44
votes
Accepted
Are drugs made bitter artificially to prevent being mistaken for candy?
Short answer
A bittering agent may be applied to therapeuticals to prevent pediatric poisonings, but many drugs inherently taste bitter by themselves.
Background
Bitter taste is thought to have ...
- 51.8k
36
votes
Accepted
Why does my room suddenly look 'reddish'? My eyes seem to adapt to color
Short answer
The phenomenon you describe can be explained by the negative afterimage effect, which indeed is elicited by adaptive processes in the retinae.
Background
In the retina there are three ...
- 51.8k
33
votes
Accepted
Can one see flickering of a light bulb at 50 Hz?
Short answer
Yes, the flickering of a light bulb may be noticeable, and yes, that's directly related to the mains frequency. However, since the flickering of a bulb is about two times higher than the ...
- 51.8k
30
votes
Accepted
Why do mints make your mouth feel cold?
The feeling of cold from mints is caused by menthol. Menthol affects the TRPM8 receptor on skin and also in the mouth. TRPM8 is also a general cold receptor: so if you are in contact with menthol the ...
- 2,878
21
votes
Are some animals, like dogs and cats, color-blind and how do we know that?
TL;DR: We have a good physiological understanding of how eyes work, so by examination of other species' eyes, we can tell a lot about what colours they are capable of seeing.
First, a little bit ...
- 3,304
14
votes
Accepted
Why is wind cold for humans?
One important point that you might not be considering is the heat of vaporization.
You may be aware that while it normally takes 4.18 J (1 calorie) of heat to raise 1 gram of water 1 °C, it takes ...
- 1,544
12
votes
Why do I still see a bright light after looking directly at it?
Short answer
The effect you describe is called a negative after image. It can be explained by adaptation effects of the photoreceptors in the eye.
Background
source: Dresden University
Steadily ...
- 51.8k
10
votes
Accepted
What is the smallest touch sensation that a human can feel?
Short answer
The detection threshold of static indentation stimuli on the palm of the hand is approximately 10 to 40 micrometers, dependent on the exact location under investigation.
Background
The ...
- 51.8k
10
votes
Best colour for a dog to track an object against green background
Dogs are a dichromatic species, featuring only a long wavelength (L) and a short wavelength (S) cone (source: Smithsonian). As such, they are thought to perceive mainly blues and yellowish hues (Fig. ...
- 51.8k
9
votes
Accepted
Is brain plasticity such that we can train ourself to see with our ears?
Short answer
Yes, we can see with our ears.
Background
Bach-y-Rita famously stated "We see with our brains, not our eyes". Bach-y-Rita worked for decades on sensory substitution. Sensory substitution ...
- 51.8k
8
votes
Accepted
How precisely can we sense temperature differences?
Short answer
Temperature differences of 0.02 degrees Celcius can be distinguished, dependent on various factors including experimental conditions and bodily location.
Background
The ability to ...
- 51.8k
8
votes
Can one see flickering of a light bulb at 50 Hz?
A lamp flickers at 2x the mains frequency, i.e. 100 or 120 Hz, and that is typically not noticeable to human eyes. It is visible to chicken and insects.
That being said, a low quality lamp or a lamp ...
- 181
7
votes
Why is wind cold for humans?
This phenomena has nothing to do with any different kinds of receptors.
When we are wet, we have lots of water on our surface. The evaporation of water causes cooling.
Blowing wind tends to make ...
- 1,669
7
votes
Accepted
Are two eyes necessary for 3D vision?
It seems like you suffer from a misconception. "The left eye sees more of the left side of an object..." is not how distance perception works. Otherwise we wouldn't be able to estimate the ...
- 421
7
votes
Accepted
Perception of white in the absence of rods
Short answer
Cones mediate the perception of white in photopic conditions. Rods mediate the perception of white in scotopic conditions. The rod system is not needed for cones to mediate white ...
