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How to Get Beyond Intuition?

The question for this section is,

Can humans perceive causal interactions?

Let my try and show you stimuli that were used in an experiment (without yet telling you anything about the experiment). What do you see?
[If the animation doesn't work, there's a static version on the next slide.]

Thines et al (1991)

OK, so adults: (a) verbal reports. So what?
‘There are some cases … in which a causal impression arises, clear, genuine, and unmistakable, and the idea of cause can be derived from it by simple abstraction in just the same way as the idea of shape or movement can be derived from the perception of shape or movement’ \citep[p.\ 270--1]{Michotte:1946nz}
Adults will also report experiencing causal interactions including pullling, ...

Scholl & Tremoulet 2001, figure 2

... disintegration ...
... and bursting.

Heider & Simmel 1946, figure 1

Can humans perceive causal interactions?

So can humans, adult and infant, perceive causal interactions?
So far I don't think we have strong reasons to accept that they do. In infants we have discrimination and in adults we have verbal reports. But we shouldn't trust verbal reports. After all, people will say all kinds of things about their experiences. This is nicely illustrated by a famous experiment on apparent behaviour by \citet{Heider:1944ts}.

How to get beyond intuition?

Michotte: the experience of launching depends on interactions among various factors including

  • the relative speeds of the two objects
  • the delay between the first and second objects’ movements
  • the spatial gap between the two objects
  • the trajectories of the two objects.
But how does this help us? Importantly, tiny variations in the parameters will make big differences in the experiences reported. Let me illustrate this for the delay between the objects' movements.
adults: (b) they can discriminate between short gaps and long gaps.
That is, the can discriminate gaps of around 50ms.

Michotte 1946 [1963], p. 115 table IX (part)

Maybe this is clearer as a figure.

Michotte 1946 [1963], p. 115 table IX (part)

People can distinguish between stimuli that differ only in that the gap between two movements is approximately 50ms longer in one than the other. A 50ms difference makes the difference between reporting launching and reporting two movements.
We need to do more to understand the effect, ...
NB: Rips 2011 notes that missing out the third category of judgement makes the case for categorical perception seem different than it is.

Consider an encounter with three two-object movements where the delays between movements are 50, 100 and 150ms.

1. The phenomenal difference between the first two encounters is larger than the phenomenal difference between the second two.

2. This difference in differences is a fact in need of explanation.

3. The fact cannot be explained by perceptual experience of objects or their motion.

4. The best explanation for (1) is that we perceptually experience causal interactions.

An alternative argument ...

‘… why it is that in our experiments certain particular conditions were found necessary in order to give rise to a causal impression. They correspond to the different characteristics of reproduction. …

anyone not very familiar with the procedure involved in framing the physical concepts of inertia, energy, conservation of energy, etc., might think that these concepts are simply derived from the data of immediate experience’


Michotte, 1946

(1) A distinctive experience occurs under certain conditions.

(2) The best explanation for (1) is that the experience in question is the experience of a collision.

The question was how we can get beyond intuition in understanding the verbal reports. I don’t think the argument offered about how to explain the conditions under which the launching effect works is obvious successful. But I do think it’s right to ignore verbal reports in favour of an attempt to get at the nature of the processes that explain the launching effect.

How to get beyond intuition?

The launching effect: detecting a 50ms difference in the delay between two movements.

Part of the answer is this. We don't worry about the content of the verbal reports. We just focus on the fact that their content changes depending on a tiny, 50 millisecond difference in the delay between two movements. Call this \emph{launching effect}.
This doesn't tell us what people are detecting. But it does tell us that the effect is not merely confabulation or making it up. So we have taken a tiny step beyond intuition. But we also have to answer two questions.
  1. How is launching detected? For example, does it involve perceptual processes?
  2. Why is a delay of up to around 70ms consistent with the launching effect occuring?