The doubt-certainty continuum in psychopathology, lay thinking, and science

J. Behav. Ther. & Exp. Psychiat. xxx (2015) 1e7

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The doubt-certainty continuum in psychopathology, lay thinking, and science Omri Ron 1, Ela Oren 1, Reuven Dar* Tel Aviv University, Israel

a r t i c l e i n f o

a b s t r a c t

Article history: Received 7 July 2015 Received in revised form 10 August 2015 Accepted 11 August 2015 Available online xxx

This paper presents a theoretical model suggesting that doubt and certainty are two extremes of a continuum. Different people can be located in different locations on this continuum, according to how much they tend to seek refutation vs. confirmation. In both ends of the continuum lay mental disorders, which can be seen as extreme deviations from the usual relatively stable equilibrium between the two thinking processes. One end is defined by excessive skepticism and manifested as obsessive compulsive disorder (OCD), a disorder characterized by incessant doubt. The other end is defined by excessive certainty and lack of doubt, manifested as delusional disorders. Throughout this article, we demonstrate that the differences between normative thoughts and delusional thoughts are relatively vague, and that in general, the human default tendency is to prefer certainty over doubt. This preference is reflected in the confirmation bias as well as in other cognitive constructs such as overconfidence and stereotypes. Recent perspectives on these biases suggest that the human preference for confirmation can be explained in evolutionary terms as adaptive and rational. A parallel view of the scientific enterprise suggests that it also requires a certain equilibrium between skepticism and confirmation. We conclude by discussing the importance of the dialectic relationship between confirmation and refutation in both lay thinking and scientific thought. © 2015 Elsevier Ltd. All rights reserved.

Keywords: Obsessive-compulsive disorder Doubt Delusions Certainty

1. Obsessive doubt Obsessive compulsive disorder (OCD) is formally defined by its two components: obsessions and compulsions (American Psychiatric Association, 2013). However, another central symptom of OCD is relentless and tormenting doubt, particularly in regard to typical concerns such as fears of contamination or of harming others. For example, a person with OCD trying to lock the door of the office might turn the key in the lock again and again, continuously doubting that the door is indeed locked, although s\he can see that the key is in place, hear the action of the lock, and manually feel that the door is locked (Dar, 1991). Incessant doubts are believed to trigger a variety of pathological behaviors typical of OCD, such as washing and cleaning, counting, demanding reassurance from others, excessive self-monitoring, mental reconstruction and especially repeating and checking. Esquirol (1837),

* Corresponding author. Department of Psychology, Tel Aviv University, Tel Aviv 69978, Israel. E-mail address: [email protected] (R. Dar). 1 Made equal contributions to the article.

who is considered the first to have written a detailed medical description of OCD, named the disorder “folie du doute”, literally meaning “madness of the doubt”. Some years later, Janet, who studied obsessions and compulsions following Esquirol, emphasized the lack of will and the inability to make decisions or to trust one's own perception (reviewed in Insel, 1990). According to Shapiro (1965), the obsessive-compulsive (OC) person's doubt can be conceptualized as “the loss of the experience of conviction.” Due to the inability to experience conviction, the OC person to be faced with everlasting doubt in regard to his thoughts, feelings, actions and experiences. More recent models of OCD have also hypothesized that the pervasive doubts and related symptoms in OCD stem from deficient “subjective conviction” or “feeling of knowing.” Szechtman and Woody (2004) have used the term “feeling of knowing,” defined as “a subjective conviction functionally separate from knowledge of objective reality” (p. 115) in their account of OCD. They suggested that in contrast to normal individuals, the behavioral output of individuals with OCD fails to generate this inner feeling, living them in a continuous state of anxiety and doubt regarding their safety and ability to avoid potential harm. In a similar account, Boyer and

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Please cite this article in press as: Ron, O., et al., The doubt-certainty continuum in psychopathology, lay thinking, and science, Journal of Behavior Therapy and Experimental Psychiatry (2015), http://dx.doi.org/10.1016/j.jbtep.2015.08.005

