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Towards scientific realism in eating research
Appetite, 1992, 19, 56-60
Commentary Towards
Scientific
Realism
in Eating Research
D. A. BOOTH School of Psychology, University of Birmingham
Herb Meiselman has unique quantities and variety of data on frequencies of choice among foodstuffs and the average amounts consumed at real meals in real situations. Although he purports to exclude verbal data from his review (don’t fieldworkers make records?), he has also been known to ask the customers questions, in writing at least. Meiselman (1992) pleads eloquently for more use of real-life methods like his. It’s unclear to me, though, how this will help “theory in human eating research” which is coupled with methodology in the title of his article. Field studies to date have unfortunately been even less help than laboratory studies in understanding factors that control eating by people, to which Meiselman (1992) states his research interests have shifted. The diagnosis of mine he quotes, that “The study of human food consumption [is] subscientific” (Booth, 1987a), was applied to uptakes and ratings from catering situations no less than to observations from sensory tests or test-snack intakes. I was pointing out that current research of all sorts typically confounds the factors liable to be controlling eating. Often, important sources of influence are not even measured, let alone factored out, be they sensory, somatic or social. Even how the eater’s thinking is affected by particular factors is generally not assessed. That is, the quotation was not referring in the first instance, as Meiselman takes it, to neglect of individualized causal analysis-essential though that is to characterize interactions among factors where they really operate. Nonetheless, it should be noted that individual methodology is not limited to ‘laboratory-based experiments on simple food models” (Meiselman, 1992); we have applied it to ethnographic (open-ended) interviews (Figure l), as indicated in papers alluded to by Meiselman (Booth, 1987~; Booth & Blair, 1989) and elsewhere (Booth, 1988a, 1990); it is applicable to food uptake observations in the field, as indicated indirectly in different ways in the work Meiselman cites by de Castro et al. (1990) and our withinsubject experiments in animals (e.g. Baker et al., 1987; Booth & Davis, 1973; Gibson & Booth, 1989). The first prerequisite for scientific understanding of eating and drinking is not individualization. It is observations that separate out the different factors operating within and across perceptions of the foods, the body and the social and physical Address correspondence to David Booth, Edgbaston, Birmingham B15 2TT, U.K. 0195-6663/92/040056+05 %08.00/O
School of Psychology,
University
of Birmingham,
0 1992 Academic Press Limited
57
D. A. BOOTH
environment. Responses to a cafeteria meal service are liable to confound different sources of influence worse than responses to a test yogurt in a laboratory snack. When controlling factors are intercorrelated (and not even measured) it is impossible to identify what it is in the situation that is making the observed difference (Booth, 19874. Mere attributions to different sources of influence (e.g., ratings of palatability of the food, sensations in the body and appropriateness to the occasion) do not identify factors either. Different ratings do not even distinguish unidentified influences if the ratings are highly interrelated, as is found to be the case when correlations are run (Booth, 1987b; Hill et al., 1987). The minimum scientific requirement on observational data is to measure enough of the real causes and effects in a sufficiently disconfounded set of situations for canonical, path or latent analysis to yield strong relationships between theoretically likely inputs and outputs. In consequence, field studies generally can test only the limited number of aggregate predictions that can be made from analysis of the patterns of causal processes within individuals. Field observation may also suggest hypotheses for such tests of the effects of measured and disconfounded factors. This relationship between scientific investigation and real-life data has been illustrated in other discussions (e.g. Booth, 19883) and in reports on theoretically predicted long-term effects of real-life food intake that Meiselman’s searches seem to have missed (Blair et al., 1989, 1990). In other words, we should not only treat people as individuals; we should also treat them as real. The participants in experiments, quizzes or field research are being treated as real people only if the investigator is using their cooperation (unobtrusively or not) to improve our understanding of why they are behaving as observed. This is only possible if sufficient of the logic of controlled experiment is introduced into the field study (Kemm & Booth, 1992) and sufficient of real life is introduced into the field or laboratory experiment (Booth, 1988~~)for either sort of results to be theoretically interpretable.
