general incompatible with faith and received little attention. However, one interesting topic is of relevance to naming of our sense perceptions. The problem of universals concerned the status for universalia (name of properties) versus particularia (the real thing). For example, redness is a general name of a property, while a tomato and a mailbox are both red objects. The discussion resulted in three positions. The “exaggerated realism” claimed that names (concepts, ideas) exist before, and independent of things (universalia ante res). The confusing word “realism” as historically used for this position, points to the view that the ”real” world is names and ideas, thus, linking it to the Plato's world of ideas, later to inspire phenomenalism. “Nominalism” constituted the opposite position saying that universalia has no existence independent of things, only as names of properties “after” the things (universalia post res). The “moderate” position combined the two others by claiming that universalia exists Image the thing (universalia in rebus). The view that essential properties make the thing, goes back to Aristotle and leads forward to combination positions to follow.The topics of relevance to sense perception through the Renaissance (not, vert, similar1500–1700) were marked by the scientific revolution bringing the human subject into the center of the universe. According to Galileo ‘everything' can be measured and explained mathematically giving raise to a mechanistic view on the world. Especially vision was studied. The science of seeing became the science of optics and light waves, and the eye was considered as an instrument for detection. A clear distinction between object (external world) and subject (internal world) was made reactivating the Democritus separation of primary and secondary qualities; the former being properties belonging to the object (e.g. form and size) while the latter was human perceived properties as colour, taste and smell.The controversies between empiricism and rationalism ruled the following period (not, vert, similar1600–1800). What constitutes the epistemological foundation: sense perceptions or rational thinking? Rationalism, as developed in France and Germany, claimed rational thinking as giving “true” knowledge. Descartes expressed that as Cogito, ergo sum (I think, therefore I am). “It seems to me that I can establish as a general rule that things which I perceive very clearly and very distinctly are true.” Empiricism, on the other hand, as developed in England (Locke, Berkeley, Hume), assigned experiences through the senses as the ultimate source of knowledge about the external world. The intellect passively receives these simple ideas about the environment like a tabula rasa position indicating that nothing is in the intellect without passing through the senses. Sensations are the chief source of knowledge, and the mind operates on the conveyed ideas given. Thus, induction constitutes a major place in empiricism, versus deductive thinking in rationalism. In Locke's Essay Concerning Human Understanding he presented a theory of primary and secondary qualities (cf. Galileo above). He makes a distinction between ideas and qualities and a further distinction between qualities that are inseparable from a body, whatever changes it undergoes.
“These I call original or primary qualities of a body, which I think we may observe to produce simple ideas in us, viz. solidity, extension, figure, motion or rest, and number. Besides these primary qualities there are also secondary qualities. The latter are ‘nothing in the objects themselves but powers to produce various sensations in us by their primary qualities'. Such are colours, sounds, tastes and odours. Ideas of primary qualities really resemble things; ideas of secondary qualities do not, they are subjective. But if we know immediately our ideas, how can we ever know whether these ideas do or do not resemble things? How, for the matter of that, can we be certain that things other than our ideas even exist?”

Berkeley (1685-1783) maintained Locke's arguments to show that colour, taste, odour and so on are ideas in our minds and not real qualities of objects, also the primary qualities of objects. The perceived size and shape of an object vary with the position of the percipient subject and with the physical conditions just as much as secondary qualities vary. According to Berkeley anyone can have knowledge of the fact that sensible objects do not and cannot exist independently of minds. Esse est percipi i.e. a sensible object exists when it is perceived.The epistemology of Kant (1724–1804) draws upon both empiricism and rationalism constituting a combination theory. The source of knowledge is somehow based on an interaction between sensing and thinking: The external world is brought into concepts given by the internal intellect, and the match is organized by a presupposed scheme of faculties. Kant sees the notion of judgement as of central importance in considering thoughts about the world. However, the external world or ‘things-in-themselves' can only be grasped as appearances (Erscheinung) in time and space. The answer to the question of what basically exists must be to the effect that there are sensations or appearances organized by the understanding. But what is the status of the appearances of an object being seen?This discussion continued into the 19th and 20th centuries. The term “sense-datum” (plural “sense data”) originates from Moore (1873–1958). Moore was careful to distinguish between sensations and sense-data. When, for example, I see a colour, seeing the colour is the sensation, and what is seen, the object, is the sense-datum. But can sense-data exist when they are unperceived? It would hardly make sense to ask whether a ‘seeing' can exist when no sentient subject is seeing. Sensations are acts of awareness. But it does make sense to ask whether a colour exists when it is not perceived. Russell suggested that the paradox can be avoided by calling these unsensed sense-data sensibilia, potential sense-data. And the physical objects of common sense and of science are to be interpreted as functions of sense-data and sensibilia or, to put the matter in another way, as the classes of their appearance.Moore's view that sensations are acts of awareness was shared by William James (1842–1910),