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nard (2006) postulated that OCD symptoms are related to Lie missing “satiety feedback feelings,” a deficit that leads to doubts and uncertainty regarding the proper performance of actions as a precaution in response to the detection of potential dangers. Finally, in her account of the OCD-related phenomenon of incompleteness, Summerfeldt (2004, 2007) also postulated a missing “feeling of knowing” in OC individuals, which specifically leads to a sense of incompleteness and to “not just right” experiences. Empirical studies found that OC doubts may concern a variety of cognitive functions including memory (e.g., Constans, Foa, Franklin, & Mathews, 1995; Cougle, Salkovskis, & Wahl, 2007; Dar, 2004; Dar, Rish, Hermesh, Fux & Taub, 2000; McNally & Kohlbeck, 1993; Sher, Frost, & Otto, 1983; Tolin et al., 2001), decision-making and concentration (Nedeljkovic & Kyrios, 2007; Nedeljkovic, Moulding, Kyrios, & Doron, 2009), as well as attention and perception (Hermans et al., 2008; Hermans, Martens, De Cort, Pieters, & Eelen, 2003; van den Hout, Engelhard, de Boer, du Bois, & Dek, 2008; van den Hout et al., 2009). Interestingly, as we shall elaborate below, the tendency of OC individuals to doubt these internal states contrasts with the finding that people in general tend to be overconfident in their assessment of their performance (Koriat, Lichtenstein, & Fischhoff, 1980). In addition to establishing the extent and generality of OC doubt, researchers also examined processes that perpetuate doubt in OCD. Of particular importance has been the work of Marcel van den Hout and his colleagues, who showed that doubt not only causes excessive checking, a core symptom of OCD, but is also caused by checking. Specifically, these authors found that excessive checking related to one's own memory and perception has the ironic effect of reducing one's confidence and increasing doubt in these processes (van den Hout & Kindt, 2003a, 2003b). Their findings were later replicated and extended (e.g., Ashbaugh & Radomsky, 2007; Moshier, Molokotos, Stein, & Otto, 2015; Radomsky, Gilchrist, & Dussault, 2006). In addition, Toffolo, van den Hout, Hooge, Engelhard, and Cath (2013) showed that individuals with high OC tendencies respond with more checking behavior to mildly uncertain situations than individuals with low OC tendencies. This finding, which was later replicated by Toffolo, van den Hout, Engelhard, Hooge, and Cath (2014), extends beyond the previous studies that linked OC doubt and checking behaviors. It seems that even mild uncertainty promotes actual checking behaviors in individuals with high OC tendencies, which in turn has the paradoxical effect of reinforcing uncertainty, possibly creating a vicious cycle of increased uncertainty and repetitive checking behaviors. OC doubt has been the focus of a recent model of OCD, termed Seeking Proxies for Internal States (SPIS; Lazarov, Dar, Oded, & Liberman, 2010; Liberman & Dar, 2009). These authors suggested that OC individuals are generally uncertain about their internal states, including what they feel, what they know, what they believe, and what they prefer. According to the SPIS model, OC doubt can manifest itself in relation to any internal state, be it cognitive (e.g., perception, memory, comprehension), affective (e.g., attraction, specific emotions) or bodily (e.g., muscle tension, proprioception). Moreover, the SPIS model postulates that OC doubts are related to actual attenuation of internal states, so that OC individuals not only feel uncertain in regard to their internal states, but also have reduced access to these states. Therefore, when they must answer questions in regard to their internal states, OC people must seek and rely on external “proxies” for these internal states. Proxies were defined as substitutes for the internal state that the individual perceives as more easily discernible or less ambiguous, such as indicators, rules, procedures, behaviors or environmental stimuli (Liberman & Dar, 2009). For example, an OC person who lacks access to her/his own feelings towards her/his partner might resort to monitoring the number of times s/he calls her/him, or the amount

