Confound. A design problem in which some additional variable (or nuisance variable) exists that (a) may influence the dependent variable and that (b) varies systematically along with the independent or predictor variable(s). this is a threat to internal validity.

selection bias

Pretest sensitization

Why are confounds a concern in an experimental study? They make it unclear what was responsible for a change observed in the dependent variable.

With chronic sinusitis and decreased sense of smell, inflammation interferes with the ability of your sinuses to drain and is why you experience a loss of your sense of taste and smell.

Here are five science-backed ways you can try to improve your sense of smell:

1. Smell different things. The more you use your senses, the better they get.
2. Sniff a bit more.
3. Build your scent IQ.
4. Supplement your power to smell.
5. Quit smoking.

Studies have also shown that certain genetic conditions such as duplication or overexpression of the KAL1 gene – which produces a protein (anosmin-1) that appears to control the growth and movement of nerve cells that help process smell – and other genetic mutations are linked to heightened sense of smell.

Many children and adults on the autism spectrum show sensory irregularities, which manifest as sensitivities, under-responsiveness and/or sensory -seeking behaviors. This is also true for the sense of smell.

A man can smell when a woman is ovulating – and the proof is in his testosterone, says a new study from Florida State University that had undergraduate men sniffing sweaty T-shirts for course credit.