New Worlds: Human whisking

Some men may have moustaches, but only rodents can move their facial hairs to locate objects in their environment.

Rats have this “whisking” ability, and they are able to move their whiskers about eight times a second for “radar.” Could humans acquire this sense? And if they can, what could understanding the process of adapting to new sensory input tell us about how humans normally sense?

Researchers at the Weizmann Institute investigated this by attaching plastic “whiskers” to the fingers of blindfolded volunteers and asking them to carry out a location task. The findings, which recently appeared in the Journal of Neuroscience, have yielded new insight into the process of sensing, and they may point to new avenues in developing aids for the blind.

The scientific team, including Drs. Avraham Saig and Goren Gordon, and Eldad Assa in the group of Prof. Ehud Ahissar and Dr. Amos Arieli, all of the neurobiology department, attached a “whisker” – a 30 centimeter- long elastic “hair” with position and force sensors on its base – to the index finger of each hand of a blindfolded subject. Then two poles were placed at arm’s distance on either side and slightly to the front of the seated subject, with one a bit farther back than the other. Using just their whiskers, the subjects were challenged to figure out which pole – left or right – was the back one. As the experiment continued, the displacement between front and back poles was reduced, up to the point when the subject could no longer distinguish front from back.

On the first day of the experiment, subjects picked up the new sense so well that they could correctly identify a pole that was set back by only eight centimeters.

An analysis of the data revealed that the subjects accomplished this by moving their bewhiskered hands together. This allowed them to feel which pole was the back one because the whisker on that hand made contact first.

On the second day of testing, the volunteers improved their whisking skills significantly: The average sensory threshold went down to just 3 cm, with some being able to sense a displacement of just 1 cm.

“Our findings reveal some new principles of active sensing and show us that activating a new artificial sense in a ‘natural’ way can be very efficient,” said Arieli.

“Our vision for the future is to help blind people ‘see’ with their fingers. Small devices that translate video to mechanical stimulation, based on principles of active sensing that are common to vision and touch, could provide an intuitive, easily used sensory aid.”

Interestingly, the ability of the subjects to sense time differences had not changed over the two days.

Rather, they had improved in the motor aspects of their whisking strategies: Slowing down their hand motions – in effect lengthening the delay time – enabled them to sense a smaller spatial difference.

Low-pitched candidates

There are more women heads of political parties today than ever before. But how do they sound? A study at Duke University and the University of Miami found that people prefer leaders with more masculine voices, even in feminine leadership roles.

Male and female leaders with masculine voices are preferred by both men and women in the US. However, even in leadership roles that are typically held by women, both sexes prefer women leaders with low-pitched voices, according to research published recently in the open-access journal PLOS ONE.

Drs. Rindy Anderson and Casey Klofstad said that although earlier studies have shown that people prefer leaders with more masculine voices, this research adds a caveat: What happens when the leadership position is one that is typically held by women or perceived as more feminine, such as being a school board member or president of a parent- teacher association?

In hypothetical elections for such positions, the researchers asked people to listen to the phrase: “I urge you to vote for me this November” spoken by two voices that differed only in pitch.

They found that both men and women preferred female candidates with masculine voices. Men also preferred men with masculine voices, but women did not discriminate between the male voices they heard.

According to the authors, their results suggest that the influence of voice pitch on perceptions of leadership capacity is consistent across different domains of leadership and independent of social context.

Klofstad explains, “We often do not consider how our biology can influence our decision making. The results of this study show that voice pitch – a physiological characteristic – can affect how we select our leaders.”