The Role of an Incubation Period in Creative Problem Solving

This experimental study tested the spreading-activation hypothesis that an incubation period helps to sensitize problem solvers to relevant concepts. The study also tested the selective forgetting hypothesis that an incubation period helps to desensitize problem solvers to irrelevant concepts. Chinese Chess GO players, 28 experts and 29 novices, solved 18 remote association tasks (RAT) and lexical decision tasks (LDTs) under immediate, rest, and incubation conditions. After each RAT, a set of LDTs incorporating the RAT solution and the irrelevant concept were presented, either immediately, or after a 2-min delay, or after a 2-min delay filled with incubation tasks. The findings of the study support the spreading activation hypothesis and suggest that spreading activation occurs only in a fixated mind. No support was found for the selective forgetting hypothesis. Anecdotal reports (Ghislin, 1985; Wallas, 1926; Woodworth & Schlosberg, 1954) have documented that a flash of insight occurs after the problem solver puts the problem aside and shifts his or her attention to other areas for a while. This temporary abstention from the problem has been labeled the incubation period (Wallas, 1926). Several hypotheses have been proposed in an attempt to account for the incubation effect (Seifert, Meyer, Davidson, Patalano, & Yaniv, 1995). Two of the most prominent hypotheses are the spreading activation and selective forgetting hypotheses. The spreading activation hypothesis (Smith, 1995b; Yaniv & Meyer, 1987) proposes that during an incubation period, activation spreads to the nodes representing the relevant concepts. Thus, problem solvers become more sensitive to them, and the problem solving process is facilitated. The selective forgetting hypothesis (Simon, 1966; Smith, 1995b; Smith & Blankenship, 1991) states that an incubation period provides time for suppressing the activation of the nodes representing the irrelevant concepts that fixate problem solvers’ minds, and in turn, problem solvers will become less sensitive to these irrelevant concepts. Thus, they can have a fresh view towards the problem and the problem solving process is facilitated. Experimental studies have been carried out to provide empirical support for the incubation effect. The setting of the early studies was, however, rather uniform. Namely, one group of participants was interrupted with a break (incubation period) while solving a creative problem, whereas the other group worked on the creative problem continuously. A number of studies have reported that the interrupted participants outperformed those working continuously (Fulgosi & Guilford, 1968, 1972; Mednick, Mednick, & Mednick, 1964; Murray & Denny, 1969), yet, none of them can offer support to the spreading activation or the selective forgetting hypotheses. This is because the superior performance may simply be the outcome of the reduction of mental fatigue or The procedures and the data reported in this article are part of a research project funded by the City University of Hong Kong. Correspondence should be sent to Ut Na Sio, Psychology Department, Lancaster University, Fylde College, Lancaster, LA1 4YF, United Kingdom. E-mail: [email protected] Creativity Research Journal 2007, Vol. 19, Nos. 2–3, 307–318 Copyright # 2007 by Lawrence Erlbaum Associates, Inc. Creativity Research Journal 307 participants’ covert consciousness working on the problem during the incubation period. To correct this problem, ensuing incubation studies have modified the setting of the incubation. Instead of being unoccupied during the incubation period, participants had to engage in some intervening activities, thus preventing participants from working on the problem covertly or having any rest. These studies have shown that participants who had a filled incubation period performed better than those working on the problem continuously (Murray & Denny, 1969; Patrick, 1986; Penney, Godsell, Scott, & Balsom, 2004; Silveira, 1971) and than those who had a rest while solving the problem (Patrick, 1986; Penney et al., 2004; Smith & Blankenship, 1989). Moreover, participants performed better if they were exposed to a longer incubation period (Silveira, 1971; Penney et al., 2004). These findings not only offered substantial empirical support to the existence of an incubation effect, but also warranted that the performance improvement was not due to the mental fatigue dissipation or additional covert conscious work. However, it is still unclear whether the incubation effect is due to the occurrence of spreading activation, selective forgetting, or other unknown mechanisms. There are other studies claiming that they have adopted a more critical approach to examining the processes underlying an incubation. Dodds, Smith, and Ward (2002) and Dorfman (1990) examined the spreading activation hypothesis by investigating the effect on creative problem solving of presenting related cues during incubation. They argued that the spread of activation during an incubation should sensitize the problem solvers to related concepts, and thus