This sense of simulation has little to do with ST as understood in the mindreading literature. On the contrary, computational modeling is more like using a theory to predict and/or explain a system’s behavior. Thus, compu-tational simulation should not be confused with simulation in the sense in-tended by simulationists of mindreading. They (we) understand simulation in the sense of duplication or replication. Indeed, Jane Heal (1986) used the term replication in her first article on the subject, and in some ways that’s a better term because it avoids connotations associated with computer simu-lation. However, simulation is the entrenched term in the mindreading lit-erature, and there is little point in forswearing it. Let us simply mark the vital distinction between the two senses of simulation: computational modeling simulation and replication simulation. For purposes of the theory of mind-reading, only the latter interests us.10
The last remark is not meant to exclude the possibility that mental pro-cesses are computational propro-cesses. Both first-order mental propro-cesses and second-order, metarepresentational processes might be computational pro-cesses. All I am saying here is that being computational does not make a mental process a simulation in the sense relevant to ST. We need a different meaning to attach to ST. The meaning I shall introduce is plainly inspired by the term’s etymology.
The English verb simulate is derived from the Latin simulare, which means
‘‘imitate’’ or ‘‘feign.’’ This in turn is derived from the adjective similis, which means ‘‘similar’’ or ‘‘like.’’ So a generic notion of simulation is best approached in terms of similarity, likeness, or (approximate) copying or duplication. Let us proceed by constructing a more precise definition of simulation from this starting-point. From there, we can move to mental simulation as a special case and to mental simulation for mindreading as a special case of that.
The first two definitions I offer are definitions of successful simulation.
These are followed by a definition of attempted simulation. Attempted sim-ulations and successful simsim-ulations will count equally as simsim-ulations for pur-poses of mindreading, but successful simulation is the logically prior concept.
Here is a first pass at defining generic simulation.
Generic Simulation (initial): Process P is a simulation of another process P¢ ¼df.
P duplicates, replicates, or resembles P¢ in some significant respects (sig-nificant relative to the purposes of the task).
P and P¢ are token processes or episodes, rather than process types. An example of generic simulation is flight-training simulation. A flight simulator is a system or device that duplicates the actual situation of a pilot in significant respects, but not all respects. A flight simulator is not a real airplane and does not become airborne. However, it comprises an environment that resembles a genuine
airplane cockpit, with the same instruments. Instrument readings resemble readings occurring in actual flight and respond in similar ways to actions per-formed on the controls. Thus, a token process that transpires in the flight simulator resembles in significant respects what occurs, or would occur, during a real flight. In general, a simulating activity can have any temporal relation to an activity it simulates: earlier, later, or contemporaneous. Furthermore, a simulated (target) activity P¢ can be merely hypothetical rather than actual. For example, a particular flight simulation that eventuates in a (simulated) crash might not correspond to any real crash. The simulation could still be accurate in the sense that it corresponds to what would happen to a real airplane if a pilot performed the maneuvers actually performed in the simulation.
This initial definition of generic simulation needs refinement. One problem is that duplication, or resemblance, is symmetrical, whereas simulation is not.
It is not generally the case that when P simulates P¢, P¢ also simulates P. In cases of mindreading, we want to be able to say that the attributor’s mental activity simulates that of the target, but we don’t want to say the converse.
A patch to the definition might seem straightforward. Simply require that the simulating process occur out of the purpose, or intention, to replicate the simulated process. That won’t hold in the reverse direction. This won’t quite work, however, because it is doubtful that all simulation is purposeful. Some simulation may be automatic and nonpurposeful. Even without purposeful-ness, however, a phenomenon intuitively counts as a simulation of another if it is the function of the former to duplicate or resemble the other. I lack a theory of functions to provide backing for this approach, but I shall none-theless avail myself of this notion. This enables us to revise the definition of generic simulation as follows:
Generic Simulation (revised): Process P simulates process P¢ ¼df.
(1) P duplicates, replicates, or resembles P¢ in some significant respects (significant relative to the purposes or function of the task), and (2) in its (significant) duplication of P¢, P fulfills one of its purposes or
functions.11
Generic simulation is a notion that applies to all sorts of processes, mental and nonmental. Let us next introduce the notion of mental simulation, the simu-lation of one mental process by another mental process.12Mental simulation comes in two varieties: intrapersonal and interpersonal. Intrapersonal mental simulation occurs when P and P¢ are mental processes in the same individual mind, and interpersonal mental simulation occurs when P and P¢ are in dif-ferent minds.
Mental Simulation: Process P is a mental simulation of target process P¢ ¼df.
Both P and P¢ are mental processes (though P¢ might be merely hypothet-ical), and P and P¢ exemplify the relation of generic simulation as previ-ously defined.
