Piecing Together the Neural Basis of Creative Cognition Adam S. Bristol and Indre V. Viskontas
Memory is essential for creativity. Consider, for example, the classical four- stage model of creativity proposed by Wallas (1926), based on the ideas of Helmholtz (1896). In this model, creative achievement occurs through preparation, incubation, illumination, and verification. Clearly, memory processes figure prominently at every stage of this model. Preparation, the stage in which adequate knowledge of the creative domain is acquired, necessarily involves extensive encoding of information and the ability to retain that information over time. Verification, the stage in which creative output is evaluated in terms of its accuracy or utility, must involve the retrieval of information and skills necessary for the appraisal. The incu- bation and illumination stages involve memory processes insofar as pre- viously acquired information is recombined to generate and recognize a novel idea. How can memory be so flexible such that information acquired in one way can be manipulated and recapitulated in so many other ways?
What clues are there to the brain mechanisms underlying these dynamic memory processes?
We attempt to address these questions in this chapter by conceptualizing creative cognition as a set of separable but interdependent cognitive pro- cesses that collectively generate creative output. We are particularly inter- ested in processes that interact with information stored in memory to either facilitate or hinder the novel recombining of ideas that is characteristic of creative cognition. We first describe the associationist approach to creativ- ity, one that is amenable to a variety of cognitive and neuroscientific anal- yses. This discussion provides a precursor to our integration of recent dis- coveries on the nature of human memory retrieval with cognitive processes that have been defined in creative thinkers. More specifically, we consider one oft-cited attribute of creative individuals, reduced behavioral and cog- nitive inhibition (reduced behavioral and cognitive inhibition, for exam- ple, Eysenck, 1995; Martindale,1999), and merge it with recent insights
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into inhibitory processes regulating retrieval from semantic memory stores.
Last, we apply the results of functional neuroimaging studies on inhibitory process in memory retrieval to generate a possible neurobiological mecha- nism underlying this aspect of creative cognition. Thus, this chapter offers two central ideas: (1) a distinct mechanism by which inhibitory cognitive mechanisms may alter the expression of creativity and (2) an improved outline of the neurobiological systems over which this mechanism operates.
associative memory networks in creative cognition
This chapter focuses on the cognitive processes that occur during the incu- bation and illumination stages of Wallas’s (1926) four-stage model because these stages involve the dynamic memory processes distinctive of creative cognition. An influential approach to this issue has drawn from theories of associationism, the notion that connections or relations between thoughts, feelings, ideas, or sensations are the basic components of cognition. Within an associative framework, memory is conceptualized as an expansive net- work of mental representations linked together according to some dimen- sion(s), such as semantic relatedness (e.g., drink and scotch) or perceptual similarity (e.g., penguin and tuxedo). Thus, one can consider the relations between different concepts as associative connections linking these con- cepts to each other and to other relevant bits of information.
Associative frameworks can be applied to different types of memory.
This structure can describe semantic memory with nodes representing words or facts and learning providing the associative links between differ- ent nodes. The structure is also appropriate for conceptualizing episodic and autobiographical memory. In this case, information about one’s past may be considered as represented by a linkage of facts about one’s life and knowledge of one’s history across time (e.g., the name of one’s elementary school, how many siblings one has), with a set of memories for specific events associated with each time period (e.g., during college, that time when the football team won during homecoming).
Associationism is also the basis for many early variations on the idea that creativity entails the novelrecombinationof existing mental representa- tions. A common theme among these theories is that the nature of creativity lies in the processes that bring together mental elements to form new or unusual combinations (Coney & Serna,1995). Thus, one might suppose that during the incubation and illumination stages, some process(es) occur that result in the reorganization of the existing memory store such that asso- ciations between previously – unassociated or weakly associated elements are newly formed or strengthened.
Response Potential
Chair Food Desk Top Cloth Leg -- Ocean Victory steep AH
shallow AH
figure 3.1. Schematic illustration of two associative hierarchies around the word table.