James (1890)
who translated the philosophical problem into psychological terms. In The Principles of Psychology he explains sensation and perception as cognitive functions, as processes for getting knowledge about the world. As such he was early to point out a ‘combination' position within contemporary epistemology.In trying to give a short overview of contemporary sense perception theories it is common to classify them into three main positions: direct and indirect realism and phenomenalism (
Dancy, 1993
). Realism may be characterized as the view that the existence of the objects we perceive is independent of the existence of any perceiver. This is a typical natural scientific position. The “truth” is sought in the physical world. Direct realism claims that we are directly aware of the existence of the physical world, while the indirect view relies on a representative non-physical object for perception. Phenomenalism holds that the only possible object of awareness is experience; there is no reality apart from that. ‘Qualia' or ‘sensa' are often used names of the subjectively experienced object, and this is a typical humanistic position. The “truth” is here found as subjective meaning in the mental world.The phenomenology of Merleau-Ponty (1908–1961) is an example of trying to combine the extreme positions. In Phenomenology of Perception he is concerned with perception as the mode of existence of the body-subject; i.e. the dialogue between the body, as subject, and its world at a level which is presupposed by consciousness. There is indeed a causal interaction. For instance, food acts on the organism, and the organism acts on the food by assimilating it. But the food is food only in virtue of the structure, needs and activity of the organism.Pragmatism is another approach to avoid the extreme positions of realism and phenomenalism by changing the focus of verification from true/false or subjective meaning, respectively, to a more dynamic and action-oriented “truth”. In simple terms: A judgement about an object is true if “it works”, i.e. if it has practical consequences in problem solving. “Truth” is then linked to an instrumental value as an action or statement being useful and satisfying to the problem at stake. This understanding of “truth” has close relationships to the hermeneutics within philosophy of science emphasizing interpretation and understanding as bases for what is true. The hermeneutic circle as a research process underlines that “truth” is not a static true/false conclusion, but a relational interaction between the “part” and the “whole” in a large meaning context. And the understanding of what meaning is, leads us into another important topic of philosophy concerning language. Wittgenstein's famous words that “meaning is use” point at problems with having a private language (
Wittgenstein, 1958
). Each of us may have a private word for our sense perceptions; however, then it is hard to communicate with each other.Some very interesting academic discussions today of relevance to sensory science take place within philosophy of mind and consciousness science, drawing upon both realism and phenomenalism. Consciousness science is a broad term for studies of the content and structure of consciousness (see
Chalmers, 1996
) including a more pronounced cognitive direction (see
Dennett, 1991

It is beyond the scope of this paper to go into details of the various directions within sense perception. In one way we might say that sensory science has developed along a pragmatic direction introducing methods and validity criteria “that work” without even being aware of the realism–phenomenalism dichotomy. A sensory food scientist would rewrite Descartes' words to “I eat, therefore I am”, which is probably right.

Nevertheless, I am personally convinced that the sensory science community can gain much from interacting with philosophers, not necessarily to learn about history, but to get new ideas for their practices and to enhance the consciousness of what we are already doing. This will be illustrated in the last section discussing future issues.

2.3.2. Sense perception in psychology

The 50 years old history of sensory science relies heavily on experimental psychology (Schutz, 1998). According to Schultz and Schultz (1992) the history of psychology originated in the middle 19th century by scientists inspired both by philosophy and by scientific discoveries, especially within neurophysiology. In the beginning experimental psychology concentrated on sensory physiology, e.g. Helmholtz's investigations of the speed of neural impulse and his research on vision and audition. The experimental research on the two-point threshold by physiologist Weber provided a way of measuring a stimulus and a subject's perception of it, resulting in the Weber's law. In the same period Fechner discovered a logarithmic law for the relationship between stimulus and response, he and Weber together laying out the groundwork for modern psychophysics. However, with a few exceptions (Thurstone in the 40s and Stevens in the 60s) there has been little interest in the quantitative relationship between mind and body in philosophical terms, as Fechner expressed his work.