A possible example of mental simulation is visualization. In visualizing something, the mind seems to undergo a process somewhat similar to seeing the thing. If it’s a familiar object, the specific content of the visualization might resemble the content of the seeing, at least in significant respects. At a minimum, one has the introspective impression that visualization approxi-mates seeing. Whether this introspective impression is confirmed by cognitive science is addressed in chapter 7. Evidence will be presented that supports this introspective feeling.
The resemblance claim made here must not be confused with another resemblance claim sometimes made by imagery theorists. The second re-semblance claim, emphatically rejected here, is that visual images resemble objects or scenes visualized. By contrast, the resemblance claim endorsed here is not a mind-world resemblance. What transpires in the mind when one visualizes the sea presumably bears little interesting resemblance to the sea.
The mind isn’t blue, it isn’t a body of water, and so forth. But visualizing the ocean might substantially resemble an episode of seeing the ocean, either an actual seeing or a hypothetical one.13 This is the relationship between visu-alizing and seeing that might exemplify mental simulation.
Our current definitions of simulation require simulation to be a success-ful14process; P must duplicate, in significant respects, process P¢. However, a reasonable version of ST would not hold that the mental processes of mindreaders always match, or even approximately match, those of their targets. ST, like any plausible theory of mindreading, should tolerate highly inaccurate specimens of mindreading. For example, a mindreader badly misinformed about her target might construct inaccurate pretend states, with minimal correspondence to those of her target. What ST essentially maintains is that mindreading (substantially) consists of either successful or attempted mental simulations. To accommodate this idea, we first need a definition of attempted mental simulation. So let us offer the following two definitions.
Attempted Generic Simulation: Process P is an attempted generic simu-lation of process P¢ ¼df.
P is executed with the aim of duplicating or matching P¢ in some signif-icant respects.
Attempted Mental Simulation: Process P is an attempted mental simulation of process P¢ ¼df.
P and P¢ are both mental processes, and P is executed with the aim of duplicating or matching P¢ in some significant respects.
The term aim in these definitions includes covert or implicit aims, not con-sciously available to the simulator.
Let us now consider the following factual thesis (not a definition).
Mental Simulations Are Used for Question Answering: People sometimes use successful or attempted mental simulations when answering a question (or forming a belief).
The use of mental simulation for question answering can also be illustrated by visualization. People often visualize things in order to answer questions about them (either self-generated or other-generated questions). A classic cognitive science example comes from Roger Shepard’s study of ‘‘image rotation’’
(Shepard and Cooper, 1982). In so-called image-rotation tasks, subjects were shown pairs of line drawings portraying three-dimensional objects in space, and they were asked to determine, as rapidly as possible, whether the two depicted objects were the same or different, that is, whether they were congruent. Sub-jects’ reaction time to pairs of congruent shapes was a remarkably linear function of the angular difference in their portrayed orientation. This led ex-perimenters to conclude that subjects tried to answer the question by mentally rotating images of the objects in their heads. Of course, we needn’t suppose that any mental entities (e.g., ‘‘sense-data’’) were literally being rotated. Rather, on each trial subjects engaged in a process of visualizing one of the objects being rotated in space. Talk of a visualizing process is noncommittal vis-a`-vis the architecture of the process, whether, for example, it is fundamentally ‘‘pictorial’’
or ‘‘discursive.’’ Whatever the architecture of visualization, the tacit aim of the subjects’ visualization was to undergo a vision-like process, a process of seeing one of the portrayed objects rotated in space. Of course, the subjects didn’t see any three-dimensional shapes being rotated; there were no three-dimensional shapes to be seen. The simulated seeing processes were purely hypothetical.
However, our definitions allow simulations of hypothetical processes, and it is highly plausible that subjects (tacitly) tried to produce such simulations. The simulations were undertaken, moreover, to answer the question posed, namely, whether the portrayed shapes were congruent.
We turn next to the central notion here, that of mental simulation to answer a mindreading question. Again we advance a factual thesis.
Mental Simulations Are Used to Answer Third-Person Mindreading Questions: People often use mental simulations or attempted mental sim-ulations to answer questions (form beliefs) about other people’s mental states.
This says not only that people execute mental simulations and attempted mental simulations but also that some of these simulations are used to answer
person mindreading questions, that is, to generate beliefs about third-person mental states. Notice that the thesis does not imply that all simulational mindreading is purposeful or intentional. Mental simulations might occur automatically, without intent, and then get used to form beliefs about mind-reading questions. So it is left open whether token simulations are purposeful or nonpurposeful, but cases of purposeful simulations that misfire are clearly allowed.