of money s/he spends on buying her\him a present. Research within the framework of the SPIS model showed that as predicted, OC individuals had not only reduced confidence in but also attenuated access to the internal states of relaxation, muscle tension and affective states (Lazarov et al., 2010; Lazarov, Cohen, Liberman, & Dar, in press; Lazarov, Dar, Liberman, & Oded, 2012a, 2012b; Lazarov, Liberman, Hermesh, & Dar, 2014). The excessive doubt has implications for the assessment and treatment of OCD. Clark (2004) argued that obsessional features such as intolerance of uncertainty and pathological doubt are prominent clinical features of OCD that can interfere with the assessment of the disorder. For instance, an OC individual may have difficulty with answering a questionnaire with multiple response options, due to his\her own doubts about his\her feelings, perceptions, thoughts and behaviors. These concerns make it necessary to pay special attention to this possible difficulty and to the relevance of excessive doubt in the assessment process. Moreover, Clark (2004) proposed that the OC doubt should also be considered in the treatment of OCD. For example, one of the common tools used in Cognitive Behavioral Therapy (CBT) is the Socratic questioning (DeRubeis & Beck, 1988). In the case of OCD, however, the therapist may need to modify this tool, as OC individuals suffering from severe doubt may insist on providing the “most correct” answer to each question, and as a result may feel overwhelmed, stressed and possibly even paralyzed. Clark suggested that the modification of Socratic questioning can include, inter-alia, using more summary statements and suggestive probes. Furthermore, based on the SPIS model, Lazarov, Dar, Liberman, and Oded (2012b) suggested that doubt and uncertainty can be understood in therapy as emanating from deficient access to internal signals, at least to some extent. Compulsive behaviors can be reframed as a form of proxies, designed to compensate for attenuated access to internal states. The potential disadvantages of this compensation strategy can be explained to patients, i.e., the fact that using proxies excessively can lead to vicious cycles, such as repeatedly questioning and examining their own feelings and preferences. In the future, different tools (such as biofeedback training) may be used to help patients learn to identify and control basic internal states (muscle tension, anxiety etc.) in regard to which patients experience doubt and uncertainty. 2. Delusional disorders If obsessions can be conceptualized as an inability to experience conviction, delusions seem to represent the polar opposite phenomenon. Delusions have been variously defined by many researchers of psychosis over the past century. For example, Kraepelin, who is often described as the founder of modern scientific psychiatry, defined psychosis as a deductive disorder, meaning that an individual suffering from it is interpreting reality based on an irrefutable set of delusional beliefs (Kraepelin, 1919). Jaspers (1913/1997) defined a delusion by three criteria: certainty, incorrigibility and impossibility or falsity of content. According to Rycroft (1972), a delusion is a belief which is both unreal and cannot be inferred logically, whereas according to Redlich and Freedman (1966) “Delusions are incorrigible false beliefs that are not shared or sanctioned by a group”. As the above examples illustrate, definitions of delusion have traditionally included three characteristics of belief: its truth value (a delusion is a false belief), its normality (a delusion is deviant in terms socio-cultural norms), and its rigidity (a delusion is resistant to change). Of these criteria, the first is the most problematic, as the determination of true vs. false (or right vs. wrong) is likely to be subjective and context-dependent. The criterion of deviance is also difficult to justify, as defining a belief as delusional based on its

Please cite this article in press as: Ron, O., et al., The doubt-certainty continuum in psychopathology, lay thinking, and science, Journal of Behavior Therapy and Experimental Psychiatry (2015), http://dx.doi.org/10.1016/j.jbtep.2015.08.005

