Empirically grounding grounded cognition: the case of color.

Grounded cognition theories hold that the neural states involved in experiencing objects play a direct functional role in representing and accessing object knowledge from memory. However, extant data marshaled to support this view are also consistent with an opposing view that perceptuo-motor activations occur only following access to knowledge from amodal memory systems. We provide novel discriminating evidence for the functional involvement of visuo-perceptual states specifically in accessing knowledge about an object's color. We recorded event-related brain potentials (ERPs) while manipulating the visual contrast of monochromatic words ("lime") in a semantic decision task: responses were made for valid colors ("green") and locations ("kitchen") and withheld for invalid colors and locations. Low contrast delayed perceptual processing for both color and location. Critically, low contrast slowed access to color knowledge only. This finding reveals that the visual system plays a functional role in accessing object knowledge and uniquely supports grounded views of cognition.

Alive and grasping: stable and rapid semantic access to an object category but not object graspability.

How quickly do different kinds of conceptual knowledge become available following visual word perception? Resolving this question will inform neural and computational theories of visual word recognition and semantic memory use. We measured real-time brain activity using event-related brain potentials (ERPs) during a go/nogo task to determine the upper limit by which category-related knowledge (living/nonliving) and action-related knowledge (graspable/ungraspable) must have been accessed to influence a downstream decision process. We find that decision processes can be influenced by the living/nonliving distinction by 160ms after stimulus onset whereas information about (one-hand) graspability is not available before 300ms. We also provide evidence that rapid access to category-related knowledge occurs for all items, not just a subset of living, nonliving, graspable, or ungraspable ones, and for all participants regardless of their response speed. The latency of the N200 nogo effect by contrast is sensitive to decision speed. We propose a tentative hypothesis of the neural mechanisms underlying semantic access and a subsequent decision process.

Perceptual and motor attribute ratings for 559 object concepts.

To understand how and when object knowledge influences the neural underpinnings of language comprehension and linguistic behavior, it is critical to determine the specific kinds of knowledge that people have. To extend the normative data currently available, we report a relatively more comprehensive set of object attribute rating norms for 559 concrete object nouns, each rated on seven attributes corresponding to sensory and motor modalities-color, motion, sound, smell, taste, graspability, and pain-in addition to familiarity (376 raters, M = 23 raters per item). The mean ratings were subjected to principal-components analysis, revealing two primary dimensions plausibly interpreted as relating to survival. We demonstrate the utility of these ratings in accounting for lexical and semantic decision latencies. These ratings should prove useful for the design and interpretation of experimental tests of conceptual and perceptual object processing.

Projectors, associators, visual imagery, and the time course of visual processing in grapheme-color synesthesia.

In grapheme-color synesthesia, seeing particular letters or numbers evokes the experience of specific colors. We investigate the brain's real-time processing of words in this population by recording event-related brain potentials (ERPs) from 15 grapheme-color synesthetes and 15 controls as they judged the validity of word pairs ('yellow banana' vs. 'blue banana') presented under high and low visual contrast. Low contrast words elicited delayed P1/N170 visual ERP components in both groups, relative to high contrast. When color concepts were conveyed to synesthetes by individually tailored achromatic grapheme strings ('55555 banana'), visual contrast effects were like those in color words: P1/N170 components were delayed but unchanged in amplitude. When controls saw equivalent colored grapheme strings, visual contrast modulated P1/N170 amplitude but not latency. Color induction in synesthetes thus differs from color perception in controls. Independent from experimental effects, all orthographic stimuli elicited larger N170 and P2 in synesthetes than controls. While P2 (150-250ms) enhancement was similar in all synesthetes, N170 (130-210ms) amplitude varied with individual differences in synesthesia and visual imagery. Results suggest immediate cross-activation in visual areas processing color and shape is most pronounced in so-called projector synesthetes whose concurrent colors are experienced as originating in external space.

Close, but no garlic: Perceptuomotor and event knowledge activation during language comprehension.

