Causation, Force, and the Sense of Touch

Causation, Force, and the Sense of Touch Phillip Wolff (pwolff@emory.edu) Department of Psychology, 36 Eagle Row Atlanta, GA 30322 USA Samuel Ritter (swritter@Princeton.edu) Department of Psychology, Green Hall Princeton, NJ 08540 USA Kevin J. Holmes (kjholmes@berkeley.edu) Department of Linguistics, 1203 Dwinelle Hall Berkeley, CA 94720 USA relevant today because they continue to be used in defense of probabilistic accounts of causation (e.g., Cheng, 1997; Cheng & Novick, 1991, 1992). In this paper, we report a set of findings that addresses Hume’s main criticism against force accounts of causation: specifically, that forces cannot be linked to internal or external sensory impressions. The criticism certainly holds in the case of the visual modality. However, once we consider the potential contributions of other senses, in particular touch, it becomes clear that people’s sensory experience is not as deficient as Hume (and many modern theorists) have claimed. According to what we will call the causal force hypothesis, people’s mental representation of causation is based on the feeling of force as understood through the sense of touch (see Fales, 1990; White, 2012). Abstract It is widely acknowledged that causation entails more than spatial-temporal contiguity or correlation, but efforts to specify that extra component of experience have been elusive. In this paper, we argue that the representation of causal relations is based on the feeling of force as understood through the sense of touch. Grounding causation in people’s sense of touch allows us to address long-standing challenges that have been raised against force-based approaches to causation. In support of our proposal, we report a series of experiments showing that the perception of causation is associated with the notion of force, as indicated by changes in people’s sensitivity to a physical force acting against their hand. We also show that when people associate correlations with force, they view those correlations as causal. Implications for understanding the origins of causal knowledge are discussed. Keywords: Causation; Causal perception; Force Perception; Haptics; Causal Induction; Abstract Concepts Perception of forces Introduction Several recent theories of causation have proposed that the mental representation of causation is based on the notion of force (Copley & Harley, 2014; Fales, 1990; Gardenfors, 2000; Mumford & Anjum, 2011; Hubbard & Ruppel, 2014; White, 2012; Warglien, Gardenfors, Westera, 2012; Wolff, 2007; Wolff, et al. 2010). These theories have provided explanations of how causal relations might be recognized from a single occurrence of an event (Ahn & Kalish, 2000; Bigelow, Ellis, & Pargetter, 1988; Wolff, 2007) as well as how different kinds of causal relationships might be related to one another (Talmy, 1988; see also Wolff, 2007; Wolff, et al., 2010). Despite these successes, there has been strong criticism of force-based accounts of causation (Cheng, 1997; Cheng & Novick, 1992; Schulz, Kushnir, & Gopnik, 2007; Woodward, 2007; Sloman, Barbey, & Hotalling, 2009). Arguably the most fundamental of these criticisms was initially made by Hume (1748/1975). He pointed out that the notion of force could not be linked to any internal or external sensory impression and that, therefore, forces could not be the basis for our mental representation of causation. He noted that after many repetitions of conjunctions of objects or events, people could develop an expectation that gives rise to a sense of power or force, but that this sense only emerged from statistical regularities, which were the only legitimate bases for inducing causation. Hume’s arguments remain Several lines of research have established that people are able to represent forces. These studies have shown that people are skilled at perceiving forces from the environment when those forces impinge directly on the skin. For example, Wheat, Salo, and Goodwin (2004) found a nearly linear relationship between participants’ estimates of a force acting on their fingers and the actual magnitude of the force. Panarese and Edin (2011) found that people are quite good at discriminating the direction of forces applied to the index finger. Of particular relevance to the induction of causation, several neuroimaging studies have reported evidence for the encoding of forces even in the absence of physical contact. For example, Keysers et al. (2004) observed activity in the somatosensory cortex not only when people were touched directly on their legs, but also when they observed other people being touched on their legs. Even more impressively, activity in the somatosensory cortex was observed when participants observed one inanimate object touch another inanimate object. Keysers et al.’s (2004) findings have been replicated and extended in several other studies (see Blakemore, Bristow, et al., 2005; Ebisch, et al., 2008). Indeed, the representation of forces through the visual modality is revealed in common everyday tasks. Many of us, for example, have had the experience of reaching for a suitcase or box and over-lifting it because we thought it was full when, in fact, it was empty. Such events presumably