Abstract
Introduction
The mnemonic benefit from processing words for their survival value, relative to other, well-known memory strategies, is known as the “survival advantage” (Nairne, Thompson, and Pandeirada, 2007). In their seminal work, Nairne, Thompson, and Pandeirada (2007) described findings from four related experiments. In each experiment, participants rated the relevance of a list of neutral, unrelated words to the following survival scenario: In this task, we would like you to imagine that you are stranded in the grasslands of a foreign land, without any basic survival materials. Over the next few months, you’ll need to find steady supplies of food and water and protect yourself from predators. We are going to show you a list of words, and we would like you to rate how relevant each of these words would be for you in this survival situation. Some of the words may be relevant and others may not—it’s up to you to decide.
Nairne, Pandeirada, and Thompson (2008) extended their previous findings by comparing the benefit of survival processing against other conditions that traditionally produce high retention. In Experiment 1, participants were assigned to the standard survival condition or one of several important control conditions: pleasantness, imagery, self-reference, generation, or intentional learning. Across all comparisons, survival processing promoted the best recall performance. These results were also upheld in an additional experiment that compared survival processing with another scenario: a vacation-processing condition. These findings have led Nairne et al. (2008) to argue that survival processing “is one of the best—if not
Recently, researchers have begun to investigate the potential mechanisms underlying the survival advantage. For example, some have argued that survival processing is particularly effective for promoting better memory performance because it invokes self-referential processing (Klein, 2012, 2014) and planning (Klein, Robertson, & Delton, 2010). Burns and colleagues have also indicated that survival processing promotes both item-specific and relational processing, while control conditions often rely on just a single type of processing during encoding (Burns, Burns, & Hwang, 2011; Burns, Hart, Griffith, & Burns, 2013). Others have noted that survival processing leads to increased elaboration on the to-be-remembered words during the encoding task. According to Kroneisen and Erdfelder (2011), this elaborative encoding during survival processing leads to a larger mnemonic benefit. Their modified survival passage—which described just a single survival problem in a need for water—did not promote better memory when compared with the typical control conditions. Similarly, Röer, Bell, and Buchner (2013) have observed that participants generate a significantly greater number of ideas for how the to-be-remembered words might be used in survival settings, relative to how they might be used in other settings. Together, these findings indicate that modifying the specific task used within the experiment can bring us closer to uncovering the precise mechanisms underlying the advantage.
However, results are mixed regarding the use of additional tasks to test the survival advantage. For example, researchers have found that survival processing can promote better compound remote association task performance (Garner & Howe, 2013), location memory (Nairne, Van Arsdall, Pandeirada, & Blunt, 2012), and picture recall (Otgaar, Smeets, & van Bergen, 2010) than control conditions. On the other hand, survival processing does not appear to benefit face memory (Savine, Scullin, & Roediger, 2011), implicit task performance (McBride, Thomas, & Zimmerman, 2013; Tse & Altarriba, 2010), paired-associate learning (Schwartz & Brothers, 2014; unless they are animate paired-associates, VanArsdall, Nairne, Pandeirada, & Cogdill, 2015), or spatial N-back performance (Altarriba & Kazanas, 2014). Thus, an interesting area of inquiry for this area of research is determining the precise conditions when survival processing does and does not enhance cognitive performance (Kazanas & Altarriba, 2015). As the majority of studies conducted within this area of research have used rating tasks designed to promote word memory, we believe that it is important to investigate whether survival processing can improve performance on other tasks as well.
One task that has not been used within this area of research is the Stroop (1935) color-naming task. In this task, words are printed in color, and participants respond to each word by naming the color. When color words (e.g.,
Why would the Stroop color-naming task provide a unique contribution to this area of research? Very few studies have examined the role of survival processing on evolutionarily-relevant tasks (but see Savine et al., 2011 for a failure to replicate the survival advantage with faces). Studies from related paradigms, such as the emotion literature, indicate that processing threatening stimuli can have a facilitative effect on color-naming performance. For example, Shibasaki, Isomura, and Masataka (2014) determined that both adults and children were able to detect the color of snakes faster than the color of flowers. These findings indicate that negative emotion, and perhaps fear in particular, can have a motivating effect on cognitive processing.
Detecting color and identifying items by color are also rooted in evolutionary theory (for recent reviews, see e.g., Jacobs, 2009; Lucas et al., 2003; Melin et al., 2012; Sumner & Mollon, 2003). For example, Bompas, Kendall, and Sumner (2013) have determined that normal trichromats (organisms with three types of color receptors on their retina, including humans) detect fruit better than those with color deficiencies, with the largest differences in detection performance at long distances. Other selection pressures may have included a need to detect predators, young leaves, or social signals related to reproduction (Kawamura et al., 2012; Melin et al., 2012; Pessoa et al., 2014; Surridge, Osorio, & Mundy, 2003). Several of these hypotheses have also been assessed using animal models, including macaque (Horwitz, 2015) and capuchin (Melin et al., 2014) monkeys. These hypothetical accounts for the evolution of color vision lend themselves to the survival-processing paradigm in that they are the goals outlined within the survival passage itself.