In this light, sensory science as a field for bridging mind and matter is indeed challenging. Rushing through the history of psychology in the 20th century we may conclude that sense perception and psychophysics are topics for the next century. From structuralism and functionalism to behaviourism and gestalt psychology the current trends in cognitive sciences and psychology again ask for a combination of ‘hard facts' natural scientific knowledge and ‘soft' knowledge from human responses. In the book The Senses Considered as Perceptual Systems, Gibson (1968) starts by asking “What are the senses?” He discusses the two different meanings of the verb ‘to sense': first, ‘to detect something', and second, ‘to have a sensation'. This is an early criticism of looking at the senses as a one-way channel of sensation from the external world invading a passive receptor and tabula rasa system. As mentioned above, this argument was later stressed within sensory science by Harper, but not brought much further within the realm of sensory psychology. McBride and MacFie (1990) have edited a book Psychological Basis of Sensory Evaluation, stimulating probable future debates from marketing-oriented psychologists.

We shall certainly be hearing from and seeing more on the internet as a future source for sensory knowledge. It is already producing an enormous amount of pages on Sensory Words and Definitions (e.g. http://www.wordfocus.com/word-activities-list.html).

2.4. Sensory science is ‘existential and integrating'

Sensory science is unique in the way it focuses on the human senses as an integrated part of our existence. In food science we may add that it is a science dealing with the simple fact that we have to eat in order to live. And since humans will not eat just anything, it deals with what we choose to eat, involving emotions and cognitive issues. Sense perception is timeless in the history of mankind, as discussed above. Sensory perceptions are also timeless within the history of one person since sensory processing starts even before we are born. Amniotic fluid, saliva, mother's song are examples of stimuli we receive as fetus. Upon birth, mother's milk gives us early taste impressions in life; the first pure sensations are the universe constituting a mental map or schema which we continue to develop throughout life.

According to schema theories (Eckbald and Ellis), schema are cognitive structures comprising (temporally and spatially) organized knowledge about e.g. objects, people, situations and ourselves. The role is to ensure continuity, allocate capacity for interpretation of new incoming information, and to help to orient us in the world. Schema influence what we perceive, and how we perceive, organize and remember information. Thus, the very first taste of milk will somehow follow us later in life and influence our sensory judgements through memory.

In the history of sense perception in philosophy, all the five (or more) senses get attention, while within experimental psychology there has been a heavy focus on vision from the very beginning. Vision and hearing are of course of interest in sensory science, but sensory science seems to be unique in the way it also focuses on the other senses as smell and taste. However, more research is needed on the sense of touch and kinesthesia and on proprioception (senses in muscles, joints and the inner ear; see e.g. Gibson, 1968 and Harper, 1972).

Another unique issue in sensory science is the focus on integration of the different sense modalities. In a study of comparative behaviour of instruments and human subjects, Pangborn (1987) stressed that the senses behave as integrators in a multivariate and relative way, while instruments are characterized by being separators in a univariate and absolute way. Nevertheless, in most of the sensory literature there is a tendency to deal with one sense modality at a time, not even reflecting upon interactions from other senses, e.g. the colour of a product influences the perception of the flavour. During the history of instrumental development we have viewed many instruments as elongation of the individual senses, e.g. the electronmicroscope helps the eyes, the loudspeaker helps the ear, and in recent years, the artificial nose and smart tongue appear. Time will show the strength and weaknesses in these latter developments, and sensory science is very important for calibration of the instruments towards the human senses.

2.5. Sensory science deals with “real world” problems

Sensory science as a problem-oriented science is unique in the way that it started as an empirical field, and from thereon developed into more basic studies in academia. Producing food that no one wants to eat, although the food may be safe and nutritious, is meaningless in most cases. Although basic research requires knowledge from model systems, most of the sensory research is carried out on real food products. Especially solving “real world” problems involving the whole chain from laboratory to consumers, means the ability to bridge the gap between sensory evaluation and market research.

