Ready, set, yellow! color preference of Indian free-ranging dogs

Abstract

Most of the research on color vision related behaviors in dogs has involved training the dogs to perform visual discrimination tasks. We investigated the importance of color to untrained Indian free-ranging dogs (FRDs). Using one-time multi-option choice tests for color preference in 134 adult dogs, we found the dogs to prefer yellow objects over blue or gray ones while there was no preference between blue and gray. We next pitted a yellow object against a gray object that had food. Here, the dogs ignored the food (biscuit or chicken) to approach the yellow object first indicating the color preference to be quite strong. Color preference has previously been investigated in many other animals and has implications for behaviors like mate choice and foraging. Our study provides a new perspective into the ecology of Indian FRDs and might have implications for companion dogs as well, if they too show this preference.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10071-024-01928-9.

Highlights

Indian free-ranging dogs (FRDs) show preference for the color yellow over blue and gray.

Indian FRDs show no preference between blue and gray colors.

Attraction towards a yellow object can be stronger than attraction towards food rewards for Indian FRDs.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10071-024-01928-9.

Introduction

Color vision and color preference have been subjects of research for over a century (reviewed by Staples 1931). Decades of research have confirmed color vision in most vertebrates and arthropods (Baden and Osorio 2019; Kelber et al. 2003; Yilmaz et al. 2022). The presence of color vision in a species does not automatically suggest the presence of color preference, but to have color preference, the faculty of color vision is essential. There are multiple biological underpinnings for color preference, which may vary from species to species, while color vision essentially requires just the presence of cone cells (Kelber et al. 2003). Color preference has been found in many animals across myriad taxa. Humphrey (1971 & 1972) investigated color preference of Rhesus monkeys and found the monkeys to demonstrate a preference for different hues and brightness of colored fields just like they prefer the content of one picture over another. Humphrey (1972) suggested interest (towards the content of stimulus pictures) and pleasure (reaction to hue and brightness) to be the two drivers of the monkeys’ visual preference. Preference towards colors on an animal’s body is often linked with mate choice (reviewed by Higham and Winters 2016). Burley (1982, 1986) found zebra finches to prefer conspecific body colors (species confidence) in their leg bands, which affected the birds’ mate choice. However, Wang et al. (2018) noted that zebra finch color preference has had poor replication across studies, and hitherto observed significant results might not be generalizable at a species level.

Ecological valence or the usual role of a particular color in an animal’s life, has been suggested as another driver for color preference (Palmer & Schloss, 2010). Several studies have explored the psychological impact of colors which are often linked with ecological valence (reviewed by Elliot 2015). It is postulated that the redness of primate faces being an indicator of health and mood might have been a driver for primates developing red-green color vision (Changizi et al. 2006). Preference of bowerbirds (Amblyornis inornatus) towards colors of decorative objects (they decorate their bowers with colorful objects - both natural and human-made) seem to be culturally transmitted, which means color preference varies across populations of the same species located in different areas, whereas within population the patterns appear quite similar (Diamond 1986). In summary, color preference is a widespread phenomenon. It can be both innate or learned, and in some cases, might be driven by what the color usually signifies in an animal’s life.

In dogs (Canis lupus familiaris), color vision was established by Neitz et al. (1989) who characterized their cone cell activities to peak at 429 nm and 555 nm, indicating a dichromatic color vision (blue-yellow spectrum) similar to red-green colorblind humans. Further behavioral study (Siniscalchi et al. 2017), electroretinogram photometry (Jacobs et al. 1993), and topographical study of retinal cone cells (Mowat et al. 2008) have solidified our understanding of dog color vision and it is now possible to digitally simulate a dog’s vision (Pongrácz et al. 2017: https://dog-vision.andraspeter.com). However, all behavioral research related to canine color cognition so far has been focused on color discrimination tasks after a period of training: to mainly understand the limits of canine color vision (Byosiere 2018, Kasparson et al. 2013; Tanaka et al. 2000). It was hitherto unknown if and how untrained dogs are affected by color cues in their environment. The only available direct research on this topic is a non-peer-reviewed article on canine color preference regarding chew toys by Wong (2007) where the dogs had prior experience with chew toys of unreported colors. Cimarelli et al. (2023), as part of another experiment, investigated preference of Moroccan FRDs for blue and yellow colored objects and found no preference. However, this experiment was not specifically designed to test color preference, and one of the used objects had white patterns on it. Thus, a specific color preference experiment is still needed.

