Incubation processes during problem solving

Transcription

1 Final Report to ESRC on grant RES August 28, 2009 K.J. Gilhooly & G. Georgiou Incubation processes during problem solving Background Introduction Wallas (1926) proposed that an Incubation stage in problem solving, during which the problem is set aside and not consciously addressed, is beneficial. Dodds, Ward & Smith (2003) identified 39 relevant experiments of which 75% reported significant beneficial effects of incubation. More recently, Sio & Ormerod (2009) have reported an extensive meta-analysis which supports the beneficial effects of incubation in insight and divergent thinking tasks. The four main hypotheses regarding incubation effects that were addressed in the present project studies are as follows. 1. Intermittent Conscious work: This suggests that although incubation is intended to be a period without conscious work on the target task, nevertheless participants may carry out intermittent conscious work (Seifert, Meyer, Davidson, Patalano & Yaniv, 1995, p.82). Any conscious work during the supposed incubation period would reduce the time required when the target problem was re-addressed but would impair performance on the interpolated task. As a check against this possibility, performance on the interpolated task during the incubation period should be compared with performance of a control group working on the same interpolated task without being in an incubation condition. A deficit in the interpolated task on the part of the incubation group would be consistent with the hypothesis of some conscious work on the target task during incubation. Although this seems a rather basic methodological check, surprisingly it has not been routinely carried out in previous research (Dodds et al., 2003). All the studies reported here incorporated suitable checks for conscious work on the target task during the incubation period. 2. Unconscious work: This approach argues that incubation effects occur through active but unconscious processing of the problem materials. Poincaré (1929) suggested that the subliminal self unconsciously combined and recombined ideas until an interesting relevant combination was formed whereupon the valuable idea would become conscious (i.e., Wallas s Inspiration stage). More recently, Dijksterhuis and Meurs have applied a theory of unconscious thought (Dijksterhuis & Nordgren, 2006) to incubation. On this view, unconscious thought, compared to conscious thought, has a large capacity, proceeds relatively slowly, tends to be bottom up, is good at integrating many sources of information, is relatively poor at following rules and tends to be divergent rather than convergent. Dijksterhuis and Nordgren report a number of studies in which better decisions and better creative thinking were found when the tasks were not worked on consciously. Their studies did not follow the classical method of incubation research in which the problem is set aside after an extended period of conscious work. Rather, Dijksterhuis and Meurs had the participants immediately put aside the problem for a period after the task was presented, and before any conscious work could be carried out. 13

2 3. Selective Forgetting: This view (e.g., Simon, 1966) proposes an important role for automatic reduction in idea strength or activation. The proposal is that misleading strategies, mistaken assumptions and related mental sets weaken through forgetting and thus a fresh start or set shifting is facilitated when the problem is resumed. 4. Attention Withdrawal hypothesis: On this view (Segal, 2004), nothing happens during the incubation break. The break removes attention from a misleading assumption and on returning to the task there is a chance to set shift and adopt a more helpful assumption. This account is very close to the Selective Forgetting view; however, Segal argues that the two can be distinguished in that the Attention Withdrawal hypothesis predicts no effect of length of incubation interval as simple withdrawal of attention is sufficient on that hypothesis, while the Selective Forgetting view would suggest that longer incubation intervals which allow more forgetting would be more beneficial than shorter intervals. Segal (2004) reported a study with long and short incubation intervals in which both intervals were effective compared to no incubation interval but length of incubation interval was immaterial. This result is also counter to the Unconscious Work hypothesis according to which a longer incubation period would permit more unconscious work and hence more facilitation than would be found for a shorter interval. Unconscious work v. Attention Withdrawal: A current issue The hypotheses outlined above to explain incubation effects are not all mutually exclusive. Some of the hypothesised processes could co-exist and play roles within an individual problem solving episode. Different tasks may benefit from different processes and the exact positioning of the incubation period may affect which processes occur. However, among the hypotheses outlined above, a particularly stark contrast is offered by the Unconscious Work and the Attention Withdrawal hypotheses. Segal (2004), espousing the latter, argued that his results supported the view that nothing happens during incubation while Dijksterhuis and Meurs (2006) proposed that active unconscious thought processes must be invoked to explain their data. The conflicting conclusions of Segal (2004) and Dijksterhuis & Meurs (2006) may have resulted from a number of factors. One possibility is that the different conclusions are due to differences between the types of task used viz., a convergent spatial insight problem in Segal (2004) as against a divergent verbal task in Dijksterhuis and Meurs (2006). It is possible that Unconscious Work is helpful for divergent tasks where many alternatives are sought but not helpful for convergent tasks where only one solution path is possible. It seems a reasonable hypothesis that the positioning of the incubation period may also be significant. Incubation before any conscious work would minimise the role of forgetting (nothing yet to forget) or set switching (no sets established) and maximise any effects of Unconscious Work. The studies reported here investigated the explanations of the conflicting findings of Segal on the one hand and Dijksterhuis & Meurs on the other hand, by examining the effects of positioning of incubation opportunities on insight and divergent thinking tasks in different combinations from those represented by previous studies. It is notable that both Segal (2004) and Dijksterhuis and Meurs (2006) used interpolated tasks that were different in character from the target tasks. Segal s target task was spatial while the interpolated tasks were verbal; Dijksterhuis and Meurs s target task was verbal but the interpolated task was visuo-spatial. From Dodds et al. s (2003) extensive review, the issue of similarity between target and interpolated tasks does not appear to have been addressed hitherto. The similarity relationship between target and interpolated tasks could be important in that different hypotheses suggest different effects of similarity. If the main process underlying incubation is beneficial forgetting then interpolated tasks similar to the 14

