Creative Stimulation in Conceptual Design - CiteSeerX

DTM TOC Proceedings of DETC’02 Proceedings of ASME DETC’02 2002 Design EngineeringTechnical Technical Conferences and ASME ASME 2002 Design Engineering Conferences Computers and Information in Engineering Conference and Computer and Information in Engineering Conference Montreal, Canada, September 29 – October 2, 2002 Montreal, Canada, September 29-October 2, 2002

DETC2002/DTM-34023 DETC2002/DTM-34023 CREATIVE STIMULATION IN CONCEPTUAL DESIGN Yan Jin Dept. of Aerospace & Mechanical Engineering, OHE430 University of Southern California Los Angeles, CA 90089-1453 [email protected] Tel: (213) 740-9574 Fax: (213) 740-8071

Oren Benami IMPACT Laboratory, DRB101 University of Southern California Los Angeles, CA 90089-1111 [email protected] Tel: (213) 740-9621 Fax: (413) 556-9533

ABSTRACT Conceptual design is a process of creating functions, forms and behaviors. Although cognitive processes are utilized in the development of new ideas, conventional methodologies do not take human cognition into account. However, it is conceivable that if one could determine how cognitive processes are stimulated, then more effective conceptual design methods could be developed. In this paper, we develop a Cognitive Model of Creative Conceptual Design to capture the relationship between the properties that stimulate cognitive processes and the design operations that facilitate cognitive processes. Through cognitive modeling, protocol analysis, and cognitive experiments, this research showed that designers exhibit patterns of creative design behavior, and that these patterns can be captured and instilled into the design process, to promote creativity.

One way to increase the number of high quality ideas is to allocate more time for brainstorming [1]. Other intuitive techniques that attempt to stimulate human creativity include Method 635 [2], Syntectics [3], and C-Sketch [4]. However, there is very little formal evidence to prove the benefit of using intuitive creativity techniques [4], and even if intuitive techniques are useful, designers may not be able to generate ideas without the proper experience. Inexperienced individuals tend to overlook deep features of problems that are more easily seen by those with experience [5]. Another approach is to develop programs that automatically generate ideas (e.g. am [6], bacon [7]). However, these kinds of computational programs have yet to discover something of interest that is novel not only to it, but also to the world [8]. At the present time, human-based creativity appears to be the most pragmatic approach. Research in cognitive science, computer science, and design theory and methodology provides a foundation for development of human-based, computer assisted creative design methods. Cognitive science research on creativity began after Chomsky [9] convinced many fellow researchers that it was necessary to address internal mechanisms to account for high-level cognitive functions. The seminal works in human information processing ensued after that time [10-12]. The advent of the modern digital computer provided a rich theoretical metaphor for theorizing about human information processing [13-15], and in more recent years, the field of design theory and methodology emerged with prescriptive or normative methods [16,17], to specify how design information should be processed. Though research in design theory has identified important design principles and research in Cognitive Science and Computer Science has identified cognitive processes involved in creativity, the linkage between creativity, cognitive processes, and design operations has not been investigated.

Key Words: Analogy, Cognitive Model, Cognitive Process, Conceptual Design, Creative Stimulation, Design Behavior, Design Entity, Design Experiment, Design Operation, Protocol Analysis

1

INTRODUCTION Conceptual design is essentially a creation process. It is the creation of functions to fulfill customer needs, and the creation of forms and behaviors to realize those functions. Early-stage design ideas have a large impact on the cost and quality of a product. Designers have the freedom to generate and explore ideas without being constrained by parameters that exist at the later design stages. If many ideas are created during conceptual design, there can be plenty of options to choose from, and consequently it is more likely that a good design can be attained.

1

Copyright © 2002 by ASME

lacked taxonomy of entities [20,21]. Following Gero et al. [18], who classified the contents of architectural thought, we classify three elements of a design entity. Function (F) : A design task for achieving a purpose. Designers think about what functions need to be achieved to fulfill customer needs. For example, in designing a car a designer may think about function “move at safe speed” or “release airbag” to fulfill safety requirements. Form (f): The shape and structure of a component of the design artifact. Designers create mental images of mechanical parts and make sketches of forms in design notebooks. Behavior (b): The manner in which something operates. Behaviors can be a designed response (e.g. dynamics of a wheel turning) or an unintentional response (e.g. fatigue or creep). Mechanical designs usually involve multiple types of behavior. For example, in designing a washing machine, there are issues related to the dynamics of the carousel, the number of cycles that the machine can handle, the temperature of the water, and the signals that are sent from machine to user.

What is needed are method to evaluate the relationship between these components and means to measure creativity in conceptual design. In this paper, we develop a descriptive model of the thinking process in conceptual design, utilizing protocol analysis to evaluate the model, and behavioral experiments to test our hypotheses about creativity in design. Our main research questions are: 1) what stimulates creativity in conceptual design? and 2) how do designers create? In section 2, we present our cognitive model of creative conceptual design, which captures the cognitive components of creative conceptual design. In section 3, we evaluate the model by protocol analysis of design sessions. In section 4, we describe our experiments on creativity in conceptual design. Finally, in section 5, we summarize the contents of this paper, and present plans for future work. 2

COGNITIVE MODEL OF CREATIVE CONCEPTUAL DESIGN Previous investigations of the design process have recognized that there are design entities that represent the contents of our thoughts [18]; there are cognitive processes that produce creative ideas [19]; and there are design movements, or operations that forward a design [18]. However, the interaction between these components has not been considered. Our framework is the first to investigate the relationship between cognitive processes, design operations, and design entities in a creative conceptual design context. Design entities are the basic components of a design artifact. Cognitive processes are thoughts that produce design operations- the actions that bring design entities into the design context. Once created, design entities stimulate further cognitive processing and production of design operations (Figure 1). The important feature of this framework is that design entities are both the object of creation and catalysts for further creation.

