Norms are rules and expectations by which a society guides the behavior of its members.

Interim summary

Social norms vary not only depending on with a specific culture but also with age, gender, social roles and situations that people find themselves in or engage with. We distinguish injunctive norms, i.e. a person’ viewpoint on what is right based on one’s own beliefs, moral and others’ views on appropriate behavior, depending on the context and the group they are currently with and descriptive norms, i.e. distributions of such beliefs in a population. The latter are usually the focus of social norms interventions, which will be discussed later in this chapter.

The Normative Basis of Group Behavior

Social norms are rules of behavior. They inform group members how to construe a given situation, how to feel about it, and how to behave in it. They exert social influence on group members by prescribing which reactions are appropriate, and which are not (Abrams, Wetherell, Cochrane, Hogg, & Turner, 1990). Social norms hence direct individuals’ cognitions, emotions, and behaviors. They also serve as evaluative standards, against which individuals’ reactions are judged. Quite evidently, social norms are subject to consensus within specific groups—eating with a fork is appropriate in some groups while eating with sticks is more appropriate in others.

While people sometimes behave in accordance with norms of salient groups they are not members of (e.g., taking one’s shoes off when entering a Hindi temple as a Christian tourist), social norms exert their full influence and are internalized only when they originate from ingroups. Because adhering to an ingroup’s social norms is a major component of what it means to be a member of that social group, this kind of normative pressure increases in tandem with identification with the group. Individuals who identify strongly with an ingroup in a specific situation are likely to exhibit the normative behaviors prescribed by that group (e.g., fans chanting together as their team’s mascot enters the field). This referent informational influence (see also Hogg & Turner, 1987) is a marker of social identification, enabling people to distinguish between members and non-members of a group, and between groups on the basis of their observably different norms. This difference in norms is a part of the normative fit referred to in the social identity approach: a group’s norms are contextually informative and socially meaningful.

Because norms also supply group-members with an evaluative standard, they can contribute to a process known as group polarization. The result is that norms within the ingroup can shift to more extreme positions, as members observe their peers acting in increasingly extreme ways, and expressing more extreme versions of the original norm (Isenberg, 1986). This process may sound familiar to anyone who has participated in an online discussion of a political (or any other charged) issue: Individuals quickly organize themselves into opposing camps, and often end up competing with each other at slinging insults at the other camp. Unfortunately, this dynamic has very real implications to contemporary political life, an issue we explore in detail in Chapter 5.

3.3 Society

Social norms, continuously constructed and reconstructed in everyday interactions and transmitted by the socialization agents (family, school, social and work organizations, church, mass media, etc.), play an important role in the process of IA. Social factors influence what is socially desirable, as well as the configuration of an individual’s personality, which in turn influences what each person considers personally desirable in others. Thus IA, as well as physical attraction and love, is not simply a psychological process, as it is commonly perceived by laypeople, but more precisely is a sociopsychological (in fact, biosociopsychological) process.

Procrastinatory behavior from a norms perspective

Social norms are cognitive representations of what relevant others, often called a reference group, would typically think, feel, or do in a given situation, which people use as reference points to guide and assess their own thoughts, feelings, and behavior (Turner, 1991). Once acquired through social learning, the norms can be retrieved from memory automatically and influence our actions whether or not others are present (Aarts, Dijksterhuis, & Custers, 2003; Aarts & Dijksterhuis, 2003; Nolan, Schultz, Cialdini, Goldstein, & Griskevicius, 2008). By using the term “automatic,” we mean that this process may occur without conscious intent and awareness; we do not mean that the influence of norms is uncontrollable or demands no attention (see Bargh, 1994; Jacobson, Mortensen, & Cialdini, 2011). Thus, social norms motivate the self-regulation of both private and public actions by informing individuals of what is likely to be either adaptive or problematic behavior in a given situation.

