Picture naming tasks are crucial for assessing language processing and lexical retrieval in both clinical and non-clinical populations [1-4]. Standardized tests like the Boston naming test [5], hundred picture naming test [6], renfrew word-finding test [7], and multilingual naming test [8] use black-and-white contour drawings, while others like the graded faces test [9] and graded buildings test [10] use either grayscale or colored images. However, there is no consensus in the literature on which type of image best supports naming performance in individuals across the lifespan. Visual confrontation naming is a multistage process where perceptual features like shape, color, and texture are encoded, matched with semantic representations, and then followed by lexical retrieval and articulation of the name [11,12]. Image complexity can impact naming performance even in individuals without neurological deficits [13].

Surface-based theories support that, factors such as color, texture, and brightness of an image impact the lexical retrieval. On the other hand, edge-based theories state that the contours of images, as reflected in line drawings, are sufficient for recognition and naming of objects [14]. Studies have shown that colored images improve naming accuracy and speed compared to black-and-white drawings [15-17], supporting surface-based over edge-based recognition theories [18,19]. In contrast, there are studies that reported adding color enrichment to images did not improve naming performance [20]. Performance in naming tests can also vary across ageing. Age-related declines in naming accuracy and latency are well-documented, often linked to slower cognitive processing rather than purely lexical deficits [21-23]. However, Rogalski, et al. [20] found no benefit of color enrichment of images on naming in both young and older adults. Tanaka and Presnell [19] showed that color of the image played a significant role in the naming of those items that were highly color diagnostic. Methodological differences between the studies (between-vs. within-subjects designs, stimulus selection, etc.) may explain the inconsistent results.

Theories of visual object recognition offer differing perspectives on the contribution of surface versus contour information. If surface properties such as color, brightness, and texture facilitate recognition by enriching perceptual encoding and providing stronger links to semantic memory [18,19], colored photographs should enhance naming performance yielding higher accuracy and faster latencies than black-and-white drawings. In contrast, if edge-based theories hold good, then contour information alone should be sufficient for recognition, yielding no systematic differences between recognition of colored and black-and-white images [4]. The present study evaluated if differences existed in the recognition of colored photographs versus black-and-white contour drawings, specifically for commonly used noun targets. A within-subjects manipulation of image type (color vs. black-and-white) was employed, enabling direct comparison of the same items across conditions while controlling for individual variability. The participants were stratified into four age groups spanning adolescence to older adulthood, each with equal sample sizes, allowing systematic analysis of both age effects and age × image type interactions. Guided by these theoretical and methodological considerations, the study tested the following hypotheses. Hypothesis 1 (H1) if surface-based theories hold well, participants will show higher accuracy and faster naming latencies for colored photographs compared to black-and-white drawings. H2 if edge-based theories are correct, no systematic differences will emerge between image types. H3 across both conditions, accuracy will decrease and latencies will increase with age, reflecting age-related slowing of lexical access. A secondary expectation, consistent with surface-based accounts, was that older adults may derive greater benefit from color cues as compensatory support. The current study explicitly tested these competing predictions and analyzed if accuracy and latency of visual confrontation naming varied when blackand-white drawings and colored photographs of common words are used for evaluating naming abilities in individuals across four age groups using a mixed factorial design.

This cross-sectional study was conducted in two phases: preparation of test materials and assessment of naming performance. The study was approved by the Institutional Ethics Committee of SRM Medical College Hospital and Research Centre, SRM Institute of Science and Technology (IEC no.: 8525/IEC2023). All procedures were in accordance with the ethical standards set by the ethics committee.

The details of participants are summarised in Table 1. All participants exhibited high cognitive functioning, with MMSE scores close to the maximum of 30. Inter-rater reliability for naming accuracy showed a perfect intraclass correlation coefficient (ICC) of 1.000. For naming latency, the ICC was 0.993 (95% confidence interval, 0.988 to 0.997), indicating excellent consistency and strong agreement between ratings.

Comparing naming accuracy between black-and-white contour drawings and colored photographs within each age group using Mann-Whitney U-tests revealed no statistically significant differences in accuracy in any of the age groups (Table 2). Kruskal-Wallis test examining the effects of age on naming accuracy revealed a statistical significance, H-statis-tics (3) = 19.36; p < 0.001, with a small to moderate effect size (ε2 = 0.081), with group-3 having the least accuracy. Itemwise analysis using chi-squared analysis (χ²) showed no significant difference (p > 0.05) in naming accuracy across the two conditions for any stimulus item.