For example, Mednick (1962), ascribing to the view that creative thinking processes entail the formation of new combinations of elements in mem- ory, argued that theorganizationandaccessibilityof the associative memory store had important consequences for the creative process. First, he postu- lated that the organization of associations influences the probability and speed with which a creative solution is obtained. Second, he asserted that
“the more mutually remote the elements of the new combination, the more creative the process or solution.” Mednick relied on the notion of the asso- ciative hierarchy (AH), a quantitative summary of the probabilistic rela- tionships between a word and the verbal responses it evokes. For instance, if a subject is given a word association task and presented with the word
“table,” the most likely response is “chair.” A word such as “chemistry”
is unlikely to be given, and “horse” is even less so. It is possible through repeated testing to generate an AH for each word stimulus and plot the probability of each response, such as those shown in Figure3.1. Not sur- prisingly, people differ in the slopes of the curves that describe their AHs:
a steep AH indicates that only a few words are highly associated with the target word. A shallow AH indicates that remote associates have relatively high associative strengths with the target word. Therefore, a combination of higher strengths for remote associates and less competition from close associates makes remote associates more accessible.
Mednick argued that creative people demonstrate shallow AHs and, since they recall remote associates with a higher probability, they are more likely to produce a novel combination of associative elements. The opposite is true of relatively uncreative people. They exhibit steep AHs and, because most associations with a word or concept are concentrated around a small number of associates, they are unable to generate novel
combinations. Thus, Mednick differentiated creative and uncreative peo- ple by their ability to access remote associates and subsequently use them as part of new associative combinations. Indeed, although the relative order- ing of elements in AHs may be similar across individuals, what differs is theaccessibilityof the remote responses. This can be seen in continuous word association tasks, wherein the initial responses given by steep and shallow AH subjects are similar (that is, both may give a first response of
“chair” to the “table” probe word), but the steep AH subject quickly runs out of responses, whereas the shallow AH subject continues to generate new responses at a steady rate (Bousfield, Sedgewick, & Cohen,1954). Med- nick, Mednick, and Jung (1964) found that more creative subjects gave more response at a higher steady rate than did less creative subjects in a continu- ous association task. Similar results were obtained by Desiderato and Sigal (1970) and by Forbach and Evans (1981). Mednick (1962) further hypoth- esized that situations that favor the coactivation of remote associates in creative individuals should promote creativity. He suggested three such situations: (1) serendipity, the unintended, accidental contiguity of acti- vated ideas; (2) similarity, the generalization of activated ideas to those ideas similar on a stimulus dimension; and (3) mediation, the activation of remote elements mediated by an element common to each.
processes underlying the modification of associative hierarchies
The important assumption here is that creative ability is determined, in part, by the accessibility of remote associates in memory stores. In other words, remote associates are the building blocks of creativity and their access and recombination are the products of creative cognition. If this were true, then one would suppose that any process that limits access to remote associates would hinder creative cognition. Moreover,any process that weakens strong associates would enhance creativity because recall would be more likely to include remote associates. Together, these ideas bear on the issue of how AHs become steep or become shallow and whether access to remote associates can be modified, either transiently or over long durations. The- oretically, any process that decreases the associative status of the primary associates or increases the associative status of the remote associates would serve to flatten AHs. Likewise, any process that favors the recall of close associates (i.e., increases their associative strength with the target words) at the expense of remote associates would result in steeper AHs. In general, a powerful factor influencing access to remote associates (and even closely related associates, as we shall see) isrepetitionacross retrieval episodes:
repeated recall of associates increases the probability of subsequent recall of those associates while decreasing the likelihood of access to remote
associates. By contrast, diversity in recall of associates promotes access to remote associates.
For example, numerous studies have demonstrated that successful rec- ollection can facilitate later recall of the retrieved items (e.g., Allen, Mahler,
& Estes, 1969; Carrier & Pashler, 1992). It is now generally agreed that retrieval of information itself is a learning event that affects the ease with which the information is called to mind in the future (Benjamin & Bjork, 1996). Although storage capacity appears to be unlimited, the number of items that can be retrieved at any given time is limited by competitive pro- cesses in working memory. These competitive processes create a situation in which retrieval of an item comes at cost of decreasing the likelihood that items that share the same retrieval cues will be retrieved in the future. In turn, the successfully retrieved item is more likely to be retrieved again in the near future (Bjork & Bjork,1992).