3 target task should promote more forgetting due to interference and hence bigger incubation benefits; however, if unconscious work is the main process then interpolated tasks similar to the target task should interfere with any unconscious work using the same mental resources and so lead to weaker (or even reversed) incubation effects when compared with effects of dissimilar interpolated tasks. Objectives 1. To fill a gap in the literature, in which insight problems had not been studied hitherto with incubation immediately after task presentation. 2. To examine effects of varying incubation durations and similarity of interpolated activities (verbal or spatial) with target task activities (verbal or spatial) in divergent and insight tasks. 3. To assess the theoretical implications of the results obtained. Methods and Results There were three experiments. Experiment 1 used a divergent task with delayed incubation and Experiments 2 and 3 used convergent insight tasks (one spatial and one verbal, respectively) with immediate incubation. Experiment 1. Effects of post-impasse incubation periods and congruence of interpolated activities on a divergent thinking task. In this experiment the target task was the divergent production of alternative uses for a brick. The positioning of the incubation periods was post-conscious work as used by Segal (2004) while the target task was as used by Dijksterhuis and Meurs (2006). Participants: A total N of 143 (106 female, 37 male) students at the University of Hertfordshire, with a mean age of (SD = 3.89, range 18 40). Design: A 2 (incubation periods: 4 v. 8 mins.) X 2 (interpolated task: verbal v. spatial) independent groups design was used. The Ns per experimental group were as follows: 4 mins incubation and spatial interpolated task (N = 25); 4 mins incubation and verbal interpolated task (N = 23); 8 mins incubation and spatial interpolated task (N = 22); 8 mins incubation and verbal interpolated task (N = 26). There was also a control group () that provided baseline performance data for target and interpolated tasks in the absence of incubation periods. Procedure: Participants were told that they would be asked to write down possible uses for a Brick different from the usual use. After 5 minutes working, participants were then assigned randomly to one of 2 incubation time periods (4 or 8 minutes) or to a control condition with no incubation period to continue for a further 2 minutes with no break. Participants assigned to the incubation conditions were told that they would be returning to the Brick Uses task later in the study. During the incubation periods participants either undertook verbal tasks (Anagrams) or spatial tasks (Mental Rotation items) presented in booklets. Sets of 73 five-letter single solution anagrams (from Gilhooly & Hay, 1977) and 48 mental rotation items (from Peters et al., 1995) were used and performance was scored in terms of numbers of items attempted and correct solutions during the period allowed. After the incubation periods there were further 2 minutes periods of work on the Uses task. 15