they should be able to make use of the externally presented related cues to solve the problem. Yet, their argument may not have been correct, as one could argue assimilating external cues may also depend on how deep the problem solvers process the cues. In addition, these studies presented mixed results and cannot be accepted as strong evidence to support or reject the spreading activation hypothesis. The findings of studies testing the selective forgetting hypothesis are more convincing. Smith and Blankenship (1989, 1991) carried out a series of experiments that yielded consistent results, indicating that an incubation period helped problem solvers increase their performance on creative problems. In these studies, participants had to solve a list of creative tasks, some of which were presented with irrelevant information. The presentation of irrelevant information fixated the participants’ minds and inhibited their performance. When solving the problems containing irrelevant information, participants performed better with an incubation period than if they had worked on the problem continuously. Also, a longer incubation period resulted in a higher performance and a larger degree of forgetfulness of the irrelevant concepts among the groups (Smith & Blankenship, 1989). This pattern of findings is consistent with the selective forgetting hypothesis that an incubation period can help to resolve the fixation effect and improve problem solvers’ performance by providing time for the irrelevant information to fade out. However, these findings cannot be generalized because, in these studies, the irrelevant information hindering the participants’ minds has been limited only to that externally encountered. In some situations, fixation may not be caused by the externally encountered stimuli, but can be internally generated by the automatic activation of the problem solver’s knowledge. A classic example of this type of fixation has been demonstrated in Duncker’s study (1945), which asked participants to fix a candle on a wall in a way preventing the wax from dripping onto the floor. They were presented with a box of matches and a few tacks. Participants could solve the problem only if they perceived the box as a platform rather than as a container. However, the participants’ traditional concept of the function of a box hindered their minds in perceiving the box as a platform. Another, more recent investigation demonstrating this type of fixation was Wiley’s (1998) study among baseball experts. Using Mednick’s (1962) method of remote association task (RAT), Wiley created RATs in which the first two stimuli were baseball-related, and the third stimulus and the solution were baseball-unrelated. The results revealed that baseball experts’ domain relevant knowledge would be activated automatically by the first two stimuli. Although the activated U. N. Sio & E. Rudowicz 308 Creativity Research Journal baseball knowledge was irrelevant to the tasks at hand, the baseball experts still could not ignore these internally generated irrelevant concepts. Thus, their performance was inhibited due to the fixation effect. Yet, the role of an incubation period in helping problem solvers to forget these kinds of irrelevant concepts has been not fully explained because the past incubation studies focused mainly on examining the role of an incubation period in desensitizing externally imposed irrelevant stimuli. The current study adopted a new approach to examine the spreading activation and selective forgetting hypotheses. First, instead of comparing participants’ creative problem-solving performance under different experimental conditions, this study used lexical decision task to directly assess participants’ sensitivity towards relevant and irrelevant concepts, before and after an incubation period. Conclusions from previous studies, showing that a person’s lexical decision time to a word is negatively correlated with the person’s sensitivity to that word (Meyer & Schvaneveldt, 1971; Scarborough, Cortese, & Scarborough, 1977), allow us to treat the lexical decision time as an indicator of a person’s sensitivity to these two types of concepts. Additionally, unlike the past incubation studies, the irrelevant concepts adopted in this study were automatically generated internally in the minds of the GO experts during the process of solving GO-misleading RATs. Based on the existing literature on the subject and with the focus of explaining the role of incubation period in creative problem solving, two hypotheses were formulated: 1. Spreading activation hypothesis: After an incubation period, both experts and novices will become more sensitive to concepts relevant to the unsolved RATs. Thus, the lexical decision time concerning these concepts will be shorter for both, the experts and novices. 2. Selective forgetting hypothesis: After an incubation period, experts will become less sensitive to the irrelevant domain-related concepts activated by the content of the RATs, whereas a similar effect will not be observed in novices. Thus, the experts’ lexical decision time concerning these concepts will be longer. Method