The Current Study
The current study was motivated by a set of related goals. First, we were interested in the impact of manipulating levels of processing within the survival-processing paradigm. While researchers have begun to investigate the role of deeper processing within the survival passage relative to control conditions (e.g., Kroneisen & Erdfelder, 2011; Röer, Bell, & Buchner, 2013), the current study aims to compare depth of processing within the encoding tasks themselves. By using the Stroop task specifically, we can investigate a second but related line of research. As human color vision is strongly believed to be evolutionarily adaptive in nature (e.g., Bompas, Kendall, & Sumner, 2013), using the Stroop task will allow us to determine whether survival processing can boost color-naming performance. Additionally, we are able to determine whether a congruency between the survival passage and the adaptive nature of the color-naming task can promote better memory performance. Finally, by using multiple variants of the Stroop task, we can directly test whether differences in color-naming performance reported by Besner et al. (1997) replicate within this paradigm.
Method
Participants
Participants in this experiment (
Experimental Conditions
Participants were randomly assigned to one of the five conditions ( In this task, we would like you to imagine that you are stranded in the grasslands of a foreign land, without any basic survival materials. Over the next few months, you’ll need to find steady supplies of food and water and protect yourself from predators. We are going to show you a list of words, and we would like you to rate how relevant each of these words would be for you in this survival situation. Some of the words may be relevant and others may not—it’s up to you to decide.
The other two survival conditions used the Stroop color-naming task. Five colors were used (red, yellow, green, blue, and purple), with an approximately equal number of words per color (5 or 6), pseudorandomly arranged with no more than three of the same color in a row. Words were either presented in neutral (e.g., In this task, we would like you to imagine that you are stranded in the grasslands of a foreign land, without any basic survival materials. Over the next few months, you’ll need to find steady supplies of food and water and protect yourself from predators. We are going to show you a list of words, and we would like you to name each color that the word is presented in. Identifying items by color may be useful to survival.
In the second condition, the letter-color naming condition (Besner, Stolz, & Boutilier, 1997), one letter within each word, was presented in a color. The remaining letters were presented in black. Instructions for this condition read: In this task, we would like you to imagine that you are stranded in the grasslands of a foreign land, without any basic survival materials. Over the next few months, you’ll need to find steady supplies of food and water and protect yourself from predators. We are going to show you a list of words, and a single letter in each word will be colored. We would like you to name the color of that single-letter. Identifying items by color may be useful to survival.
Pleasantness rating instructions, with all words presented in black, read: In this task, we are going to show you a list of words, and we would like you to rate the pleasantness of each word. Some of the words may be pleasant and others may not—it’s up to you to decide.
One final condition was used as a baseline for the two Stroop conditions. In this condition, participants performed a simple word-color naming task (without reading the survival passage), in order to determine the effectiveness of color processing in encoding a word for later retrieval. In this condition, entire words were presented in color. Their instructions read: We are going to show you a list of words, and we would like you to name each color that the word is presented in.
Materials
All participants rated or named the color of the same set of 32 words, presented in the same order (selected from Nairne et al., 2007, Experiments 1 and 2). Five additional words (all concrete nouns, selected from Nairne et al., 2007, Experiment 3) were used to allow the participants to practice the task, but their responses to these words were not retained for analyses.
Procedure
Participants were run individually, within the Cognition and Language Laboratory. Each word was presented for 5 s, during which participants performed either the rating or naming task, via keypress. The experimenter assisted with practice trials, only. After the rating or color-naming experimental trials, all participants performed 2 min of forward digit span (set to a length of seven digits), followed by an unexpected free recall task. Each participant was given a maximum of 10 min to recall as many words as they could, in any order.
After the recall task, participants in the three survival conditions answered the following questions (from Nairne & Pandeirada, 2010): (1) How interesting was the scenario? (2) How easy was it for you to create an “image” of the scenario in your mind? (3) How emotionally arousing was the scenario? (4) How familiar are you with the situation described? Two additional questions were included in the questionnaire (from Otgaar et al., 2011; Sandry, Trafimow, Marks, & Rice, 2013): (5) How distinctive, or unusual, was the scenario? (6) How rich in detail would you rate the scenario?
After answering these questions, participants completed a brief demographic questionnaire, which included questions related to age, gender, education, and native language. Each participant received a debriefing form and was granted credit for their participation.
Results
First, participants in all five conditions were matched on age, level of education, and native language (all
Next, a one-way analysis of variance (ANOVA) was conducted to detect any differences in the proportion of correct recall among the five conditions. This ANOVA was significant,

A comparison of recall by condition, with 95% confidence intervals.
