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 ...
- 52.3k
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 ...
- 52.3k
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 ...
- 52.3k
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 ...
- 2,868
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
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 ...
- 52.3k
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 ...
- 52.3k
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. ...
- 52.3k
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 ...
- 52.3k
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
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 ...
- 52.3k
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 ...
- 52.3k
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 ...
- 3,245
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 ...
- 52.3k
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 ...
- 52.3k
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 ...
- 52.3k
4
votes
Accepted
How do we perceive weight?
This would most likely come under the category of Proprioception - the sense of how our bodies are arranged in the world, and how much effort each part of our body is expending.
From Wikipedia, 'In ...
- 827
4
votes
Does the nature of nervous impulses give us a finite number of things we can perceive?
I know we have sensors in the form of hairs that trigger a nervous
impulse to the brain when they are stimulated. But as I understand it,
each one can only send that on/off binary signal when they ...
- 3,313
4
votes
Additive property of taste
I would classify the neurological phenomenon of "taste" or "tastyness" as an emergent property (1), and therefore synergistic (i.e. not adequately explained simply by additive effects). For example, ...
- 4,671
3
votes
How we can localize sound vertically (up-down) and front-to-back?
The Wikipedia article is quite good.
In brief, as you state, the wave phase can be used only to localise sounds in the plane of the ears. To have an approximation of the position in the median plane (...
- 1,127
3
votes
Accepted
How we can localize sound vertically (up-down) and front-to-back?
Localization along the azimuth (horizontal left-right axis) is mediated by various processes: 1) First, there is the head shadow effect, which means that sounds from the left reach the right ear (AD) ...
- 52.3k
3
votes
Nature of sight/ color perception?
The color you perceive is ultimately dependent on the relative contributions of the color photoreceptors in the retina, namely the red, green and blue cones. The sensation of color, therefore, is ...
- 52.3k
3
votes
Are our ears more sensitive to low or high pitched sounds?
Short answer
Our ears are most sensitive to the mid-frequencies.
Background
There are different ways of assessing sound level. The physical one simply determines the physical sound pressure level (...
- 52.3k
3
votes
Can one see flickering of a light bulb at 50 Hz?
Let's say there is a point source of light (it could be a lamp or a highly reflective object) that undergoes large, rapid intensity changes, say 50-100 times a second.
If you quickly move your eyes ...
- 191
3
votes
Are there gaps in what our ears can hear?
Short answer
No, there are no between-hair cell induced tonotopical gaps in frequency perception.
Background
Young people are able to hear over a frequency range of about 10 octaves, with a ...
- 52.3k
3
votes
Are there gaps in what our ears can hear?
To add to the good answer by @AliceD, take a look at some tuning curves for hair cells, the sound receptors in the cochlea (these happen to be fairly low frequencies and a turtle cochlea, though those ...
- 44k
3
votes
Are there people blind to touch?
Short answer
In a way, yes.
Background
One prime example where the sense of touch is diminished is when peripheral sensory neurons degenerate, which is called sensory neuropathy. Diabetes is ...
- 52.3k
2
votes
Accepted
What causes a selective shift of colour perception after removing wavelength filtered glasses?
The short answer is you don't see light you see a reconstruction of your environment made by a learning organ, your brain adapts to changes in stimuli. Color in particular is tricky because there is ...
- 14.3k
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