John McMahon | University of the West of Scotland (UWS) (original) (raw)

Papers by John McMahon

Research paper thumbnail of Diagnosing and dealing with the 'new British disease

Research paper thumbnail of Commentary Establishing Rates of Binge Drinking in the Uk: Anomalies in the Data

Abstract—Aims: Several studies funded by the UK government have been influential in understanding... more Abstract—Aims: Several studies funded by the UK government have been influential in understanding rates of ‘binge drinking ’ in the UK. This analysis aims to establish consistency between results and clarify UK rates of binge drinking.Method: The relevant sections

Research paper thumbnail of Normative Beliefs, Misperceptions, and Heavy Episodic Drinking in a British Student Sample

Journal of Studies on Alcohol and Drugs, 2007

Research paper thumbnail of Binge drinking behaviour, attitudes and beliefs in a UK community sample: An analysis by gender, age and deprivation

Drugs: Education, Prevention and Policy, 2007

Binge drinking has sparked considerable interest and concern. However despite this interest littl... more Binge drinking has sparked considerable interest and concern. However despite this interest little is known about the lay understanding of binge drinking and whether there are differences in understanding by gender, age and level of deprivation. Aims: This study investigated the beliefs and attitudes of a sample in the Inverclyde area to binge drinking. Methods: Using both cluster and quota sampling, 586 subjects completed a structured interview, using open questions about their beliefs on binge drinking and was it a problem generally and locally. Findings: Definitions of binge drinking tended to concentrate on intoxication and some described a dependent drinking pattern. Causes and solutions offered were varied but pointed up levels of deprivation in respect of jobs and entertainment. More subjects regarded binge drinking as a problem in society than locally, which is consistent with research suggesting that misperceptions of others' drinking increases with social distance. Differences in beliefs were found by age and level of deprivation but not gender. It was marked that no subject offered the 'official' definition of bingeing or even an approximation of it. Conclusions: Further research is required if future mass media campaigns and interventions are to be relevant to the population.

Research paper thumbnail of Establishing Rates of Binge Drinking in the Uk: Anomalies in the Data

Alcohol and Alcoholism, 2006

Aims: Several studies funded by the UK government have been influential in understanding rates of... more Aims: Several studies funded by the UK government have been influential in understanding rates of 'binge drinking' in the UK. This analysis aims to establish consistency between results and clarify UK rates of binge drinking. Method: The relevant sections of these surveys were compared: the Scottish Health Survey (SHS) 1998, the General Household Survey (GHS) 2002, and the Health Survey for England (HSE) 2003. In addition the methodology used by the Health Protection Agency in the Adult Drinking Patterns in Northern Ireland (2003) was compared with the approach used by the SHS, GHS, and HSE. Results: Marked differences were observed between the results of the GHS 2002 and both the SHS 1998 and the HSE 2002 despite each using a similar methodology, with the HSE 2003 reporting a rate of 'binge drinking' in young males of 57%, and the GHS reporting a rate of 35%. This difference may be largely attributed to variations in the criteria in binge drinking in each study. These differences in interpretation do not appear to have been acknowledged. Indeed several key documents on alcohol harm reduction made inaccurate citations of previous surveys. Conclusion: The media rhetoric on escalating rates of binge drinking in the UK should be regarded with caution until trends are based on standardized recording and reporting.

Research paper thumbnail of Is it Time for a Change of Direction in Treatment Research?

Addiction Research, 1998

The editor of this journal opened a lecture on addiction to my students by stating that the longe... more The editor of this journal opened a lecture on addiction to my students by stating that the longer he worked in the addiction field the less certain he was about anything (John B. Davies 1998). An enigmatic, although somewhat hackneyed, start, I thought at the time. However, I find myself more and more echoing these sentiments (although not in public and certainly not in front of my students, at least not yet).

Research paper thumbnail of Social Drinkers' Negative Alcohol Expectancy Relates to Their Satisfaction with Current Consumption: Measuring Motivation for Change with the Naeq

Alcohol and Alcoholism, 1994

Negative alcohol expectancy (NAE) discriminates between social drinkers satisfied with their curr... more Negative alcohol expectancy (NAE) discriminates between social drinkers satisfied with their current consumption and those who are not (even when the variable, consumption, is controlled). The potential treatment use of NAE as a measure of motivation to change and the bottom-up approach that it represents is discussed and contrasted with the top-down approach represented by the more traditional 'readiness to change' measures. consumption: measuring motivation for change with the Negative Alcohol Expectancy Questionnaire.