4 At the end of the Uses task participants were asked to indicate which of the uses they reported were subjectively novel i.e. had first occurred to them during the task rather than being previously known (following Gilhooly et al., 2007). The control group was tested to measure baseline performance on the intervening tasks (Anagrams and Mental Rotation) over 8 minute periods. From these data we also obtained baseline performance over a 4 minute period by marking progress every minute. These baseline measures were compared with performance on the tasks when used as intervening activities during the incubation periods. The same baseline data were used in our subsequent studies (rather than collect fresh baseline data for the same interpolated tasks repeatedly) which gave useful savings in costs and research time. Results Effects of interpolation on the incubation period tasks Tables 1 and 2 below show performance on the rotation and anagram tasks when performed in control conditions for 4 or 8 mins and as interpolated tasks in the incubation conditions Table 1. Mental Rotation performance when carried out as an interpolated (incubation) task or as control task. Mean scores (max = 48) and SDs in brackets. Control Interpolated Task Time 4 mins 8 mins 4 mins 8 mins n items attempted 6.69 (2.65) (4.54) 7.12 (3.14) (5.60) n items correct 3.76 (2.58) 7.24 (4.53) 4.72 (2.89) 8.18 (4.43) From Table 1 it appears that carrying out Mental Rotation as an interpolated task during incubation periods did not affect Mental Rotation performance negatively and t-tests showed no significant differences at 4 minutes or 8 minutes interpolated v control performances in either number of items attempted or in number solved correctly. Table 2. Anagram performance when carried out as an interpolated (incubation) task or as control task. Mean scores (max = 73) and SDs in brackets. Control Interpolated Task Time 4 mins 8 mins 4 mins 8 mins n items attempted (5.27) (10.73) (8.14) (14.32) n items correct (5.70) (7.50) (6.31) (12.12) From Table 2 it appears that carrying out Anagrams as an interpolated task during incubation periods did not affect Anagram performance negatively and t-tests showed no significant differences at 8 minutes interpolated v control performances in either number of items attempted or in number solved correctly. At the 4 minute time period there was a significant increase in the number of anagrams attempted (t =2.24, df = 65, p <.05) when the anagrams were interpolated as against carried out under control conditions. The results in Tables 1 and 2 do not support the hypothesis that incubation periods involve intermittent conscious work on the target task since under that hypothesis we would expect an impairment of performance on the anagram and rotation tasks when performed as interpolated activities as against as control activities. 16

5 Effects of increasing incubation intervals (1): Verbal interpolated task Table 3 below shows the average numbers of uses and the average numbers of self judged novel uses produced in the last 2 minutes of work following 0 mins of incubation (Control data) or 4 or 8 mins of incubation with a verbal interpolated task (anagrams). Table 3. Mean number of uses and mean number of self judged novel uses in final 2 mins after varying periods of incubation with a verbal interpolated task (after 5 mins initial work). SDs in brackets. Incubation Period n Uses n Self rated novel 0 mins 1.85 (1.25) 0.77 (0.79) 4 mins 2.17 (1.07) 1.34 (0.93) 8 mins 2.19 (1.69) 1.12 (1.28) Anovas indicated that there was no significant effect of anagram filled incubation period on the number of uses reported after incubation but there was a borderline significant increase in the number of self judged novel uses with anagram filled incubation period (F(2) = 3.01, p = 0.054, part 2 =.06). Post Hoc tests indicated a significant difference between 0 mins incubation and 4 mins anagram filled incubation (p<0.05) Effects of increasing incubation intervals (2): Spatial interpolated task Table 4 below shows the average numbers of uses and the average numbers of self judged novel uses produced in the last 2 minutes of work following 0 mins of incubation (Control data) or 4 or 8 mins of incubation with a spatial interpolated task (Mental Rotations). Table 4. Mean number of uses and mean number of self judged novel uses in final 2 mins after varying periods of incubation with a spatial interpolated task (after 5 mins initial work). SDs in brackets. Incubation Period n Uses n Self rated novel 0 mins 1.85 (1.25) 0.76 (0.79) 4 mins 2.76 (1.85) 1.56 (1.22) 8 mins 2.54 (1.50) 1.45 (1.01) Anovas indicated that there was a significant effect of mental rotation filled incubation period on the number of uses reported after incubation (F (2) = 3.58, p <0.05, part 2 =.07) and there was also a significant increase in the number of self judged novel uses with rotation filled incubation period (F(2) = 6.96, p < 0.01, part 2 =.13). Post Hoc tests indicated a significant difference between 0 mins incubation and 4 mins rotation filled incubation (p<0.05) for number of uses and between 0, 4 and 8 mins rotation filled incubation on self judged novelty (p <0.05 for all comparisons). Experiment 2. Effects of immediate post-instruction incubation periods and congruence of interpolated activities on a spatial insight problem solving task. In this experiment the positioning of the incubation period was as used by Dijksterhuis & Meurs (2006) while the spatial insight target task was as used by Segal (2004). Participants: A total N of 74 (55 female, 19 male) students at the University of Hertfordshire, with a mean age of (SD = 6.86, range 17 48) 4 experimental groups of: Unconscious Work group 3 mins verbal interpolated task (N = 7); Unconscious Work group 5 mins verbal interpolated task (N = 7); Unconscious Work 17