- 51.8k
6
votes
What effect does a bat's echolocation have on other bats?
Bat echolocation is an incredible and complex process. Bats can emit two kinds of ultrasonic signals. One is a short pulse (less than 5 ms long) that sweeps a wide range of frequencies (100 Hz to 25 ...
- 534
6
votes
Accepted
How exactly does sensory substitution work?
Tot start of with your definition:
Sensory substitution, when one of sensory modality changes into another sensory modality to help someone restore the ability to perceive defective sensory using a ...
- 51.8k
5
votes
Are some animals, like dogs and cats, color-blind and how do we know that?
Short answer
Dichromats can discriminate colors;
Color vision in animals can be tested behaviorally;
Trichromatic vision is not essential for most animals, but is believed to be beneficial to ...
- 51.8k
5
votes
Why is wind cold for humans?
As other answers and comments have stated the reason that you feel cooler when the wind is blowing (wind chill factor often gets talked about on the news) is because evaporation is speed up by the ...
- 3,064
5
votes
Accepted
Do humans perceive temperature or heat-flux? (or both?)
Short answer
Humans sense temperature differences.
Background
(Including edits based upon comments)
Because the question is "Do humans perceive temperature or heat-flux?", I will answer the answer ...
- 51.8k
5
votes
What is it called when one human eye is seeing brighter color than the other?
The phenomenon in question is anisochromatopsia, however this term is rarely used. This phenomenon is always present, however it is rarely mentioned subjectively, while objective color testing will ...
- 5,650
5
votes
Accepted
What determines the perceived pitch (frequency) of tinnitus?
Short answer
Perceived tinnitus pitch tends to resemble the frequency content of the loud sound that induced the tinnitus.
Background
Solid, laboratory-controlled studies to the perceived pitch of ...
- 51.8k
5
votes
Do humans perceive temperature or heat-flux? (or both?)
This is the modified answer in response to the discussion:
Facts:
There are warmth and cold receptors in the body at two places: The Peripheral receptors and the Central Receptors
The peripheral ...
- 3,030
5
votes
Accepted
Congenital blindness due to retinitis pigmentosa - does it exist?
I have only ever heard of one case where RP caused blindness in a newborn. Unfortunately, I am unable to release the name or any details of the patient because of privacy issues and so forth.
...
- 1,836
5
votes
Accepted
Is synesthesia caused by crossing the circuitry of different sensory inputs?
Short Answer
Synesthesia happens at a point during processing where we are not dealing with "raw visual input" or "raw auditory input" anymore, but already with more abstract ...
- 3,210
5
votes
Understanding the "Waterfall Illusion"
The motion after-effect (MAE) is believed to be primarily due to adaptation of direction sensitive cells in the middle temporal area (MT) (Fig. 1.). The directional cells in this area of the cortex ...
- 51.8k
4
votes
Accepted
Receptors for red and far-red light in plants: Shade avoidance
As far as I know there are 5 receptors for far-red and red light which are the phytochroms(phyA-phyE) Its all about the ratio between red and far-red light.
Each phytochrom has an inactive(PR) and ...
- 174
4
votes
Do humans perceive temperature or heat-flux? (or both?)
Flux is defined as amount of heat transferred per unit area per unit time.
Our body does not perceive heat flux. It perceives temperature and tries to adjust heat exchange mechanisms until thermal ...
- 35.2k
4
votes
Accepted
Is there an absolute minimum intensity level to the stimuli we can perceive?
There are limits to what a sensory system can detect, which is called the detection threshold. To determine the detection threshold psychophysical methods can be used. A straightforward way to ...
- 51.8k
4
votes
Can low temperatures induce a withdrawal reflex?
The withdrawal reflex is a nociceptive flexor reflex and is a spinal reflex intended to protect the body from damaging stimuli.
In other words, activation of heat receptors is not the trigger of the ...
- 51.8k
Only top scored, non community-wiki answers of a minimum length are eligible