Research paper thumbnail of Negative and positive alcohol expectancies as predictors of abstinence after discharge from a residential treatment program: a one-month and three-month follow-up study in men

Journal of studies on alcohol, 1994

Male alcohol dependent clients (N = 53), who were given the Alcohol Expectancy Questionnaire and ... more Male alcohol dependent clients (N = 53), who were given the Alcohol Expectancy Questionnaire and the Negative Alcohol Expectancy Questionnaire upon admission to a residential alcohol treatment program, were successfully followed-up 1 month and 3 months after discharge to assess their compliance with the treatment goal of total abstinence. At 1 month, neither demographic variables nor alcohol expectancies were associated with outcome consumption. At 3 months, however, the demographic variable, age, total negative expectancy (but not total positive) and the two subscales, global positive expectancy and continued-drinking negative expectancy (representing longer term expected negative consequences), were. The potential importance of negative alcohol expectancy in drinking decisions and the limitations of the study were identified.

Research paper thumbnail of Changes in alcohol expectancies during treatment relate to subsequent abstinence survivorship*

British Journal of Clinical Psychology, 1996

l a p w , G l a p w G 12 SQQ, UK When negative alcohol expectancies are measured appropriately th... more l a p w , G l a p w G 12 SQQ, UK When negative alcohol expectancies are measured appropriately they form at least as secure associations with measures of consumption as has been demonstrated by mainstream expectancy research for positive alcohol expectancies and they can be usefully used to represent a component of motivation to restrain consumption or recover in dependent drinkers. A study is reported in which (i) negative outcome expectancies assessed at admission to treatment reliably predicted number of days t o first drink; (ii) the same relationship is discovered for discharge measures (iii) and, although the change in negative expectancies between admission and discharge does not, itself, predict the number of days to first drink, it does when the corresponding admission measure is also taken into account. The same predictive relationships were not found for positive expectancies. Implications for planning treatment are discussed in terms of treatment enhancement rather than treatment matching. Recent conceptions of alcohol problem treatment place client motivation for change or recovery at its centre making it a legitimate treatment target. Client motivation is claimed to impact treatment outcome in a number of ways: as apre-treatment to enable better advantage to be taken of traditional treatment (Chafatez, 1968; Southwick &

Research paper thumbnail of Internet lists supporting addiction Research

Addiction Research & Theory, 1994

Research paper thumbnail of Binge drinking behaviour, attitudes and beliefs in a UK community sample: An analysis by gender, age and deprivation

Drugs-education Prevention and Policy, 2007

Binge drinking has sparked considerable interest and concern. However, despite this interest litt... more Binge drinking has sparked considerable interest and concern. However, despite this interest little is known about the lay understanding of binge drinking and whether there are differences in understanding by gender, age and level of deprivation. Aims: This study ...

Research paper thumbnail of Post-Treatment Abstinence Survivorship and Motivation for Recovery: The Predictive Validity of the Readiness to Change (RCQ) and Negative Alcohol Expectancy (NAEQ) Questionnaires

Addiction Research & Theory, 1996

Addiction Research 19% Vol. 4, No. 2, pp. 161-176 Reprints available directly from the publisher ... more Addiction Research 19% Vol. 4, No. 2, pp. 161-176 Reprints available directly from the publisher Photocopying permitted by license only ... 0 1996 OPA (Overseas Publishers Association) Amsterdam BV Published in The Netherlands by Hanvood Academic Publishers GmbH Printed in ...

Research paper thumbnail of Comparing Positive and Negative Alcohol Expectancies in Male and Female Social Drinkers

