Abstract concepts, concepts without a clear reference in the perceptual world, constitute an essential part of the human conceptual system. Think of morality, time, magnitude, social status, or intimacy, to name just a few well-studied examples. Lacking direct correspondences with perceptuo-motor experiences, how can people represent them and reason about them? A prominent answer to this question is the Metaphor View (Boroditsky, 2000; Casasanto & Boroditsky, 2008; Lakoff & Johnson, 1980, 1999; Williams, Huang, & Bargh, 2009), which proposes that our conceptual system recycles concrete concepts to help understanding the abstract. Representations of location, motion, size, color, brightness, weight, smell, temperature, and other perceptually based dimensions of experience are used to understand more abstract concepts as if, at least in part, the latter were examples of such concrete experiences. Take time as a case in point. There is now ample evidence supporting that time is often understood as motion along a path, from a past location to a future location, either along the front–back axis (Boroditsky, 2000; Clark, 1973; Lakoff & Johnson, 1980, 1999) or along the left–right axis (Frassinetti, Magnani, & Oliveri, 2009; Fuhrman & Boroditsky, 2010; Oliveri, Koch, & Caltagirone, 2009; Santiago, Lupiáñez, Pérez, & Funes, 2007; Santiago, Román, Ouellet, Rodríguez, & Pérez-Azor, 2010; Torralbo, Santiago, & Lupiáñez, 2006; Tversky, Kugelmass, & Winter, 1991; Vallesi, Binns, & Shallice, 2008). Experimental evidence regarding many other conceptual mappings also seems to be mostly consistent with the Metaphor View. Numerical sequence also runs in space from side to side (originally reported by Dehaene, Bossini, & Giraux, 1993; and widely replicated later), as well as agency and action flowing (Chatterjee, Maher, Gonzalez-Rothi, & Heilman, 1995; Chatterjee, Southwood, & Basilico, 1999; Maas & Russo, 2003; Maher, Chatterjee, Gonzalez-Rothi, & Heilman, 1995). Numerical magnitude is related to physical size (Besner & Coltheart, 1979; Henik & Tzelgov, 1982). Social status is thought of as deploying people along a vertical spatial axis (Giessner & Schubert, 2007; Schubert, 2005) or as objects of varying size (Marsh, Yu, Schechter, & Blair, 2009; Schubert, Waldzus, & Giessner, 2009). Social relations vary in temperature (IJzerman & Semin, 2009, 2010; Kang, Williams, Clark, Gray, & Bargh, 2011; Williams & Bargh, 2008; Zhong & Leonardelli, 2008). Sex-related personality styles are related to tactile sensations of softness–hardness (Slepian, Weisbuch, Rule, & Ambady, 2011). Both morality and emotional valence have to do with cleanliness (Schnall, Benton, & Harvey, 2008), brightness (Meier, Robinson, & Clore, 2004; Meier, Robinson, Crawford, & Alhvers, 2007; Sherman & Clore, 2009), vertical locations (Meier & Robinson, 2004, 2006), and lateral left–right locations (Casasanto, 2009; Casasanto & Chrysikou, 2011; Casasanto & Jasmin, 2010). Importance has to do with weight (Jostmann, Lakens, & Schubert, 2009) and similarity with proximity (Casasanto, 2008a).
The vast majority of this research relies on conceptual congruency tasks. In such tasks, participants are typically asked to carry out a judgment on an abstract conceptual dimension (e.g., discriminate past from future, good from bad, higher status from lower status), while a concrete conceptual dimension is manipulated (e.g., stimuli are responded to with the left or right hand, presented at different locations, with different levels of brightness, weight, softness, temperature, size, and so on). The levels of the concrete dimension are fully crossed with the abstract dimension, and they are completely irrelevant to the task. Nevertheless, conceptual congruency effects can be found: the values of the concurrent concrete experiences being able to affect the easiness (speed and/or accuracy) of the abstract conceptual judgment or to bias the judgment itself in a particular direction. Conceptual congruency effects are the central empirical pillar of the Metaphor View of concepts, as they lend support to the idea that concrete experiences are somehow involved in highly abstract thinking.