Time
of
Puts on weight
66
Affects
Wish to
i:l:&&&ock
Compony Dresent
661 Flovour
eot 011 I like
day
48
FIGURE 1. Linear bivariate evidence (percentage correlations, all that reached p < 0.05) for cognitive processes in ratings by a dieter of the disposition to snack in described real-life variants of her situation at home in the late morning of a weekday (M. Armstrong & D. A. Booth, unpublished data). This is a within-person path analysis but, more crucially, levels of the hypothesized factors influencing eating have been estimated and disconfounded in the descriptions presented (cp. Booth & Blair, 1989).
58
TOWARDS
SCIENTIFIC
REALISM IN EATING RESEARCH
Despite Meiselman’s remarks, participants in human experiments are just as much real people as are restaurant customers. An ecologically valid experiment respects the reality of human beings better than a field study that lumps all the customers’ choices together without elucidating any of the influences on them. The label “customer” is no better than the label “subject” if the person is being treated as mere fodder for the production of data on food consumption. It should be added that samples of dieters, overweight people or alcohol consumers are statistically no more abnormal than populations full of young, healthy men from poorer backgrounds. It is by no means clear either that bingers or even self-starvers are mentally abnormal, any more than, say, those returning to base after a stressful military exercise or highly dedicated and ambitious army officers. Any scientifically interpretable investigation of eating by a number of people of known characteristics is a good way of learning how, why and what human beings actually eat and drink. I hope that this Journal continues that as its prime criterion for publication (and in any species too). Sadly, however, the reality of the mental organization determining an eater’s behaviour in a context is too ghostly for most contemporary biologists and even for some psychologists of food and nutrition. In so many research reports, only the eaten food seems to be regarded as real and objective; intake is confused with eating behaviour. This is quite paradoxical because “food” is not a physicochemically defined material, even though the term can be given a loose biological sense as sources of nutrition. “Food” is a perceptual construct-whatever stuff eaters regard as edible. “Food” intake is conventionally reported in the highly abstract and dubiously measured units of supposed metabolic energy, a factor having weak, imprecise and indirect control of eating behaviour, even in those who read the nutrition labels! Human eating research needs to face up to the soul in the behaviour. In other words, food choice and intake is an individual performance that requires analysis along lines indicated by Wittgenstein (1953) and Broadbent (1960), for example, which it is now fashionable to call cognitive science. Further contrary to Meiselman, realism does not preclude experiments on just sensory factors, or indeed just social or physiological factors. What it excludes is experiments varying a single factor (such as sweetener level, volume in the stomach, number of people present or dietary restraint score) that either fail to distinguish multiple causal mediation of the effects of the controlled factor or present the variation out of its familiar context. An experiment on just sweetness or saltiness levels, without postingestional or ambience differences, can advance understanding of the factors in eating (psychometrically and in quantitative aggregate too) so long as the taste variation is in familiar foods and drinks consumed in sufficiently close to normal circumstances (e.g. Booth et al., 1983; Conner & Booth, 1988; Conner et al., 1988). Similarly, an experiment on just one physiological factor, in a context in which it commonly operates in the participant (cf. Booth, 1972; Booth & Jarman, 1976), would increase our understanding of postingestional influences on eating as no other sort of study could. What Meiselman could justly have a beef against is so-called sensory analysis that tries to sort out consumers’ perceptions of a menu by analysing ratings of component materials sampled by anybody who can be dragooned into the booths at any time of day (Booth et al., 1991) or so-called satiety measurement that maps the time-course of appetite or intake reduction after ingesting a test food without regard to the sensory, physiological and cultural factors that mediate the observed effects
D. A. BOOTH
59
(Booth, 1989, 1991). The resulting statistics apply only to the tests they came from and they can tell us little if anything of why people eat. Worse still, the artificiality endangers the precision that it is assumed to protect. Naturalism is a necessary condition for the high resolution required to achieve fundamental advances in understanding the interactions of factors in eating motivation (Booth, 1987~; Booth & Conner, 1991; Booth et al., 1991). So the merits of ecological validity are not limited to those interested in applicability. The best way to do science is to collect theoretically interpretable data.
biFERENCE.3
Baker, B. J., Booth, D. A., Duggan, J. P. & Gibson, E. L. (1987) Protein appetite demonstrated: learned specificity of protein-cue preference to protein need in adult rats. Nutrition Research, 7, 481-487.
Blair, A. J., Booth, D. A., Lewis, V. J. & Wainwright, C. J. (1989) The relative success of official and informal weight reduction techniques: retrospective correlational evidence. Psychology
and Health, 3, 195-206.