Design Operations

Produce

2.2

Given this classification of a design entity, the next question is: how do entities evolve during the conceptual design process? Prototypes, genetic code, and neural networks, take a computational view of the evolution of ideas. The genetic approach [22] utilizes design grammars as a genetic code for creation. Design prototypes [23] provide a framework for storing design experience. More unusual design evolutions come out of unfixed boundary schemas or neural networks [24]. Our approach is different than computational approaches in that we attempt to understand human based creativity. The goal is to provide a tool to support human based evolution of design entities, rather than to replace the human with a “creative” computer. Therefore, this research requires an investigation of creative thought processes. The Geneplore Model [19] provides a framework to understand how human thought evolves during creative processes. There are two phases of creativity in the Geneplore Model; a generative phase, and an exploratory phase. In the generative phase, one constructs a mental representation called a preinventive structure having various properties that promote creative discovery. These properties are then exploited during an exploratory phase in which one seeks to interpret the preinventive structure in meaningful ways. Finke et al. [19] conceived of preinventive structures as representations of novel visual patterns, object forms, mental blends, category exemplars, mental models, and verbal combinations. What these structures have in common is that they are initially formed without full anticipation of their resulting meaning and interpretation. They are distinguished from the final externalized creative product, which, in contrast, is often fully interpreted. The preinventive structures that are formulated during conceptual design have a more refined characterization than

Generate

Stimulate

Design Entities

Cognitive Processes

Figure 1: Framework for Creative Conceptual Design

2.1

Design Evolution

Design Entities

Previous studies did not classify the content of mechanical engineering design thought into well-accepted categories. Several studies classified the content of the design process, but

2


Category reduction is another process that is not verbally heeded (in most cases). It is difficult to understand from design protocol if a designer is simplifying an entity from memory or creating an entity for the first time. Memory retrieval and association, on the other hand, are more easily recognizable from design protocol. Previous protocol analysis studies [26] identified two reasons that designers retrieve information from memory. One reason is to divide a problem into sub problems. The other reason is to draw new information from existing information; that is to make an association, which can help in grouping elements, finding similarity/uniformity, difference/ contrast, how people interact with the design artifact, and how the design artifact interacts with the environment. Videotape recordings of design sessions indicate that designers pronounce the name of elements when they retrieve them from memory, talk about associations between elements, and point to elements as they create mental connections. The next cognitive process that we looked at was mental transformation. Mental transformation is identifiable in design protocol, and is not only heeded verbally as mental images, but also displayed visually in sketches. Lastly, we investigated analogical transfer, which is actually a succession of more primitive processes: memory retrieval, association, and transformation. During analogy making, one first finds an association to a source, retrieves information about the source from memory, and attempts to transform the information in the source to adapt it to the target domain [5]. In summary, there are three remaining generative processes that may be used to capture creativity in conceptual design. They are memory retrieval, association, and transformation. Memory Retrieval (MR) and Association (A) : The most basic types of generative processes. Elements are retrieved from memory and associated with one another. For example, when designing a mouse, a designer might think about the diameter of the ball in relation to how fast the pointer moves on the screen. Retrieval and association processes usually happen quickly and automatically, but sometimes they are inhibited resulting in mental blocks and fixation effects. Transformation (TF): Elements are rearranged and reassembled to make interesting and useful entities. For example, when designing a boat, a designer may retrieve a bicycle wheel from memory, and then transform it into a paddlewheel.

other cognitive structures. They are functions, forms, and behaviors- the elements that make up a design entity, and they can be classified as preinventive at the point of inception because their relationships with other functions, forms, and behaviors has not been fully interpreted. The initial generation of a design element signifies the creation of a preinventive entity. As new elements are generated and existing elements are explored, the preinventive entity evolves into a knowledge entity. For example, in designing a lake water sampler, a preinventive form (f) evolves into a knowledge entity containing form (f), function (F), and behavior (b) (Figure 2).

Design Entity

Move

F

Evolution b Knowledge Entity

f

Stop

f

Preinventive Entity

Figure 2: Evolution of Design Entity

2.3

Cognitive Processes in Conceptual Design

The evolution of design entities occurs as a result of many types of mental processes. As in the Geneplore Model [19], these processes can be separated into two types: generative and exploratory. Finke et al. [19] described several types of generative processes: memory retrieval, association, mental synthesis, mental transformation, analogical transfer, and categorical reduction; and exploratory processes: attribute finding, conceptual interpretation, functional inference, contextual shifting, hypothesis testing, and searching for limitations. These processes, which do not produce creative results in isolation, give rise to creativity ideas when iterated in a cycle of generation and exploration.

2.3.2

Exploratory Processes

The generation of new ideas often occurs after a period of exploration, so the next question is: what are the exploratory processes that exploit design entities? Shah [27] conducted the first attempt to identify the occurrence of exploratory processes in design protocol, and made several suggestions. First, the Geneplore Model [19] seems to assume that designers are always aware of the solution that they are looking for; yet this is not usually the case in engineering design. Therefore, monitoring the status of a solution, previously described as analyzing a problem (problem analysis) and evaluating a proposed solution (solution analysis) [18] are important

2.3.1 Generative Processes Working with the base of generative processes recommended by Finke et al. [19], we studied the role of idea generation in creative conceptual design, starting with mental synthesis. In simple controlled experiments mental synthesis is clearly identifiable [25]. However, mental synthesis is difficult to identify in design protocol because it is not verbally heeded.

3


producing creative ideas. Therefore, meaningfulness and relevance are important creative design stimuli. The next creative property that we investigated was ambiguity, which refers to the existence of numerous interpretations of a preinventive structure; and divergence, which is the capacity for finding multiple uses for a preinventive structure. The use of something is its meaning in a design context, so ambiguity and divergence are similar. Since the focus of design is on interpreting functionality, divergence is the more applicable term than ambiguity. However, divergence is a property that stimulates creativity in art more than creativity in engineering design. Artists tend to search for interpretations of what has been created by “feel”, while engineers tend to create entities that fulfill specific technical purpose(s). Therefore, we do not anticipate finding many occurrences of divergence in conceptual engineering design. Other creative properties that are relevant to design research are incongruity and emergence. Incongruity has played a major role in previous theories of creativity such as TRIZ [29] and Koestler’s theory of bisociation [30]. Emergence has also been the subject of creative design research [31]. In summary, the stimulating properties most relevant to creative conceptual design are: Meaningfulness (M): A general, perceived sense of meaning in an entity. A sense of meaning in an entity can be fairly abstract, and is related to a preinventive entity’s potential for inspiring or eliciting new interpretations. For example, if one wants to design a comfortable steering mechanism for a new type of vehicle, a steering wheel may be more meaningful than a bicycle handle. Relevance (R): Has pertinence to the matter at hand. If information is relevant to a design problem, the designer will begin to ask questions about the meaning of the information within the current design context. Divergence (D): The capacity for finding multiple uses or meanings in the same entity. For example, in designing a transportation vehicle for paraplegics, one may find that a handle can be used for both steering, and propelling a vehicle. Incongruity (I): Conflict or contrast among elements in a preinventive entity. Incongruity often encourages further generation and exploration to overcome the conflict and reduce psychological tension. For example, in designing a propulsion system for a boat, a designer may make an analogy to a bicycle wheel, and then realize that the bicycle wheel is too smooth to propel through the water; so then the designer may conceive of a paddle wheel to overcome incongruity of features “movable surface” (water) and “smooth surface” (wheel). Emergence (E): The extent to which unexpected features and relations appear in a preinventive entity. These features and relations are not anticipated in advance and become apparent only after the preinventive entity has evolved. For example in designing a breaking system, one might design a break handle first, then design the braking mechanism. After these two systems have been developed, a behavior may emerge, which links the handle to the breaks.