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rarity in the population has doubtful scientific rationale. This reasoning is reflected in the current official diagnostic manuals of mental disorders. The DSM V (American Psychiatric Association, 2013) defines delusions as fixed beliefs that are not amenable to change in light of conflicting evidence. Delusions are deemed bizarre if they are clearly implausible and not understandable to same-culture peers and do not derive from ordinary life experiences. As Mason and Claridge (2015) noted, this definition differs from its predecessor in the DSM IV. Whereas the DSM IV considered delusions as false beliefs, the DSM V identifies them as fixed beliefs. Hence the current definition has abandoned the notion of delusions as errors, a judgment focused on the content of the beliefs, in favor of focusing on the thinking process itself, i.e., on their persistence and rigidity. Interestingly, the same focus on thought process had also been emphasized by David Shapiro, whose definition of OC doubt was discussed above. According to Shapiro (1965), the “paranoid style” is characterized by rigidity and bias: the paranoid person attends only to information that confirms her\his beliefs. Importantly, the DSM V notes that the distinction between a delusion and a strongly held idea is sometimes difficult to make. This distinction depends, at least in part, on the degree of conviction with which the belief is held despite clear or reasonable contradiction regarding its veracity (American Psychiatric Association, 2013). The difficulty of defining delusions and separating them conceptually from strongly held beliefs is recognized in modern research in this area. Radden (2014) came to the conclusion that normal belief and delusion are so deeply entwined that only by understanding the one we can expect to clarify the other. In the same vein, the model of delusions suggested by Hohwy (2013) emphasizes the normative aspects of delusions, claiming that inference under uncertainty is the key element for understanding the development and persistence of delusions. To explain this, the model focuses on the common characteristics of illusions and delusions. Among other shared characteristics, both illusions and delusions are perceived as compelling. For example, when we encounter a visual illusion such as the Muller-Lyer illusion, we are unable to not perceive one line as longer than the other. The same is true for delusions: the delusional person is certain that s\he is being followed by the police, for instance. In other words, both illusions and delusions usually go unnoticed, in the sense that people are not aware (at least at first) that they are experiencing an illusion or a delusion, perhaps due to the intensity of the experience. An important conclusion, derived from this model as well as from other psychological models of delusions (see Mason & Claridge, 2015), is that categorical distinctions between delusional and everyday beliefs and perceptions is quite challenging, if not impossible. 3. Doubt and delusions as opposite poles of a continuum Our discussion so far suggests that OCD and delusional disorders represent polar opposites along a dimension of conviction, as Shapiro (1965) would call it, from excessive doubt to excessive certainty. The OC person is focused on clues or thoughts that might disconfirm his favored belief, ignoring evidence that might reassure her/him. For example, a man with OCD wants to believe that he had remembered to lock the car, but cannot feel convinced that he had done so as he begins to consider scenarios that undermine this belief (e.g., perhaps he was distracted by thoughts about work just as he was pressing the button on the electronic key thus inadvertently unlocking the car again). Conversely, the delusional person is focused on confirming clues or thoughts that support her/his favored beliefs, ignoring facts that refute them. For example, the delusional person might insist that s\he is under constant police surveillance, focusing on a police car s\he often sees next to her\his

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apartment and ignoring the fact that the police officers driving this . car stop by everyday to buy coffee in a nearby cafe Moulding and Kyrios (2007) suggested that OC symptoms are linked with a high desire to control (DC) on the one hand, but a low sense of control (SC) over the self and the environment on the other hand. This gap between the DC and the SC can lead to the compulsive behaviors characterizing OC individuals: the compulsions allow those individuals to artificially increase their SC. Looking at it from the perspective of OC doubt, we might suggest that such doubt is related to the low SC; If one feels that s\he doesn't have sufficient authorship over her\his own body, actions and surrounding, then her\his confidence in her\his own feeling, thoughts etc. may diminish, hence enhancing excessive doubt. The very same low SC, sometimes referred to as low sense of agency (SoA), might have very different implications in the case of delusional disorders. It has been repeatedly shown that individuals suffering from delusional disorders, and specifically Schizophrenia, have a low SoA (e.g., Blakemore, Wolpert, & Frith, 2002; Jeannerod, 2009; Synofzik, Thier, Leube, Schlotterbeck, & Lindner, 2010). According to Jeannerod (2009), the low SoA is related to the psychotic patients' loss of ability to attribute their own thoughts, internal speech, covert or overt actions to themselves. The result is the attribution of one's thoughts and actions to others, which becomes entrenched and experienced as certain due the processes described above: The delusional individual is focused on confirming clues or thoughts that support her/his uncompromising belief in these attributions, ignoring facts that refute them. The OC individual and the delusional individual can thus be described as representing two poles of a doubt-certainty continuum. In contrast, the “normative” or “rational” person is more flexible: s\he holds a fundamental view of the world, but is capable of questioning this view. The normative person is therefore positioned between the two extremes of the continuum, a position characterized by a dynamic equilibrium between doubt and certainty. As we will see, however, this normative position does not lie in the middle of the doubt-certainty continuum. Rather, normal thinking tends to be closer to the certainty pole than to the doubt pole. This tendency is manifested in several well-studied cognitive biases, which have been proposed to confer important advantages to human functioning. In the next sections, we will review these biases and discuss their potential benefits. 4. The asymmetry between doubt and certainty: The “delusional” aspects of normal thinking In the past three decades, cognitive processes related to doubt and certainty were the focus of many theories and empirical studies in cognitive and social psychology. It has been shown repeatedly that lay people often experience unwarranted certainty and are not willing or able to doubt their own knowledge and beliefs. Below, we review several of these cognitive processes, focusing primarily on the confirmation bias and its importance in our everyday functioning. 4.1. The confirmation bias The confirmation bias is the tendency to make predictions and examine them by searching for information that is expected to confirm anticipations or desirable beliefs, avoiding the collection of potential refuting evidences (Friedrich, 1993). The bias is based on the tendency to raise evidence that supports the preferred hypothesis and to overweigh it, while underestimating facts that are not consistent with the preferred hypothesis (Koriat et al., 1980) and ignoring information which supports alternatives (Gilbert, 1991). The bias enhances one's obligation to the hypothesis or