Addiction Research & Theory, 1994

Negative alcohol expectancy has been poorly represented in empirical studies of alcohol consumpti... more Negative alcohol expectancy has been poorly represented in empirical studies of alcohol consumption because (i) conceptions of negative expectancy have been limited and, as a result, (ii) tools to measure it have been crude. In developing the Negative Alcohol Expectancy Questionnaire (NAEQ), Mc Mahon and Jones have addressed this neglect. This paper demonstrates that when measured appropriately, negative expectancy rather than positive expectancy (as measured by the Alcohol Expectancy Questionnaire, AEQ) appears to be associated with consumption in social drinkers. Multiple stepwise regression analyses showed that for 163 subjects (81 males, 82 females): gender and proximal negative expectancies (those surrounding consumption) were associated with the consumption measure, units/session; gender and distal negative expectancies (those relating to the 'next day') were associated with sessions/week; gender and both proximal and distal negative expectancies were associated with units/week. For males: associations with units/session and sessions/week remained but only distal expectancies were associated with units/week. For females: distal negative expectancies and positive expectancies (sexual enhancement) were associated with units/session; age with sessions/week; age, proximal negative expectancies and positive expectancies (physical and social pleasure) with units/week.

Research paper thumbnail of Negative and positive expectancies in lone and group problem drinkers

Addiction, 1992

In this experiment we show that measuring positive expectancy of alcohol use does not discriminat... more In this experiment we show that measuring positive expectancy of alcohol use does not discriminate between lone and group problem drinkers whereas measuring negative expectancy does. Reliably, lower measures in group drinkers is consistent with; (i) our view that negative expectancy provides the motivation for problem drinkers to quit and that anything which inhibits the translation of negative experience into negative expectancy will correspondingly inhibit motivation; and with (ii) the observations of others that social (or group) support can, indeed, often inhibit recovery.

Research paper thumbnail of Negative alcohol expectancy predicts post-treatment abstinence survivorship: the whether, when and why of relapse to a first drink

Addiction, 1994

Using survival analysis, the association was explored between positive and negative alcohol expec... more Using survival analysis, the association was explored between positive and negative alcohol expectancies measured on admission to a non-residential alcohol dependence treatment unit and post-treatment relapse to a first drink (first slip). A reliable association between negative alcohol expectancy (but not positive) and relapse was found. The active negative alcohol expectancies were distal rather than proximal: proximal expectancies surround consumption (‘same day’ expectancies) and distal expectancies relate to the ‘next-day’ following consumption or those longer term expectancies coming from ‘continued drinking’. Only the ‘next day’ component of distal expectancies formed a reliable association with relapse. The use to which negative alcohol expectancy as measured by the Negative Alcohol Expectancy Questionnaire might be put is discussed in terms of (i) a bottom-up representation of motivation for recovery to help treatment match and (ii) a provisor of detailed, client-specific information for structuring motivational interventions.

Research paper thumbnail of The change process in alcoholics: client motivation and denial in the treatment of alcoholism within the context of contemporary nursing

Journal of Advanced Nursing, 1992

Despite being constantly cited as a critical intervening variable in the recovery from alcohol pr... more Despite being constantly cited as a critical intervening variable in the recovery from alcohol problems, there is a paucity of literature on client motivation This paper reviews the current literature which impacts on motivation and its importance in treatment and develops in a stepwise manner the revised expectancy/motivation hypothesis, tentatively explaining both motivation and denial as a natural process in behavioural change Because of the revised expectancy/motivation hypothesis’ distinctly denned stages which closely relate to the process of nursing and the qualitative and quantitative measurement it entails which the nursing process demands, it offers a particularly appropriate model for treatment within nurse practice

Research paper thumbnail of A comparison of positive and negative alcohol expectancy and value and their multiplicative composite as predictors of post-treatment abstinence survivorship

Addiction, 1996

Within social learning theory, positive alcohol expectancies represent motivation to drink and ne... more Within social learning theory, positive alcohol expectancies represent motivation to drink and negative expectancies, motivation to restrain. It is also recognized that a subjective evaluation of expectancies ought to moderate their impact, although the evidence for this in social drinkers is problematic. This paper addresses the speculation that the moderating effect will be more evident in clinical populations. This study shows that (i) both expectancy and value reliably, independently and equally predict clients' abstinence survivorship following discharge from a treatment programme (and that this is almost entirely confined to the negative rather than positive terms). When (ii) expectancy evaluations are processed against expectancy through multiplicative composites (i.e. expectancy x value), their predictive power is only equivalent to either expectancy or value on its own. However (iii) when the multiplicative composite is assessed following the statistical guidelines advocated by Evans (1991) (i.e. within the same model as its constituents, expectancy and value) the increase in outcome variance explained by its inclusion is negligible and casts doubt upon its use in alcohol research. This does not appear to apply to value, however, and its possible role in treatment is discussed.