exploratory processes in design. Second, functional inference and conceptual interpretation should be combined because it is difficult to tell the difference between these two processes. Third, hypothesis testing is better interpreted as functional analysis or simulation to determine conceptually how a device will satisfy its intended function(s). Working to consolidate the base of exploratory processes suggested by Finke et al. [19], the modification made by Shah [27], and the investigations in Gero and McNeill [18], we found that hypothesis testing and searching for limitations can be recognized as methods of solution analysis. Functions and attributes (detailed aspects of forms) are already classified as types of elements in the model. In fact, functional inference is actually a design operation declare acting on design element function, and attribute finding is actually a cognitive processes problem analysis or solution analysis acting on a design element form. Therefore, we eliminated cognitive processes: attribute finding and functional inference, leaving two remaining exploratory processes: problem analysis and solution analysis: Problem Analysis (PA): The study of the parts and interrelationships of a problem. For example, in designing a spindle, a designer may investigate tolerances, range of spindle speeds, and the kinds of lubricant that work best at those speeds. Solution Analysis (SA) : To examine and judge a potential solution based on the knowledge that one has about it. For example to analyze the production costs of a system, a designer may calculate the number of parts, the cost of manufacturing each part, and labor costs. 2.4

Creative Properties

Generative and exploratory processes may lead to the creation of new design entities, so one may ask: what stimulates idea generation and exploration? Suwa et al. [26] found that perceptual and physical actions play a central role to initiate and control cognitive processing. Other research has focused on how problem-solving strategies, plans, goals, and knowledge initiate and control further processing [8,28]. Finke et al. [19] suggest that properties of preinventive structures stimulate further cognitive processing: novelty, ambiguity, meaningfulness, emergence, incongruity, and divergence. These properties have proven to be effective stimuli in artistic design, where imagery and sketches play a central role. However, they have not been studied in the context of engineering design, so we have investigated how these properties stimulate creativity in conceptual engineering design. The first creative property that we investigated was novelty, which can either stimulate or inhibit creative cognitive processes. If designers find novel information to be meaningful and also relevant to the problem at hand, then novelty will probably work as a stimulant. However, if designers find that information is not meaningful or relevant to a design problem, then novelty will probably work as a deterrent, because designers will be spending time analyzing information without

4


paper by writing and sketching, by moving pens in various directions (simulate), and gesturing (point). Designers often write down the functions or objectives that they want to achieve, sketch mental images, point to design entities, and simulate behavior of design entities. In collaborative design situations, designers draw sketches on a whiteboard and talk about design features. The external operations involved in conceptual design are defined as follows. Talk (t): To give expression in words. Designers talk about most everything from functions that they want to achieve, to relationships between forms, to behavior of forms. Write (w): To form with alphanumeric characters, on a surface such as paper, with an instrument, such as a pen. Typical entities that designers write down during conceptual design are functions and the names of forms and features. Sketch (s): A hasty drawing made as a preliminary study. Designers create sketches of forms, features, and behaviors during conceptual design. Point (p): To bring something to notice by indicating with a finger. For example, in designing a gearbox, a designer, may point to a gear, and then point to a box, to indicate the proposed location of the gear. Simulate (s): To have or take on the appearance, form, or sound of. Designers simulate behavior with hand motions. For example, in designing a cycle, a designer may simulate the movement of a pedal by making circular hand motions. The components of the creative conceptual design framework have now been defined. Yet, the essential question remains: how do the various components of the creative conceptual design framework interact with one another to stimulate creativity? A cognitive model is needed to link the components in the creative conceptual design framework.

If creative properties stimulate cognitive processes, how are the cognitive processes put into operation to physically create new entities? There must be some important design operations that facilitate the creation of entities by cognitive processing. 2.5

Conceptual Design Operations

There are several different views of design operations in the literature. Goldschmidt [21] defined a design move (design operation) as ‘an act of reasoning that presents a coherent proposition pertaining to an entity that is being designed’. Masaki [32] described different modes of designers’ actions. Physical actions have direct relevance to physical depictions on paper. Perceptual actions are attention to visuo-spatial features. Conceptual actions refer to setting up goals. Our view of design operations is similar to that of Goldschmidt [21]. Design operations are actions that manipulate design entities. However, while Goldschmidt [21] defined design operations by the entities that are created, we separate design entities from design operations to allow for a wider array of possible operation-entity interactions. There are two types of operation-entity interactions. Internal operations deal with strategy and steps of a design. External operations deal with physical symbols and depictions. 2.5.1 Internal Operations Gero [31] introduced the concept of micro-strategy categories to account for actions that relate to the state of a process. Micro-strategy categories include operations: propose a solution (suggest), and calculate a solution (computing). Other internal operations that can be inferred from observation of the design process are: question, declare, suppose, and explain. Suggest (g): To offer for consideration. For example, a designer might suggest that an idea that worked for a previous design might work in the current design. Compute (c): To ascertain by calculation. Designers make calculations to determine requirements, feasibility, and design limitations. Question (q): An expression of inquiry that invites a reply. Questions are often followed by other design actions such as suggestions, inferences, and deductions. Declare (d): To state emphatically or authoritatively. For example, a designer may declare that a certain form will be used in a design. Suppose (u): To assume to be true for the sake of exploration. The ill-defined nature of conceptual design oblige designers to make many assumptions. Explain (e): To establish by reasoning. Designers use reasoning to analyze design problems and evaluate design solutions.

