PHYSICS
Experiment Five
METHOD
Subjects: 134 undergraduate students participated in this experiment. The average age of these students was 20.6. 56.9 percent of them were female and 43.1 of them were male. 31.6 percent of these students had taken college Physics, 43.9 percent of them had taken high school Physics, and 24.6 of them had never taken a physics class. The subjects were separated into two groups with 67 students in each group.
Stimuli: The same basic stimulus material in Experiment 2, drawings of the spiral tube, the 17 white ping-pong balls, water pipe, and a lead ball were used in this experiment. In particular, the same Fast/LB and the Water stimuli were used under two within-subject conditions of this experiment. A new stimulus, the Impact stimulus, was created for another condition of the experiment. In this stimulus, everything remained exactly the same as the Fast/LB stimulus except that another lead ball, labeled as ball B, was introduced into the new stimulus and placed at the exit end of the tube and the original lead ball was now label as ball A; The instruction about the stimulus was also kept as much the same as possible except the information about ball B.
Procedure: Before the experiment, the Fast stimulus and the Water stimulus were stapled together, with the Fast stimulus preceding the Water stimulus. 70 sets of the Fast and Water stimuli were mixed up with 70 sets of Impact stimulus, shuffled into random order, and then put into a pile ready for the experiment. At the beginning of the experiment, the subjects were instructed that 1) the experiment is not a test; 2) use the gut-feeling to answer the questions. For the Fast and Water group, the subjects would start with their responses on the Fast stimulus first and then on the Water stimulus. In both stimuli, they were instructed about what the drawings stood for: a metal spiral tube was lying flat on the smooth table; they were looking down on the surface of the table as they were looking at graph. Depending on either the Fast condition or the Water condition, they were then told that either a lead ball or water was shot into the inner end of the spiral tube and asked to indicate which of the white ping-pong ball would get hit by either the lead ball or water coming out the tube. The Impact group was given the Impact stimulus. The instruction for this group was quite similar to that given to the Fast/Water group except that they were asked to indicate which of the white ping-pong balls would get hit by ball B, instead of ball A.
Design: There were two between-subject conditions for this experiment: the Fast/Water condition and the Impact condition. Under the Fast/Water condition, the Fast condition and the Water condition were the two within-subject conditions. No counterbalance between the Fast condition and Water condition was in the design of the experiment because the stimuli for these two conditions were exactly the same except the difference between the lead-ball/ water distinction.
RESULTS
The responses in this experiment were the white ping-pong balls (the measurement positions) marked as hit by either ball A, water, or ball B coming out of the tube. Response frequencies are listed in Table 6. The responses under the Impact condition was compared with responses under the Fast-ball condition and those under the Water condition. ANOVA tests the difference between the Impact responses and Fast responses and the difference between the Impact responses and Water responses with respect to the sample means and variances. The results show that the responses from the Impact group are significantly different from those under the Fast-ball condition (F=4.4, p=0.037), but, not significantly different from those under the Water condition (F=0.00, p=0.997). Two T-tests produced exactly the same numbers of result. A paired sample T-test further indicated the significance of difference between the Fast responses and the Water responses (t=2.44, p=0.018).
DISCUSSION
In Experiment 2, many subjects believed that a fast lead ball, coming out the tube, would curve to the left of the 17 measurement positions. However, they did not believe that water would curve as much as a lead ball. So, essentially, it is the left-curvedness that had made the responses under the Fast/LB condition different from the responses under the Water condition in that experiment. In the present experiment, the responses of the Impact group were found to be, on one hand, significantly different from the responses under the Fast/LB condition and, on the other hand, not significantly different from the responses under the Water condition.
The Impetus Theory claims that a ball travels in a curved path because it carries a curved impetus and, moreover, the curved impetus can be imparted from one object to another object. This theory can not explain the results in the present experiment. No subjects would doubt that ball B had acquired its impetus from ball A, so that it could travel to hit one of the white ping-pong balls. But, in their responses, the acquired impetus has not made ball B travel in a curved path as ball A itself would. Therefore, either the curved impetus was conceived as becoming straight through the impact or the subjects did not have a concept of curved impetus in the first place.
The idea that an impact, as conceived, can straighten out a curved impetus seems puzzling, to say the least. Admittedly, an impact, according to the Impetus Theory, is merely an occasion for impetus transmission from one object to another and it does nothing to the impetus itself. Therefore, the subjects, if they really had a belief of the Impetus Theory, would believe that ball A sets ball B in motion by imparting some of its own impetus to ball B. That is, an impact is conceived as a process for impetus transmission, rather than a processor that transforms the impetus itself in ball A. As a result, conceptually, the impetus in ball A and the impetus in ball B would have to be qualitatively the same impetus. Then, ball B should also travel in a curved path just as ball A did.
Notice, the Impetus Theory does not specify how an impetus, either curved or straight, can be conceived as impartible from one object to another object, because it has attributed the curvedness of object motion to the mysterious impetus that is 'curved', which somehow is also conceived by the cognitive system. Let's look at the responses of Experiment 2 in the Fast/LB condition in more detail to see where the curvedness in these responses have come from. For the lead ball, which was believed as traveling a curved path outside the tube by many of our subjects, it is in fact quite impossible to explain the source of such curvedness in the responses based on the Impetus Theory. No one probably would believe that the curved impetus has been imparted to the lead ball by either the gun or the tube in the sense of the Impetus Theory, because neither of them have any curved impetus. When a ball was first shot into the tube, the impetus in the ball should certainly be not conceived as a curved one. Then, where does the belief of curved impetus come from? It is unlikely that people would have the belief that it is the tube that imparts to the ball a curved impetus of its own either. It appears, therefore, that a curved impetus as it is conceived can only come about through how dynamic motion is conceived, rather than what is imparted directly from another object.
Further, the only difference in the responses of our subjects between the Fast/LB condition and the Impact condition is that ball B did not have a history of traveling in a curved path as did ball A. In other words, it is the mechanical history of ball A, not the particular type of 'force', which seemed to have been conceived by the subjects as they were drawing a curved path of ball A. But the idea that it is in conceiving the mechanical motion of an object that the cognitive system projects the object's future state of motion appears to be quite different from the Impetus Theory.
A similar result was also found in a pilot study I have carried out as I was running the experiments presented. The stimulus is shown in Figure 14, where a ball is shown shot into a spiral tube and a heavy metal bar is drawn placed by the tube. The subjects were asked to draw the path of the ball ourside the tube. As shown in the figure, a typical incorrect response indicates that the ball coming out the tube would curve to the left, hit the metal bar, and travel in a straight path afterwards. In this pilot study, almost every subject who had drawn a curved path before the bar ended up drawing a straight path after the bar. We can ask the same questions referring to the result of this pilot study as we did in the present experiment. Where is the curved impetus after the ball hits the bar? Doesn't the ball have the same impetus after the impact as before? Can an impact straighten out a curved impetus?
Therefore, we conclude that the response of a curved motion as we are dealing with here has not resulted from the conception of any energy-like entity, but from the conception of dynamic motion. More specifically, an object moving in a curved path is conceived to have a mechanical tendency to continue to curve in the same way; The more mass and the higher speed the object has, the stronger is this tendency. As we have aleady shown in Expeirment 2, the representation of such a mechanical tendency is particularly related to the representation of the dynamic motion. It is quite reasonable to believe that such a mechanical tendency is not conceived as a 'thing' in the object, but a representational constraint for the continuity of dynamic motion or process of the object.