Adaptive Memory: Independent Effects of Survival Processing and Reward Motivation on Memory

Humans preferentially remember information processed for their survival relevance, a memorial benefit known as the survival processing effect. Memory is also biased towards information associated with the prospect of reward. Given the adaptiveness of these effects, they may depend on similar mechanisms. We tested whether motivation drives both effects, with reward incentives that are known to boost extrinsic motivation and survival processing perhaps stimulating intrinsic motivation. Accordingly, we manipulated survival processing and reward incentive independently during an incidental-encoding task in which participants chose between pairs of words concerning their relevance for a scenario, and examined the effects on encoding event-related potentials (ERP) activity and later performance on a surprise recall test. We hypothesized that if survival processing fosters intrinsic motivation, it should reduce the beneficial effects of extrinsic motivation (reward incentive). In contrast to this prediction, we found that reward incentive and survival processing independently improved memory and that the P300, a measure of lower-level cognitive resource allocation, was increased by reward incentive independent of survival processing. Further, survival processing and reward incentive independently increased the frontal slow wave (FSW), a measure of higher-level elaboration. These findings suggest that while survival processing and reward incentive may both increase encoding elaboration, the memory-enhancing effect of survival processing does not depend on increased intrinsic motivation. Additionally, we replicated a recent finding whereby the survival processing effect generalizes to a choice-based encoding task and further showed that the beneficial effect of choice on memory likely does not interact with either survival processing or reward.

Does the Survival Processing Memory Advantage Translate to Serial Recall?

The survival processing effect describes the phenomenon that memory for items is better after they have been processed in the context of a fitness-related survival scenario as compared to alternative processing contexts. In the present study, we examined whether the survival processing memory advantage translates to memory for the order of processed items. Across two serial-recall experiments, we replicated the survival processing effect for free recall but did not find an additional survival processing advantage for serial recall when we controlled serial recall performance for the total number of words recalled per person. Adjusted serial recall performance was not better in the survival processing condition when compared to a moving and a relational pleasantness processing condition (Experiment 1), even when processing of the relational order of stimuli was explicitly endorsed in the survival processing task (Experiment 2). This finding is in line with the idea that enhanced item-specific rather than enhanced relational processing of items underlies the survival processing effect. Moreover, our findings indicate that survival processing does not increase memory efficiency for temporal context information.

Adaptive Memory: Survival Processing and Social Isolation

Social isolation was examined to assess its potential influence on the survival processing effect, which shows that individuals are more likely to remember something when it is processed with regard to their survival. Participants imagined being stranded in the grasslands, going on a space mission, or moving to a foreign land while alone or with a group of friends and rated a list of words for their relevance to the assigned scenario. An incidental memory test showed the typical survival processing effect on recall memory, with a significant interaction showing that the effect occurred in the isolated condition but not in the group condition. A second experiment examined rates of recognition for an isolated and group condition for the grasslands and moving scenarios and found a marginally significant effect of isolation in addition to the typical survival processing effect. Further, in both experiments, the perceived isolation of the isolated and group survival grasslands scenarios was significantly higher than the other conditions. The results are discussed with regard to the self-reference effect and the object-function account of the survival processing effect.