2.6

Cognitive Model of Creative Conceptual Design

Our Cognitive Model of Creative Conceptual Design (Figure 3) builds upon a rich body of literature in Design Theory and Methodology and Cognitive Science. Using a generate-and-test scheme in cognitive psychology and artificial intelligence [33,34], designers go through a cyclic process of creative generation and exploration.

s,t,w,p,z Design Operation s

b

Knowledge Entity

F

Record Evolve

Internal q,u,d,g,e,c

f

b

F

Preinventive Entity

Produce M,R,E,I,D MR TF

2.5.2

f

External

External Operations

PA

AS

Stimulate

Creative Properties

SE

Cognitive Processes

Suwa [26] studied the physical depictions of ideas during a design process, and found that designers make depictions on

Figure 3: Cognitive Model of Creative Conceptual Design

5


3.2

The first step in the Cognitive Model of Creative Conceptual Design addresses the stimulation process. Designers are stimulated to generate and explore ideas after viewing existing design entities in catalogues and other documentation. Entities that are meaningful (M), relevant (R), emergent (E), divergent (D), and incongruous (I) stimulate memory retrieval (MR), associations (AS), and transform (T). The second step in the Cognitive Model of Creative Conceptual design is the production of internal design operations. Designers ask questions (q), make suppositions (u), suggestions (g), and declarations (d), explain (e) themselves, and make computations (c). The third step in the Cognitive Model of Creative Conceptual Design is the production of external design operations. Sketches (s) are often the easiest way to record design ideas. They are rapid and spontaneous, but their residual traces are stable and can be subsequently examined by the designer at his or her leisure. They embody abstract and high-level design ideas; they allow a degree of uncertainty about particular physical attributes and they impose constraints [35]. Designers also express their ideas in writing (w). While images lead to access of more perceptually based knowledge, words lead to access of conceptual knowledge [36]. Designers also talk out loud (t) to communicate their ideas, point (p) to forms, and simulate (z) behavior. As more and more design elements are generated, design entities evolve from preinventive entities into knowledge entities. However, the creative process is not complete until stimulation of cognitive processes, production of design operations, and generation of design entities is iterated many times, to produce a set of acceptable ideas.

Four senior and graduate level mechanical engineering students participated in the study. The students were asked to think out loud while being videotaped for 30 minutes. Data from three subjects were used to evaluate and update the Cognitive Model of Creative Conceptual Design. Transcripts from the first two subjects were used to evaluate and update the model, and transcripts from the third subject were used to verify the model. Finally, transcripts from a fourth subject were used to capture the relationships between design entities, cognitive processes, and design operations; to identify patterns of creative thought. 3.3

Creative Design Episodes

When analyzing protocol, it is customary to encode an entire design session. However, our goal was to perform an in depth study of creativity in conceptual design; so after transcribing the entire design session, we divided the transcripts into creative design episodes (groups of statements that produced new idea(s)). Creative design episodes can be identified in different ways. Finke et al. [19] identified originality, practicality, sensibility, productivity, flexibility, insightfulness, and usefulness as the important attributes that define creativity in general. Shah et al. [4] identified quantity, novelty, variety, and quality as the important attributes that define creativity in engineering design. There are other attributes of creativity as well [28,38]. However, the two measures of creativity that are consistently addressed in design literature are novelty and value. Novelty refers to the originality of an idea, and value refers to the sensibility of an idea. Therefore, we identify a creative design episode as one that contains entities that have not appeared previously in the current design session and one that makes sense within the design context. One may question if there can be an objective measure of sensibility when complex problems are involved. However, the design problem that was posed to the subject did not involve complex technical issues, so we found that it was not difficult to identify sensible entities.

3

MODEL EVALUATION- PROTOCOL ANALYSIS Cognitive models can be evaluated by protocol analysis. Two primary methods of protocol analysis are retrospective reports and think aloud methods [37]. Retrospective reports take less time than think aloud methods. However, designers have difficulty remembering the subtle order in which actions were performed [26]. Therefore, we use the think aloud method to evaluate our cognitive model.

3.4 3.1

Subjects

Design Problem

Segmenting and Encoding

Once creative design episodes are captured, they need to be segmented into statements, so that they can be encoded into a formal language. Some design researchers suggest segmenting the data where pauses and inflections occur [39], and others recommend segmenting the data at changes in intention [18]. Creative statement may start or end with a change of intention or a pause. Therefore, we found that a combination of these two methods was the most effective way to segment creative design episodes. Here, we show the segmentation (Figure 4(b)) of a creative design episode (Figure 4(a)), extracted from the think-aloud design session.

The problem created for the investigation was: “Oars often propel boats that operate manually (human powered). However, oars can be difficult to maneuver. Inexperienced operators tire quickly, and if the oars are not used correctly, they rock the boat, and splash water on the deck where people are sitting. Your task is to develop designs for alternative means (besides oars) to manually propel boats.” This problem was chosen because it is not too technically challenging, the design space is relatively opened, and subjects have an opportunity to generate many original ideas.

6


understanding of the design context. If one operator interprets the design context differently than another operator, then they will have different encoding results.

Propulsion system, somehow, the boat needs to be propelled through the water. There are propeller options to use the water. Like you can use something for the air. You can somehow use the ground under the water, such as in poling. (a) Creative Design Episode 1) 2) 3) 4)

3.5

Propulsion system, somehow, the boat needs to be propelled through the water. There are propeller options to use the water. Like you can use something for the air. You can somehow use the ground under the water, such as in poling.

Analysis

After the creative design episodes were encoded, the data was analyzed. The episode in Figure 4(c) is one instance of the creation of a preinventive design entity. In the first segment, meaningfulness (M) of function (F) stimulated form (f) creation. In the second segment, relevance (R) of form (f) and behavior (b) stimulated form (f) creation. In the third segment, relevance (R) of behavior (b) stimulated form (f) and behavior (b) creation. In the fourth segment, relevance (R) of form (f) stimulated behavior (b) creation (Figure 5). This example illustrates only one creative design episode. However, there were nine creative design episodes that occurred during the thirty-minute design session. By compiling the data from the episodes into matrices, we can develop a profile of each designer. The profile describes creative patterns of behavior. Patterns of stimulation reveal how design entities stimulate cognitive processes; patterns of production reveal how cognitive processes produce design entities; and patterns of generation reveal how design operations generate design entities.