Indeed, Mednick (1962) noted that the more often one has solved a problem with a given solution, the less likely he or she is to create a novel solution given the same problem. He interpreted this phenomenon as an increase in the probability of recalling close associates at the expense of alternative, remote associates. Such observations are clearly consistent with the notions of overlearning and functional fixedness, each of which refers to the stereotypy that results from extensive repetition (e.g., Bernstein & Goss, 1999; Dougherty & Johnston,1996) and which may act as a mental set to hin- der creative problem solving (Wiley,1998). This stereotypy is clearly seen in a series of studies examining the effects of previously observed exemplars on later attempts at creative output. For example, Smith et al. (1993) asked participants to generate new toy designs and varied whether the partic- ipants were shown example designs prior to designing their own. They found that participants who were shown examples generated designs that were much more likely to contain features of the examples, even when they were explicitly instructed to produce designs as different as possible from the examples. In a similar study, Jansson and Smith (1991) showed that professional engineers are susceptible to fixation resulting from pre- viously seen exemplars. Furthermore, Smith and Tindell (1997) showed that participants experience more difficulty solving word fragments (i.e., A L GY) after seeing incorrect but similar solutions (i.e., ANALOGYM).
This influence of recently activated information is likely to be present for AHs as well; that is, the repeated retrieval of primary associates further increases the likelihood that they were be recalled at a later time. Con- versely, avoiding repetition may help to flatten AHs and promote access to remote associates. For example, in a series of studies, Maltzman and colleagues (1958a,1958b,1962) found that subjects urged to generate novel responses across multiple iterations of a word associate task showed higher originality scores on a subsequent new test word list than did control sub- ject not required to generate novel responses.
If steep AHs result, in part, from recall repetition, then what processes account for the loss of access to remote associates? One possibility is that primary associates gain additional associative strength at the expense of secondary associates during repeated retrieval. An alternative possibility is that repetitive retrieval engages an active inhibitory process that sup- presses access to remote associates. These two alternatives make different predictions regarding the fate of remote associates. The former posits that remote associates lose associative strength to the primary associates, thus constituting a process that is qualitatively similar to forgetting. The latter predicts that remote associates retain their associations with the target cue, but may only be recalled if the inhibitory process can be suppressed. In thenext section, we discuss how recent findings on inhibitory processes in memory retrieval can have implications for associative accounts of cre- ativity cognition. Therefore, in essence, we consider whether inhibitory processes hinder or enable creativity, presuming that insights on creative processes can be gleaned not only from the study of creative people and their creative output but also from the study of the cognitive processes that potentially limit creativity.
associate suppression and retrieval-induced forgetting Proponents of connectionist models of memory often postulate that when one item is brought into consciousness, or working memory, other items associated with that item’s representation are also activated. If one is try- ing to bring into working memory a particular item, search strategies often include thinking of related items, be they related by semantics, initial learn- ing context, or some other relationship. Therefore, if one tries to think of a particular item, competing items (that is, those that are similar in one way or another) have to be rejected so that they do not clutter up the scratchpad of consciousness. There is a mountain of data concerning ways in which a target itemfacilitatesaccess to related items, including the many forms of priming and the theoretical processes of spreading activation in asso- ciative networks (e.g., Neely,1976; Warren,1977). Interestingly, however, there is now a growing body of data indicating that repeated retrieval of a particular item not only increases the recall probability of that item but also may act to suppress recall of related items.
That this suppression does indeed occur has been shown in a series of studies of retrieval-induced forgetting (RIF). Anderson, Bjork, and Bjork (1994) presented participants with a list of word pairs, each consisting of a category name and an exemplar of that category (e.g., fruits–banana, fruits–orange, drinks–gin). After an initial study session, the experimenters had participants practice retrieving half of the associates in half of the categories by providing them with the category and word stem (fruits–
or ). Thus, of the original list of word pairs, some category and exemplars
Recall Probability
Number of Repetitions
Practiced Items / Category 1
Unpracticed Items / Category 2 Unpracticed Items / Category 1
figure 3.2. Schematic illustration of retrieval-induced forgetting.
were practiced, other exemplars within the same category were not, and yet other category and exemplar pairs were not retrieved at all. A short time later, subjects were given a recall test that included all the original word pairs. As expected, they found facilitated recall of practiced word pairs relative to exemplars in unpracticed categories. Most interestingly, however, they noted impaired retrieval for the unpracticed items in the practiced categories (e.g., fruits–banana). That is, memory for unpracticed items in a practiced category was worse than that for items in a category given no additional training. Figure3.2illustrates the RIF effect.