Research paper thumbnail of Diagnosing and dealing with the 'new British disease

Research paper thumbnail of Commentary Establishing Rates of Binge Drinking in the Uk: Anomalies in the Data

Abstract—Aims: Several studies funded by the UK government have been influential in understanding... more Abstract—Aims: Several studies funded by the UK government have been influential in understanding rates of ‘binge drinking ’ in the UK. This analysis aims to establish consistency between results and clarify UK rates of binge drinking.Method: The relevant sections

Research paper thumbnail of Normative Beliefs, Misperceptions, and Heavy Episodic Drinking in a British Student Sample

Journal of Studies on Alcohol and Drugs, 2007

Research paper thumbnail of Binge drinking behaviour, attitudes and beliefs in a UK community sample: An analysis by gender, age and deprivation

Drugs: Education, Prevention and Policy, 2007

Binge drinking has sparked considerable interest and concern. However despite this interest littl... more Binge drinking has sparked considerable interest and concern. However despite this interest little is known about the lay understanding of binge drinking and whether there are differences in understanding by gender, age and level of deprivation. Aims: This study investigated the beliefs and attitudes of a sample in the Inverclyde area to binge drinking. Methods: Using both cluster and quota sampling, 586 subjects completed a structured interview, using open questions about their beliefs on binge drinking and was it a problem generally and locally. Findings: Definitions of binge drinking tended to concentrate on intoxication and some described a dependent drinking pattern. Causes and solutions offered were varied but pointed up levels of deprivation in respect of jobs and entertainment. More subjects regarded binge drinking as a problem in society than locally, which is consistent with research suggesting that misperceptions of others' drinking increases with social distance. Differences in beliefs were found by age and level of deprivation but not gender. It was marked that no subject offered the 'official' definition of bingeing or even an approximation of it. Conclusions: Further research is required if future mass media campaigns and interventions are to be relevant to the population.

Research paper thumbnail of Establishing Rates of Binge Drinking in the Uk: Anomalies in the Data

Alcohol and Alcoholism, 2006

Aims: Several studies funded by the UK government have been influential in understanding rates of... more Aims: Several studies funded by the UK government have been influential in understanding rates of 'binge drinking' in the UK. This analysis aims to establish consistency between results and clarify UK rates of binge drinking. Method: The relevant sections of these surveys were compared: the Scottish Health Survey (SHS) 1998, the General Household Survey (GHS) 2002, and the Health Survey for England (HSE) 2003. In addition the methodology used by the Health Protection Agency in the Adult Drinking Patterns in Northern Ireland (2003) was compared with the approach used by the SHS, GHS, and HSE. Results: Marked differences were observed between the results of the GHS 2002 and both the SHS 1998 and the HSE 2002 despite each using a similar methodology, with the HSE 2003 reporting a rate of 'binge drinking' in young males of 57%, and the GHS reporting a rate of 35%. This difference may be largely attributed to variations in the criteria in binge drinking in each study. These differences in interpretation do not appear to have been acknowledged. Indeed several key documents on alcohol harm reduction made inaccurate citations of previous surveys. Conclusion: The media rhetoric on escalating rates of binge drinking in the UK should be regarded with caution until trends are based on standardized recording and reporting.

Research paper thumbnail of Is it Time for a Change of Direction in Treatment Research?

Addiction Research, 1998

The editor of this journal opened a lecture on addiction to my students by stating that the longe... more The editor of this journal opened a lecture on addiction to my students by stating that the longer he worked in the addiction field the less certain he was about anything (John B. Davies 1998). An enigmatic, although somewhat hackneyed, start, I thought at the time. However, I find myself more and more echoing these sentiments (although not in public and certainly not in front of my students, at least not yet).

Research paper thumbnail of Social Drinkers' Negative Alcohol Expectancy Relates to Their Satisfaction with Current Consumption: Measuring Motivation for Change with the Naeq

Alcohol and Alcoholism, 1994

Negative alcohol expectancy (NAE) discriminates between social drinkers satisfied with their curr... more Negative alcohol expectancy (NAE) discriminates between social drinkers satisfied with their current consumption and those who are not (even when the variable, consumption, is controlled). The potential treatment use of NAE as a measure of motivation to change and the bottom-up approach that it represents is discussed and contrasted with the top-down approach represented by the more traditional 'readiness to change' measures. consumption: measuring motivation for change with the Negative Alcohol Expectancy Questionnaire.