(b) Segmenting 1) M(F): PA[e(propel boat) p(f)] 2) R(f,b): MR[g(water prop) w(f)] 3) R(b): MR[g(air prop) w(f,b)] 4) R(f): MR[g(ground)g(poling) w(b)] (c) Encoding M(F)- Meaningfulness of Function, R(f,b) - Relevance of form and behavior, R(b) - Relevance of behavior, R(f) - Relevance of form, PA- Problem Analysis, MR- Memory Retrieval, eexplain, g - suggest, p(f)- point to form, w(f) - write form, w(f,b)- write form and behavior, w(b) - write behavior (d): Explanation of Code

Figure 4: Segmenting and Encoding

After the data is segmented, it is encoded into cognitive processes, design entities, and design operations (Figure 4(c,d)). For each segment the following information is recorded from left to right: 1) The creative properties and elements that stimulated the segment, 2) the cognitive process that best characterizes how the designer is thinking, 3) the internal operations, which facilitate cognitive processing, and 4) the external operations, which are seen in the video recording. In an ideal situation, multiple operators encode all of the creative design episodes, so that the accuracy of the accuracy of the entire design session can be evaluated. However, due to resource limitations, the creative design episodes were spot checked by a second operator. The spot checker was asked to randomly select three creative design episodes and encode them by the same procedure used by the first operator.

External

p Design Operations

Record

w

b

Internal

e

F

g R

Design Elements

f

R

M Creative

Properties

Produce Stim ulate

MR

Table 1: Correlation Between Operators

PA Cognitive Processes

Correlation (%)

Figure 5: Evolution of a Design Entity

Design Elements

93

Stimulating Properties

67

3.5.1

Cognitive Processes

89

Internal Operations

82

External Operations

95

The encoding of creative stimulation from an entire design session has been input into the stimulation matrix (Table 2). The matrix identifies the creative properties of form, function, and behavior that stimulate each cognitive process during an entire design session.

Data analysis results from the two operators were compared (Table 1). There was a 93% correlation between design elements, a 67% correlation between stimulating properties, an 89% correlation between design operations, an 82% agreement between internal operations, and a 95% agreement between external operations. The most abstract components (creative properties) had the lowest correlation between operators, while the least abstract components (design elements and external operations) had the highest correlation between operators. These results are to be expected because the abstraction process requires an operator to have a thorough

Patterns of Stimulation

Table 2: Stimulation Matrix MR Design Elements

Function Form Behavior

M,R,E M,R,E

Cognitive Processes AS TF PA M R M M,R,I

SA E

Cognitive Processes: Memory Retrieval (MR), Association (AS), Transformation (TF), Problem Analysis (PA), Solution Analysis (SA) Creative Properties: Meaningfulness (M), Relevance (R), Emergence (E), Incongruity (I)

7


solution analysis, questions, declarations, and explanations (Figure 7)

Meaningfulness and relevance of form and behavior stimulated the most creativity. In fact, meaningfulness and relevance were found in every creative design episode. If the subject found that information was not meaningful and relevant, it was not used in a creative process. Once the designer found that the information was meaningful and relevant, additional properties were also found. Emergence of form and behavior stimulated memory retrieval and solution analysis. Incongruity of behavior stimulated problem analysis. Cognitive Processes:

PA

Design Elements:

Creative Properties:

Stimulate

Cognitive Processes

f

b

M

M,R,E

M,R,E,I

Cognitive Processes

+ +

+ +

+

SA

External Design Operations sketch write point simulate Internal Design Operations

Question Suggest Suppose Declare Explain Compute

f

f,b

f,b f,b

f

talk

b f f

N/A

b b

The matrix does not identify how new entities are generated in every design situation. However, it does identify a pattern of generation that occurs under the prescribed conditions. The matrix reveals that sketching was the most pervasive external operation performed by the designer. This is in agreement with previous research, which shows that sketching plays a central role in creativity [40]. Other important external operations were writing, pointing, and simulating. Talking was not an issue because the designer was working alone. The essential internal operations were suggestions, explanations, and declarations (Figure 8).

Table 3: Production Matrix e + + + + +

PA

TF

AS

Produce Produce

Table 4: Generation Matrix

3.5.2 Patterns in Production If one can identify patterns of creative stimulation, then one may also identify how cognitive processes produce design operations. We composed of a second matrix (Table 3) to identify the relationships between cognitive processes and internal design operations that occurred during the design session. Memory retrieval produced suggestions, explanations and computations; associations and transformations produced explanations; problem analysis produces questions, declarations, and explanations; and solution analysis produced suggestions, declarations, and explanations.

MR AS TF PA SA

Produce Produce

u,d,g, e

Patterns of Generation If one can identify creative patterns of stimulation and production, then one may also identify a pattern of production. The Generation Matrix (Table 4) identifies relationships between internal design operations, external design operations, and design entities. Suggestions were made while sketching forms, writing descriptions of forms, writing about behaviors and simulating behaviors. Declarations were made while sketching, writing, and pointing to forms; sketching and simulating behaviors. Explanations were made while sketching and pointing to forms, sketching and simulating behaviors.

The dominant pattern was meaningfulness, relevance, and emergence of form and behavior stimulating memory retrieval, problem analysis and solution evaluation (Figure 6).