Conceptual congruency effects can be symmetric or asymmetric. Symmetry is observed when it is possible to find a corresponding same-sized influence of the abstract dimension on the processing of the concrete dimension. The issue of the symmetry or asymmetry of conceptual congruency effects carries important theoretical implications (Boroditsky, 2000; Casasanto & Boroditsky, 2008; Casasanto, Fotakopoulou, & Boroditsky, 2010; Merritt, Casasanto, & Brannon, 2010).
Lakoff and Johnson (1980) first noted that it is much more common to talk about abstract concepts in terms of more concrete concepts than the opposite (e.g., “the future is ahead of us,” where time is talked about as if it were a location, versus “the station is one minute away,” where distance is talked about in terms of duration). They suggested that such linguistic patterns unveil the structure of the human conceptual system: more abstract, less delineated concepts are thought about in terms of concrete concepts, of which we have more detailed knowledge. Under this view, to think of an abstract concept, it would be necessary to activate the concrete domain on which it is construed. Boroditsky (2000) called this the Strong Metaphor View and distinguished it from a Weak Metaphor View. The weaker formulation allows for the borrowed structure to be stored directly at the abstract domain, such that the concrete domain does not need to be activated every time people think about the abstract domain. Boroditsky (2000) reasoned that the Strong View predicts symmetric cross-domain priming effects, whereas the Weak View predicts asymmetric priming effects: Processing the concrete domain should bias subsequent processing of the abstract domain, whereas processing the abstract domain would not necessarily entail activation (priming) of the concrete domain. She observed that spatial primes were able to bias temporal thought, whereas analogous temporal primes did not bias spatial thought, thereby supporting the Weak View.
In subsequent writings in this tradition (Casasanto, 2008b, 2009; Casasanto & Boroditsky, 2008) the prediction of asymmetry in cross-domain effects was linked to the exposure to the asymmetric linguistic patterns noted by Lakoff and Johnson (1980). It is assumed that mental metaphors can thus arise both from perceptuo-motor experiences (such as the experience of moving from one location to another and arriving at a later time) as well as from conceptualizations induced by language. Under this account, language can guide how people think about concepts in terms of other concepts. From here it follows that if linguistic expressions that talk about the abstract in terms of the concrete are more frequent than the converse, people will tend to think of the abstract in terms of the concrete. However, sometimes people can also think about the concrete in terms of the abstract (as when distances are described in terms of durations, see above). Therefore, the degree of asymmetry in cross-domain priming is expected to follow the degree in which linguistic patterns are themselves asymmetric. If two concepts were talked about in terms of the other with roughly the same frequency, symmetric priming would be expected.
Before we turn to review the available evidence regarding the degree of symmetry in cross-domain priming, it is very important to note that asymmetric priming plays a crucial theoretical role for the Metaphor View. If cross-domain priming is symmetric, it could mean that the representation of abstract conceptual domains is fully parasitic on more concrete domains, as suggested by the Strong View. However, it could just as well support the alternative views that (a) the representation of concrete domains completely depends on the conceptualization of abstract domains; or (b) that both concrete and abstract domains share an underlying representation or mechanism responsible for the cross-domain interactions. In other words, asymmetric cross-domain priming fulfils the crucial role of providing an empirical index of the progressive building of upper (abstract) levels of the human conceptual structure on the lower (concrete) levels, which grounds the whole structure on perceptuo-motor foundations (a view that Santiago, Román, & Ouellet, 2011, termed the Solid Foundations View of concepts). Without asymmetric priming, only the asymmetric linguistic patterns remain as evidence for this view. However, relying only on how people speak is considered to be insufficient to substantiate claims about underlying thought representations (Murphy, 1996, 1997). This view, thus, looks much less solid without asymmetric priming.