For the most part the influence of norms operates through social comparison (Cialdini, Kallgren, & Reno, 1991; Prentice, 2000). Instead of relying on an in-depth analysis to determine the goals that are best suited to our current circumstances, as well as the best-suited course of action and the optimal time to pursue them, we can simply turn to social norms, look at what we think others do or should do in similar situations and do the same thing. People go along with (observed or verbally communicated) normative ways of behaving because, in part, they rely on other people’s behavior as a source of information to help them define social reality and act in an adaptive way (Cialdini & Trost, 1998; Turner, 1991).

Social norms will typically evolve in order to facilitate the interaction of individuals with others in social groups (Cialdini & Trost, 1998; Turner, 1991). Our ability to adhere to normative expectations is key to fulfilling our fundamental need to belong (Baumeister & Leary, 1995). Social affiliation and exclusion are assumed to play a central role in the motivational component of normative influence (Cialdini & Trost, 1998; Turner 1991). They can be associated with the actual presence of others, such as being congratulated by or receiving disparaging comments from another person. Social norms can also be associated with the imagined or implied presence of others, such as recalling being congratulated by or receiving disparaging comments from another person (Cialdini & Trost, 1998; Turner, 1991). Social norms can thus have a motivational impact on the actions of individuals through the actual, imagined, or implied presence of others. As other socially learned contingencies, these expectations can dynamically change as a function of situational demands and repeated experiences (Giguère, Vaswani, & Newby-Clark, 2015; Vaswani, Newby-Clark, & Giguère, 2015; see Prentice, 2000).

A dominant assumption, which can be traced to early social influence research (cf, Deutsch & Gerard, 1955), is that people learn that adherence to norms will lead to social affiliation and positive social emotions (e.g., pride), while transgression of norms will lead to social exclusion and negative social emotions (e.g., shame) (see Cialdini & Trost, 1998; Leary, 2000; Rossano, 2012). Thus, social emotions play an integral role in the comparative process by which social norms influence our behavior and well-being.

By directing the self-regulation process, norms are a primary contributor to the well-being of these groups and the people comprising them (Heine, 2012; Turner, 1991). For example, although instant gratification may have been an adaptive strategy at certain points in human evolution (e.g., when much uncertainty resided as to when food would be next available), the emergence of social networks and collaborative efforts toward the satisfaction of primary needs make the principle of reciprocity a more functional option. Collaboration among individuals in this regard is essential to the well-being of all. In a well-functioning group, self-regulation failures will typically transgress social norms, because if they were normative, that is, if the majority of individuals did such behaviors most of the time, the vitality of groups would be jeopardized. Self-regulation failures are therefore often a challenge to a well-functioning group. They have, by definition, long-term costs for the person and his or her community. For example, procrastination may prevent one from fulfilling the demands of the norm of reciprocity, a norm which would benefit the group as a whole by facilitating interactions among individuals and fostering support.

When engaging in procrastinatory behavior, people avoid pursuing an intended goal and instead engage in behaviors that are easier and/or more pleasurable. In most situations, this course of action will lead them to transgress one or more expectations set by social norms. These failures may affect the requirements of the goal they intended to pursue (e.g., poor Halloween costumes) and/or the timeliness of the goal completion (e.g., starting to trick-or-treat late). As such, procrastinatory behavior is a form of self-regulation failure that leads to the transgression of social norms. Thus, procrastinatory behavior should typically be met by cues of social devaluation and rejection that are actually communicated by others following a transgression or automatically activated from learned social contingencies (Giguère et al., 2015; Vaswani et al., 2015).

When people are repeatedly unable to fulfill normative expectations, others around them will devalue them as a person. This devaluation is certainly one commonly ascribed to procrastinators, who because of their procrastination habit, cannot be trusted to fulfill the commitments tied to normative expectations. People use the normative behavior of others to give them information as to who they are as a person. Procrastinatory behavior communicates a variety of less than flattering personal attributes that are commonly associated with procrastinators: that the person has low self-control, poor time-management skills, lack of consideration for others, is lazy, and that he or she struggles to delay gratification and is likely to pursue impulses as they arise. Indeed, past work that observed that procrastination is associated with low self-control (Ferrari & Emmons, 1995; Sirois, 2004). Procrastination may hamper the ability of individuals to fulfill their obligations and commitments made to others, making them less valuable from a cooperation perspective as a valuable person to affiliate with (van Eerde, 2003).