Blair, A. J., Lewis, V. J. & Booth, D. A. (1990) Does emotional eating interfere with attempts at weight control in women? Appetite, 1.5, 151-157. Booth, D. A. (1972) Postabsorptively induced suppression of appetite and the energostatic control of feeding. Physiology and Behavior, 9, 199-202. Booth, D. A. (1987a). Objective measurement of determinants of food acceptance: sensory, physiological and psychosocial. In J. Solms, D. A. Booth, R. M. Pangborn & 0. Raunhardt (Eds.), Food acceptance and nutrition. Pp. l-27. London: Academic Press. Booth, D. A. (19876) Cognitive experimental psychology of appetite. In R. A. Boakes, M. J. Burton & D. A. Popplewell (Eds.), Eating habits. Pp. 175-209. Chichester: Wiley. Booth, D. A. (1988a). Practical measurement of the strengths of actual influences on what consumers do: scientific brand design. Journal of the Market Research Society (U.K.), 30, 127-146.
Booth, D. A. (19886) Mechanisms from models-actual effects from real life: the zero-calorie drink-break option. Appetite, 9 (Suppl.), 94-102. Booth, D. A. (1989) The effect of dietary starches and sugars on satiety and on mental state and performance. In J. Dobbing (Ed.), Dietary starches and sugars in Man: a comparison. Pp. 225249. London: Springer-Verlag. Booth, D. A. (1990) Designing products for individual customers. In R. L. McBride & H. J. H. MacFie (Eds.), Psychological bases of sensory evaluation. Pp. 163-193. London: Elsevier Applied Science. Booth, D. A. (1991) Are low-calorie substitutes compensated? Appetite, 17, 159. Booth, D. A. & Blair, A. J. (1989) Objective factors in the appeal of a brand during use by the individual consumer. In D. M. H. Thomson (Ed.), Food acceptability. Pp. 329-346. London: Elsevier Applied Science. Booth, D. A. & Conner, M. T. (1991) Characterisation and measurement of influences on food acceptability by analysis of choice differences: theory and practice. Food Quality and Preference, 2, 75-85.
Booth, D. A. & Davis, J. D. (1973) Gastrointestinal factors in the acquisition of oral sensory control of satiation. Physiology and Behavior, 11, 23-29. Booth, D. A. & Jarman, S. P. (1976) Inhibition of food intake in the rat following complete absorption of glucose delivered into the stomach, intestine or liver. Journal of Physiology, 259, 501-522.
Booth, D. A., Thompson, A. L. & Shahedian, B. (1983) A robust, brief measure of an individual’s most preferred level of salt in an ordinary foodstuff. Appetite, 4, 301-312. Booth, D. A., Freeman R. P. J. & Lahteenmiiki, L. (1991) Likings for complex foods and meals. Appetite, 17, 156. Broadbent, D. E. (1964) Behaviour. London: Methuen.
60
TOWARDS SCIENTIFIC REALISM IN EATING RESEARCH
Conner, M. T. & Booth, D. A. (1988) Preferred sweetness of a lime drink and preference for sweet over non-sweet foods, related to sex and reported age and body weight. Appetite, 10, 25-35. Conner, M. T., Haddon, A. V., Pickering, E. S. & Booth, D. A. (1988) Sweet tooth demonstrated: individual differences in preference for both sweet foods and foods highly sweetened. Journal of Applied Psychology, 73, 275-280. de Castro, J. M., Brewer, E. M., Ehnore, D. K. & Orozco, S. (1990) Social facilitation of the spontaneous meal size of humans regardless of time, place, alcohol or snacks. Appetite, 15, 89-101. Gibson, E. L. & Booth, D. A. (1989) Dependence of carbohydrate-conditioned flavor preference on internal state in rats. Learning and Motivation, 20, 36-47. Hill, A. J., Blundell, J. E. & Leathwood, P. D. (1987) Effects of meal composition on appetite, satiety and food preferences. Human Nutrition, 41A, 224-257. Kemm, J. R. & Booth, D. A. (1992) Promotion of healthy eating: planning, monitoring and evaluation. London: HMSO. Meiselman, H. L. (1992) Methodology and theory in human eating research. Appetite, 19, 49-55. Wittgenstein, L. (1953) Philosophical investigations. Oxford: Blackwell.
