Inês Bramão

The role of color information on object recognition: a review and meta-analysis.

In this study, we systematically review the scientific literature on the effect of color on object recognition. Thirty-five independent experiments, comprising 1535 participants, were included in a meta-analysis. We found a moderate effect of color on object recognition (d=0.28). Specific effects of moderator variables were analyzed and we found that color diagnosticity is the factor with the greatest moderator effect on the influence of color in object recognition; studies using color diagnostic objects showed a significant color effect (d=0.43), whereas a marginal color effect was found in studies that used non-color diagnostic objects (d=0.18). The present study did not permit the drawing of specific conclusions about the moderator effect of the object recognition task; while the meta-analytic review showed that color information improves object recognition mainly in studies using naming tasks (d=0.36), the literature review revealed a large body of evidence showing positive effects of color information on object recognition in studies using a large variety of visual recognition tasks. We also found that color is important for the ability to recognize artifacts and natural objects, to recognize objects presented as types (line-drawings) or as tokens (photographs), and to recognize objects that are presented without surface details, such as texture or shadow. Taken together, the results of the meta-analysis strongly support the contention that color plays a role in object recognition. This suggests that the role of color should be taken into account in models of visual object recognition.

Electrophysiological correlates of impaired reading in dyslexic pre-adolescent children

In this study, event related potentials (ERPs) were used to investigate the extent to which dyslexics (aged 9-13 years) differ from normally reading controls in early ERPs, which reflect prelexical orthographic processing, and in late ERPs, which reflect implicit phonological processing. The participants performed an implicit reading task, which was manipulated in terms of letter-specific processing, orthographic familiarity, and phonological structure. Comparing consonant- and symbol sequences, the results showed significant differences in the P1 and N1 waveforms in the control but not in the dyslexic group. The reduced P1 and N1 effects in pre-adolescent children with dyslexia suggest a lack of visual specialization for letter-processing. The P1 and N1 components were not sensitive to the familiar vs. less familiar orthographic sequence contrast. The amplitude of the later N320 component was larger for phonologically legal (pseudowords) compared to illegal (consonant sequences) items in both controls and dyslexics. However, the topographic differences showed that the controls were more left-lateralized than the dyslexics. We suggest that the development of the mechanisms that support literacy skills in dyslexics is both delayed and follows a non-normal developmental path. This contributes to the hemispheric differences observed and might reflect a compensatory mechanism in dyslexics.

The impact of reading and writing skills on a visuo-motor integration task: A comparison between illiterate and literate subjects

Previous studies have shown a significant association between reading skills and the performance on visuo-motor tasks. In order to clarify whether reading and writing skills modulate non-linguistic domains, we investigated the performance of two literacy groups on a visuo-motor integration task with non-linguistic stimuli. Twenty-one illiterate participants and twenty matched literate controls were included in the experiment. Subjects were instructed to use the right or the left index finger to point to and touch a randomly presented target on the right or left side of a touch screen. The results showed that the literate subjects were significantly faster in detecting and touching targets on the left compared to the right side of the screen. In contrast, the presentation side did not affect the performance of the illiterate group. These results lend support to the idea that having acquired reading and writing skills, and thus a preferred left-to-right reading direction, influences visual scanning.

The Influence of Color Information on the Recognition of Color Diagnostic and Noncolor Diagnostic Objects

ABSTRACT In the present study, the authors explore in detail the level of visual object recognition at which perceptual color information improves the recognition of color diagnostic and noncolor diagnostic objects. To address this issue, 3 object recognition tasks with different cognitive demands were designed: (a) an object verification task; (b) a category verification task; and (c) a name verification task. The authors found that perceptual color information improved color diagnostic object recognition mainly in tasks for which access to the semantic knowledge about the object was necessary to perform the task; that is, in category and name verification. In contrast, the authors found that perceptual color information facilitates noncolor diagnostic object recognition when access to the objects structural description from long-term memory was necessary—that is, object verification. In summary, the present study shows that the role of perceptual color information in object recognition is dependent on color diagnosticity.

The Interaction between Surface Color and Color Knowledge: Behavioral and Electrophysiological Evidence.

In this study, we used event-related potentials (ERPs) to evaluate the contribution of surface color and color knowledge information in object identification. We constructed two color-object verification tasks - a surface and a knowledge verification task - using high color diagnostic objects; both typical and atypical color versions of the same object were presented. Continuous electroencephalogram was recorded from 26 subjects. A cluster randomization procedure was used to explore the differences between typical and atypical color objects in each task. In the color knowledge task, we found two significant clusters that were consistent with the N350 and late positive complex (LPC) effects. Atypical color objects elicited more negative ERPs compared to typical color objects. The color effect found in the N350 time window suggests that surface color is an important cue that facilitates the selection of a stored object representation from long-term memory. Moreover, the observed LPC effect suggests that surface color activates associated semantic knowledge about the object, including color knowledge representations. We did not find any significant differences between typical and atypical color objects in the surface color verification task, which indicates that there is little contribution of color knowledge to resolve the surface color verification. Our main results suggest that surface color is an important visual cue that triggers color knowledge, thereby facilitating object identification.