Research paper thumbnail of Negative and positive alcohol expectancies as predictors of abstinence after discharge from a residential treatment program: a one-month and three-month follow-up study in men

Journal of studies on alcohol, 1994

Male alcohol dependent clients (N = 53), who were given the Alcohol Expectancy Questionnaire and ... more Male alcohol dependent clients (N = 53), who were given the Alcohol Expectancy Questionnaire and the Negative Alcohol Expectancy Questionnaire upon admission to a residential alcohol treatment program, were successfully followed-up 1 month and 3 months after discharge to assess their compliance with the treatment goal of total abstinence. At 1 month, neither demographic variables nor alcohol expectancies were associated with outcome consumption. At 3 months, however, the demographic variable, age, total negative expectancy (but not total positive) and the two subscales, global positive expectancy and continued-drinking negative expectancy (representing longer term expected negative consequences), were. The potential importance of negative alcohol expectancy in drinking decisions and the limitations of the study were identified.

Research paper thumbnail of Changes in alcohol expectancies during treatment relate to subsequent abstinence survivorship*

British Journal of Clinical Psychology, 1996

l a p w , G l a p w G 12 SQQ, UK When negative alcohol expectancies are measured appropriately th... more l a p w , G l a p w G 12 SQQ, UK When negative alcohol expectancies are measured appropriately they form at least as secure associations with measures of consumption as has been demonstrated by mainstream expectancy research for positive alcohol expectancies and they can be usefully used to represent a component of motivation to restrain consumption or recover in dependent drinkers. A study is reported in which (i) negative outcome expectancies assessed at admission to treatment reliably predicted number of days t o first drink; (ii) the same relationship is discovered for discharge measures (iii) and, although the change in negative expectancies between admission and discharge does not, itself, predict the number of days to first drink, it does when the corresponding admission measure is also taken into account. The same predictive relationships were not found for positive expectancies. Implications for planning treatment are discussed in terms of treatment enhancement rather than treatment matching. Recent conceptions of alcohol problem treatment place client motivation for change or recovery at its centre making it a legitimate treatment target. Client motivation is claimed to impact treatment outcome in a number of ways: as apre-treatment to enable better advantage to be taken of traditional treatment (Chafatez, 1968; Southwick &

Research paper thumbnail of Internet lists supporting addiction Research

Addiction Research & Theory, 1994

Research paper thumbnail of Binge drinking behaviour, attitudes and beliefs in a UK community sample: An analysis by gender, age and deprivation

Drugs-education Prevention and Policy, 2007

Binge drinking has sparked considerable interest and concern. However, despite this interest litt... more Binge drinking has sparked considerable interest and concern. However, despite this interest little is known about the lay understanding of binge drinking and whether there are differences in understanding by gender, age and level of deprivation. Aims: This study ...

Research paper thumbnail of Post-Treatment Abstinence Survivorship and Motivation for Recovery: The Predictive Validity of the Readiness to Change (RCQ) and Negative Alcohol Expectancy (NAEQ) Questionnaires

Addiction Research & Theory, 1996

Addiction Research 19% Vol. 4, No. 2, pp. 161-176 Reprints available directly from the publisher ... more Addiction Research 19% Vol. 4, No. 2, pp. 161-176 Reprints available directly from the publisher Photocopying permitted by license only ... 0 1996 OPA (Overseas Publishers Association) Amsterdam BV Published in The Netherlands by Hanvood Academic Publishers GmbH Printed in ...

Research paper thumbnail of Comparing Positive and Negative Alcohol Expectancies in Male and Female Social Drinkers

Addiction Research & Theory, 1994

Negative alcohol expectancy has been poorly represented in empirical studies of alcohol consumpti... more Negative alcohol expectancy has been poorly represented in empirical studies of alcohol consumption because (i) conceptions of negative expectancy have been limited and, as a result, (ii) tools to measure it have been crude. In developing the Negative Alcohol Expectancy Questionnaire (NAEQ), Mc Mahon and Jones have addressed this neglect. This paper demonstrates that when measured appropriately, negative expectancy rather than positive expectancy (as measured by the Alcohol Expectancy Questionnaire, AEQ) appears to be associated with consumption in social drinkers. Multiple stepwise regression analyses showed that for 163 subjects (81 males, 82 females): gender and proximal negative expectancies (those surrounding consumption) were associated with the consumption measure, units/session; gender and distal negative expectancies (those relating to the 'next day') were associated with sessions/week; gender and both proximal and distal negative expectancies were associated with units/week. For males: associations with units/session and sessions/week remained but only distal expectancies were associated with units/week. For females: distal negative expectancies and positive expectancies (sexual enhancement) were associated with units/session; age with sessions/week; age, proximal negative expectancies and positive expectancies (physical and social pleasure) with units/week.