Procrastinatory behaviors give rise to the type of norm transgressions that signal that the procrastinator is a “bad person” to associate with because they will struggle to consistently fulfill his or her commitments and obligations to others, such as fulfilling the obligations of reciprocity. Indeed, procrastination is frequently depicted as an irrational act of putting things off for “no good reason,” particularly by people who do not think of themselves as procrastinators (Burka & Yuen, 1983; Ferrari et al., 1995). The habit of procrastinating is viewed as self-defeating by lowering the quality of performance because one ends up with less time to work (Baumeister & Scher, 1988; Ellis & Knaus, 1977). Others view procrastination as a self-destructive strategy, akin to self-handicapping such as when people withhold effort so as to give themselves an excuse for any future poor performance (Jones & Berglas, 1978; Fee & Tangney, 2000). People will often refer to the unnecessary stress that procrastinators expose themselves to by repeatedly completing tasks at the last minute, and more generally to the burdens on procrastinators’ physical or mental health (Boice, 1996; Flett, Blankstein, & Martin, 1995; Sirois, 2007, 2014). In general, people who regularly procrastinate are often viewed as being lazy and sloth (Schouwenburg & Lay, 1995). Ascribing a sin deemed so problematic that is a “deadly sin” to people who frequently engage in procrastinatory behavior clearly denotes the level of social devaluation tied to procrastinatory behavior. It is no surprise that historically procrastination has had a negative moral connotation; it implies not living up to societal expectations (Ferrari et al., 1995; Sabini & Silver, 1982).

Descriptive versus Injunctive Norms

Social norms have also been described as being of two types: descriptive and injunctive. Descriptive norms, also called popular norms and behavioral norms, refer to the prevalence, quantity, and/or frequency of a given behavior. Believing that most college students engage in heavy drinking would be an example of a perceived descriptive norm. Injunctive norms refer to degree of approval or disapproval of a given behavior. They are similar to subjective norms described above but do not necessarily focus on one's own behavior or important others as a reference group. Believing that most people strongly disapprove of drinking and driving would be an example of an injunctive norm. Descriptive and injunctive norms are moderately correlated and independently associated with behavior. Recent work suggests that descriptive and injunctive norms often interact such that perceiving a behavior like smoking to be common (descriptive norm) is more strongly associated with behavior when perceived approval for the behavior (injunctive norm) is also high. Thus, an individual who believes most others disapprove of smoking will be less likely to smoke even if he or she sees many people smoking. In sum, perceived descriptive and injunctive norms are both positively associated with behavior.

Gender Norms and Roles

Social norms in most cultures permit alcohol use more for men than for women. For men, drinking can serve as a demonstration of their masculinity, their nonconformity, their willingness to take risks, and their superior status. Women who drink, however, are viewed in some cultures as less moral and responsible, more sexually promiscuous, and more sexually vulnerable. Women’s drinking is often seen as a threat to their roles as mothers and as the purveyors of “family values.” Women are aware of these norms and, to a large extent, enforce them. In a US national survey, 65% of the women said they strongly disapproved of a woman getting drunk, while 58% disapproved of a man getting drunk. In studies in which participants read vignettes about men or women drinking alcohol or cola in the context of a heterosexual date, women drinking alcohol are rated by participants as more sexually available and aggressive than women drinking cola, but no differences in judgments are made about the males in the vignettes. Recent studies using implicit measures instead of self-reports also find that men view women as more sexually available if they are drinking than if they are not.