RIF, as we have described it, is a laboratory phenomenon. Under highly constrained conditions such as those described earlier, RIF effects are rela- tively small. Nonetheless, these data show that repeated recall of an item can hinder the later recall of semantically similar items. In addition, when the cues at recall are only category names and do not include letter stems of exemplars, the RIF effects can reach25% of unpracticed items. In fact, these less constrained conditions are closer to those experienced by individ- uals engaged in creative thinking. How might RIF occur in a real-world situation? Imagine a film critic who prides himself on his encyclopedic knowledge of the casts and crews of countless movies. Yet, his repeated dis- cussions of the Oscar-winning roles of a particular actress, which represent only a subset of her work, leaves him unable to recall her less successful roles, even though he can recall details of these films in the context of other actors. An explanation of the film critic’s memory lapse in terms of RIF would charge that his repeated recall of the subset of award-winning films led to an inhibition of recall for the remaining films. By the same token, had the critic not concentrated his recall on the critically acclaimed movies, he might be better able to recall the less praiseworthy ones.
What mechanism underlies the impaired memory for related associates in the practiced category? Several lines of evidence indicate that an active
inhibition causes RIF. Anderson et al. (1994) found that one alternative, the strength-dependence assumption, which states that recall probability of an item will decrease as the associative strengths of its competitor’s increase, does not account for RIF; increasing associative strength of prac- ticed items did not correlate with retrieval impairment with unpracticed items in the same category. Rather, what was important was the initial state of the association between the category and exemplar. For example, RIF occurred among unpracticed items if they were strong items in a category (e.g., fruits–banana), but not if they were weak items (e.g., weapon–lance).
It is possible that response competition and blocking explain why strong, but not weak, associates are sensitive to RIF. For example, if a cue gener- ates multiple possible responses, then response competition develops. If particular responses are dominant, as is the case with strong associates, then competing items block recall of a desired response. To overcome this block, some suppression of the undesired responses must take effect.
A later study by Anderson and Spellman (1995) found that the sup- pression of unpracticed exemplars was not the result of a degradation of the association between the category name and the exemplar. They asked participants to undergo the same study and retrieval practice conditions as described above, but some of the exemplars were semantically related to more than one category. For example, participants first studied asso- ciates of the wordred(e.g., red–blood, red–strawberry) and associates of the wordfood (e.g., food–crackers, food–cherry) and then practiced half of these exemplars for half of the categories (e.g., red–blood). During the test phase, the authors found that unpracticed items in the practiced cat- egory (e.g., red–strawberry) were harder to recall, as were items in the unpracticedcategory that were possible exemplars for the practiced cate- gory (e.g., food–cherry). Collectively, these findings strongly suggest that an inhibitory process impedes recall of items related to recently practiced items, even when those items are initially learned within a different cate- gory. In other words, RIF is not because of a simple strengthening of the practiced category–exemplar pairs alone, but rather to some other process that generalizes across retrieval cues.
There are also other kinds of memory phenomena in which retrieval adversely affects recall of related items. Retroactive interference (Barnes &
Underwood,1959) and part-set cueing (reviews by Nickerson,1984, and by Roediger & Neely,1982) are two well-known examples. In retroactive interference, the learning of new material leads to forgetting of old mate- rial, although the mechanism by which this occurs is generally thought to be either by weakening of the associations with the old material or by overshadowing these associations with a stronger new association. Part-set cueing involves asking participants to remember a set of items, only some of which are associated with the given retrieval cues. Participants are then less likely to retrieve items from the list that do not share those retrieval