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belief being held (Lewicka, 1998). The confirmation bias was first described in the early 17th century by Bacon (Bacon, 1889, 1960), and in modern psychology by Wason (1960), who showed that subjects use more confirming strategies than refuting ones when facing a test and make more mistakes when using the latter strategy (Wason & Johnson-Laird, 1972). Klayman and Ha (1987) defined the confirmation bias as “a positive test strategy”, referring to the fact that it is a search heuristic that might lead to mistakes but is generally cognitively easier and more efficient than “negative test strategies”, which include alternative strategies and possible alternative results. Friedrich (1993) claimed that people act as naive pragmatics, aiming to reduce mistakes more than to reveal the truth. Consequently, people tend to use economically more efficient cognitive strategies. According to Trope and Liberman (1996), testing hypotheses can be diagnostic or pseudo diagnostic, depending on the extent to which alternative hypotheses are considered. Diagnostic testing considers both the sufficiency of a hypothesis (i.e., the probability of the evidence if the hypothesis is true) and its necessity (i.e., the probability of the evidence if the hypothesis is false), whereas pseudo diagnostic testing considers only the sufficiency of a hypothesis. Diagnostic hypothesis testing requires extensive gathering and processing of information, as opposed to pseudo diagnostic hypothesis testing. When sufficient resources and motivation are available, the effortful diagnostic hypothesis testing may be preferred. More often, however, people rely instead on the more default, automatic strategy. In their analysis of the motivational processes related to both strategies, Trope and Liberman (1996) emphasized that false acceptance and false rejection of a hypothesis frequently have unequal subjective costs, depending on the desirability of the hypothesis, the context and the individual's tendencies (for example, some are high in desire for control or in dogmatism, whereas others are high in need for cognition). When false acceptance is more costly, acceptance thresholds will be higher than rejection thresholds, and vice versa. As a result, the amount of information needed to accept a hypothesis may differ from the amount of information needed to reject it. Higgins (1996) considered the availability of knowledge in our memory to be an important component in the process that leads to the confirmation bias. In the process of hypotheses testing, according to him, more attention is given to data that match our primary hypothesis because of their higher accessibility, even when their correspondence with the hypothesis is low. This leads to excessive reliance on matching, confirming data, and as a result to the tendency to confirm hypotheses based on data that fit them. In the context of Higgins' model, delusions can be understood as an extreme case of the confirmation bias. In parallel to the activation of the bias, any contradictory knowledge, even highly applicable, is inhibited, enhancing the potency of the delusion. To other people and from a so-called objective point of view, the judgment of the delusional person will appear impaired, but for the person her\himself it will obviously seem rational, since s\he is acting based on the only information accessible to her\him. 4.2. The advantages of the confirmation bias When the confirmation bias began to be studied and discussed in the literature, it was perceived as an undesirable deviation from rational thinking. Over time, however, researchers began questioning the irrationality of the bias. For example, Tversky and Kahneman (1981) noted that acting on the most readily available frame can sometimes be justified by reference to the mental effort required to explore alternative frames and avoid potential inconsistencies. Klayman and Ha (1987) referred to the confirmation