Ethnographic studies suggest that in cultures in which gender roles are more traditional and pronounced, the gender differences in drinking behavior are greater. Similarly, in US ethnic minority groups that more widely accept traditional gender roles, such as Hispanics and recent Asian immigrants, the gender gap is greater than among European Americans, due largely to high percentages of minority women who completely abstain.

Further, women who endorse traditionally feminine traits (nurturance, emotional expressivity) report less quantity and frequency of alcohol use and adolescent girls and young women who hold more traditional gender role attitudes are less likely to drink at all. On the other hand, males who hold traditional beliefs toward male and female roles are more likely to use alcohol and to show heavy drinking and drinking problems. A study by Rebecca Huselid and Lynne Cooper found that gender-role attributes and ideologies statistically accounted for the relationship between gender and measures of alcohol use. Gender roles completely mediated the gender differences in drinking to intoxication, and partially mediated gender differences in quantity consumed, frequency of heavy drinking (five or more drinks per occasion), and drinking problems. Thus, the theories that differences in social norms and gender roles contribute to the gender differences in drinking behavior have been supported in a variety of studies.

2.1 Social Norms

A social norm is “a generally accepted way of thinking, feeling, or behaving that is endorsed and expected because it is perceived as the right and proper thing to do. It is a rule, value or standard shared by the members of a social group that prescribes appropriate, expected or desirable attitudes and conduct in matters relevant to the group” (Turner, 1991, p. 3). Group norms are further defined as “regularities in attitudes and behavior that characterize a social group and differentiate it from other social groups” (Hogg & Reid, 2006, p. 7). Norms are therefore shared thoughts, attitudes, and values, governing appropriate behavior by describing what one ought to do, and in essence prescribe moral obligations (Cialdini & Trost, 1998). Social norms are communicated by what people do and say in their everyday lives, which can be indirect (e.g., inferring norms from others’ behaviors) but also direct (e.g., intentionally talking about what is and is not normative of the group; Hogg & Reid, 2006). Deviation from the social norms of a group can result in loss of social status or exclusion, particularly if the social norm is important to the group (Festinger, 1950). Thus, norms serve to reinforce conformity by promoting the need for social acceptance and avoidance of social punishments (e.g., Deutsch & Gerard, 1955).

Social norms have a profound impact on influencing attitudes and behaviors, even though people are typically unaware of how influential social norms are (Nolan, Schultz, Cialdini, Goldstein, & Griskevicius, 2008). In fact, people are strongly influenced by social norms even when they explicitly reject such norms (McDonald, Fielding, & Louis, 2013). In a classic study, Prentice and Miller (1993) asked Princeton undergraduates how comfortable they vs the average Princeton undergraduates are with drinking. Results across several studies converged on the same conclusion—individuals believe others are more comfortable with drinking than themselves. This phenomenon is referred to as pluralistic ignorance (e.g., Prentice & Miller, 1996), which occurs when people personally reject a group norm, yet they incorrectly believe that everyone else in the group engages in the behavior. This introduces a “perceptual paradox”—in reality the behavior is not the norm since nobody engages in it, yet it is the group norm because everyone thinks everyone else does engage in the behavior (Hogg & Reid, 2006). Adolescents also misjudge the behaviors of their peers and close friends. Referred to as the false consensus effect, adolescents misperceive their peers’ attitudes and behaviors to be more similar to their own or even overestimate their peers’ engagement in health-risk behaviors (Prinstein & Wang, 2005). Thus, adolescents overestimate the prevalence of their peers’ behaviors and use their (mis)perceptions of social norms as a standard by which to compare their own behavior.

Norms, Values, and Expectations

Social norms are widely believed to account for differences in substance use and abuse across cultures. The social norms surrounding the use of alcohol in various cultures provide a good example of this. There are many cultural groups which prohibit the consumption of alcohol in all contexts. These groups include Mormons, Muslims, Alcoholics Anonymous organizations, and some Protestant factions. However, it is important to keep in mind that teetotalism is not strictly adhered to by all members of these groups. For example, in some Muslim groups, consumption of alcohol is not unheard of.

