Judgements about the relation between force and trajectory variables in verbally described ballistic projectile motion

Abstract

How accurate are explicit judgements about familiar forms of object motion, and how are they made? Participants judged the relations between force exerted in kicking a soccer ball and variables that define the trajectory of the ball: launch angle, maximum height attained, and maximum distance reached. Judgements tended to conform to a simple heuristic that judged force tends to increase as maximum height and maximum distance increase, with launch angle not being influential. Support was also found for the converse prediction, that judged maximum height and distance tend to increase as the amount of force described in the kick increases. The observed judgemental tendencies did not resemble the objective relations, in which force is a function of interactions between the trajectory variables. This adds to a body of research indicating that practical knowledge based on experiences of actions on objects is not available to the processes that generate judgements in higher cognition and that such judgements are generated by simple rules that do not capture the objective interactions between the physical variables.

Keywords:

• Force judgement
• Naive theories of object motion
• Impetus theory

Acknowledgments

Thanks to Lorraine Woods for assistance with Figure 1.

Notes

¹ Information about motor exertion in the actions of others can be derived by inference or simulation, possibly by means of mirror neurons, so the difference is not as profound as it might seem (Rizzolatti, Fadiga, Gallese, & Fogassi, 1996; White, 2012).

² Using the term “outcome” for a quantitative variable is a little clumsy. The problem is that the outcome could be measured on either of the parameters x _max and y _max, and there is no convenient term that covers both of these parameters.

³ This study was carried out in Britain, where “football” is normally taken to refer to soccer. Participants would assume that the ball was a spherical soccer ball.

⁴ The equations use metric units. However, it was decided to use imperial units in Experiments 1–3 because British people habitually think of speeds in mph and not m/s or even kph. Figure 2 was created by converting from imperial to metric and then solving Equation 3. The same is the case for Figures 4 and 6. In Experiments 4 and 5, metric distance units were used in the materials so no conversion was required. Ordinal comparisons are the main concern in this research, so it is not likely that trends in judgements would be significantly influenced by the kind of distance unit used, as long as participants understand the ordinal relations between different distances.