It could be argued that the alternative views mentioned above are not plausible. However, a view like option b above has actually been proposed and is receiving considerable attention in the psychological and neuroscientific literature. Walsh (2003) proposed the A Theory of Magnitude (ATOM) view, which suggests that the parietal lobes hold a common representation for all prothetic dimensions, that is, all dimensions that can be characterized by “more than - less than,” relations. Walsh (2003) explicitly mentioned three of them: space, time, and number, but his later work extended this view to other dimensions such as weight (Lu, Hodges, Zhang, & Zhang, 2009), brightness, and size (Pinel, Piazza, Le Bihan, & Dehaene, 2004). The reasons why such a common representational substrate may have evolved have to do with representational and processing economy, or it might be just a consequence of the evolutionary strategy of reusing neural substrates for new tasks (Anderson, 2010). Most research in this tradition has also used conceptual congruency tasks, but no claims of differences in terms of degree of abstraction are made regarding the manipulated dimensions. Thus, space, time, size, brightness, and number are often pitted against each other (e.g., Agrillo, Ranpura, & Butterworth, 2010; Cappelletti, Freeman, & Cipolotti, 2009; Dormal, Seron, & Pesenti, 2006; Kiesel & Vierck, 2009; Lu et al., 2009; Oliveri et al., 2008; Roitman, Brannon, Andrews, & Platt, 2007; Vicario et al., 2008; Xuan, Zhang, He, & Chen, 2007). In contrast to the Metaphor View, ATOM predicts symmetric effects between all pairs of prothetic dimensions. ATOM has the advantage of being able to integrate observed congruency effects between dimensions which seem to be at similar levels of concreteness, such as time and number (e.g., Dormal et al., 2006) or space and pitch (Rusconi, Kwan, Giordano, Umiltà, & Butterworth, 2006).
What does available evidence say about the symmetry or asymmetry of conceptual congruency effects? Several studies have tested both directions of influence, but few have done it in a single design, and even fewer have focused on the more theoretically diagnostic kind of conceptual metaphor for this debate: those that have an asymmetric manifestation in language. The overall pattern of results is far from providing a clear picture.
The clearest case for unidirectional effects has been made for the relation of time to the domain of space. As mentioned above, time is talked about in terms of space more often than space is talked about in terms of time. Boroditsky (2000) reported that spatial primes were able to bias a subsequent temporal judgment, but that temporal primes did not succeed in biasing an analogous spatial judgment. Using nonlinguistic tasks (estimating either the length or duration of a growing line), Casasanto and Boroditsky (2008) observed clear effects of irrelevant spatial length on duration judgments, whereas irrelevant durations were unable to affect spatial judgments. Several manipulations intended to increase the saliency of time were also ineffective (see also Casasanto et al., 2010; for developmental data, and Merritt et al., 2010; for additional adult data). In a very interesting contrast with human data, Merritt et al. (2010) recently reported that monkeys do show bidirectional effects between space and time.
However, effects of temporal primes on spatial judgments have been found using a variety of paradigms and measures by Teuscher, McQuire, Collins, and Coulson (2008) and Ouellet, Santiago, Funes, and Lupiáñez (2010). The main problem of these cross-study comparisons to evaluate the degree of asymmetry of the effects is the diversity in tasks and measures. A closer procedural correspondence is found in the studies of two classic psychophysic effects, the Tau and Kappa effects, which suggest that both space and time can affect each other (Cohen, Hansel, & Sylvester, 1953; Helson & King, 1931; see Jones & Huang, 1982; for a review of the initial findings; for more recent studies, see Kawabe, Miura, & Yamada, 2008; Sarrazin, Giraudo, Pailhous, & Bootsma, 2004; Sarrazin, Giraudo, & Pittenger, 2007; Sarrazin, Tonnelier, & Alexandre, 2005). The standard task involves the sequential presentation of three stimuli at different spatial locations. This defines two spatial and two temporal intervals between stimuli. When the spatial intervals are unequal and participants are asked to adjust the temporal intervals until they seem equal, they are affected by the distance between the stimuli (the Kappa effect): A greater spatial interval is perceived as having a longer duration. Conversely, when the temporal intervals are unequal and participants are asked to make the spatial intervals equal, they are affected by the duration of the intervals (the Tau effect): A longer temporal interval seems to encompass a greater space. Nevertheless, to our knowledge no direct comparisons of effect sizes are available.
