No matter how: Top-down effects of verbal and semantic category knowledge on early visual perception

Abstract

Language is assumed to augment human cognition. But can language also affect basic mechanisms of perception, suggesting cognitive penetrability of perception? This idea is highly controversial: linguistic categorization may induce top-down effects on ongoing perceptual processing. Alternatively, such effects may not concern perception proper, but pre-perceptual shifts of attention or downstream processes, such as perceptual judgment. This study provides a critical test of these views by investigating categorical perception (CP) of novel objects in a balanced learning design, controlling for perceptual experience and low-level visual differences. To better understand which linguistic representations induce CP, we manipulated the type of information categories were based on: bare verbal labels, in-depth semantic knowledge, or the combined information from labels associated with semantic knowledge. We used event-related brain potentials (ERPs) derived from the EEG in a visual search task to localize CP effects at perceptual or pre/post-perceptual stages. The results replicated behavioral CP with facilitated visual search when target and distractors belonged to different linguistic categories. ERPs revealed CP effects in the P1 and N1 components, associated with early visual processing. Attentional selection, reflected in the N2, also was influenced by linguistic categories. The N2 and the N400, a measure of high-level semantic processing, were sensitive to the depth of semantic knowledge associated with objects. CP, however, did not differ between category types, suggesting that any linguistic categorization can lead to CP. The findings support cognitive penetrability of perception, with linguistic categories informing perceptual predictions down to the processing of low-level visual features.

Conceptual knowledge affects early stages of visual mental imagery and object perception

“…Yet, the time course of imagery and the timing of the involvement of early visual cortex are still open questions. In line with predictive processing accounts one hypothesis holds that perception engages top-down predictions even during low-level processing 25,26,31,47 , and that imagery might share this mechanism.…”

“…This theoretical framework is neurally plausible 15-20 and supported by evidence that even early stages of perception are subject to top-down influences 15,[21][22][23][24][25][26][27][28][29][30][31] . This suggests that initial aspects of imagery could be fast enough to generate early top-down effects.…”

“…The fact that we find the same knowledge effects on the P1 in imagery and perception also teaches us something relevant about perception. Recently, the debate if there are any true top-down effects on perception has sparked new controversy 25,[62][63][64] . Here we show semantic top-down influences on early visual processing in the absence of the relevant physical stimulus.…”

“…Indeed, imagery and perception recruit overlapping neural circuits, including primary visual areas 1-8 , and the vividness of imagination correlates with the similarity of brain activities accompanying imagery and perception 9 . Predictive processing accounts posit that perception arises from hierarchical Bayesian predictions-essentially imaginations-that are constrained by bottom-up sensory input 10-14 .This theoretical framework is neurally plausible 15-20 and supported by evidence that even early stages of perception are subject to top-down influences 15,[21][22][23][24][25][26][27][28][29][30][31] . This suggests that initial aspects of imagery could be fast enough to generate early top-down effects.This suggestion contrasts with alternative accounts assuming that perception first runs through a strictly hierarchical succession of increasingly complex visual representations, with early stages mainly driven by bottom-up sensory processes.…”

“…This is achieved by manipulating the semantic knowledge associated with a given object. Knowledge stored in semantic memory, for example, about the functions of objects 24,27,31,46 , and categories defined by the language we speak 25,26,28,[47][48][49] , have all been shown to influence early visual processes.…”