6 group 3 mins spatial interpolated task (N = 9); Unconscious Work group 5 mins spatial interpolated task (N = 8) 3 control groups of: Immediate Work control group (N = 23); Conscious Work control group 3 mins (N = 12); Conscious Work control group 5 mins (N = 8). Design: 2 (Length of incubation period before solution reporting stage: 3 v. 5 mins) X 2 (Nature of interpolated activity: verbal. v. spatial) independent groups. Procedure: The target problem was the geometric insight problem used by Segal (2004). Participants were presented with the target problem and were then were split into groups as follows. An Immediate Work control group tackled the problem until solved or for a maximum of 20 minutes. Two Conscious Work control groups were given 3 or 5 minutes to think about the problem but were not allowed to state any answer until the solution reporting stage (20 mins maximum). Four Unconscious Work groups were given 3 or 5 minutes to work on either a verbal (Anagrams) or a spatial task (Mental rotations) immediately after the target task instructions. The interpolated tasks were the same as in Experiment 1 above, following which they had a solution reporting stage of up to 20 minutes to work on the target geometric insight task. Baseline levels of performance for 3 or 5 minutes work on the verbal and spatial intervening tasks (when no preceding task is being incubated) were derived from the relevant baseline data gathered in Experiment 1 above. These baseline measures were compared with performance on the tasks when used as intervening activities during the incubation periods. After the target task instructions participants that were in groups that involved an interpolated task were instructed that they would be returning to the target task later in the study. Results Table 5 below shows the proportion of participants in each group who solved the spatial problem within 20 mins., and the mean spatial task latency in secs (non-solutions scored as 1200 secs). SD s shown in brackets. Table 5. Total N = 74 Immediate N = 23 Conscious Work N = 20 Incubation N = 31 Proportion Target Task solved in 20 mins. Mean Target task latency in secs. (SD) (95.3) (363.1) (314.2) From Table 5, there seemed to be a trend for better performance on the spatial target task following either type of activity (Conscious Work or Incubation) carried out after the postinstruction period. Comparisons of proportions correct indicated a difference between the Immediate and Conscious work conditions (z = 1.80, p =.04, 1 tail) and a borderline difference between the Immediate and the Unconscious Work conditions (z =1.62, p =.05, 1 tail). A one way ANOVA showed no significant difference in the mean target task latencies between the three groups. 18

7 Effects of increasing incubation intervals (1) : Verbal interpolated task Table 6 below shows the average task latencies and proportions of solutions following 0 minutes or 3 or 5 minutes of immediate Incubation after the instructions with a verbal interpolated task (anagrams). Table 6. Performance on Segal s spatial problem following 0 minutes of immediate incubation or 3 or 5 minutes of immediate Incubation after the instructions with a verbal interpolated task (anagrams). Average latency scores in secs., SDs in brackets. Incubation period (minutes) Latency (95.3) (289.14) (387.33) Prop. Solved.09 (.28).15 (.35).23 (.44) One way Anovas indicated no significant effect of anagram filled immediate incubation on performance on Segal s spatial insight task as measured by latency scores or accuracy scores. Effects of increasing incubation intervals (2) : Spatial interpolated task Table 7 below shows the average task latency and accuracy scores following 0 minutes of immediate incubation or 3 or 5 minutes of immediate Incubation after the instructions with a spatial interpolated task (rotations). Table 7. Performance on Segal s spatial problem following 0 minutes of immediate incubation or 3 or 5 minutes of immediate Incubation after the instructions with a spatial interpolated task (rotations). Average latency scores in secs., SDs in brackets. Incubation period (minutes) Latency (95.3) (265.12) (339.8) Prop. Solved.09 (.28).23 (.44).45 (.52) One way Anovas indicated no significant effect of duration of rotation filled, immediate incubation, on performance on Segal s spatial insight task for latency scores but a borderline effect (F(2) = 2.82, p =.07) for proportion correct. Post hoc tests indicated a significant difference between control and 5 minutes incubation (p =.02) for proportion correct. Effects of interpolation on the incubation period tasks Table 8 below shows the mean items correct and attempted for the verbal (anagrams) and spatial (mental rotations) interpolated tasks for the 3 mins and 5 mins incubation work groups and the interpolated task control group data from Study 1. Standard deviations are shown in brackets. 19