Emotional valence (positive–negative) and its relation to vertical space provide another interesting case to test, as emotions are often talked about in spatial terms (e.g., “I am feeling low today”), but the opposite pattern is not attested (e.g., “I am going happier,” meaning to go up). However, here we also find similar difficulties for symmetry comparisons in published studies: Meier and Robinson (2004) observed clear effects of an evaluative judgment on a subsequent spatial discrimination (Study 2), whereas no effects of a spatial discrimination were found on an evaluative judgment (Study 3). Unfortunately, the procedures of these two studies varied in crucial aspects and are not, therefore, directly comparable.
A better comparison is available for the relation between emotional valence and brightness, although this conceptual metaphor is not so asymmetrical in its linguistic manifestation: It is common both to talk about evaluations in terms of brightness (e.g., “the dark side”) and, to a certain extent, about brightness in terms of emotions (e.g., “she was dressed in sad colors”). Meier et al. (2004) asked their participants to judge either the affective evaluation of words (Study 1a) or the brightness of the words’ font (Study 4) in tasks otherwise identical. Brightness affected evaluative judgments, but evaluation did not affect brightness judgments, supporting asymmetric effects. However, in a different study, when Meier et al. (2007) made the brightness judgment more difficult, they did find an effect of evaluation on brightness.
If the clearest case for asymmetric effects comes from the study of time and space, the clearest case for symmetric effects comes from number magnitude and size. However, this conceptual projection is also highly symmetric in linguistic patterns, being common to talk about numbers in terms of size (e.g., “a large number”) as of size in terms of numbers (e.g., “a 25-ton truck”). When two numbers are compared, judgments of their magnitude are affected by their relative physical sizes (Besner & Coltheart, 1979). It is faster to judge that 2 is a smaller number than 6 when 2 is presented in small font and 6 in large font (2–6) than the opposite (2–6). The converse influence of numerical magnitude on judgments of physical size has also been reported (Henik & Tzelgov, 1982; see Pansky & Algom, 1999; for detailed references). Importantly, some studies have manipulated the relative discriminability and perceptual salience of numerical and size information within a single study (Fitousi & Algom, 2006; Pansky & Algom, 1999, 2002; Schwarz & Ischebeck, 2003). The more discriminable-salient dimension always had stronger effects on the less discriminable-salient dimension. When stimuli were matched in discriminability and salience, effects were completely symmetric in both directions.
Finally, studies including more than two dimensions in a single design are scarce, and their results puzzling. Pinel et al. (2004) assessed the influence of number, size, and brightness on each other. They observed that the dimensions of size and number, on one hand, and of size and brightness, on the other hand, showed symmetric interference. Size and number, as mentioned above, are often talked about in terms of each other in language, but size and brightness are never used to talk about each other. Moreover, number interfered with brightness judgments, but brightness did not interfere with number judgments, showing that it is also possible to find asymmetric effects between dimensions which show similar (in this case, null) frequencies of linguistic patterns. Note that such variations in the size of the effects in each direction cannot be explained by differences in neural overlap, as this construct is inherently symmetric.
To summarize, currently available evidence partially supports asymmetric conceptual congruency effects when the relevant conceptual metaphor also shows asymmetric linguistic manifestations, whereas the effects tend to be more symmetric as the patterns in language are also more symmetric. However, the issue is far from being settled, and there are clear exceptions to this rule (e.g., the Kappa effect and the interactions reported by Pinel et al., 2004), so available evidence does not clearly support either the metaphoric or the ATOM views. The evidence also points at several mediating factors, such as the relative saliency, discriminability or processing difficulty of the manipulated dimensions (see Santiago et al., 2011, for a review). Thus, available evidence succeeds in showing the limitations of both approaches: None of them postulates mechanisms that could account for conceptual congruency effects of varying sizes in the same task under different conditions.