The question of usefulness of color cues is especially important for FRDs, as unlike companion dogs, they are not under direct human supervision (Serpell 1995), and they need to make numerous important decisions daily in order to survive. It is possible that each available cognitive ability, including color vision, is important to these dogs even though their sense of smell is highly sensitive (Beaver 2009; Hayes et al. 2018; Kokocińska-Kusiak et al. 2021). Notably, olfactory cues are limited by wind directions and the slow nature of diffusion (Fick, 1885). Visual cues thus might be much more reliable for a quick introductory assessment of an object. Indian FRDs are primarily scavengers of human-generated waste (Bhadra et al. 2015; Biswas et al. 2024) from garbage dumps and bins that are often overwhelmingly smelly (personal observation) and can demand utilization of visual cues. Previous work with FRDs suggests that FRDs use both visual and olfactory cues during scavenging, though the decision to eat something is mostly guided by a Rule of Thumb “If it smells like meat, eat it” (Bhadra et al. 2015; Sarkar et al. 2019). There already is experimental evidence (Polgár et al., 2015) that companion dogs can fail to use olfaction for approach-based decision-making if their distance from the object is too great (3 m). It is not impossible that reliance on olfaction breaks down in other contexts as well.

Around the mid-2010s, India saw a craze of “blue bottles” where people were keeping plastic bottles filled with indigo-dyed water around their houses, in the hope of keeping FRDs away (Jaipuriar 2016). Masih and Bhadra (2019, unpublished) found that FRDs in and around Kolkata, West Bengal, did not show any specific response towards the bottles. However, people’s attempt at modifying dog behavior by use of color acted as a seed towards our exploration of color preference.

We carried out choice tests with FRDs in India to test if they have any color preferences. In Experiment 1, we used yellow, blue, and gray colors as they are the hues visible to dogs. Under null hypothesis, each color should be chosen a similar number of times. After finding the dogs’ preferred color, in Experiment 2, we gave them a choice between their non-preferred colors to find out their secondary preference, if any. We conducted Experiment 3 to ensure only the color, not the smell of the painted options were dictating the dogs’ preference. Further, to ascertain whether this preference affects the dogs in their usual lives at all, in Experiment 4 (4a and 4b) we tested the strength of their color preference by pitting their preferred color against a food reward. If dogs ignore food and approach their preferred color instead, they risk losing a vital resource. We hypothesize that the dogs would ignore their preferred color and approach the food first if the amount and type of food is attractive enough to them.

Materials and methods

Subjects, locations, and time

The experiments were conducted in urban, semi-urban, and rural locations in Nadia and North 24 Parganas districts, and the city of Kolkata in West Bengal, India (details available in Online Resource 1). A total of 458 visibly fit adult FRDs successfully participated in the experiments. The sexes of the dogs were noted visually based on to their genitals. To avoid learning bias due to repetitions, each dog was tested only once, and we did not test dogs that had observed others participate in the experiment. We chose new experiment locations each day to avoid repeating dogs by mistake. All trials were done in daylight and all the options (bowls) in one trial were placed equally under direct sunlight, or equally in shade to ensure they were under the same lighting conditions.

General experimental protocol

The general protocol followed the one-time multi-option choice test (OTMCT) module described by Bhadra and Bhadra (2014). We used different colored terracotta bowls as the options. Two experimenters conducted each experiment. On different days, different people acted as experimenter 1 and 2. While traveling on the streets of the aforementioned locations, when an FRD was located, experimenter 1 approached the dog with the experimental setup (see below). At about 1.5–2 m from the dog, the experimenter vocalized positively towards the dog (Bhattacharjee et al. 2017) and placed the setup on the ground in a way that would keep the options approximately equidistant from the dog. Then, experimenter 1 slowly backed away a few steps and assumed a neutral pose. The experimenter avoided making eye contact with the dog. Experimenter 2 video-recorded the whole experiment for later analysis. A trial was deemed unsuccessful if the dog did not initiate an approach within 1 min, or if the dog showed clear disinterest (e.g., going away from the area, closing its eyes and lazing). In case multiple dogs were present nearby, a trial was considered successful if no other dog came near the focal dog or the setup before the choice was made.