“There is much to be gained from an integration of sensory evaluation and market research to provide a full understanding of the overall evaluation and acceptance of food. This can be achieved if research paradigms and practical applications are broadened to address key issues: the choice of appropriate research subjects, the use of realistic foods and of more complex and realistic environments, the appropriate selection of sensory methods, and the consideration of contextual influences. Improved research paradigms will contribute to our theories of how human eating is controlled and, hence, to the use of this information in product development and biomedical applications” (Meiselman, 1994).

In the modern technological world we are strongly stimulated by visual impressions, through televisions, videos, computers and advertisements etc. It seems important to reflect upon the need to use not only sight, but the other senses as well. Do we want an odourless, tasteless world with no allowance to touch anything? What might happen to a sense modality that is understimulated during a long period? More research on sensory interactions is indeed needed.

3. The role of sensory science

Sensory science, as an action-oriented discipline, is carried out in different contexts in academia, industry and society at large.

3.1. Sensory science in society

Rose Marie Pangborn's list of publications is a significant documentation of the important role of sensory science in health and nutritional issues, as well as in food culture studies (Pangborn, Guinard & Davis, 1988). Today, interest in sensory science is increasing among health and nutritional professionals in relation to food intake of for example, fat and sugar. Also, consumer groups are requiring reduction of additives and development of ecological products still ‘tasting good'. Another example is environmental groups now asking for scientific results concerning human perception of contaminants in air, water and soil. Lastly, the increased awareness of food culture and food choice behaviour gives a signal to society that all the senses, not only vision, are on the menu.

3.2. Sensory science in industry

Sensory science has proven success in R&D and quality assurance in the food and beverage industries (Meilgaard, Civille & Carr, 1991 and Stone). The potential of using sensory evaluation to link product development to marketing was recognized earlier ( Moskowitz, 1994), and is now receiving more attention. However, the value of sensory science has increasingly reached other industries producing, pharmaceuticals, textiles, cars, and cosmetics. Strong international competition has forced producers to provide goods that satisfy consumers' stated and implied needs, including the demand for high sensory quality. International standards for sensory analysis draws attention to a worldwide discussion about a consensus in sensory practices.

3.3. Sensory science in research

The increasing number of scientific publications, conferences, courses, research programmes and open positions in the field of sensory science speaks for itself. Trying to categorize the various activities, also being represented at the 3rd Pangborn Symposium, sensory basic research contributes to at least four issues:

• method development, i.e. ensuring reliability and validity in sensory results;

• understanding sensory and psychophysical relationships; i.e. ensuring relevance of instrumental measurements in predicting sensory quality;

• understanding underlying physiological and psychological factors influencing sensory judgements;

• understanding sources of knowledge and “truth” as dealt with in philosophy.

In broad terms we may add that the role of “A philosophy for sensory science” is to enhance understanding and communication by bridging production and marketing, technologists and humanists, realism and phenomenalism, product and person and finally in philosophical terms: mind and matter. Thereby, we avoid reducing man to a machine or reducing sensory science to a question of marketing prices and advertisement issues.

3.4. Some ethical considerations

Substantially the same general ethical principles apply to the problems across all the different professions within the sensory science community. The reason or motivation to work may be that we want to do something useful to society, or we are just curious, or we just need to earn money etc. The reason to act and the consequences of actions may be justified in mainly three different ways (Beauchamp, 1991).

• Act good: i.e. act such as to bring the most happiness (and least damage) to the greatest number of people. A value-based action is legitimized by its consequences and is dealt with in ethical theories of consequensialism and utilitarianism.

• Act right: i.e. you act right when you follow an ethical norm like ‘never treat another person merely as a means to your own goals'. Professional ethical codes are examples of norm-based guides for right action.

• act the best you can: i.e. act according to your cultivated character traits such as benevolence, honesty, being responsible etc. covered by virtue ethics.

In practice, we try to act both good and right and the best we can. Nevertheless, we are often facing ethical dilemmas (Beauchamp, 1991). Furthermore, the sensory scientist should be aware of specific ethical aspects of applying sensory methods. This concerns first of all the relationship between you as an experimenter, and the panelists and/or the consumer. For example, the panelist or respondent should always give their informed consent to participate in a test, and the experimenter is responsible for not overloading the participants by unnecessary stress (e.g. serving rotten samples), or, of course, not poisoning the panelist. Scientific ethics also include your collection and handling of data. Without going into details here, the most obvious norm is that you should never cheat with your experimental design and data.