Recently, Santiago et al. (2011) proposed a model that includes such mechanisms. This view defends a profound change in the way conceptual congruency effects have been interpreted so far. Instead of being taken as direct empirical indexes of the structure of long-term semantic memory representations, this view proposed that conceptual congruency effects arise because of interactions between the representations included in the working memory model of the current task. Thus, congruency interactions are indexes of working memory processes and representations, and only indirectly do they index long-term semantic representations. The theory proposes a view of working memory as consisting of mental models which are set up to deal with the task at hand and which are constrained to be as internally coherent as possible (thus the chosen name Coherent Working Models theory). It is proposed that all the elements of working models (including abstract conceptual dimensions) are represented as concrete perceptually based elements, either objects, properties, relations, or spatio-temporal dimensions. When abstract concepts have to be included in the model of the task, they take the form of concrete elements (e.g., when the task includes affective evaluation, this dimension may be introduced in the model as one of a number of possible concrete alternatives: a vertical spatial dimension, a brightness dimension, and so on). All elements vary in activation level, which is a weighted sum of the influence of a number of factors, including attentional cueing, task requirements, prior practice, salience, and discriminability. The constraint of internal coherence leads to interactions among the elements. Configurations which are not internally coherent (such as a word located in upper physical space and also in lower evaluative space) are more difficult to process. Such a nonoptimally coherent configuration will produce behavioral effects whenever the response is based on the less active dimension in the task (otherwise, the troublesome elements may be removed from the model). Santiago et al. (2011) describe and discuss the representational and processing assumptions of the theory in detail.
One central prediction from this view is that the manifestation and the directionality of congruency interactions may be manipulated by changing the level of activation of the interacting conceptual dimensions. For conceptual congruency effects to be observed, both dimensions must be part of the working model of the task, and the response must be based on the weaker dimension. If the dimension that guides responding is stronger, the irrelevant dimension will not be able to pose constraints on its processing, and it will probably be dropped altogether from the model and no congruency effect will be observed. If the level of activation of the irrelevant dimension is increased by any of many possible means, it will gain the ability of constraining the processing of the relevant dimension and the effect will be observed.
The aim of the present research is to assess the effect of one of the many ways in which such level of activation can be changed: attention. It is a well-established fact that attention can be directed to a stimulus either endogenously or exogenously (Jonides, 1981; Müller & Rabbitt, 1989; Posner, 1980). While endogenous attention is driven by instructions or by signals needing to be semantically processed, exogenous attention is automatically captured by aspects of the signal (abrupt onset, motion, sudden changes and so on). Together with a third system controlling the general level of vigilance or alertness, these are the attentional systems of the brain (Corbetta, Patel, & Shulman, 2008; Posner & Petersen, 1990). Our aim was to evaluate whether exogenous and endogenous attentional cues are an efficient modulating factor of conceptual congruency effects. In other words, we set up to assess whether it is possible to observe conceptual congruency effects when the level of activation of the irrelevant dimension is boosted by either exogenous or endogenous means, and whether this modulation varies depending on whether the irrelevant dimension is the more concrete or the more abstract one.
In the present experiments, we will use the vertical space-affective valence conceptual metaphor as our testbed, because it is a clear case in which asymmetric cross-domain effects are predicted by the Metaphor View. As discussed above, emotional valence is often talked about in vertical terms (e.g., “I’m feeling up,”“That boosted my spirits,”“My spirits rose,”“I fell into depression”; Lakoff & Johnson, 1980), but the opposite is never attested (e.g., “A happy mountain,” meaning a high mountain). In this respect, Spanish (the language in which the experiments were run) behaves exactly as English. Under the Metaphor View, effects of vertical space over evaluation judgments should be stronger than the reverse. Under the ATOM view, symmetric effects are expected. Only the Coherent Working Models theory predicts that attentional cueing will be able to control the presence–absence of the congruency effect.
In a well-known study, Meier and Robinson (2004, Study 1) found that the vertical location of a word on a screen (upper or lower) affects the speed of judging its valence (positive or negative). They suggested that this was a proof of the existence of a conceptual mapping between valence and vertical space in semantic memory. We will first try to replicate Meier & Robinson’s results (Experiment 1) and then show how they depend critically on the presence of an automatic (exogenous) attentional cue calling attention to word location (Experiment 2). Next, we will show how the same effect can be obtained by voluntarily (endogenously) directing attention to the vertical spatial axis (Experiment 3). We will then proceed to explore the effect in the opposite direction, from evaluative meaning on spatial processing (Experiments 4–6), without finding it. Finally, we will show how an attentional voluntary strategy succeeds in obtaining the effect in this opposite direction (Experiment 7).