8 Table 8. Group Incubation Incubation Interpolated Task Control Interpolated Task Control Interpolated Task Time Mean Anagrams correct Mean Anagrams attempted Mean Rotations correct Mean Rotations attempted 3 mins 5 mins 3 mins 5 mins 9.57 (7.61) N= (6.96) N = (2.37) N = (2.06) N = (5.59) N = 7 26 (6.27) N = (3.88) N = (3.38) N = (5.16) (5.15) 2.87 (2.21) 5.02 (2.22) (6.07) (6.96) 4.62 (3.07) 8.55 (3.26) From Table 8 it appears that carrying out Anagrams as an interpolated task during an incubation period of 5 mins affected Anagram performance positively compared to the control group. T-tests show that the number of Anagrams correct (t = 2.93, df = 52, p < 0.01) and Anagrams attempted (t = 3.12 df = 52, p < 0.01) in a 5 mins period were higher for the incubation group compared to the control group. All other comparisons were not significant. Experiment 3. Effects of immediate post-instruction incubation periods and congruence of interpolated activities on a verbal insight problem solving task. In this experiment the positioning of the incubation period was as used by Dijksterhuis & Meurs (2006) while the verbal insight target task (Marrying Man) was drawn from our previous research (Gilhooly & Murphy, 2005). Participants: A total N of 71 (55 female, 16 male) students at the University of Hertfordshire, with a mean age of (SD = 6.57, range 17 48) Design, group sizes and procedures were nearly identical to Experiment 2 above, but used a verbal insight task (Marrying Man) as the target task rather than a spatial geometric task and had a 5 minute solution stage as against the 20 minutes allowed in Study 2 in which the target is more difficult. The Marrying Man problem asks participants to explain how a man could have married 20 women (all being still alive) in the same town in a few months and not broken the applicable law against polygamy. (Answer: he is licensed to carry out wedding ceremonies). Our previous work found a medium solution rate of c. 50% over 5 minutes study time for this task (Gilhooly & Murphy, 2005) and so performance under various conditions should not have been affected by floor or ceiling effects. Results Table 9 below shows the proportion of participants in each group who solved the verbal problem within 5 mins., and the mean verbal task latency in secs, (non-solutions scored as 300 secs). SDs in brackets. 20

9 Table 9. Total N = 71 Immediate N = 14 Conscious Work N = 15 Incubation N = 42 Proportion solved Mean Target task solution latency in secs. (SD) (127.6) (111.5) (100.7) From Table 9 it appears that the type of activity (incubation or conscious work) carried out after the post-instruction period did not affect the verbal task solution rates and no significant differences between the 3 groups in solution rates were found. In addition, the type of activity carried out after the post-instruction period did not affect the verbal task latency and a one factor Anova showed no significant difference in the mean target task latencies between the three groups. Effects of increasing incubation intervals (1) : Verbal interpolated task Table 10 below shows the average task latencies and solution rates following 0 minutes or 3 or 5 minutes of immediate Incubation after the instructions with a verbal interpolated task (anagrams). Table 10. Performance on verbal Marrying Man problem following 0 minutes or 3 or 5 minutes of immediate Incubation after the instructions with a verbal interpolated task (anagrams). Average latency scores in secs. SDs in brackets. Incubation period (minutes) Latency (126.7) (189.14) (187.33) Prop. Solved.39 (.50).42 (.51).19 (.40) One way Anovas indicated no significant effect of anagram filled immediate incubation on performance on the verbal Marrying Man insight task for latencies or solution rates. Effects of increasing incubation intervals (2) : Spatial interpolated task Table 11 below shows the average task latencies and solution rates following 0 minutes or 3 or 5 minutes of immediate Incubation after the instructions with a spatial interpolated task (rotations). Table 11. Performance on verbal Marrying Man problem following 0 minutes or 3 or 5 minutes of immediate Incubation after the instructions with a spatial interpolated task (rotations). Average latency scores in secs., SDs in brackets. Incubation period (minutes) Latency (126.7) (165.12) (139.8) Prop. Solved.39 (.50).25 (.46).58 (.51) 21