bias as a “positive test strategy”. That is, people tend to test hypotheses by looking at instances where the target property is hypothesized or is known to be present. According to them, the positive test strategy is a good heuristic for hypotheses testing, even if it may occasionally lead to errors. Other than the fact that this strategy is cognitively less costly, compared to other strategies, under some circumstances, this strategy may be the only way to discover falsifying instances. They concluded that the best strategy depends on the characteristics of the specific task at hand. Friedrich (1993) proposed that in the context of decision making, the focus should not be on the revelation of the truth, but rather on pragmatic, survival-oriented considerations. These considerations are derived from the motivation to gain profits and reduce errors, as opposed to the considerations that are relevant for logical, scientific hypotheses testing. These confirmatory directions of thought proved to be more efficient and reinforcing than others in the past, and therefore were adopted during the evolutionary process. According to Haselton et al. (2009), much of the research on cognitive biases, including the confirmation bias, can be understood in evolutionary terms. From this perspective, the confirmation bias is not irrational but rather an important component of the human survival kit: It ensures certain profits while avoiding unnecessary exposure to uncertainty and risks, and thereby facilitating habits acquisition and the automation of routine actions. Automation is of course crucial, as it allows us to manage our everyday lives efficiently and fluently (Lewicka, 1998). In sum, the evolutionary perspective underscore the advantages of the confirmation bias and the adaptive nature of the human tendency to prefer certainty over doubt. 4.3. The need for closure; stereotypes, conservatism and dogmatism The “Need for Closure” (NFC) is another cognitive construct related to doubt and certainty. Like the confirmation bias, the NFC has also been the focus of considerable research. Kruglanski (1990) defined the NFC as the desire for “an answer on a given topic, any answer … compared to confusion and ambiguity” (pp. 337). Kruglanski and Webster (1996) portrayed the motivation toward closure as lying on a continuum with a high need to attain closure at one end and high need to avoid closure at the other end. In other words, having a high need to attain closure is the tendency to be extremely motivated to gain certainty over doubt. The NFC is one of the common explanations for the tendency to internalize stereotypes and display prejudice (Roets, Kruglanski, Kossowska, Pierro, & Hong, 2015). Stereotypes have been defined as beliefs about the characteristics, attributes, and behaviors of members of certain groups (Hilton & Von Hippel, 1996). Evidence inconsistent with stereotypes is more readily ignored or discarded than supportive evidence, creating an erroneous sense of certainty. The NFC is also related to conservatism (Kossowska & Hiel, 2003) and dogmatism (Jost, Glaser, Kruglanski, & Sulloway, 2003). According to Jost et al. (2003), conservatism can be characterized by means of a universal set of rules for organizing and processing information about social reality. Dogmatism has been described by Altemeyer (2002) as “relatively unchangeable, unjustified certainty” (pp. 20). Hence the different constructs related to the NFC (stereotypes, conservatism and dogmatism) can all be seen as examples of the tendencies of beliefs to be self-confirming. In the case of the NFC and its related constructs, as previously discussed in relation to the confirmation bias, it has been shown that excessive choice (as opposed to certainty) in everyday life may have a negative effect on our mental health (Roets & Soetens, 2010). Hence high need for closure, and consequently high need for certainty, has concrete positive outcomes. This is also true for stereotypes, as often we are forced to make quick judgments about people. Salient features are processed

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automatically and quickly, saving us resources and precious time (Tobena, Marks, & Dar, 1999). 4.4. Overconfidence Another psychological construct related to the confirmation bias and the need for closure is overconfidence. As Tobena et al. (1999) noted, even people who are trained to rule out biases tend to be overconfident in estimating their performance and the accuracy of their assessments. For example, Koriat et al. (1980) gave participants a dual-choice general knowledge test, and asked them to rate their confidence in the chosen answer for each item. They found that participants' confidence in their answers was higher than justified by their actual performance. Koriat and colleagues showed that this overconfidence resulted from selective focusing on facts which support the chosen answers and ignoring contradicting facts. In other words, overconfidence may be a direct consequence of the confirmation bias. In support of this hypothesis, the authors found that overconfidence was reduced when the participants were requested to justify the alternative answers (those that were not chosen by them). If the confirmation bias and overconfidence are the norm, obsessive doubt seems to represent an anomaly, perhaps more so than do the over-confirmatory processes reflected in delusions. A study by Dar et al. (2000) used the same procedure of Koriat et al. (1980) with a sample of OCD participants. As predicted, they found that these participants were not overconfident in regard to their general knowledge compared to non-clinical participants. Moreover, OCD participants were actually under-confident in their general evaluation of their performance, despite the fact that their actual performance was equally as good at that of the control participant. Following the logic of Koriat et al. (1980), Dar and colleagues suggested that these findings can be explained by postulating a lack of confirmation bias in OCD. In fact, the process of incessant doubting can be conceptualized as a “disconfirmation bias,” or the tendency to be over-skeptical. 4.5. Intermediate summary As we have seen, the dialectic relationship between the two modes of thinking (doubting vs. confirming), which characterizes normative thought processes and is the basis of rationality, is asymmetric. The default tendency is to be relatively certain of ourselves. Casting doubt, even when logically required by the problem at hand, is the less preferred option by default. The confirmation bias is the manifestation of this asymmetry, and can be explained by evolutionary considerations; feeling certain, while taking the risk of conducting errors, is more adaptive than actionsstalling doubts. In the next section, we discuss the ideal of criticism and refutation in the philosophy of science, suggesting an intriguing analogy between scientific thought and normal functioning. We will show that in normative approaches to the philosophy of science, the confirmation bias is perceived as rational and constructive for scientific growth. 5. Refutation and confirmation processes in scientific thought The development of modern empirical scientific methods reflects the dialectic relationship between doubt and certainty. In this section, we review two of the main approaches in the philosophy of science that dealt with the tension between refutation and confirmation in the scientific method. The critical approach was most famously advocated by Popper (1959), who claimed that the appearance of a phenomenon does not necessarily mean that the theory that predicted it was correct.