Recent research has shown that language comprehension is guided by knowledge about the organization of objects and events in long-term memory. We use event-related brain potentials (ERPs) to determine the extent to which perceptuomotor object knowledge and event knowledge are immediately activated during incremental language processing. Event-related but anomalous sentence continuations preceded by single-sentence event descriptions elicited reduced N400s, despite their poor fit within local sentence contexts. Anomalous words sharing particular sensory or motor attributes with contextually expected words also elicited reduced N400s, despite being inconsistent with global context (i.e., event information). We rule out plausibility as an explanation for both relatedness effects. We show that perceptuomotor-related facilitation is not due to lexical priming between words in the local context and the target or to associative or categorical relationships between expected and unexpected targets. Overall our results are consistent with the immediate and incremental activation of perceptual and motor object knowledge and generalized event knowledge during sentence processing.

Metaphors are physical and abstract: ERPs to metaphorically modified nouns resemble ERPs to abstract language.

Metaphorical expressions very often involve words referring to physical entities and experiences. Yet, figures of speech such as metaphors are not intended to be understood literally, word-by-word. We used event-related brain potentials (ERPs) to determine whether metaphorical expressions are processed more like physical or more like abstract expressions. To this end, novel adjective-noun word pairs were presented visually in three conditions: (1) Physical, easy to experience with the senses (e.g., "printed schedule"); (2) Abstract, difficult to experience with the senses (e.g., "conditional schedule"); and (3) novel Metaphorical, expressions with a physical adjective, but a figurative meaning (e.g., "thin schedule"). We replicated the N400 lexical concreteness effect for concrete vs. abstract adjectives. In order to increase the sensitivity of the concreteness manipulation on the expressions, we divided each condition into high and low groups according to rated concreteness. Mirroring the adjective result, we observed a N400 concreteness effect at the noun for physical expressions with high concreteness ratings vs. abstract expressions with low concreteness ratings, even though the nouns per se did not differ in lexical concreteness. Paradoxically, the N400 to nouns in the metaphorical expressions was indistinguishable from that to nouns in the literal abstract expressions, but only for the more concrete subgroup of metaphors; the N400 to the less concrete subgroup of metaphors patterned with that to nouns in the literal concrete expressions. In sum, we not only find evidence for conceptual concreteness separable from lexical concreteness but also that the processing of metaphorical expressions is not driven strictly by either lexical or conceptual concreteness.

Semantic richness, concreteness, and object domain: an electrophysiological study.

Results from previous event-related potential (ERP) studies of semantic richness and concreteness effects have been mixed. Feature production norms have been used to derive one measure of semantic richness, the number of listed semantic features (NOF) for a given concept. Whereas some ERP studies have found evidence for a semantic richness continuum from abstract concepts, to concrete concepts with few features, to concrete concepts with several features, other studies have not. The present study assessed the effects of NOF (within concrete concepts) and concreteness (concrete vs. abstract concepts), on ERP amplitudes and behavioural decision latencies during a concrete/abstract decision task. It is important we also manipulated object domain, which has been found to influence ERP amplitude and topography. High and low NOF concepts were selected from animal and nonliving thing categories and all four conditions were matched on several potential confounds. We show that although decision latencies support a semantic richness continuum, electrophysiological activity does not. Whereas concrete concepts produce a larger negativity than abstract concepts, low NOF concepts are associated with larger negativities than high NOF concepts. We also replicate an increased posterior positivity for processing animal concepts, and report an interaction between object domain and semantic richness such that the NOF effect is larger within animal concepts.

Tracking real-time neural activation of conceptual knowledge using single-trial event-related potentials.

Empirically derived semantic feature norms categorized into different types of knowledge (e.g., visual, functional, auditory) can be summed to create number-of-feature counts per knowledge type. Initial evidence suggests several such knowledge types may be recruited during language comprehension. The present study provides a more detailed understanding of the timecourse and intensity of influence of several such knowledge types on real-time neural activity. A linear mixed-effects model was applied to single trial event-related potentials for 207 visually presented concrete words measured on total number of features (semantic richness), imageability, and number of visual motion, color, visual form, smell, taste, sound, and function features. Significant influences of multiple feature types occurred before 200ms, suggesting parallel neural computation of word form and conceptual knowledge during language comprehension. Function and visual motion features most prominently influenced neural activity, underscoring the importance of action-related knowledge in computing word meaning. The dynamic time courses and topographies of these effects are most consistent with a flexible conceptual system wherein temporally dynamic recruitment of representations in modal and supramodal cortex are a crucial element of the constellation of processes constituting word meaning computation in the brain.