Proportion of Correct Recall: Means and
A series of one-way ANOVAs and planned contrasts were conducted to detect any differences in each of the scenario ratings among the three survival conditions. Two of these ANOVAs were significant. The rating for how “interesting the scenario was” was significant,
Survival scenario ratings: Means and
Approximately half of our participants recalled words that were not included on either the practice or the experimental trials. Intrusions were analyzed in two ways. First, we analyzed the total number of intrusions according to condition, using a one-way ANOVA. This ANOVA was significant,
Finally, to determine whether the survival scenario motivated better Stroop performance, we conducted several analyses across the three color-naming conditions. First, we assessed overall color-naming accuracy with a one-way ANOVA. There were no significant differences across these conditions (
Discussion
Findings from the current study are numerous and provide a significant contribution to this area of research. First, we have replicated the survival advantage in memory, when comparing the effects of survival-relevance ratings against pleasantness ratings and new color-naming conditions. Importantly, this advantage was not due to any significant difference in RTs or ratings during encoding. However, results from the scenario ratings indicate that the survival advantage may be due, in part, to relevance rating being a more imageable task. There was some evidence that survival-relevance rating may be a more interesting task as well. In other words, the encoding portion of the task is likely to be the most critical portion of the task, overall.
Findings from the color-naming conditions were novel to this paradigm. First, recall performance in these conditions was significantly worse than the survival-relevance and pleasantness rating conditions. Encouraging participants to consider a survival situation while color naming impaired later recall performance. Importantly, there is a precedent for this pattern of data within the survival literature. In a study examining the role of cognitive load in the survival advantage, Kroneisen, Rummel, and Erdfelder (2013) found that increasing load with an additional task reduced word recall and eliminated the survival advantage. Similarly, when comparing recall performance in the current study across the color-naming conditions, differences in recall performance were minimal. In addition, as was the case with Kroenisen et al. (2013), recall performance was significantly impaired, with participants in our three color-naming conditions recalling less than 10% of the word list (near floor performance). Particularly, poor recall, with little variation across these conditions, indicates that the survival advantage may rely on additional processing, relative to less effortful control conditions.
Results also indicate that survival processing did not motivate better color-naming performance, relative to the baseline color-naming condition. When comparing word color-naming accuracy, participants who read the survival passage actually performed numerically
With respect to both survival-processing and color-naming interference, it is possible that the incongruent items (e.g., a green
However, can poorer performance in a color-naming task be considered adaptive? Perhaps coming across an unusual fruit or vegetable requires additional inspection, to ensure it is safe to ingest, as our general pattern of interference data from the color-naming task would indicate. In other words, it may be the case that being in a survival setting puts us “on high alert” to find good nutrients. Likewise, our intrusion analyses indicate that participants who read the survival passage recalled more survival-relevant intrusions than those who had not read the survival passage. We surmise that these false memories are a strong indicator that survival processing encourages spreading activation from the related words to other words that would be useful in survival situations (e.g., a
Sellers and Bjorklund (2014) have hypothesized that negative emotions, such as those related to fearing the consequences of a survival situation, may be driving these effects. Thus, these seemingly negative consequences of survival processing may actually have adaptive value when conceptualized within both memory
Implications and Future Directions
Although these results are not the most straightforward examples of a survival advantage, we believe that they greatly extend the original conception of the advantage (Nairne et al., 2007). In fact, it may be the case that survival processing has far-reaching implications for understanding behavior, such as color-naming performance described in the current study. Thus, this area of literature would greatly benefit from additional studies investigating the generalizability of the survival advantage to new tasks and experimental procedures, particularly those with adaptive value, such as the unconventional intrusion findings reported in the current study. The number of experiments designed to study the limits of the advantage are greatly outnumbered by the number of experiments designed to replicate the advantage with different control conditions, participant populations, or modified passages (for a review, see Kazanas & Altarriba, 2015). Thus, we encourage greater exploration of how the advantage fares with tasks that tap into cognitive domains other than episodic memory (e.g., attention, working memory, etc.). Additional research might also explore real-world applications or more realistic situations for adult-age populations (e.g., the first day of school at a new university, starting a new job, etc.). Perhaps future work would benefit from additional control conditions, such as these familiar situations, to compare memory following survival and nonsurvival processing. A limitation of our study lies in our lack of a situation-based control condition, although we did include a pleasantness rating task.
We also encourage additional research investigating the relationship between considering ones’ survival needs and identifying items by color. For example, how would results from a study using picture stimuli (e.g., having participants name the color of a red
Conclusion
Our overall findings indicate that engaging in survival processing increases memory for a set of unrelated words. In addition, this task led participants to spend more time on words that were presented in incongruent colors, relative to participants who were not thinking about the survival scenario. These results support a survival advantage specifically guided by ancestral priorities: Our ancestors would have benefited from turning their attention toward objects that violated their expectations, especially if they were in danger or needed to quickly gather survival materials. Additionally, having carefully classified and analyzed participants’ intrusions—a measure often associated with false memory—we believe that survival processing may also promote spreading activation from one survival item to an entire set of related items. Together, these findings replicate the survival advantage and extend its generalizability to a new task with adaptive value.