10 One way Anovas indicated no significant effects of rotation filled immediate incubation on performance on the verbal Marrying Man insight task for task latencies or solution rates. Effects of interpolation on the incubation period tasks Table 12 below shows the mean items correct and attempted for the verbal (anagrams) and spatial (mental rotations) interpolated tasks for the 3 mins and 5 mins incubation work groups and the interpolated task control group data from Study 1. Standard deviations are shown in brackets. Table 12. Group Incubation Incubation Interpolated Task Control Interpolated Task Control Interpolated Task Time Mean Anagrams correct Mean Anagrams attempted Mean Rotations correct Mean Rotations attempted 3 mins 5 mins 3 mins 5 mins 8.81 (7.35) N = (10.53) N = (1.93) N = (2.00) N = (7.93) N = (8.88) N = (2.75) N = (2.66) N = (5.16) (5.15) 2.87 (2.21) 5.02 (2.22) (6.07) (6.96) 4.62 (3.07) 8.55 (3.26) From Table 12 it appears that carrying out Rotations as an interpolated task during an incubation period of 5 mins affected Rotation performance negatively compared to the control group. T-tests show that the number of Rotations attempted in 5 mins were lower for the incubation group compared to the control group (t = 2.51 df = 57, p < 0.05). All other comparisons were not significant. Discussion The results of Experiment 1, which examined delayed incubation in a divergent thinking task, indicated that when the incubation period was filled with a task drawing on different resources (the spatial condition here) the incubation effect was stronger. Overall, this is more consistent with the Unconscious Work Hypothesis of delayed incubation than the Selective Forgetting Hypothesis (which predicts the opposite pattern) or the Attention Withdrawal and Returning Act hypothesis which predicts no difference due to type of interpolated activity or to duration of interpolated activity. The Intermittent Conscious work hypothesis was also not supported by the non-effects on the intervening task due to its being used as an incubation activity. The results of Experiment 2, as with Experiment 1 lent no support to the Intermittent Conscious Work hypothesis. The effects of immediate incubation in Experiment 2 which used the spatial geometric problem of Segal (2004) appeared to be weak with a borderline (although positive) effect of Incubation overall. The beneficial effects of spatial incubation activity appeared to have been somewhat greater than those of verbal incubation especially with the longer (5 min) incubation period. Since positive effects of immediate post-instruction incubation have been taken to indicate underlying unconscious work, it is surprising that a spatial interpolated task led to better 22