Many cultures, while allowing the use of alcohol, nonetheless have norms which discourage excessive alcohol consumption and drunkenness. This is seen in particular in Jewish culture, but also in Chinese, Italian, and French cultures. However, these norms are not static; they change over time and they differ across various sectors of society. Also, the strength of the influence of cultural norms and values depends on the extent to which an individual is immersed in his or her cultural environment. Interestingly, one study found that Russian Jews who had immigrated to Israel had higher rates of alcohol use than Israeli Jews – perhaps because of the culturally accepted pattern of heavy drinking in Russia. Thus, in some cases, individuals who move to a new cultural environment will continue with the pattern of substance use that they learned in their country of origin. Another study found that American-born Chinese generally consume more alcohol than Asian-born Chinese and this exemplifies the significance of social–cultural factors in patterns of use.

One of the most widespread cross-cultural norms pertaining to the use of alcohol relates to women. In almost all countries, alcohol use is seen as being less acceptable in women than it is in men. Furthermore, in some countries it is forbidden for women to drink. In Nigeria and Lesotho, women who abuse or become dependent on alcohol are judged harshly by their society and are often marginalized and ostracized. In other societies, such as Japan, Mexico, and Peru, the stigmatization is not as extreme but still drinking in women is widely discouraged.

In many Western societies, heavy drinking by both men and women is viewed as normal. Although heavier patterns of drinking are more often seen in young men. In New Zealand, individuals who refuse to drink in social settings may be subjected to criticism and ridicule by others. Thus, there is often social pressure to binge drink to the point of significant physical illness. Also, in many Western societies, even the signs of physical illness (e.g., vomiting and loss of consciousness) that accompany binge drinking are normalized. However, in contrast, alcohol addiction would probably not be seen as normative in most Western societies and would normally be frowned upon by mainstream society. While regular excessive alcohol consumption is seen as reasonably normal and acceptable, the sort of use seen with dependence would not be accepted. On the other hand, dependence on other drugs, such as methamphetamine, would probably be normalized in some social groups in the West. Therefore, whether addiction is seen as acceptable in Western societies would depend on the drug and the social context.

Another important dimension of the interaction between cultural factors and the effects of a substance on an individual is the beliefs and expectations of the individual. In Mexico, drinking sessions associated with drunkenness and violence are common. Similar links between alcohol and violence are also seen in some Papua New Guinean tribes. And of course, in many Western countries, such as the United States and New Zealand, there is a strong association between drinking and violence. However, in contrast, there are many cultural environments in which high levels of alcohol consumption are not associated with violence, such as among the Camba of Eastern Bolivia and the Yaruna Indians who reside in the Amazon. Thus, many researchers have concluded that the behaviors that arise following the consumption of alcohol depend on the beliefs and expectations of the individual and these have their roots in cultural norms.

Several studies have explored the connection between alcohol use and expectations (often referred to as expectancies). They have found that expectancies have a profound effect on the individual’s response to drinking. For example, studies have found that if people believe they have been consuming alcohol, when in fact they have been imbibing a nonalcoholic beverage, then they will behave as if they are intoxicated. Further, with regard to other substances, it has been reported that the cultural context influences the content of the drug user’s experience. For instance, if an individual has a vision while taking a drug in the context of a ceremony, the vision will typically reflect the purpose or context of the ceremony.

Beliefs and expectations can also influence the process of addiction. For example, some researchers have argued that if people believe that they have no control over their drug use, then they will be more likely to develop an addiction. Accordingly, if people believe that cocaine is highly addictive then they will be more likely to become addicted and to have an ongoing addiction problem. The drug-related attitudes and beliefs that an individual adopts probably come from his or her immediate sociocultural environment. Particular important sources within that environment might include media reports, cultural norms, personal experiences, and family knowledge that is passed down over the generations.