4. Sensory methods

4.1. Linking goals to methods

In the history of sensory science there seems to have been a change in terminology from sensory measurement to judgement to evaluation. However, independent of these words the same main sensory methods have been used. Fig. 2 gives a broad overview of the main methods often categorized into laboratory tests and consumer tests.

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Figure 2. Main sensory methods.

As discussed above, sensory science is unique in the way product–person interactions are studied in a continuum. In product development and quality control the goals often focus on the product, and laboratory methods are mostly relevant. In consumer and marketing studies when the goals focus on the person in a context or situation, methods measuring affective, cognitive or behavioural factors are more relevant. Sensory science thus links the chain through the chemical–sensory–descriptive interface and the sensory–descriptive–affective–behaviour interface. No method is good or bad; the critical issue has to do with fitting the right method to the goal at stake (O'Mahony, 1995).

4.2. A philosophical perspective

From a philosophical perspective the various sensory methods have three different bases.

1. We DESCRIBE the world: In sensory descriptive analysis and profiling the goal is to find sensory quality criteria that describe a product in a quantitative way. For example, the apple Image red, hard, fruity and sweet. In quality control tests we describe deviations from norms e.g. in the food industry, the product properties Image in conformance to standard specifications. The first example belongs to descriptive-based methods, the second is normative-based. However, both are traditionally called objective methods understood as ‘intersubjectivity' between trained assessors in a sensory panel. We describe the real world from a 3rd person perspective, as observers of a product.

2. We EXPERIENCE the world: In consumer tests the goal is to focus on the affective and emotional aspects of a product. For example, the subjective experience of an apple is expressed as goodness, liking, acceptance or preference. These are value-based methods. We express our feelings and experiences from a 3rd person perspective, as observers of ourselves.

3. We LIVE in the world: Being in the world just expresses being and actions from a 1st person perspective changing the role from an observer to an actor. ‘Can we ever feel another person's pain?' is a central question within philosophy. ‘Can we ever feel another person's taste?'

The latter point may seem ridiculous to natural scientists examplifying why philosophy is often considered to be irrelevant to practical problem solving. On the other hand, it may serve as a reminder of the inherent limits of understanding individual differences in sensory judgements. Why is it often easier to obtain agreement between panelists about appearance and colour than between odour and taste, while texture properties lies somewhere in the middle? How do people perceive themselves when judging a product? How do our judgements of goodness change with situation and time? The Finnish philosopher G. von Wright (1963) in his book The Varieties of Goodness inquires into six different ways of understanding what is goodness: Instrumental goodness (e.g. a good knife, hammer, car); Technical goodness (e.g. good at cutting); Medical goodness (e.g. good for your health); Beneficial goodness (e.g. good of a being); Utilitarian goodness (e.g. good of a being as an end); Hedonic goodness (e.g. pleasure, liking). In general, we may distinguish between “goodness” as something good of man (or object) relative to a notion of the nature of a man, and as something relative to the needs and wants of individual men. Inquiries into goodness and value theories in philosophy directly contribute to recent research and discussions about ‘quality'; i.e. the quality concept and quality analysis in practice (Martens, Risvik & Martens, 1994).

Pangborn (1981) stressed the importance of understanding individual differences from physiological and psychological points of view. During the last decade much research has been done on the physiology of receptor mechanisms ( Kinnamon, 1996). However, I do miss a deeper understanding of individual sensation–perception–cognition processing in view of modern cognitive science and consciousness studies. Viewing stimulus–response relations as information processing instead of just receptor excitation means that chemical and physical stimuli from the product interact with mental and bodily stimuli resulting in human responses. Thus, sensory judgements occur when patterns are formed from sensory signals matched with information from memory to attain meaning to the product. As said above, recent trends in philosophy of mind and cognitive psychology merge into each other and give new platforms for sensory science.

4.3. A multivariate perspective

Sensory perception as an act of becoming aware of a multitude of chemical and physical information about a product (e.g. chemical compounds, light, pressure, sound, temperature) by a multitude of senses (e.g. sight, smell, taste, hearing, touch,) requires a multivariate relational approach. The more we realize and accept the multivariability the stronger is the requirement for multivariate thinking and modelling. Multivariate psychophysics is needed simply because the real world is multivariate. Combining multivariate psychophysics and multivariate data analysis allows us to find the latent phenomena common to the sensory and physical worlds (Fig. 3).