Research paper thumbnail of Negative and positive expectancies in lone and group problem drinkers

Addiction, 1992

In this experiment we show that measuring positive expectancy of alcohol use does not discriminat... more In this experiment we show that measuring positive expectancy of alcohol use does not discriminate between lone and group problem drinkers whereas measuring negative expectancy does. Reliably, lower measures in group drinkers is consistent with; (i) our view that negative expectancy provides the motivation for problem drinkers to quit and that anything which inhibits the translation of negative experience into negative expectancy will correspondingly inhibit motivation; and with (ii) the observations of others that social (or group) support can, indeed, often inhibit recovery.

Research paper thumbnail of Negative alcohol expectancy predicts post-treatment abstinence survivorship: the whether, when and why of relapse to a first drink

Addiction, 1994

Using survival analysis, the association was explored between positive and negative alcohol expec... more Using survival analysis, the association was explored between positive and negative alcohol expectancies measured on admission to a non-residential alcohol dependence treatment unit and post-treatment relapse to a first drink (first slip). A reliable association between negative alcohol expectancy (but not positive) and relapse was found. The active negative alcohol expectancies were distal rather than proximal: proximal expectancies surround consumption (‘same day’ expectancies) and distal expectancies relate to the ‘next-day’ following consumption or those longer term expectancies coming from ‘continued drinking’. Only the ‘next day’ component of distal expectancies formed a reliable association with relapse. The use to which negative alcohol expectancy as measured by the Negative Alcohol Expectancy Questionnaire might be put is discussed in terms of (i) a bottom-up representation of motivation for recovery to help treatment match and (ii) a provisor of detailed, client-specific information for structuring motivational interventions.

Research paper thumbnail of The change process in alcoholics: client motivation and denial in the treatment of alcoholism within the context of contemporary nursing

Journal of Advanced Nursing, 1992

Despite being constantly cited as a critical intervening variable in the recovery from alcohol pr... more Despite being constantly cited as a critical intervening variable in the recovery from alcohol problems, there is a paucity of literature on client motivation This paper reviews the current literature which impacts on motivation and its importance in treatment and develops in a stepwise manner the revised expectancy/motivation hypothesis, tentatively explaining both motivation and denial as a natural process in behavioural change Because of the revised expectancy/motivation hypothesis’ distinctly denned stages which closely relate to the process of nursing and the qualitative and quantitative measurement it entails which the nursing process demands, it offers a particularly appropriate model for treatment within nurse practice

Research paper thumbnail of A comparison of positive and negative alcohol expectancy and value and their multiplicative composite as predictors of post-treatment abstinence survivorship

Addiction, 1996

Within social learning theory, positive alcohol expectancies represent motivation to drink and ne... more Within social learning theory, positive alcohol expectancies represent motivation to drink and negative expectancies, motivation to restrain. It is also recognized that a subjective evaluation of expectancies ought to moderate their impact, although the evidence for this in social drinkers is problematic. This paper addresses the speculation that the moderating effect will be more evident in clinical populations. This study shows that (i) both expectancy and value reliably, independently and equally predict clients' abstinence survivorship following discharge from a treatment programme (and that this is almost entirely confined to the negative rather than positive terms). When (ii) expectancy evaluations are processed against expectancy through multiplicative composites (i.e. expectancy x value), their predictive power is only equivalent to either expectancy or value on its own. However (iii) when the multiplicative composite is assessed following the statistical guidelines advocated by Evans (1991) (i.e. within the same model as its constituents, expectancy and value) the increase in outcome variance explained by its inclusion is negligible and casts doubt upon its use in alcohol research. This does not appear to apply to value, however, and its possible role in treatment is discussed.