The naming latencies for the two stimulus types within each age group was analyzed using independent-samples t-test, and the results are depicted in Table 3. Participants in group 1 (12~24 years) and group 2 (25~44 years) named items significantly faster in the BW over colored condition, p < 0.001. Participants in group 3 (45~60 years) showed no significant difference between the conditions (p = 0.907), while those in group 4 (61~75 years) showed a slight advantage for black-and-white images (p = 0.037). Mann-Whitney U-test comparing the item-wise naming latencies under both image conditions revealed significant differences (p ≤ 0.05) in latencies between the two conditions for 18 out of the 30 items, all of them favoring BW conditions (reduced latency). Even among the items that had no significant difference, only four items (Onion, Crane, Dragonfly, and Hen) had better median values in colored stimulus conditions. These differences suggest a potential facilitative effect of black-and-white imagery for most lexical items (Table 4).

Repeated-measures ANOVA examining the effect of individual items across groups and conditions revealed that the main effect of the item was not significant, F(29, 207) = 1.341; p = 0.124, indicating that item-level differences in naming latency were not substantial overall. However, a significant interaction between item and condition was observed, F(29, 207) = 1.652; p = 0.024, indicating that item-level latency was influenced by whether the images were shown in black-andwhite or color. Additionally, there was a significant interaction between item and group, F(87, 627) = 1.615; p = 0.001, suggesting that naming performance of specific items varied significantly across age groups, when the combined means of both conditions were analysed. Post hoc Bonferroni comparisons revealed significant item-age group effects in latency (Table 5). The 12~24 years group showed longer latencies for crane, crab, rabbit, and fan; the 46~60 years group for coconut and idly; and the 61~75 years group for leg, baby, and bed. These findings indicate that naming latency varies by both age and item characteristics.

This study examined the effect of image condition (blackand-white contour drawing vs. colored photograph) on naming performance across age groups using familiar nouns in Tamil. No significant differences in naming accuracy were found in any of the age groups between the image conditions, suggesting that shape cues alone are sufficient for recognition when stimuli are visually and lexically familiar [14,17,20]. Accuracy was notably lower in the 45~60 years age group, possibly reflecting transitional cognitive changes or attentional load [23]. In contrast, naming latencies favored black-and-white images across most age groups, with significant differences in 18 of 30 items. This suggests that contour drawings may facilitate quicker lexical access by reducing visual complexity and cognitive load [26,27]. Color offered small, non-significant advantages for visually complex items (Onion, Crane, Dragon-Fly, and Hen), but did not signifi-cantly enhance performance. The reason for this could be attributed to factors such as individual experiences, color diagnostic nature of the item, etc. It is possible that prototypical color features such as the white color of the crane, purple or brown skin of an onion, or the iridescent greenblue body of a dragonfly, or the red comb of a hen provide strong diagnostic cues, reducing ambiguity and narrowing lexical search, thereby facilitating slightly faster recognition, though not statistically significant. While this study focused on controlling the frequency and familiarity of the word, the stimulus items were not graded or controlled for the color diagnostic feature.

Findings support the use of black-and-white drawings in clinical and experimental naming tasks [5,20], given their perceptual clarity and reduced color bias [28]. Results based on naming accuracy and latency aligned with H2 (edgebased theory), showing that contour cues are sufficient for object recognition. Analysing the age-related effects partially supported H3 with a significant dip in naming accuracy in the 45~60 years age group. Minimal, non-significant advantages of color for very few complex items failed to support H1 (surface-based prediction). While colored photographs may enhance ecological validity, line drawings remain optimal for controlled assessments.

From a clinical perspective, these findings have direct implications for assessment and intervention practices. First, the results underscore the validity of using black-and-white line drawings in naming tests, particularly in standardized tools where perceptual clarity and control over visual features are crucial [5]. For populations with slowed processing speed (e.g., older adults, individuals with mild neurocognitive disorder), black-and-white images may provide a more reliable measure of lexical retrieval by reducing extraneous visual demands. Second, the findings caution against assuming that colored photographs necessarily enhance performance; while they may increase ecological validity in intervention contexts, their added visual detail may in fact slow retrieval. Finally, clinicians may still incorporate colored photographs for functional communication training in intervention context; however, line drawings appear optimal for diagnostic assessments requiring precise control of perceptual variables.

We recognise that future work would benefit from controlling for color diagnostic features of incorporated items and the use of systematic image-analysis techniques to ob-jectively equate visual parameters across conditions. Future studies could also account for factors such as education, stimulus complexity, semantic category, and cultural context, while extending investigations to clinical populations, including individuals with aphasia. Black-and-white contour drawing conditions facilitated faster response times, possibly reflecting underlying aspects of reduced cognitive load. By integrating quantitative image analyses like objective measures of visual complexity (e.g., pixel density, edge density) and real-time measures of visual attention like processing effort (e.g., eye-tracking), the evidence base could be further strengthened, positioning black-and-white contour drawings as a robust and clinically valuable tool.