Prolonged development of forced-choice recognition when targets are paired with non-corresponding lures.

Previous research suggests that mnemonic discrimination (i.e., the ability to discriminate between previously encountered and novel stimuli even when they are highly similar) improves substantially during childhood. To further understand the development of mnemonic discrimination during childhood, the current study had 4-year-old children, 6-year-old children, and young adults complete the forced-choice Mnemonic Similarity Task (MST). The forced-choice MST offers a significant advantage in the context of developmental research because it is not sensitive to age-related differences in response criteria and includes three test formats that are theorized to be supported by different cognitive processes. A target (i.e., a previously encountered item) is paired with either a novel item (A-X), a corresponding lure (A-A'; i.e., an item mnemonically similar to the target), or a non-corresponding lure (A-B'; i.e., an item mnemonically similar to a different previously encoded item). We observed that 4-year-olds performed more poorly than 6-year-olds on the A-X and A-A' test formats, whereas both 4- and 6-year-olds performed more poorly than young adults on the A-B' test format. The MINERVA 2.2 computational model effectively accounted for these age-related differences. The model suggested that 4-year-olds have a lower learning rate (i.e., probability of encoding stimulus features) than 6-year-olds and young adults and that both 4- and 6-year-olds have greater encoding variability than young adults. These findings provide new insight into possible mechanisms underlying memory development during childhood and serve as the basis for multiple avenues of future research.

SARS/CoV-2: Behavioral Host Manipulation.

INTRODUCTION: Though it has not been extensively studied, host manipulation has been documented for various pathogens. Examples of this phenomenon can be seen in cases of toxoplasmosis, rabies, and the influenza virus. An examination of the possible means by which SARS/CoV-2 alters the behavior of its host to spread among populations is elaborated. Indirect evidence that serves as indicators of this phenomenon is presented. METHODS: This is primarily a theoretical document. Many of the ideas raised are not amenable to direct testing due to ethical concerns. However, several indirect means by which to test the hypothesis are discussed. Primary data from cell phones regarding miles traveled, number of times leaving home, etc., are among the possible indirect measures. RESULTS: The rapid ability of the SARS/CoV-2 virus to spread through society suggests that it may cause behavioral changes of the host to increase its transmission. Numerous cases of super spreader events are noted that have provided meaningful measures of host manipulation. CONCLUSION: In the case of SARS/CoV-2, the largest advantage of the pathogen is likely that between 50% and 70% of those infected are asymptomatic (John's Hopkins Coronavirus Resource Center, John's Hopkins University Corona Virus Resource Center. Available at https://coronavirus.jhu.edu/map.html , 2020). This component is a threat to elderly individuals and those immunocompromised who are more likely to have severe complications from the virus and die. To spread within these groups, a seemingly healthy host is necessary to carry the virus to them. The goal of the virus is not to kill the host, but to survive and reproduce.

Event-related potentials during encoding coincide with subsequent forced-choice mnemonic discrimination.

Computational models and eye-tracking research suggest that encoding variability accounts for the reduced recognition of targets (A) when paired with non-corresponding lures (B') relative to corresponding lures (A'). The current study examined whether neural activity during learning coincided with subsequent performance on the forced-choice Mnemonic Similarity Task (MST). Event-related potential responses were collected during encoding while young adults completed A-B' and A-A' trials of the forced-choice MST. Consistent with previous research, performance was lower on A-B' trials than A-A' trials. The subsequent memory effect was not significant for the A-A' test format. However, for A-B' trials, we observed a significant Accuracy × Stimulus interaction 1000-1200 ms poststimulus onset across frontal and fronto-central electrodes. As hypothesized, subsequently correct A-B' trials were associated with a larger amplitude response at encoding to the target (A) than the original version of the non-corresponding lure (B). However, subsequently incorrect trials were associated with a larger amplitude response to the non-corresponding lure (B) than the target stimulus (A). These findings provide additional support for the effect of encoding variability on mnemonic discrimination.

Hypothesized behavioral host manipulation by SARS-CoV2/COVID-19 infection.

Although not widely studied, behavioral host manipulation by various pathogens has been documented. Host manipulation is the process by which a pathogen evolves adaptations to manipulate the behavior of the host to maximize reproduction (Ro) of the pathogen. The most notable example is rabies. When a host is infected with the rabies virus it gets into the host's central nervous system and triggers hyper aggression. The virus is also present in the rabid animal's saliva so being bitten transmits the infection to a new host and the old host is left to eventually die if untreated. Toxoplasmosis is another example. When mice are infected they demonstrate a fearlessness toward cats, thus increasing their chances of being eaten. Toxoplasmosis needs the digestive tract of the feline to survive. Recent studies have shown that exposure to toxoplasmosis in humans (e.g., through cat feces) has also been associated with behavioral changes that are predicted to enhance the spread of the pathogen. Even the common influenza virus has been shown to selectively increase in-person sociality during the 48-hour incubation period, thus producing an obvious vector for transmission. Here we hypothesize that the novel coronavirus, SARS-CoV2, which produces the COVID-19 disease may produce similar host manipulations that maximize its transmission between humans.