Internal Operations u d g + + +

q,d,e

3.5.3

Figure 6: Patterns of Stimulation

q

MR

e

e

Figure 7: Patterns of Production

Stimulate

F

q,u,d,g,e,c

Produce

MR, PA , SA

MR,PA,SA

Stimulate

Design

Operations

c

Cognitive Processes: Memory Retrieval (MR), Association (AS), Transformation (TF), Problem Analysis (PA), Solution Analysis (SA) Internal Operations: question (q), suppose (u), declare (d), suggest (g), explain (e), compute (c)

Design Elements:

The matrix does not identify how design operations are produced in every design situation. However, it does identify a pattern of production that occurs under the current conditions. The matrix reveals that exploratory processes were externalized in more ways than generative processes; and the dominant relationships were memory retrieval, problem analysis, and

f

b Generate

Generate Design Operations: g,d,e,s,w,p,z

g,d,e,s,w,z

Figure 8: Patterns of Generation

8


Table 5: Function Stimulation

Function Stimuli (F)

A fish swims under water (F) 1

Subject 1Design Entities Generated (F,f,b)

scuba fin action (F,f,b)11

A duck paddles on the water (F) 2

paddle action (F,f,b)12

An otter dives under water (F) 3

Submarine (F,f,b)13

Fins (F,f,b)21


Oars often propel boats that operate manually (human powered). However, oars can be difficult to maneuver. Inexperienced operators tire quickly, and if the oars are not used correctly, they rock the boat, and splash water on the deck where people are sitting. Your task is to develop alternative boat designs that are also human powered.

bottom fin for stabilization (F,f,b)31 dorsal fin acts as a ruder (F,f,b)32

(a) Design Problem Try to use these functions to stimulate your thinking: A fish swims under water A duck paddles on the water An otter dives under water An elephant blows water out of its trunk A bird flaps its wings A monkey swings on branches An owl hunts at night

Paddlewheel (F,f,b)22

(b) Additional Information Provided to Group A

An elephant blows water out of its trunk (F) 4 A bird flaps its wings (F) 5


provided with additional information. Group A was provided with functions (Figure 9(b); Group B was provided with forms (Figure 9(c); Group C was provided with behaviors (Figure 9(d)); and Group D was provided with knowledge entities (synthesis of form, function, and behavior) Figure 9(e).

Try to use t hese forms to stimulate your thinking:

air pushed out at back of boat (F,f,b)23

(c) Additional Information Provided to Group B Try to use these behaviors to stimulate your thinking. The movement:

paddle action (F,f,b)14

Wings (F,f,b)24

A monkey swings on branches (F) 6

(d) Additional Information Provided to Group C Try to use the bicycle to stimulate your thinking.

An owl hunts at night (F) 7

(e) Additional Information Provided to Group D

Figure 9: Experiment Design Problem

4

CREATIVE STIMULATION The Cognitive Model of Creative Conceptual Design provided the details of how creative properties, cognitive processes, design operations, and design entities interact with one other. The origin of creativity is the creative properties that stimulate idea generation and exploration. In this section, we describe the results of our cognitive experiment, which investigated how patterns of creativity can be infused into the process to produce creative ideas. 4.1

arrows can designate force or

4.1.1

Function Stimulation

Table 5 lists the design entities (F,f,b) stimulated by each function (F). The first function (F)1 stimulated the creation of different types of fins. (F)2 stimulated paddlewheels and different ways of paddling. (F)3 stimulated the idea of underwater transportation. (F)4 stimulated the idea of using air pressure to move the vehicle. (F)5 stimulated a new type of paddling movement and wings that utilize air pressure for movement. The last two functions ((F)6 and (F)7 ) did not stimulate any new ideas. Although subjects were instructed to use functions to stimulate new ideas, they did not separate form from function. There seemed to be a certainty about how to implement the functions that was derived from an associated form. Therefore, functions did not stimulate a variety of idea. Each designer had only one idea for each function.

Stimulation Experiment

Ten senior and graduate level mechanical engineering students participated in the experiment. The students were asked to think aloud while being videotaped for 30 minutes. The same watercraft design problem (as in the protocol analysis study) (Figure 9(a)) was provided to the subjects. The students were randomly divided into four treatment groups. In addition to the design problem, each group was

9


4.1.2 Form Stimulation Forms may be more stimulating than functions because they can be seen from different points of view and in different contexts [31]. Table 6 lists the ideas stimulated by each form. (f)1 stimulated the creation of a paddlewheel. Subjects did not see much ambiguity in this form. (f)2 stimulated the idea of throwing an anchor and transporting the vehicle by pulling a rope attached to the anchor. (f)3 stimulated wheel ideas and the idea of air flowing through a pipe. (f)4 stimulated ideas about paddling movements and cycling movements. (f)5 stimulated ideas about pulling a chain and a chain drive. (f)6 stimulated ideas about nozzles; and (f)7 stimulated ideas about propellers.

experiment is that stimuli that are closely associated with forms that are already well known cause fixation. 4.1.3 Behavior Stimulation Table 7 lists the ideas stimulated by each behavior. (b)1 stimulated ideas about a wheel and peddle system. (b)2 stimulated ideas about jet propulsion. (b)3 stimulated ideas about changing the direction of jets, creating movement for propulsion, and breaking. Of all the different behaviors, this one stimulated the most variety of ideas but only from Subject 1. Other subjects bypassed (b)3 because they could not interpret it. (b)4 prompted ideas about using a gear ratio to get more leverage. (b)5 prompted an idea about using a ruder and fin action. (b)6 prompted ideas about a paddlewheel and crank. (b)7 prompted ideas about fixing oars and fins to reduce splashing.

Table 6: Form Stimulation

Form Stimuli (f)






Table 7: Behavior Stimulation

(f) 1

(f) 2

(f) 3

catapult anchor and pull rope to move (F,f,b)12 Paddlewheel (F,f,b)13 blow air through a pipe (F,f,b)14

(b) 1

spin wheel connected to paddlewheel (F,f,b)22

(b) 2

(b) 3

(f) 4 stick with hook (F,f,b)15 (f) 5

Behavior Stimuli (b)

cycling movement (F,f,b)23

Pull chain attached to bank on one end and boat on other (F,f,b)16

Paddles (F,f,b)31

Nozzle (F,f,b)33

(f) 7 Propeller (F,f,b)24

Subject 3 Design Entities Generated (F,f,b)

w heel and pedal system (F,f,b)11

paddlewheel (F,f,b)21

elongated paddlewheel (F,f,b) 31

Jet (F,f,b)12

jet propulsion (F,f,b)22

water forced through jet (F,f,b)32

pull rope to turn wheel (F,f,b)13

strap tightens over flywheel to break (F,f,b)15

(f) 6

Propeller (F,f,b)18


barrier changes direction of jet stream to change direction (F,f,b)14

chain drive (F,f,b)32

jet ski nozzle (F,f,b)17


(b) 4

gear ratio (F,f,b)16

gear ratio (F,f,b)33

(b) 5

ruder for steering (F,f,b)17

push feet back and forth to create fin action (F,f,b)34

Propeller (F,f,b)34

The increase in quantity of entities stimulated by forms, as compared with functions, can be attributed to the divergent properties of forms. For example, form 4 stimulated three different ideas from a single designer. Some forms, however, were easily associated with existing objects and did not stimulate a variety of ideas. For example, form 1 was only associated with a paddlewheel and form 7 was only associated with a propeller. An important lesson to be learned from this