Object naming in dyslexic children: more than a phonological deficit

ABSTRACT In the present study, the authors investigate how some visual factors related to early stages of visual-object naming modulate naming performance in dyslexia. The performance of dyslexic children was compared with 2 control groups—normal readers matched for age and normal readers matched for reading level—while performing a discrete naming task in which color and dimensionality of the visually presented objects were manipulated. The results showed that 2-dimensional naming performance improved for color representations in control readers but not in dyslexics. In contrast to control readers, dyslexics were also insensitive to the stimuluss dimensionality. These findings are unlikely to be explained by a phonological processing problem related to phonological access or retrieval but suggest that dyslexics have a lower capacity for coding and decoding visual surface features of 2-dimensional representations or problems with the integration of visual information stored in long-term memory.

Lexical and sublexical orthographic processing: An ERP study with skilled and dyslexic adult readers

This ERP study investigated the cognitive nature of the P1-N1 components during orthographic processing. We used an implicit reading task with various types of stimuli involving different amounts of sublexical or lexical orthographic processing (words, pseudohomophones, pseudowords, nonwords, and symbols), and tested average and dyslexic readers. An orthographic regularity effect (pseudowords-nonwords contrast) was observed in the average but not in the dyslexic group. This suggests an early sensitivity to the dependencies among letters in word-forms that reflect orthographic structure, while the dyslexic brain apparently fails to be appropriately sensitive to these complex features. Moreover, in the adults the N1-response may already reflect lexical access: (i) the N1 was sensitive to the familiar vs. less familiar orthographic sequence contrast; (ii) and early effects of the phonological form (words-pseudohomophones contrast) were also found. Finally, the later N320 component was attenuated in the dyslexics, suggesting suboptimal processing in later stages of phonological analysis.

Lexical and Phonological Processes in Dyslexic Readers: Evidence from a Visual Lexical Decision Task

The aim of the present study was to investigate whether reading failure in the context of an orthography of intermediate consistency is linked to inefficient use of the lexical orthographic reading procedure. The performance of typically developing and dyslexic Portuguese-speaking children was examined in a lexical decision task, where the stimulus lexicality, word frequency and length were manipulated. Both lexicality and length effects were larger in the dyslexic group than in controls, although the interaction between group and frequency disappeared when the data were transformed to control for general performance factors. Children with dyslexia were influenced in lexical decision making by the stimulus length of words and pseudowords, whereas age-matched controls were influenced by the length of pseudowords only. These findings suggest that non-impaired readers rely mainly on lexical orthographic information, but children with dyslexia preferentially use the phonological decoding procedure--albeit poorly--most likely because they struggle to process orthographic inputs as a whole such as controls do. Accordingly, dyslexic children showed significantly poorer performance than controls for all types of stimuli, including words that could be considered over-learned, such as high-frequency words. This suggests that their orthographic lexical entries are less established in the orthographic lexicon.

Electrophysiological evidence for colour effects on the naming of colour diagnostic and noncolour diagnostic objects

In this study, we investigated the level of visual processing at which surface colour information improves the naming of colour diagnostic and noncolour diagnostic objects. Continuous electroencephalograms were recorded while participants performed a visual object naming task in which coloured and black-and-white versions of both types of objects were presented. The black-and-white and the colour presentations were compared in two groups of event-related potentials (ERPs): (1) The P1 and N1 components, indexing early visual processing; and (2) the N300 and N400 components, which index late visual processing. A colour effect was observed in the P1 and N1 components, for both colour and noncolour diagnostic objects. In addition, for colour diagnostic objects, a colour effect was observed in the N400 component. These results suggest that colour information is important for the naming of colour and noncolour diagnostic objects at different levels of visual processing. It thus appears that the visual system uses colour information, during naming of both object types, at early visual stages; however, for the colour diagnostic objects naming, colour information is also recruited during the late visual processing stages.

The Contribution of Color to Object Recognition

The cognitive processes involved in object recognition remain a mystery to the cognitive sciences. We know that the visual system recognizes objects via multiple features, including shape, color, texture, and motion characteristics. However, the way these features are combined to recognize objects is still an open question. The purpose of this contribution is to review the research about the specific role of color information in object recognition. Given that the human brain incorporates specialized mechanisms to handle color perception in the visual environment, it is a fair question to ask what functional role color might play in everyday vision. Humans possess trichromatic color vision that most likely developed for specialized uses. For instance, color vision could be used to detect ripe fruit against a background of foliage (Gegenfurtner, 2003; Surridge, Osorio, & Mundy, 2003). Traditionally, theories of object recognition suggest that objects are recognized based on shape information, largely ignoring the role of color information (Biederman, 1987; Marr & Nishihara, 1978). However, more recently, a large body of behavioral, functional neuroimaging, and neurophysiological evidence suggests that color information make an important contribution to object recognition (for a review, see Tanaka, Weiskopf, & Williams, 2001). In the first part of this chapter we discuss the relevance of research on color effects in object recognition, while reviewing the neural mechanisms that support color perception. In the second part of the chapter we present a review of the literature exploring the color effects on object recognition and we discuss some apparently contradictory results described in the scientific literature. We also present the main results of a meta-analysis in which the behavioral literature on the effect of color in object recognition has been explored and integrated (Bramao, Reis, Petersson, & Faisca, 2011). In the third section, we review some of our own behavioral and electrophysiological data that might explain some of the conflicting results found in the literature, and we discuss the level at which color information might contributes to object recognition. We argue that the color effects in object recognition depend on the color diagnosticity status of the specific objects.