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No matter how many confirming evidences are found, universal generalization will never be possible. However, with merely one refuting case, we are logically able to conclude that the theory is false. Therefore a hypothesis should never be accepted as the absolute truth, as future tests might reveal it is false. Consequently, scientific investigations should be aimed not to achieve confirmations, but refutations. This refutation process, in Popper's view, is an ongoing, everlasting process, as new hypotheses are always confronted with their alternatives and may be refuted and replaced. Epistemologically, the evolution of knowledge is an elimination process. The potency of science and its rationality is not based on true, confirmed knowledge, as was believed by “naïve” positivists. On the contrary, science is rational only if it considers every piece of information as tentative and potentially refutable. According to the Popperian ideal, the scientific community should be willing to change or replace even the most acceptable convention (Fisch, 1997). An important distinction drawn from Popper's ideas is one between scientific and pseudo-scientific theories. Pseudo-scientific theories cannot be critically examined and refuted; when a pseudo theory is challenged, it adopts ad-hoc corrections which rescue it from refutation. As such, pseudo-scientific theories resemble delusional beliefs, which are also immune to refutation. While Popper endorsed a strong “disconfirmation bias” as the only rational methodology in science, later writers claimed that the scientific method has to be based on at least some solid assumptions that must be immune to refutation. Lakatos's approach (1976) is one of the examples to such criticism of strict Popperianism. According to Lakatos, who was Popper's student and successor, criticism of a theory does not mean that it should be abandoned, because no refuting evidence is ever sufficient to decide that a theory is false. In Lakatos' terms, the “hard core” of the theory is protected by a “protective belt” of auxiliary theories (for example, theories of the measurement tools). This means that criticism cannot be aimed at the hard core of a theory, a directive that Lakatos termed the “negative heuristic” of the scientific method. The counter directive, the “positive heuristic”, guides researchers to continue and develop their theories and test them while not being overly deterred by encountering temporary disconfirmations (“anomalies” in Lakatos' terms). Later on, the disconfirming evidence will hopefully turn into supporting evidence, as the positive heuristic continues to generate novel facts that might shed new light on the previous anomalies. To conclude, Lakatos maintained that scientists should consider certain basic concepts not as a theory that is constantly subjected to tests but as core knowledge which is accepted tentatively, while auxiliary theories are being examined. In Lakatos' system, then, a methodological “confirmation bias” is not only rationale, but also essential to the growth of science. 6. Conclusion Our sketchy discussion about rationality in science has intriguing similarities to the discussion about rational thinking. In both science and lay thinking, there is a dialectic relationship between refutation and confirmation, doubt and certainty. Without criticism, without the ability to question one's own beliefs, both scientists and lay people are liable to develop delusional theories about reality. Conversely, excessive criticism, constant doubting of one's beliefs, can stall progress and incapacitate both science and individuals, as in the case of individuals with OCD. As both research in human thinking and (at least some branches of) philosophy of science suggest, rationality may lie closer to the certainty than to the doubt pole. Various cognitive biases reflect the “normal” aspects of the delusional thought, i.e., the tendency to feel certain of something despite clear or reasonable contradiction