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Figure 3. Sensory science deals with multivariate relations between sensory and e.g. chemical data.

Fig. 3 illustrates in data analytical terms how product stimuli (X) relate to human responses (Y); i.e. a multivariate psychophysical S–R relationship (Martens & Martens, 1986). When translating consumer responses onto product specifications, the direction of X–Y may be changed. Latent phenomena, non-linearities and other statistical issues in sensory and consumer data constitute challenging aspects of modelling real world problems (Risvik, 1996 and Dijksterhuis). Further discussion into the topic goes beyond the scope of this paper. Nevertheless, the increased interest in multivariate approaches for ensuring reliability and validity in sensory science should be mentioned (cf. 4th Sensometrics Meeting, Denmark, 1998).

4.4. Sensory methods are reliable, relevant, robust and rapid (and cheap!)

In a natural scientific and technological context sensory science is often considered to be a ‘soft' discipline, while in a psychological or humanistic context sensory science is ‘hard'. Arguing that sensory methods are reliable, relevant, robust and rapid (and as such: cheap!) seems to be provocative in both camps. The technologists do not trust human measurements, while the humanists protest against viewing ‘man as an instrument'. Nevertheless, the argument that sensory methods are reliable, relevant, robust and rapid (and cheap) means: Reliable in statistical terms (i.e. reproducible) when performed in a correct way; Relevant, since sensory quality usually refers to perception of a product by human beings (e.g. the consumers). Thus, sensory methods are more likely to be more valid and relevant to the final goal, than are indirect chemical measurements. Sensory methods are Robust, in the way that the human brain has a fantastic ability to adjust for irrelevant noise in the measurements. What is complex for chemistry and physics may prove to be simple for the nose and eye. Sensory methods are Rapid because mostly no time-consuming sample preparation is needed compared to gas chromatography, for example. Further, many product properties, such as colour, flavour and texture are measured by Image instrument (i.e. the human senses) and on the same samples, instead of using spectrophotometers for colour, HPLC for flavour and instron for texture. That sensory methods are cheap is almost taboo to say. But what are the costs of buying, handling and maintaining a complete laboratory of expensive instruments covering the whole spectrum of the different sense modalities? Which other methods other than a sensory panel can be afforded in developing countries where advanced instruments are seldom found?

5. 1999–2000–2001............

“A philosophy for sensory science” has a lot of obtained knowledge and insight to build on in order to excitingly develop into the future. For strengthening the field it is of utmost importance to find common platforms for the different professions. On one hand, the psychologist should not feel that human beings are reduced to chemistry and physiology, and on the other hand, that natural scientists and technologists should not get passive, due to all the ‘talk' and ‘opinions' about the complexity of human nature. We need a non-reductive platform for new theories. Referring to the citation in the introduction (Amerine et al., 1965) as well as to the timeless history of sense perception lightly discussed above, there are indeed challenging topics to be explored through more basic sensory research and teaching.

5.1. Basic sensory research is needed

As I see it, a non-reductive theory of sense perception will consist of a number of psychophysical principles, principles connecting the properties of physical processes to the properties of experience. To achieve this, more relational and multivariate approaches to sensory science in a time domain are important. This means increased basic understanding of interactions between complex matters (e.g. food products) and complex human minds (sensation–perception–cognition processing) changing with context and in time. It also means more research into the connections between physiological measurements (e.g. brain scan or glucose status of a person) and the psychological experiences (e.g. I like this product). In other words, the field needs to continue to aim at sound sensory theories and methods based on new understanding of sensation–perception–cognition processing, multivariate psychophysics and multivariate data analysis. Some previous controversies with respect to which sensory method is best to use in e.g. product development or quality control may vanish the moment we realize that the different methods fit different goals (O'Mahony, 1995). Other controversies will get renewed interest in light of recent consciousness studies within philosophy of mind as well as cognitive science. I shall here mention two, the first one concerns validation of sensory knowledge, and the second is related to standardization of a vocabulary for sensory terms.