Commentary Towards
Scientific
Realism
in Eating Research
D. A. BOOTH School of Psychology, University of Birmingham
Herb Meiselman has unique quantities and variety of data on frequencies of choice among foodstuffs and the average amounts consumed at real meals in real situations. Although he purports to exclude verbal data from his review (don’t fieldworkers make records?), he has also been known to ask the customers questions, in writing at least. Meiselman (1992) pleads eloquently for more use of real-life methods like his. It’s unclear to me, though, how this will help “theory in human eating research” which is coupled with methodology in the title of his article. Field studies to date have unfortunately been even less help than laboratory studies in understanding factors that control eating by people, to which Meiselman (1992) states his research interests have shifted. The diagnosis of mine he quotes, that “The study of human food consumption [is] subscientific” (Booth, 1987a), was applied to uptakes and ratings from catering situations no less than to observations from sensory tests or test-snack intakes. I was pointing out that current research of all sorts typically confounds the factors liable to be controlling eating. Often, important sources of influence are not even measured, let alone factored out, be they sensory, somatic or social. Even how the eater’s thinking is affected by particular factors is generally not assessed. That is, the quotation was not referring in the first instance, as Meiselman takes it, to neglect of individualized causal analysis-essential though that is to characterize interactions among factors where they really operate. Nonetheless, it should be noted that individual methodology is not limited to ‘laboratory-based experiments on simple food models” (Meiselman, 1992); we have applied it to ethnographic (open-ended) interviews (Figure l), as indicated in papers alluded to by Meiselman (Booth, 1987~; Booth & Blair, 1989) and elsewhere (Booth, 1988a, 1990); it is applicable to food uptake observations in the field, as indicated indirectly in different ways in the work Meiselman cites by de Castro et al. (1990) and our withinsubject experiments in animals (e.g. Baker et al., 1987; Booth & Davis, 1973; Gibson & Booth, 1989). The first prerequisite for scientific understanding of eating and drinking is not individualization. It is observations that separate out the different factors operating within and across perceptions of the foods, the body and the social and physical Address correspondence to David Booth, Edgbaston, Birmingham B15 2TT, U.K. 0195-6663/92/040056+05 %08.00/O
School of Psychology,
University
of Birmingham,
0 1992 Academic Press Limited
57
D. A. BOOTH
environment. Responses to a cafeteria meal service are liable to confound different sources of influence worse than responses to a test yogurt in a laboratory snack. When controlling factors are intercorrelated (and not even measured) it is impossible to identify what it is in the situation that is making the observed difference (Booth, 19874. Mere attributions to different sources of influence (e.g., ratings of palatability of the food, sensations in the body and appropriateness to the occasion) do not identify factors either. Different ratings do not even distinguish unidentified influences if the ratings are highly interrelated, as is found to be the case when correlations are run (Booth, 1987b; Hill et al., 1987). The minimum scientific requirement on observational data is to measure enough of the real causes and effects in a sufficiently disconfounded set of situations for canonical, path or latent analysis to yield strong relationships between theoretically likely inputs and outputs. In consequence, field studies generally can test only the limited number of aggregate predictions that can be made from analysis of the patterns of causal processes within individuals. Field observation may also suggest hypotheses for such tests of the effects of measured and disconfounded factors. This relationship between scientific investigation and real-life data has been illustrated in other discussions (e.g. Booth, 19883) and in reports on theoretically predicted long-term effects of real-life food intake that Meiselman’s searches seem to have missed (Blair et al., 1989, 1990). In other words, we should not only treat people as individuals; we should also treat them as real. The participants in experiments, quizzes or field research are being treated as real people only if the investigator is using their cooperation (unobtrusively or not) to improve our understanding of why they are behaving as observed. This is only possible if sufficient of the logic of controlled experiment is introduced into the field study (Kemm & Booth, 1992) and sufficient of real life is introduced into the field or laboratory experiment (Booth, 1988~~)for either sort of results to be theoretically interpretable.
Time
of
Puts on weight
66
Affects
Wish to
i:l:&&&ock
Compony Dresent
661 Flovour
eot 011 I like
day
48
FIGURE 1. Linear bivariate evidence (percentage correlations, all that reached p < 0.05) for cognitive processes in ratings by a dieter of the disposition to snack in described real-life variants of her situation at home in the late morning of a weekday (M. Armstrong & D. A. Booth, unpublished data). This is a within-person path analysis but, more crucially, levels of the hypothesized factors influencing eating have been estimated and disconfounded in the descriptions presented (cp. Booth & Blair, 1989).