11 post incubation performance in Experiment 2 s spatial target task. Carrying out mental rotations as the conscious interpolated task might be expected to reduce resources needed for unconscious processing of the spatial target task. It may be that in this type of insight problem, sets are established immediately on interpreting the instructions and weaken during the immediate incubation period. Thus, the present results may reflect beneficial forgetting processes rather than unconscious working during immediate incubation in this task. In contrast to the previous experiments, the trend of the results in Experiment 3 was towards negative immediate incubation effects. Only the 5 minute rotation immediate incubation condition indicated positive effects while the other incubation conditions displayed negative trends. However, none of the effects in this study were significant or approached significance. It appears that, overall, this verbal insight task (Marrying man) did not show effects of immediate incubation. A possibility is that the set induced by the presentation of the task is too strong to be weakened by the fairly short incubation periods used here. Our results on the divergent, creative task are consistent with the thrust of Sio and Ormerod s meta-analysis (2009) which found that such tasks showed the strongest evidence for effects of delayed incubation when compared with visual and verbal insight tasks. Our results and those of Dijksterhuis and Meurs (2006) are consistent with the idea that Unconscious Thought plays a role in divergent thinking with both delayed and immediate incubation. We found only weak or no evidence of effects of immediate incubation in the spatial and verbal insight tasks studied here. The results of these studies seem consistent with strong, immediate sets being generated during the initial interpretation stage and these were relatively resistant to weakening by brief immediate incubation, especially in the case of the verbal insight task (Marrying Man). Again, the weak or nonexistent effects of immediate incubation in the convergent insight tasks can be taken as consistent with Dijksterhuis and Nordgren s (2006) Unconscious Thought Theory, according to which, unconscious thought is divergent in character, and so less likely to be helpful in convergent tasks. Previous studies, as indicated by Sio and Ormerod (2009) have found beneficial effects of delayed incubation in insight tasks. The relative lack of effect found here for immediate incubation could indicate that delayed incubation effects in insight tasks arise from beneficial forgetting and/or attentional shifting and set weakening rather than from active unconscious work. Activities A paper on the main findings has been accepted for the BPS Cognitive Section Annual Conference, September 1-3, Outputs No papers are available as yet. A paper is to be prepared and submitted to a leading journal such as Psychological Science, or Memory and Cognition, by end of March Impacts n/a as yet. Future research priorities The range of incubation durations and task exemplars explored here was limited and should be extended. Other hypotheses regarding incubation, such as the possible role of thought suppression will be explored in future studies. 23

12 Ethical Issues Ethical approval was obtained from the University of Hertfordshire s Faculty of Health and Human Science Ethics Panel before data collection began. References Campbell, D. T. (1960). Blind variation and selective retention in creative thought as in other knowledge processes. Psychological Review, 67, Dijksterhuis, A., & Meurs, T. (2006). Where creativity resides: The generative power of unconscious thought. Consciousness and Cognition, 15, Dijksterhuis, A., & Nordgren, L. F. (2006). A theory of unconscious thought. Perspectives on Psychological Science, 1, Dodds, R. A., Ward, T. B., & Smith, S. M. (2003). A review of the experimental literature on incubation in problem solving and creativity. In M. A. Runco (Ed.), Creativity research handbook (Vol. 3). Cresskill, NJ: Hampton Press. Gilhooly, K. J., & Hay, D. (1977). Rated characteristics of 205 five letter words having single solution anagrams. Behaviour Research Methods & Instrumentation, 9, Gilhooly, K. J., Fioratou, E., Anthony, S. H., & Wynn, V. (2007). Divergent thinking: Strategies and executive involvement in generating novel uses for familiar objects. British Journal of Psychology, 98, Gilhooly, K. J., Fioratou, E., & Parkhar, F. (in prep.). Unconscious processes and self defined novelty in divergent thinking. Gilhooly, K. J., & Murphy, P. (2005). Differentiating insight from non-insight problems. Thinking & Reasoning, 11, Ohlsson, S. (1992). Information-processing explanations of insight and related phenomena. In M. Keane, & K. Gilhooly (Eds.), Advances in the psychology of thinking. London: Harvester-Wheatsheaf. Peters, M., Laeng, B., Latham, K., Jackson, M., Zaiyouna, R., & Richardson, C. (1995). A redrawn Vandenberg and Kuse Mental Rotations Test: Different versions and factors that affect performance. Brain & Cognition, 28, Poincaré, H. (1929). The foundations of science. New York, NY: Science House. Segal, E. (2004). Incubation in insight problem solving. Creativity Research Journal, 16, Seifert, C. M., Meyer, D. E., Davidson, N., Patalano, A. L., & Yaniv, I. (1995). Demystification of cognitive insight: Opportunistic assimilation and the preparedmind perspective. In R. J. Sternberg and J. E. Davidson (Eds.), The nature of insight. Cambridge, MA: MIT Press. Simon, H. A. (1966). Scientific discovery and the psychology of problem solving. In R. Colodny (Ed.), Mind and cosmos. Pittsburgh, PA: University of Pittsburgh Press. Simonton, D. K. (1995). Foresight in insight? A Darwinian answer. In R. J. Sternberg and J. E. Davidson (Eds.), The nature of insight. Cambridge, MA: MIT Press. Sio. U.N. & Ormerod, T.C. (2009). Does incubation enhance problem solving? A meta-analytic review. Psychological Bulletin, 135, Wallas, G. (1926). The art of thought. New York: Harcourt Brace. 24