Science News

Voice Card  -  Volume 16  -  John Card Number 19  -  Mon, Oct 1, 1990 3:33 AM

A few snippets from recent issues of Science News...

Subliminal Deceptions

Audio cassettes with subliminal messages haul in $50 million annually. But two new studies suggest the tapes do not work as advertised and in some cases may not even contain subliminal suggestions.

Anthony G. Greenwald of the University of Washington in Seattle and his colleagues studied 237 volunteers who listened to commercially available subliminal tapes aimed at improving either memory or self-esteem. Messages lurked behind audible sounds of ocean waves. The researchers reversed labels on half of the cassettes so that the memory-oriented tapes carried self-esteem labels and vice versa. The remaining cassettes carried accurate labels. Each volunteer completed a series of memory and self-esteem tests before and after using a subliminal tape for one month.

People who listened to memory tapes showed no more memory improvement than did those who listened to self-esteem tapes; people who used self-esteem tapes reported no more improvement in self-esteem than did volunteers in the memory group. Nevertheless, those who used self-esteem tapes labeled as memory boosters contended that only their memories had improved, while those who used memory tapes labeled as self-esteem enhancers said that only their self-esteem had increased.

At the end of the study, all participants scored higher on both memory and self-esteem tests, regardless of which tape they had heard or how it was labeled. These improvements may have been stimulated by the memory and self-esteem tests administered at the study's outset, Greenwald asserts.

[A second study found evidence that some commercial tapes contain no subliminal messages whatsoever...]

Male-female contrasts: The vole story

The hippocampus - an inner-brain structure critical to processing spatial information - takes up a significantly greater portion of the total brain in the polygamous male meadow vole than in the monogamous male pine vole, report biologist Lucia F. Jacobs of the University of Pittsburgh and her colleagues. Females of both species show a hippocampal size closely matching that of the faithful male pine vole, they add.

Breeding male meadow voles range over large areas in search of sexually receptive mates, while male pine voles and females of both species stick close to home. The polygamous males also perform better in laboratory mazes testing different types of spatial ability. These voles apparently evolved superior spatial skills - and larger hippocampi to regulate those skills - in order to navigate efficiently throughout their surroundings during breeding season...

Sex differences in hippocampal size related to spatial ability should occur in a wide variety of mammals, they theorize, since males in most mammalian species practice polygamy. Indeed, says Jacobs, anthropological research indicates that in most human societies, men engage in polygamy and range over larger territories than women. Men consistently score higher than women on tests of spatial ability, but scientists have not studied human sex differences in relative hippocampal size...

Environmental pressures may also lead to the enlargement of as-yet-unspecified brain regions in female voles, Jacobs notes. Since females need more calories than males for lactation and child care, brain regions regulating memory for the location and contents of food storage sites may also show a female-specific size advantage, she suggests.

Fast Food Ecology

Nancy M. Eyster-Smith, who teaches ecology to business students at Bentley College in Waltham, Mass., has expanded on a somewhat bizarre theme broached several years ago... Recognizing that business often imitates biology, she uses local fast food restaurants to demonstrate concepts of niche, competition, evolution and extinction.

"The restaurants are the species," Eyster-Smith explains. "We have McDonald's species, Arby's species, Kentucky Fried Chicken species and so on." Her students note ways in which menus vary from one species to the next and how the offerings have varied over time. In addition, they survey the species' preferred habits. (Many restaurants congregate along a highway habitat called "the strip," they observe.)

In the Darwinian world of fast food competition, Eyster-Smith says, each restaurant species competes for a limited resource: customers' money. Categories of food - such as burgers, sodas and French fries - represent ecological niches, or areas of competitive expertise. Within this food service framework, students discover a smorgasbord of ecological rules.

For example, their surveys reveal that in the fast food jungle, niche dimensions (food categories) may overlap but no two species can have exactly the same food requirements and still coexist in close proximity. Ecologists recognize this as the competitive exclusion principle. Moreover, students observe that species - whether plant, animal or restaurant - engage in both interspecific and intraspecific competition, competing with other brand name chains as well as with nearby franchises of their own chain.

Like biological species, some fast food restaurants are "generalists" - trying to maximize survival by offering a wide variety of food items, or resource strategies - while others are "specialists," offering a narrower but unique menu to customers. Moreover, students find that restaurants can best share limited resources (business) by partitioning their activities in different ways, a strategy common among biological competitors. For example, rival restaurants might space themselves in distant neighborhoods, stay open late into the night, adopt marketing strategies such as kids' meals, or add special offerings such as ice cream or salad.

Eyster-Smith takes the gastronomic analogy even further by having students consider the social and environmental factors - such as neighborhood affluence and customers' increasingly busy schedules - that may have influenced the evolution of various restaurant species. She has them draw phylogenic diagrams, or family trees, describing this evolutionary process, starting with a presumed common ancestor: the "drive-in generalist."

Finally, the class performs post-mortems on restaurants that have failed to survive the evolutionary battle. "If you know the towns and you look at the data, you might get an idea about local extinctions," she says, noting that most fast food extinctions occur in neighborhoods that have become either very affluent or severely crime-ridden.