10

(b) 6

paddlewheel (F,f,b)23

crank (F,f,b)35

(b) 7

fixed oars (F,f,b)24

fin action with fixed pivot point (F,f,b)36


4.1.4 Knowledge Entity Stimulation Table 8 lists the ideas stimulated by the knowledge entity (bicycle). The bicycle was chosen because it is simple and familiar to most everyone, and because it is not too conceptually distant from watercraft design. The bicycle form (f) is visible, and since most people are familiar with bicycles, Function (F) and behavior (b) are easily inferred. The hypothesis was that designers would make analogies to the functions, forms, and behaviors in the bicycle (F,f,b)1 , which would stimulate new watercraft design ideas (F,f,b)2 . There were six different ideas that came out of analogies to the bicycle (Table 8). These ideas result from two different types of analogies: short distance analogies and long-distance analogies (Figure 10). Short distance analogies occurred between very similar concepts, and long-distance analogies are between very different concepts.

form changes. Short-distance analogies were easy to adapt from one domain to another and do not result in very original ideas. They appeared to come easily to the designer, but did not result in very original ideas. One example of a short-distance analogy is the wheel idea. The subject transformed the bicycle wheel (F,f,b) into a paddlewheel (F,f',b) (Table 8). In other shortdistance analogy situation, the design context changed. The subject adapted the chain and sprocket system of a bicycle to fit onto a boat (Table 8, Figure 10). Long-distance analogies resulted in more changes than short distance analogies. They were more difficult to make than short-distance analogies, but they also resulted in more creative ideas. Long-distance analogies occurred when the source was much different from the target and a large amount of information was brought in from outside of the analogical context. For example, a bicycle brake (F,f,b) was adapted into the context of watercraft design (F,f?,b?) (Table 8, Figure 10). While the bicycle brake works by squeezing calipers against a wheel rim, the water brake works by attaching a cable to a hand lever on the top of the boat and a bottom lever underneath the boat. The operator can brake by pulling up on the top lever, thereby restricting the flow of water under the boat.

Table 8: Knowledge Entity Stimulation Knowledge Stimuli (F,f,b)

(F,f,b)

handle

(F,f,b)

break

(F,f,b)

chain drive

Subject 1 Design Entities Generated (F, f, b)

4.1.5 Steering Wheel (F,f,b)1

There were a total of four short-distance analogies and two long-distance analogies made during the 30-minute design session. While short-distance analogies resulted in a larger quantity of ideas, long-distance analogies resulted in original ideas. However, neither short-distance analogies nor longdistance analogies resulted in a large variety of ideas. The designer appeared to be fixated by the bicycle, as if it were the only means of stimulating ideas. Previous experiments have also shown that designers are easily fixated by existing designs; even when they are told not to use them in a new design [41]. It is interesting to compare the number of ideas generated from the bicycle analogy (long-distance analogies, original ideas only) with the average number of original ideas generated from each preinventive entity stimulation (Figure 11).

Break (F,f,b)2 Direct Drive (F,f,b)3 Indirect Drive (F,f,b)4

(F,f,b)

wheel

Results

Paddlewheel (F,f,b)5 Propeller (F,f,b)6

There were six different ideas that came out of analogies to the bicycle (Table 8). These ideas result from two different types of analogies: short distance analogies and long-distance analogies (Figure 10). Short distance analogies occurred between very similar concepts, and long-distance analogies are between very different concepts.

6 5 4

Short-Distance Analogy ((F,f,b) => (F,f?,b))

Long-Distance Analogy ((F,f,b) => (F,f?,b?))

3 2 1 0

Figure 10: Ideas Generated From Analogies

Function Stimuli

Form Stimuli

Behavior Stimuli

Knowledge Entity Stimuli

Number of Creative Ideas Generated

Short-distance analogies resulted in very few changes to the analogue, and the changes that were made were mostly

Figure 11: Experiment Results

11


The focus of this paper was on individual creativity. However, in the future, we plan to extend the investigation to collaborative conceptual design; to determine how interactions between designers may stimulate creativity.

On average, functions stimulated 3 ideas, forms stimulated 5 ideas, behaviors stimulated 6 ideas, and knowledge entities stimulated 2 ideas. Therefore, behaviors stimulated twice as many ideas as functions and three times as many ideas as knowledge entities. Functions and knowledge entities are fixating, while form and behavior entities are more ambiguous and stimulate ideas that are more original. Entities that are more mature tend to be more fixating, while entities that are more ambiguous tend to be less fixating. Therefore, in an ideal situation, designers would encounter many abstract preinventive entities, and stimulate a wide variety of new ideas. Based on the results and analysis of the experiment, idea generation stimuli should be formulated as follows. The stimuli should be meaningful, relevant, and ambiguous to attract attention. There should be an interesting mix of creative properties, as was the case in behavior stimulation. The information should be novel so that the designer does not immediately assume a specific meaning of the information. There should be some incongruity in the information so that the designer will make an effort to explore. Finally, there should be divergent properties, so that in the exploration process, the designer will generate a variety of ideas.