In each trial, the order of the bowls (which colors are at left, right, or center) was randomized, and all trials happened with fresh bowls, i.e., the bowls were cleaned with water after each trial to remove any scent from previous dogs before being used again in a trial. Whichever bowl a dog investigated (nose within about 5 cm of a bowl) first, was taken as that dog’s choice. AR coded all the videos and rechecked the data twice more for possible errors.

General experimental setup

The terracotta bowls used in the experiments were all of a similar make with a diameter of 12.58 ± 0.46 cm, and height of 4.70 ± 0.23 cm. A total of 42 bowls were used. We colored these bowls using Fevicryl^® Acrylic paint. Three sets of bowls were created with the following paints: golden yellow, Prussian blue, and gray (manually created by mixing black and white). A cardboard platform (70 cm x 17 cm), made waterproof with brown packing tape, was used as a base to allow one person to present three equidistant bowls to a dog. The bowls (yellow, blue, and gray) were placed approximately 15–16 cm apart on this platform for the three-choice experiment (Fig. 1) which has been further detailed about in Experiment 1. We performed three other two-choice experiments which are discussed in Experiments 2, 3, and 4. In these three experiments, the bowls were presented approximately 50 cm apart. The cardboard platform was not used in Experiments 2 and 4 since the two bowls could be easily presented by hand.

Fig. 1.

An FRD approaching the three-choice setup in Experiment 1 that has blue, yellow, and gray (left to right) bowls

Statistical analysis

All statistical analyses were performed with R (R core team 2022) in RStudio (RStudio 2019). The following packages were used for analysis and presentation: ggplot2 (Wickham 2016), data.table (Barrett et al. 2023), and DescTools (Signorell 2023). We performed contingency χ² tests for comparing frequency of first choices between conditions and goodness of fit χ² tests for comparing observation of one condition against a null (chance) expectation. Alpha for all tests was set at 0.05 and it was adjusted according to Bonferroni correction for multiple comparisons. In the graphs, the whiskers on the bar plots show 95% Wilson’s confidence interval (Wilson 1927) for estimating the population value of variables from our sample values by assuming a binomial distribution around our observations. We report Cramér’s V (Cramér 1946) as the effect sizes of the χ² tests.

Experiment 1: three-choice experiment with yellow, blue, and gray bowls

For our initial test of color preference, we used yellow, blue, and gray since these are the three hues visible to dogs (Fig. 1). This experiment had two conditions. In the “with_food” condition, each bowl had an equal amount of food- a 1/4th piece of a Brittania^® Marie Gold^® biscuit. In the “no_food” condition, no bowl had any food. See Online Resource 2 for video of the experiment.

We successfully tested 76 dogs (50 males, 26 females) for the “with_food” and 58 dogs (27 males and 31 females) for the “no_food” condition. 45 and 52 dogs respectively were presented with the setup but they made no choice. A total of 34 “with_food” and 13 “no_food” trials had to be discarded because they did not meet all experimental criteria (all bowls not being equidistant to the dogs, interference from other dogs or humans, experimenter failing to maintain a neutral posture, experimenter placing the setup too close to the dog). No difference was observed for the first choice between the two conditions (Data: Online Resource 3, contingency χ² = 0.219, N = 134, df = 2, p = 0.896), and thus, the data were pooled for further analysis. Overall, yellow emerged as the most preferred color (Fig. 2, goodness of fit χ² = 25.134, N = 134, df = 2, p < 0.001, Cramér’s V = 0.433).

Fig. 2.

The bars denote observed frequency of choice in Experiment 1, converted to percentage. The whiskers show Wilson’s 95% CI around the observations. Different letters atop bars denote significant difference at α = 0.05

The preferred color was not different for male and female dogs (Data: Online Resource 4, contingency χ² = 1.938, df = 2, p = 0.379). The relative positions of the chosen bowls (left, right, or center) had no significant effect on the choice of color (Data: Online Resource 4, contingency χ² = 3.884, df = 4, p = 0.422).

Experiment 2: two-choice experiment with blue and gray bowls

To identify any second preference, a two-choice test was done between blue and gray. The same blue and gray bowls as described earlier were used. The bowls were placed about 50 cm away from each other. Since presence of food did not affect the choice in the previous experiment, all trials in this experiment were the “with_food” condition only. See Online Resource 5 for video of the experiment. We successfully tested 102 dogs (52 females, 47 males, and 3 dogs of unknown sex) where blue was chosen 44 times and gray was chosen 58 times. There was no significant preference for any of these colors (goodness of fit χ² = 1.921, df = 1, p = 0.165). A total of 21 dogs did not make a choice when presented with the setup, and 19 trials were discarded for not meeting all experimental criteria.