58
TOWARDS
SCIENTIFIC
REALISM IN EATING RESEARCH
Despite Meiselman’s remarks, participants in human experiments are just as much real people as are restaurant customers. An ecologically valid experiment respects the reality of human beings better than a field study that lumps all the customers’ choices together without elucidating any of the influences on them. The label “customer” is no better than the label “subject” if the person is being treated as mere fodder for the production of data on food consumption. It should be added that samples of dieters, overweight people or alcohol consumers are statistically no more abnormal than populations full of young, healthy men from poorer backgrounds. It is by no means clear either that bingers or even self-starvers are mentally abnormal, any more than, say, those returning to base after a stressful military exercise or highly dedicated and ambitious army officers. Any scientifically interpretable investigation of eating by a number of people of known characteristics is a good way of learning how, why and what human beings actually eat and drink. I hope that this Journal continues that as its prime criterion for publication (and in any species too). Sadly, however, the reality of the mental organization determining an eater’s behaviour in a context is too ghostly for most contemporary biologists and even for some psychologists of food and nutrition. In so many research reports, only the eaten food seems to be regarded as real and objective; intake is confused with eating behaviour. This is quite paradoxical because “food” is not a physicochemically defined material, even though the term can be given a loose biological sense as sources of nutrition. “Food” is a perceptual construct-whatever stuff eaters regard as edible. “Food” intake is conventionally reported in the highly abstract and dubiously measured units of supposed metabolic energy, a factor having weak, imprecise and indirect control of eating behaviour, even in those who read the nutrition labels! Human eating research needs to face up to the soul in the behaviour. In other words, food choice and intake is an individual performance that requires analysis along lines indicated by Wittgenstein (1953) and Broadbent (1960), for example, which it is now fashionable to call cognitive science. Further contrary to Meiselman, realism does not preclude experiments on just sensory factors, or indeed just social or physiological factors. What it excludes is experiments varying a single factor (such as sweetener level, volume in the stomach, number of people present or dietary restraint score) that either fail to distinguish multiple causal mediation of the effects of the controlled factor or present the variation out of its familiar context. An experiment on just sweetness or saltiness levels, without postingestional or ambience differences, can advance understanding of the factors in eating (psychometrically and in quantitative aggregate too) so long as the taste variation is in familiar foods and drinks consumed in sufficiently close to normal circumstances (e.g. Booth et al., 1983; Conner & Booth, 1988; Conner et al., 1988). Similarly, an experiment on just one physiological factor, in a context in which it commonly operates in the participant (cf. Booth, 1972; Booth & Jarman, 1976), would increase our understanding of postingestional influences on eating as no other sort of study could. What Meiselman could justly have a beef against is so-called sensory analysis that tries to sort out consumers’ perceptions of a menu by analysing ratings of component materials sampled by anybody who can be dragooned into the booths at any time of day (Booth et al., 1991) or so-called satiety measurement that maps the time-course of appetite or intake reduction after ingesting a test food without regard to the sensory, physiological and cultural factors that mediate the observed effects
D. A. BOOTH
59
(Booth, 1989, 1991). The resulting statistics apply only to the tests they came from and they can tell us little if anything of why people eat. Worse still, the artificiality endangers the precision that it is assumed to protect. Naturalism is a necessary condition for the high resolution required to achieve fundamental advances in understanding the interactions of factors in eating motivation (Booth, 1987~; Booth & Conner, 1991; Booth et al., 1991). So the merits of ecological validity are not limited to those interested in applicability. The best way to do science is to collect theoretically interpretable data.
biFERENCE.3
Baker, B. J., Booth, D. A., Duggan, J. P. & Gibson, E. L. (1987) Protein appetite demonstrated: learned specificity of protein-cue preference to protein need in adult rats. Nutrition Research, 7, 481-487.
Blair, A. J., Booth, D. A., Lewis, V. J. & Wainwright, C. J. (1989) The relative success of official and informal weight reduction techniques: retrospective correlational evidence. Psychology
and Health, 3, 195-206.