It is useful to consider the way that tobacco-smoking habits have changed in many Western countries over the last few decades. While rates of smoking have been falling steadily in many countries over the last 50 years, there has been a more significant drop-off in the last two decades. This is mostly explained in relation to the increased understanding of the harmful effects of tobacco on human health. However, this message has been delivered to varying extents around the globe. While some countries require that health warnings are placed prominently on cigarette packets, some countries do not. Also, rates of cigarette use vary around the world and it remains popular in many Asian countries. What is perhaps most important in regard to this discussion, is that the social norms surrounding the use of tobacco in the West have changed markedly such that it is no longer considered to be socially acceptable. Subsequently, many people in Western countries now hide their addiction to tobacco. In this way, the attitudes, beliefs, and behaviors surrounding tobacco addiction have changed over time and these changes have been associated with a significant reduction in tobacco use.

Introduction

Changing social norms and innovative technologies determine current law-enforcement tactics and policies of arrest, incarceration, and interrogation. The serve-and-protect role of the police requires them to ensure the safety and well-being of those in their custody. A death in police custody, therefore, initiates a public inquiry into the adequacy, appropriateness, and safety of any established policies and procedures. This public inquiry is most intense when the death is accompanied by violence, particularly when there is the application of lethal force. A death in custody is always “high-profile,” regardless of any attention afforded by the news media.

The term “in-custody death” may include a wide variety of cases, such as death within 24 h of being released from police custody, or death in state-run long-term care or mental health facility. For the purposes of this discussion, “in-custody death” in the USA refers to any individual who dies while incarcerated, or who dies during the attempt to arrest, transport, or interrogate the subject. Deaths in custody may be divided into three groups: (1) nonviolent (e.g., from natural disease, drug overdose, or drug withdrawal); (2) controlled violence (e.g., suicide, judicial electrocution); and (3) uncontrolled violence, when police attempt to restrain an agitated or violent subject and progress through a use of force continuum up to and including the application of lethal force (e.g., police use of chemical sprays, electrical stun devices, neck holds, and firearm discharge). However, for purposes of this discussion, “police” refers to all law-enforcement and correctional officers.

3.4 Group idea generation: Production blocking and cognitive interference

Because social norms dictate that group members take turns in presenting their ideas, production blocking is an inevitable consequence of verbal communication in groups. When group members wait for their turn, delays arise between the generation and articulation of ideas. These delays due to production blocking can interfere with idea generation in two ways, which are related to the two stages of idea generation: They can disrupt the activation of images, or they can interrupt the continuation of a train of thought (Fig. 4.3).

If a participant has generated an idea but cannot express it immediately, because somebody else is talking, the idea needs to be stored in WM. The longer the idea needs to be kept in WM, the greater the chance that it will be forgotten and that the image from which it was derived will be deactivated. Once an idea has been forgotten and an image deactivated, a new search cue has to be constructed. SIAM therefore predicts that the longer the delays, the greater the probability that a train of thought is interrupted. This should result in shorter clusters and also in a decrease in the number of ideas produced per category (category fluency). As a consequence, there should also be a decrease in overall productivity (Fig. 4.3, top panel).

The bottom panel of Fig. 4.3 depicts the second way in which delays can interfere with idea generation. The activation of images is a controlled process which requires cognitive resources (i.e., WM capacity). The greater the cognitive load due to other cognitive tasks, the more the individual's ability to activate images will be impaired. One major cause of cognitive load is the need for group members to monitor the current speaker in order to be ready to present their own ideas as soon as that person stops talking. Because there are usually no fixed speaking terms in brainstorming groups, it is typically unpredictable when one will have the opportunity to express one's ideas. In addition, the length of speaking terms can vary considerably (some group members take more time expressing their ideas than others), which introduces another source of unpredictability. Thus, when delays are unpredictable and hence increase cognitive load, the individual's ability to activate images will be impaired. Thus, whereas delay length results in shorter trains of thought due to forgetting and image deactivation, delay unpredictability will result in fewer trains of thought, because fewer images are activated. This can be observed in a reduction of the number of semantic clusters and consequently also in a reduction in the number of categories that are being surveyed during idea generation (i.e., a decrease in diversity). Moreover, when people's ability to activate images is impaired, this can also mean that they are less likely to return to a previously accessed category (i.e., a decrease in fluency).