Experiment 3: Control for the smell of paint with yellow and blue bowls, both covered with sieves

Since different paints (although the same brand and thus hopefully the same volatiles) were used to paint the bowls, it was important to make sure that the dogs were making their choice based on the visual cue of the paint and not the olfactory cue. Therefore, we painted two sets (blue and yellow) of terracotta bowls only on the outside and covered them with magenta colored plastic sieves (Fig. 3). This way we made sure all visual cues of the paint were blocked, but the smell could still permeate through the porous sieve. The covered bowls were placed on the same cardboard platform with about 50 cm separation. See Online Resource 6 for video of the experiment.

Fig. 3.

The setup for Experiment 3: control for the smell of paint. Blue and yellow colored bowls are present, but not visible, under the pink and white sieves. The porous portion (white) of the sieves allow smell of the paint to pass through

We successfully tested 54 dogs (29 females, 25 males). 27 dogs did not make a choice when presented with the setup and 10 trials were discarded for not meeting all experimental criteria. Blue was chosen 31 times and yellow was chosen 23 times. The observations did not significantly differ from chance (goodness of fit χ² = 1.185, df = 1, p = 0.2763).

Experiment 4a: strength of preference control: with two yellow bowls, one of which has food

The strength of preference experiment was devised to compare the dogs’ attraction towards yellow, against their attraction towards food which was associated with gray, a non-preferred color. The same bowls as before were used for this experiment, but to ensure the highest visibility of food, the bowls were upturned, and the food was placed on top of the upturned bowl (see Online Resources 7 & 8 for videos of the experiment). While presenting, the distance between the bowls was about 50 cm.

The piece of biscuit being used in our experiments was quite small (a quarter of a circle with approximately 3 cm radius) and while FRDs do eat carbohydrates, they prefer meat (Bhadra and Bhadra 2014; Bhadra et al. 2015; Sarkar et al. 2019). Thus, for the experiment to work as intended, it was important to ensure that the dogs indeed prefer to choose the biscuit over an empty bowl when the color of the two bowls are the same. We chose both bowls to be yellow because the brownish biscuit is most camouflaged against the yellow bowl and so if the dogs can identify and choose it, they should have no problem choosing it when it is atop a more contrasting gray bowl. Thus, the two options for the control trials were both yellow bowls, only one of which had a piece of biscuit on it. We successfully tested 54 dogs (20 females, 33 males, and 1 dog of unknown sex). When presented with the setup, 3 dogs did not make a choice and 6 trials were discarded for not meeting all experimental criteria. The bowls with food (biscuits) were chosen 35 times while bowls with no food were chosen 19 times (goodness of fit χ² = 4.740, df = 1, p = 0.029, Cramér’s V = 0.296).

Experiment 4b: strength of preference: “no_food” yellow bowl vs. “with_food” gray bowl

Here, we kept a piece of food on the gray bowl in a similar fashion to the control, while the yellow bowl was kept empty, thereby offering the dogs a choice between food and their preferred color. There were two conditions: (a) where the food was a piece of biscuit as mentioned before, and (b) where the food was a ~ 15 g piece of raw chicken. See Online Resources 7 and 8 for videos of the experiment. Different sets of dogs participated in Experiment 4a and 4b to avoid any bias due to learning.

We successfully tested 52 dogs (20 males, 32 females) with biscuits as food (Fig. 4). The gray bowl with food was chosen 11 times while the empty yellow bowl was chosen 41 times (goodness of fit χ² = 17.308, df = 1, p < 0.001, Cramér’s V = 0.576). In this condition, 8 dogs made no choice when presented with the setup and 6 trials were discarded for not meeting all experimental criteria. When the food was ~ 15 g of chicken, the empty yellow bowl was chosen 47 times out of 61 successful trials (28 males, 33 females, different dogs than the biscuit condition), while the gray bowl with chicken was chosen 14 times (goodness of fit χ² = 17.852, df = 1, p < 0.001, Cramér’s V = 0.540). Here, 7 dogs made no choice upon being presented with the setup and 10 trials were discarded for not meeting all experimental criteria.

