Related by context. Frequent words. (Click for all words.) 46 circadian rhythms 45 circadian 43 circadian rhythm 38 biological clocks 38 metabolism 37 ovulate 37 REM sleep 36 sleep 36 adaptively 36 hormone melatonin 35 mealtimes 35 cortisol levels 34 mealtime 34 auditory processing 34 neural circuitry 33 hibernate 33 melatonin 33 mating 33 overtired 33 estrus 33 naps 33 Stay hydrated 32 mating rituals 32 neurobiologist 32 psychology professor 32 wakefulness 32 vocalizations 32 schoolwork 32 bedtime 32 habituation 32 snorer 32 waking 32 nap 31 awake 31 serotonin 31 oversleep 31 cycle 31 eating 31 mating habits 31 orexin 31 sleep deprived 31 overeat 31 daydreaming 31 chirps 31 evolutionary biologist 31 brain circuitry 30 feedings 30 biologist 30 catnaps 30 eat 30 snooze 30 restful sleep 30 lovemaking 30 Rosenlund 30 sleeping soundly 30 meditate 29 vocalization 29 hormonal 29 naptime 29 fluid intake 29 auditory 29 asleep 29 synchronous 29 mental stimulation 29 colicky 29 DNA replication 29 playtime 29 loud snoring 29 physiological 29 sleepiness 28 neural 28 cognitive 28 zoologist 28 metabolism slows 28 overeating 28 copulation 28 aching bones 28 mockingbirds 28 arousal 28 catnap 28 blood sugar 28 sleeping 28 neuroscientist 28 snoozing 28 hunger pangs 28 oscillations 28 alarm clock 27 Clinical psychologist 27 sunspot cycle 27 grogginess 27 cuddle 27 bedtimes 27 bedtime routine 27 cycles 27 falling asleep 27 sleep disturbances 27 excessive sleepiness 27 telomere 27 tummy ache 27 Sleep deprivation 27 migrations