Nijstad et al. (2003) tested these predictions in experiments in which participants worked individually at computer workstations. Whereas participants in the control condition could enter their ideas whenever they wanted, participants in the experimental conditions often had to wait before they could enter an idea. The introduction of waiting periods was justified with the argument that these were needed to simulate the situation of interactive brainstorming groups (which in a sense was true, of course). This experimental situation enabled us to manipulate the duration and predictability of the waiting periods. In one experiment (Nijstad et al., 2003, Experiment 1), participants generated ideas about what people can do to help preserve the environment, a topic that was quite familiar to the Dutch university students who participated. Participants in the experimental conditions were blocked (i.e., had to wait) each time they wanted to enter an idea. Depending on conditions, the duration of the waiting time varied between 1 and 7 s. As predicted, longer waiting periods resulted in shorter clusters of semantically related ideas, lower clustering (ARC), a reduction of the number of ideas per category (within-category fluency), and a decrease in overall productivity (i.e., quantity of ideas produced). Moreover, the effects of delay length on within-category fluency and overall productivity were fully mediated by cluster length, which constituted further support for SIAM. However, these predictable delays had no effect on the number of clusters, nor on diversity (i.e., number of categories surveyed), presumably because little cognitive capacity was required to monitor delays (after all, participants soon found out they had to wait every time they wanted to enter an idea).

In another experiment (Nijstad et al., 2003, Experiment 3), participants again brainstormed on ways to help preserve the environment. The researchers manipulated the predictability of delays. In the condition with high predictability, participants had to wait 7 s each time they wanted to enter an idea. In the condition with unpredictable delays, 60 delay periods were randomly distributed over the 20 min session. Furthermore, the duration of delays varied between 2 and 12 s (average duration = 7 s). These participants were sometimes blocked several times before they could enter an idea, but sometimes they could also enter several ideas before they were blocked. This made the delays truly unpredictable. In the control condition, participants could enter ideas any time they wanted.

Results in the predictable delay condition replicated the findings of Experiment 1. Thus, predictable delays reduced cluster length, and this in turn reduced productivity (see Table 4.3). As in Experiment 1, predictable delays had no effect on number of clusters. In contrast, when delays were unpredictable, the number of clusters decreased, whereas cluster length was not affected. Moreover, the reduction in the number of clusters was associated with the predicted reduction in the average number of ideas per category (within-category fluency) and with a reduction in productivity. As in Experiment 1, a mediation analysis was performed, which replicated the earlier findings that cluster length mediated the effect of delays for the condition with predictable delays. In contrast, a mediation analysis performed on the data of the unpredictable delay condition suggested number of clusters as mediator: When the number of clusters was statistically controlled for, the effect of unpredictable delays on productivity became insignificant.

Table 4.3. Productivity, cluster length, number of clusters, diversity, within-category fluency, and clustering (ARC) as a function of delays (adapted from Nijstad et al., 2003, Exp. 3)

Note. Standard deviations are in parentheses. Different superscripts (a, b) indicate a significant difference on a post hoc test (LSD). ⁎, p < 0.10; ⁎⁎, p < 0.01; ⁎⁎⁎, p < 0.001.

In sum, the findings of these two experiments support the SIAM predictions that production blocking interferes with idea generation at both stages of the process (image activation and actual idea generation) and that two different processes explain the effect of delays: The duration of delays affects the length of clusters, whereas the (un)predictability of delays influences the number of clusters. Obviously, in interactive brainstorming groups, both effects should occur concurrently, because the amount of time taken to express ideas differs both between and within speakers. These blocking effects should also be stronger at the beginning of a brainstorming session, when group members are likely to think of more ideas than toward the end of a session.