Fig. 4.

Results of the strength of preference experiments (3.4). The columns denote observed frequency of choice, converted to percentage. The whiskers show Wilson’s 95% CI around the observations. Different letters atop bars (a or b) denote significant difference between choices under each experiment condition (goodness of fit χ²) and the different numbers atop the graphs (1 or 2) denote significant difference between experiment conditions (contingency χ²)

There was no significant difference between the biscuit group and the chicken group (contingency χ² = 4.05*10^-6, df = 1, p = 0.99), and each of these groups was significantly different than the control group (contingency X² tests, control and biscuit: χ² = 18.819, df = 1, p < 0.001, Cramér’s V = 0.421; control and chicken: χ² = 18.852, df = 1, p < 0.001, Cramér’s V = 0.404). With Bonferroni correction, the alpha for these three tests was at 0.017.

Discussion

Experiment 1 with the three choices revealed a preference for yellow over blue or gray in the FRDs, rejecting the null hypothesis of no color preference. We failed to reject the null hypothesis of there being no preference between blue and gray in Experiment 2. We had hypothesized the dogs would ignore their preferred color if there was attractive enough food associated with a non-preferred color. Experiment 4b shows that even ~ 15 g pieces of chicken are not enough for FRDs to ignore nearby yellow objects and thus we fail to reject this null hypothesis. Further experiments with greater amount of chicken are needed to test this hypothesis but that is beyond our current capacity. However, in earlier experiments, FRDs have been found to prefer even trace amounts of chicken over carbohydrates in choice tests (Bhadra and Bhadra 2014; Bhadra et al. 2015; Sarkar et al. 2019).

The dogs often explored all the bowls presented in Experiment 1 (three choice), and in the case of the two-choice set-up of blue versus gray (Experiment 2), they still approached the setup. In the strength of preference experiment (Experiments 4a and 4b), they frequently bee-lined to yellow even when the gray bowl had food in it and the yellow one did not. Together, these results lead us to the conclusion that the observed preference for yellow is a result of attraction towards yellow, and not due to repulsion towards other colors.

In the three-choice experiment (Experiment 1), the presence of food in the bowls did not affect the preferences while the dogs were more inclined (as per absolute numbers, the difference is not statistically significant) to participate when food was involved with the setup. Thus, in Experiments 2 and 3 only “with_food” trials were done.

In Experiment 3, control for paint smell, the amount of paint was half of what was used in other experiments since the top of the bowls were not painted to ensure zero visibility. However, since the participating dogs were not previously exposed to any of the setups used in any of these experiments, the task was a simple test of smell preference and should be unaffected by the amount of the paint and its odor.

Banerjee and Bhadra (2019) previously found Indian FRDs to prefer higher quantities of chicken based on olfactory cues. The dogs were not fooled when deceptive visual cues (spreading the pieces of chicken salami apart to show more counts of pieces, while the other option had the same amount, but stacked together as one piece) were used to inflate the amount of chicken present. The same preference however was absent when the food was biscuits. The dogs chose randomly between options of more amount of biscuits and less amount of biscuits. This indicates a difference in behavior based on preference of food (Bhadra et al. 2015). We needed to know for sure whether the dogs were sensing the presence of the biscuit and then ignoring the amount. Hence, we performed the strength of preference: control experiment, to make sure the dogs would select a small piece of biscuit, while the other option had no evident food. Since the FRDs were discriminating between different amounts of chicken (Banerjee and Bhadra 2019), such an experiment was not required for chicken.

In the strength of preference experiment with biscuits, we saw that the dogs overwhelmingly chose the empty yellow bowl over the gray bowl that had a biscuit. Next, to create a higher skew in the reward, we used chicken, a more attractive food (Bhadra et al. 2015) with the gray bowl. The ~ 15 g pieces of chicken were the largest that the bowls could comfortably hold without spillage. We tried to maximize the amount of chicken given our current setup, hoping to find a preference shift towards food instead of color, from which we may lower the food amount to find an equilibrium between color and food. Surprisingly, even with the apparent substantial amount of chicken, the preference for yellow dominated. In one trial (Online Resource 8), the focal dog pawed at and attempted to chew the yellow bowl for some time, and then proceeded to solicit from experimenter 1, only returning to obtain the chicken from the gray bowl after a few moments of futile solicitation. In the future, to find the aforementioned equilibrium, the amount of chicken may be increased.