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regarding its veracity. From an evolutionary perspective, these “normal” aspects of delusions are adaptive and therefore rational. Future research should empirically test the doubt-certainty continuum, including its extreme poles. As a first step, it will be important to construct a valid measure in order to estimate individual differences vis-a-vis the doubt-certainty continuum. Next, the hypothesized relationship between one's location on the continuum and OCD and delusional disorders can be empirically examined. This can be done by measuring the correlations between individuals' scores on measures of both disorders and the doubtcertainty continuum measure's scores. In addition, it will be interesting to test the relationship between cognitive constructs such as the need for closure (NFC), overconfidence, desire to control (DC), sense of control (SC) and the location on the doubt-certainty continuum. Such research will allow us to validate our suggested model, and crucially, to further develop it, including its possible implications for psychotherapy. To conclude, this article suggests that doubt and certainty can be seen as lying on a continuum. Both are critical to science and lay thinking, and a violation of the equilibrium between the two may result in psychopathology: OCD on the one hand and delusional disorders on the other. We hope that conceptualizing delusions and obsessions in these terms may facilitate theory and research of these extreme poles of the doubt-certainty dimension. Conflict of interests and financial support The authors declare no actual or potential conflict of interest in relation to this study. This paper was not supported by any funding. References Altemeyer, B. (2002). Dogmatic behavior among students: testing a new measure of dogmatism. The Journal of Social Psychology, 142(6), 713e721. American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (DSM-5®). American Psychiatric Pub. Ashbaugh, A. R., & Radomsky, A. S. (2007). Attentional focus during repeated checking influences memory but not metamemory. Cognitive Therapy and Research, 31(3), 291e306. Bacon, F. (1889). Novum Organum, edited with introduction, notes, etc., by Thomas Fowler. Bacon, F. (1960). In F. H. Anderson (Ed.), The new organon. Liberal Arts Press, 122e122. Blakemore, S. J., Wolpert, D. M., & Frith, C. D. (2002). Abnormalities in the awareness of action. Trends in Cognitive Sciences, 6(6), 237e242. nard, P. (2006). Precaution systems and ritualized behavior. BehavBoyer, P., & Lie ioral and Brain Sciences, 29(06), 635e641. Clark, D. A. (2004). Cognitive-behavioral therapy for OCD. Guilford Press. Constans, J. I., Foa, E. B., Franklin, M. E., & Mathews, A. (1995). Memory for actual and imagined events in OC checkers. Behaviour Research and Therapy, 33(6), 665e671. Cougle, J. R., Salkovskis, P. M., & Wahl, K. (2007). Perception of memory ability and confidence in recollections in obsessive-compulsive checking. Journal of Anxiety Disorders, 21(1), 118e130. Dar, R. (1991). Obsessive compulsive disorder: an update. International Review of Psychiatry, 1, 235e241. Dar, R. (2004). Elucidating the mechanism of uncertainty and doubt in obsessivecompulsive checkers. Journal of Behavior Therapy and Experimental Psychiatry, 35(2), 153e163. Dar, R., Rish, S., Hermesh, H., Taub, M., & Fux, M. (2000). Realism of confidence in obsessive-compulsive checkers. Journal of Abnormal Psychology, 109(4), 673. DeRubeis, R. J., & Beck, A. T. (1988). Cognitive therapy. Handbook of CognitiveBehavioral Therapies, 3, 277e316. Esquirol. (1837). In Berrios G. E. (1985), “Obsessional disorders during the 19th century: terminological and classifactory issues”. In W. F. Bynum, R. Porter, & M. Shepherd (Eds.), Anatomy of madness. , London: Tavistock. Fisch, M. (1997). Rational Rabbis: Science and talmudic culture. Bloomington: Indiana University Press. Friedrich, J. (1993). Primary error detection and minimization (PEDMIN) strategies in social cognition: a reinterpretation of confirmation bias phenomena. Psychological Review, 100(2), 298. Gilbert, D. T. (1991). How mental systems believe. American Psychologist, 46(2), 107. Haselton, M. G., Bryant, G. A., Wilke, A., Frederick, D. A., Galperin, A., Frankenhuis, W. E., et al. (2009). Adaptive rationality: an evolutionary perspective on cognitive bias. Social Cognition, 27(5), 733e763.

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Please cite this article in press as: Ron, O., et al., The doubt-certainty continuum in psychopathology, lay thinking, and science, Journal of Behavior Therapy and Experimental Psychiatry (2015), http://dx.doi.org/10.1016/j.jbtep.2015.08.005