ACKNOWLEDGMENTS The authors would like to thank Professor Steven Smith of Texas A&M University, Department of Psychology, for his advice and comments on developing the cognitive model. The authors would like to thank the USC ME-410 Fall 2001 students who participated in the design experiment. This research was supported by NSF CAREER Award under grant DMI-9734006. The authors are grateful to NSF for their support. REFERENCES 1. Osborn A, 1979, Applied imagination, Scribners, New York NY 2. Rhorbach B, 1969, Creative nach regeln: methode 635, Eine Neue Technik zum Losen von Problemen, Absatzwirtschaft 12 3. Gordon, W J J, 1961, Syntectics, the development of creative capacity, Harper NY 4. Shah J J Santosh V K and Hernandez N, 2000, Guidelines for experimental evaluation of idea generation methods, Proceedings, ASME design theory and methodology conference, Baltimore MD 5. Novick L R, 1988, Analogical transfer, in Helman D H eds, Analogical reasoning perspectives of artificial intelligence, cognitive science and philosophy, Kluwer Academic Publishers, the Netherlands 6. Lanet D B, 1977, Automated theory formation in mathematics, Proceedings of the fifth international joint conference on artificial intelligence, pp 833-842 7. Langley P, 1979, Rediscovering physics with BACON 3, Proceedings of the sixth international joint conference on artificial intelligence, pp 505-507 8. Simon H A, 1998, The science of the artificial, 3rd ed, MIT press, Cambridge MA 9. Chomsky N, 1959, Review of verbal behavior by B.F. Skinner, Language, 35 pp 26-58 10. Fitts P M and Posner M I, 1967, Human performance, Brooks Cole, Belmont CA 11. Card S K Moran T P and Newell A, 1983, The psychology of human-computer interaction, Lawrence Erlbaum Associates, Hillsdale NJ 12. Wickens C D, 1984, Engineering psychology and human performance, Charles E Merril, Columbus OH 13. Atkinson R C and Shiffrin R M, 1968, Human memory: a proposed system and its control processes, In K W Spence and J T Spence eds, Advances in the psychology of learning and motivation, 2, Academic, New York NY 14. Broadbent D E, 1958, Perception and communication, Pergamon, London Great Britain 15. Newell A and Simon H A, 1972, Human problem solving, Prentice-Hall, Englewood Cliffs NJ

5

SUMMARY AND FUTURE WORK In this paper, we developed a descriptive model of the thinking process in conceptual design. The model consists of four major components: 1) design entities, 2) creative properties, 3) cognitive processes, and 4) design operations. Some of these components exist in the Geneplore Model [19]. However, in addition to these components, The Cognitive Model of Creative Conceptual Design also considered how cognitive processes produce operations that are specific to the design process. In the area of protocol analysis, the main research result was a new method to evaluate creative design models. While previous protocol analysis methods evaluated the design process in general, the protocol analysis method that we developed, evaluated creativity in conceptual design. By this method, design entities, creative properties, cognitive processes, and design operations from a real conceptual design scenario were captured and compared with a cognitive model. In the area of behavioral analysis, the major findings were patterns in creative design behavior. The most significant pattern was that meaningfulness, relevance, and emergence of form and behavior stimulates creativity. Therefore, an experiment was designed to evaluate the stimulating effect of meaningful, relevant, and emergent properties. The essential finding from the experiment was that ambiguous entities stimulate behaviors more than nonambiguous entities. Behaviors, which tend to be the most ambiguous elements of an entity, stimulated twice as many ideas as function, and three times as many ideas and knowledge entities. Therefore, it has been shown that creative patterns can be identified by designer profiling, and infused into the design process to generate more ideas.

12


36. Peterson M A, 1993, The ambiguity of mental images: insights regarding the structure of shape memory and its function in creativity, In Roskos-Ewoldson B IntonsPeterson M J and Anderson R E eds, Imagery, creativity and discovery: a cognitive approach, Elsevier, Amsterdam, pp 151-186 37. Van Someren M W Barnard Y F and Sandberth J A C, 1994, The think aloud method: a practical guide to modeling cognitive processes, Academic Press, London 38. Ullman D G, 1997, The mechanical design process, McGraw-Hill, New York NY 39. Ericsson K A and Simon A, 1993, Protocol analysis: verbal reports as data, MIT press, Cambridge MA 40. Kokotovich V, 2000, Mental synthesis and creativity in design: an experimental examination, Design studies, 21 pp 437-449 41. Jansson D G and Smith S M, 1991, Design fixation, Design studies, 12 pp 3-11

16. Suh, N P, 1990, The principles of design, Oxford university press, New York NY 17. Pahl P G and Beitz W, 1996, Engineering design, a systematic approach, Springer, London Great Britain 18. Gero J S and McNeill T, 1998, An approach to the analysis of design protocols, Design studies, 19 pp 21-61 19. Finke R A Ward T B and Smith S M, 1992, Creative cognition – theory, research, and applications, MIT Press, Cambridge MA 20. Schon D A and Wiggins G, 1992, Kinds of seeing and their functions in designing, Design studies, 13 pp 135-156 21. Goldschmidt G, 1991, The dialectics of sketching, Creativity research journal, 4 pp 123-143 22. Woodbury R F, 1993, A genetic approach to creative design, In Gero J S and Maher M L eds, Modeling creativity and knowledge-based creative design, Lawrence Erlbaum Associates, Hillsdale NJ 23. Rosenman and Gero, 1993, Creativity in design using design prototypes, in Gero J S and Maher M L eds, Modeling creativity and knowledge-based creative design, Hillsdale NJ 24. Coyne et al, 1993, A connectionist view of creative design reasoning, in Gero J S and Maher M L eds, Modeling creativity and knowledge-based creative design, Hillsdale NJ, pp 177-210 25. Thompson A and Klatzky R L, 1978, Study of visual synthesis: integration of fragments into forms, Journal of experimental psychology: human perception and performance, 4 No 2, pp 244-263 26. Suwa M et al, 1998, Macroscopic analysis of design processes based on a scheme for coding designers cognitive actions Design studies, 19 No 4, pp 455-483 27. Shah J J 1998, Experimental investigations of collaborative techniques for progressive idea generation, Proceedings, ASME Design Theory and Methodology Conference, Atlanta. 28. Gero J S and Maher M L eds, 1993, Modeling creativity and knowledge-based creative design, Lawrence Erlbaum Associates, Hillsdale NJ 29. Altshuller G, 1984, Creativity as an exact science, Gordon and Breach, New York NY 30. Koestler A, 1964, The act of creation, Macmillan, NY 31. Gero J S, 1998, Emergence in designing, in Chase S and Schmidt L eds, AID’98 workshop on emergence in design, AID’98, Lisbon, pp 9-12 32. Masaki S Gero J and Purcell T, 2000, Unexpected discoveries and s-invention of design requirements: important vehicles for a design process, Design studies, 21 pp 539-567 33. Anderson, J R, 1990, Cognitive psychology and its implications, 3rd eds, Freeman, New York NY 34. Rich E and Knight K, 1991, Artificial Intelligence, 2nd eds, McGraw-Hill, New York NY 35. Gross M D Ervin S M Anderson J A and Fleischer A, 1998, Constraints: knowledge representation in design, Design studies, 9 No 3, pp 133-143

13