We do not yet know what exactly is causing this strong preference for yellow. The species-confidence hypothesis (Burley 1986) might be a possible reason, as many FRDs are shades of orange and brown that will appear yellowish in dog vision (colors simulated by authors using methods from Pongrácz et al. 2017). But while some dogs might appear gray, surely no dog is blue. Since we found no preference between blue and gray, species confidence does not explain the color preference of FRDs. Moreover, species confidence is more applicable in the context of mate choice, rather than in the context of foraging, and might not be a suitable hypothesis to explore by object choice tests. The ecological valence theory (Palmer & Schloss, 2010) links color preference with a color’s usual ecological role or value. Research on innate preference of honeybees (Giurfa et al. 1995) and bumblebees (Raine and Chittka 2007) had earlier found color preference to be highly correlated with flower colors and associated nectar rewards. For Indian FRDs, most of the food available to them is of human origin (Vanak & Gompper, 2009). Indians often use turmeric (yellow) and dried chili (red) in their food (personal observations), both of which will appear yellow to dogs and even raw meat (pink) and blood (red) will appear yellowish (Pongrácz et al. 2017). It is important, however, to remember that while scavenging, a dog that is looking for yellow food will come across many false positives: yellow, red, and green human-generated inedible trash. To be accepted, the ecological valence theory must explain how these false positive encounters do not end up diminishing any color preference. It is worth noting that even green grass and trees will appear yellowish to dogs. Since color preference can be both learned or innate, a test for innateness of canine color preference appears to be a prime topic for future research. Cimarelli et al. (2023), working with FRDs in Morocco, did not find any color preference between yellow and blue. This might indicate our findings are rather localized and there is no single underlying mechanism of color preference for dogs in general. However, it should also be noted that this particular study (Cimarelli et al. 2023) was not designed specifically to test for color preference.

It could have been that the yellow bowls have a “pop-out effect” due to high contrast with the other bowls and the surrounding. Experiments presented here cannot rule out this possibility. Early data from an ongoing experiment suggests against visual pop-out affecting the dogs’ choice, but it cannot yet be confirmed and demands detailed investigation.

Our experiments were limited by the availability of variations in paint color. We finally chose our particular yellow and blue paints such that their spectral peaks (see Online Resource 9 for details) overlapped with respective dog cone cell activity peaks, and thus the hues were of high contrast to the dogs. The brightness of the objects could not be controlled due to our dependence on company-manufactured paints. There are very few and conflicting reports regarding the value of brightness discrimination in dogs (Byosiere et al. 2018). So, we refrain from commenting on how the dogs will perceive the relative brightnesses of our experimental objects. Kasparson et al. (2013) found it easier for companion dogs to discriminate between objects of different hues over objects of the same hue but different brightness. We conjecture brightness to be more important while looking for preference among colors that vary more subtly in hue than in our experiment of high hue contrast. Our objects being of different brightness should not affect the color preference that we have observed.

Conclusion

Our experiments demonstrate a clear preference for the color yellow over blue and gray in FRDs of India, at least in the context of foraging. This preference is so strong that it supersedes their attraction towards food, whether biscuit or chicken. This is the first time that we have observed FRDs ignore a clear food reward in a choice test. Further experiments can help us understand the ecological advantages, if any, of this preference and the reasons behind it. Moreover, comparative studies with companion dogs and wolves can help to understand the evolutionary trajectory of this preference for yellow. The impact of color cues and color preference on training can be explored in the future.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Author contributions

AR conceived the idea and planned the experiments with inputs from AB. All authors but AB participated in the field work to perform the experiments. AR decoded all videos and analyzed the data. AR wrote the first draft of the manuscript. AB supervised the work, acquired funding, edited the manuscript. All authors gave their consent to the manuscript.

Funding

We thank the Department of Biotechnology, India (Project: BT/HRD-NWB/39/2020-21), and IISER Kolkata, for funding support. AR and SN were supported by UGC-JRF and DST-INSPIRE JRF fellowships respectively. SS was supported by IAS summer research program.

Data availability

The datasheets and RScripts can be found at: 10.17605/OSF.IO/JZY8W.

Declarations

Competing interests

The authors declare no competing interests.