5.1.1. Objectivity versus subjectivity

As discussed above, sensory methods are often categorized as objective (understood as ‘intersubjectivity' or ‘consensus' among panelists), or subjective (when associated with emotions and preferences). From an epistemological point of view it is not so critical, so to speak, how these words are used to name the methods. Rather the controversies arise when it comes to validation or justification of the results obtained by using the methods. We sense the product Image we sense ourselves with respect to the product. With what right do we conclude that an apple is sweet? This brings us back to the history of sense perception, offering three answers. A realist would say: The apple is sweet, valid by statistical significant tests of ‘objective' sensory data (analogous to ‘objective' sugar analysis data). A phenomenalist would say: The apple is sweet, because the word ‘sweet' gives meaning to my subjective sensory experience in the given context. And a pragmatic validation would be: The apple is sweet as understood by the involved partners for a given purpose. Will justification of sensory results require a multiple set of validation criteria to cut the dichotomy between subjectivity and objectivity?

5.1.2. Organoleptic versus sensory

The International Organization for Standardization (ISO)/Sub-Committee for Sensory Analysis has responsibility to work out standards for, among others, “Sensory Analysis Vocabulary”. In the last version from 1992 (ISO 5492) the term ‘sensory' is defined as ‘relating to the use of the sense organs', to be distinguished from ‘organoleptic', defined as ‘relating to an attribute of a product perceptible by the sense organs'. Citing the standard, sourness, bitterness, sweetness, flavour, texture, aroma, mouthfeel etc. are ‘organoleptic attributes.' The distinction between ‘sensory' and ‘organoleptic' has been a controversial issue in the ISO history since the end of the 60s. The origin of the word ‘organoleptic' is said to be ‘properties by which bodies act upon the senses and bodily organs', i.e. no emphasis is laid on the chemical senses (Gridgeman, 1956). One argument to keep this word in the sensory vocabulary is to give a name to substances that are capable of stimulating our organs and which can be measured chemically or physically. Product properties and experiences are logically distinct. One argument against having two words is that it is very confusing in sensory communication to operate with two words that seem artificial to separate. If the ‘organoleptic' properties are chemical and physical properties in the product, why not call it what it is? We need the sensory attributes to know what the effect a substance has on the senses. Perhaps an explanation of the controversy can be traced back to the history of sense perception, to the distinction between primary and secondary qualities or the sense-datum theories discussed above.

5.2. Teaching in sensory science is needed

Necessary development in the future heavily relies on the possibilities of educating research scientists into the field. This shall not be detailed here other than pointing at the value of a ‘Socratic dialogue' as a teaching form, stimulating curiosity and “why”-questions among students. The content should be limited to theories and inquiries necessary for real world problem solving including ethical issues with respect to using “human beings as instrument”. The start of a debate is welcome (e.g. Lawless and Schutz). “A philosophy for sensory science” aims at bridging sensory science between present and future generations.

6. Conclusions

“A philosophy for sensory science” is based on inquiries into the uniqueness, role, methods and future for the field. The UNIQUENESS of sensory science reflects the multitude of problems involved in providing food for human consumption; i.e. it deals with product–person relations. It is interdisciplinary, timeless, existential, integrating and is concerned with “real world” problem solving. Fundamental questions like “Can we trust the senses?” place the field into a 2500 years long history of sense perception. Sensory science includes the entire process from harvesting to serving; thus it plays important ROLES in the industry, research and society. The various activities involved should be justified according to professional ethics. Sound SENSORY METHODOLOGY rests on a thorough knowledge of sensory physiology and an understanding of the psychology of perception in light of modern cognitive science and consciousness of mind studies. Essential in addition is multivariate approaches to statistical design and data analyses. Finally, new understanding of sensory judgement is to be sought through correlation with physical and chemical data, and through multivariate psychophysics. In the FUTURE more basic sensory research and education of research scientists are of utmost importance to strengthen the field. Philosophical discourses should be stimulated, bringing new insight and making sensory science an attractive and exciting field to work in for many professions.


The author wants to thank many persons for giving inspiring, constructive and substantial comments to the lecture and to previous versions of this paper. Especially thanks to E. von Sydow, A. Noble, H.G. Schutz, H.L. Meiselman, E. Risvik, G. Dijksterhuis, H. Martens, S. MacRae, W. Bredie, H. Tuorila, M. Degenaar, P. Sandøe.


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Corresponding Author Contact Information Tel.: +45-352-83242; fax: +45-352-83210; email: mma@kvl.dk

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