Adaptive memory: survival processing enhances retention.

The authors investigated the idea that memory systems might have evolved to help us remember fitness-relevant information--specifically, information relevant to survival. In 4 incidental learning experiments, people were asked to rate common nouns for their survival relevance (e.g., in securing food, water, or protection from predators); in control conditions, the same words were rated for pleasantness, relevance to moving to a foreign land, or personal relevance. In surprise retention tests, participants consistently showed the best memory when words were rated for survival; the survival advantage held across recall, recognition, and for both within-subject and between-subjects designs. These findings suggest that memory systems are "tuned" to remember information that is processed for fitness, perhaps as a result of survival advantages accrued in the past.

Entomopathogenic fungi detection and avoidance by mole crickets (Orthoptera: Gryllotalpidae).

A chamber to monitor mole cricket behavior was designed using two different soil-filled containers and photosensors constructed from infrared emitters and detectors. Mole crickets (Scapteriscus spp.) were introduced into a center tube that allowed them to choose whether to enter and tunnel in untreated soil or soil treated with Beauveria bassiana (Balsamo) Vuillemin. Each time the cricket passed through the photosensor located near the entrance of soil-filled containers, the infrared light was blocked and the exact moment that this occurred was logged onto a computer using custom-written software. Data examined included the first photosensor trigger, total number of sensor triggers, presence of tunneling, and final location of the cricket after 18 h. These behaviors were analyzed to discern differences in mole cricket behavior in the presence of different treatments and to elucidate the mechanism that mole crickets use to detect fungal pathogens. The first study examined substrate selection and tunneling behavior of the southern mole cricket, Scapteriscus borellii Giglio-Tos, to the presence of five strains of B. bassiana relative to a control. There were no differences between the first sensor trigger and total number of triggers, indicating the mole crickets are not capable of detecting B. bassiana at a distance of 8 cm. Changes in mole cricket tunneling and residence time in treated soil occurred for some strains of B. bassiana but not others. One of the strains associated with behavioral changes in the southern mole cricket was used in a second experiment testing behavioral responses of the tawny mole cricket, S. vicinus Scudder. In addition to the formulated product of this strain, the two separate components of that product (conidia and carrier) and bifenthrin, an insecticide commonly used to control mole crickets, were tested. There were no differences in mole cricket behavior between treatments in this study. The differences in behavioral responses between the two species could suggest a more sensitive chemosensory recognition system for southern mole crickets.

Effect of combining imidacloprid and diatomaceous earth with Beauveria bassiana on mole cricket (Orthoptera: Gryllotalpidae) mortality.

Sublethal doses of three orthopteran-derived strains of Beauveria bassiana (Balsamo) Vuillemin were topically applied to adult southern mole crickets, Scapteriscus borellii Giglio-Tos (Orthoptera: Gryllotalpidae), and tested in combination with substrate treatments of diatomaceous earth (DE) and imidacloprid. Crickets treated only with the high doses (10(8) conidia per cricket) of each of the three B. bassiana strains exhibited the shortest survival times as well as the highest percentage mortality at 28 d after treatment. However, these treatments did.not differ significantly from any of the diatomaceous earth combination treatments. Two of the strains tested, 5977 and 3622, exhibited synergistic interactions with DE, whereas the third strain, GHA, was not significant for synergy. Mortality caused by the combination treatment was still greater than the expected additive effect. DE abrades the insect cuticle and absorbs cuticular lipids, aiding the entry of germinating conidia into the mole cricket hemocoel. None of the three strains exhibited synergy when combined with imidacloprid, and mortality of all combination treatments was less than additive. For strain 5977, there was an antagonistic interaction with imidacloprid. It was difficult to obtain <30% mortality for imidacloprid only treatments, which was considered the upper limit for sublethal doses. The mean percentage mortality caused by imidacloprid was 37.5%, and this high percentage made it difficult for any combination treatment to cause significantly more mortality than the expected additive effect. These results clarify the interactions of other control products with B. bassiana and provide a basis for a reduced pesticide approach to mole cricket control.

Aging and the perception of depth and 3-D shape from motion parallax.

The ability of younger and older observers to perceive 3-D shape and depth from motion parallax was investigated. In Experiment 1, the observers discriminated among differently curved 3-dimensional (3-D) surfaces in the presence of noise. In Experiment 2, the surfaces' shape was held constant and the amount of front-to-back depth was varied; the observers estimated the amount of depth they perceived. The effects of age were strongly task dependent. The younger observers' performance in Experiment 1 was almost 60% higher than that of the older observers. In contrast, no age effect was obtained in Experiment 2. Older observers can effectively perceive variations in depth from patterns of motion parallax, but their ability to discriminate 3-D shape is significantly compromised.

Adaptive memory: the comparative value of survival processing.

We recently proposed that human memory systems are "tuned" to remember information that is processed for survival, perhaps as a result of fitness advantages accrued in the ancestral past. This proposal was supported by experiments in which participants showed superior memory when words were rated for survival relevance, at least relative to when words received other forms of deep processing. The current experiments tested the mettle of survival memory by pitting survival processing against conditions that are universally accepted as producing excellent retention, including conditions in which participants rated words for imagery, pleasantness, and self-reference; participants also generated words, studied words with the intention of learning them, or rated words for relevance to a contextually rich (but non-survival-related) scenario. Survival processing yielded the best retention, which suggests that it may be one of the best encoding procedures yet discovered in the memory field.

Aging and the perception of 3-D shape from dynamic patterns of binocular disparity.

In two experiments, we investigated the ability of younger and older observers to perceive and discriminate 3-D shape from static and dynamic patterns of binocular disparity. In both experiments, the younger observers' discrimination accuracies were 20% higher than those of the older observers. Despite this quantitative difference, in all other respects the older observers performed similarly to the younger observers. Both age groups were similarly affected by changes in the magnitude of binocular disparity, by reductions in binocular correspondence, and by increases in the speed of stereoscopic motion. In addition, observers in both age groups exhibited an advantage in performance for dynamic stereograms when the patterns of binocular disparity contained significant amounts of correspondence "noise." The process of aging does affect stereopsis, but the effects are quantitative rather than qualitative.