Blair, A. J., Lewis, V. J. & Booth, D. A. (1990) Does emotional eating interfere with attempts at weight control in women? Appetite, 1.5, 151-157. Booth, D. A. (1972) Postabsorptively induced suppression of appetite and the energostatic control of feeding. Physiology and Behavior, 9, 199-202. Booth, D. A. (1987a). Objective measurement of determinants of food acceptance: sensory, physiological and psychosocial. In J. Solms, D. A. Booth, R. M. Pangborn & 0. Raunhardt (Eds.), Food acceptance and nutrition. Pp. l-27. London: Academic Press. Booth, D. A. (19876) Cognitive experimental psychology of appetite. In R. A. Boakes, M. J. Burton & D. A. Popplewell (Eds.), Eating habits. Pp. 175-209. Chichester: Wiley. Booth, D. A. (1988a). Practical measurement of the strengths of actual influences on what consumers do: scientific brand design. Journal of the Market Research Society (U.K.), 30, 127-146.
Booth, D. A. (19886) Mechanisms from models-actual effects from real life: the zero-calorie drink-break option. Appetite, 9 (Suppl.), 94-102. Booth, D. A. (1989) The effect of dietary starches and sugars on satiety and on mental state and performance. In J. Dobbing (Ed.), Dietary starches and sugars in Man: a comparison. Pp. 225249. London: Springer-Verlag. Booth, D. A. (1990) Designing products for individual customers. In R. L. McBride & H. J. H. MacFie (Eds.), Psychological bases of sensory evaluation. Pp. 163-193. London: Elsevier Applied Science. Booth, D. A. (1991) Are low-calorie substitutes compensated? Appetite, 17, 159. Booth, D. A. & Blair, A. J. (1989) Objective factors in the appeal of a brand during use by the individual consumer. In D. M. H. Thomson (Ed.), Food acceptability. Pp. 329-346. London: Elsevier Applied Science. Booth, D. A. & Conner, M. T. (1991) Characterisation and measurement of influences on food acceptability by analysis of choice differences: theory and practice. Food Quality and Preference, 2, 75-85.
Booth, D. A. & Davis, J. D. (1973) Gastrointestinal factors in the acquisition of oral sensory control of satiation. Physiology and Behavior, 11, 23-29. Booth, D. A. & Jarman, S. P. (1976) Inhibition of food intake in the rat following complete absorption of glucose delivered into the stomach, intestine or liver. Journal of Physiology, 259, 501-522.
Booth, D. A., Thompson, A. L. & Shahedian, B. (1983) A robust, brief measure of an individual’s most preferred level of salt in an ordinary foodstuff. Appetite, 4, 301-312. Booth, D. A., Freeman R. P. J. & Lahteenmiiki, L. (1991) Likings for complex foods and meals. Appetite, 17, 156. Broadbent, D. E. (1964) Behaviour. London: Methuen.
60
TOWARDS SCIENTIFIC REALISM IN EATING RESEARCH
Conner, M. T. & Booth, D. A. (1988) Preferred sweetness of a lime drink and preference for sweet over non-sweet foods, related to sex and reported age and body weight. Appetite, 10, 25-35. Conner, M. T., Haddon, A. V., Pickering, E. S. & Booth, D. A. (1988) Sweet tooth demonstrated: individual differences in preference for both sweet foods and foods highly sweetened. Journal of Applied Psychology, 73, 275-280. de Castro, J. M., Brewer, E. M., Ehnore, D. K. & Orozco, S. (1990) Social facilitation of the spontaneous meal size of humans regardless of time, place, alcohol or snacks. Appetite, 15, 89-101. Gibson, E. L. & Booth, D. A. (1989) Dependence of carbohydrate-conditioned flavor preference on internal state in rats. Learning and Motivation, 20, 36-47. Hill, A. J., Blundell, J. E. & Leathwood, P. D. (1987) Effects of meal composition on appetite, satiety and food preferences. Human Nutrition, 41A, 224-257. Kemm, J. R. & Booth, D. A. (1992) Promotion of healthy eating: planning, monitoring and evaluation. London: HMSO. Meiselman, H. L. (1992) Methodology and theory in human eating research. Appetite, 19, 49-55. Wittgenstein, L. (1953) Philosophical investigations. Oxford: Blackwell.