Animals can feel joy. Here’s how scientists might study it

ape: A group of rather large primates, all of which lack a tail. They include gorillas, chimpanzees, bonobos, orangutans, gibbons and humans. Most people tend to group humans into their own separate subcategory owing to a number of special traits. These include a larger brain, greater mental abilities (including being able to talk) and their ability to walk on two legs.

attention: The phenomenon of focusing mental resources on a specific object or event.

behavior: The way something (often a person or other organism) conducts itself or acts towards others.

biologist: A scientist involved in the study of living things.

birds: Warm-blooded dinosaurs with wings that first showed up at least 150 million years ago. Birds are jacketed in feathers and produce young from the eggs they deposit in some sort of nest. Most birds fly, but throughout history there have been the occasional species that don’t.

chemical: A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H₂O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.

cognition: The mental processes of thought, remembering, learning information and interpreting those data that the senses send to the brain.

cognitive: A term that relates to mental activities, such as thinking, learning, remembering and solving puzzles.

contagious: An adjective for some disease that can be spread by direct contact with an infected individual or the germs that they shed into the air, their clothes or their environment. Such diseases are referred to as contagious. Or it can be an idea or behavior that spreads from person to person.

context: The setting or circumstances that help explain an event, some statement or some conclusion.

cortisol: Also known as hydrocortisone, this is a hormone produced by the adrenal glands. It can serve as the body’s main warning that it is under stress. It helps regulate a wide range of body functions, including how we process the energy in food, create memories and control inflammation.

data: Facts and/or statistics collected together for analysis but not necessarily organized in a way that gives them meaning. For digital information (the type stored by computers), those data typically are numbers stored in a binary code, portrayed as strings of zeros and ones.

depression: (in medicine) A mental illness characterized by persistent sadness and apathy. Although these feelings can be triggered by events, such as the death of a loved one or the move to a new city, that isn’t typically considered an “illness” — unless the symptoms are prolonged and harm an individual’s ability to perform normal daily tasks (such as working, sleeping or interacting with others). People suffering from depression often feel they lack the energy needed to get anything done. They may have difficulty concentrating on things or showing an interest in normal events. Many times, these feelings seem to be triggered by nothing; they can appear out of nowhere.

develop: To emerge or to make come into being, either naturally or through human intervention, such as by manufacturing.

dolphins: A highly intelligent group of marine mammals that belong to the toothed-whale family. Members of this group include orcas (killer whales), pilot whales and bottlenose dolphins.

dopamine: A neurotransmitter, this chemical helps transmit signals in the brain.

fabric: Any flexible material that is woven, knitted or can be fused into a sheet by heat or compression and drying.

fat: A natural oily or greasy substance occurring in plants and in animal bodies, especially when deposited as a layer under the skin or around certain organs. Fat’s primary role is as an energy reserve. Fat also is a vital nutrient, though it can be harmful if consumed in excessive amounts.

forest: An area of land covered mostly with trees and other woody plants.

fruit: A seed-containing reproductive organ in a plant.

function: The specific role some structure or device plays.

hormone: (in zoology and medicine) A chemical produced in a gland and then carried in the bloodstream to another part of the body. Hormones control many important body activities, such as growth. Hormones act by triggering or regulating chemical reactions in the body.

insight: The ability to gain an accurate and deep understanding of a situation just by thinking about it, instead of working out a solution through experimentation.

intelligence: The ability to collect and apply knowledge and skills.

marker: (in biomedicine) The presence of some substance — such as the attachment of some stain or molecular flag — that usually signals some disease, pollutant or event. As such, this substance will serve as a sign — or marker — of that related thing.

mental health: A term for someone’s emotional, psychological and social well-being. It refers to how people (or animals) behave on their own and how they interact with others. It includes how people make choices, handle stress and manage fear or anxiety. Poor mental health can be triggered by disease or might reflect a short-term response to life’s challenges. It can occur in people of any age, from babies to the elderly.

New Zealand: An island nation in the southwest Pacific Ocean, roughly 1,500 kilometers (some 900 miles) east of Australia. Its “mainland” — consisting of a North and South Island — is quite volcanically active. In addition, the country includes many far smaller offshore islands.

philosopher: Researchers (often in university settings) who ponder fundamental truths about relationships between things, including people and the world. The term also is used to describe truth seekers in the ancient world, ones who sought to find meaning and logic out of observing the workings of society and of the natural world, including the universe.

primate: The order of mammals that includes humans, apes, monkeys and related animals (such as tarsiers and lemurs).

psychologist: A scientist or mental-health professional who studies the mind, especially in relation to actions and behaviors. Some work with people. Others may conduct experiments with animals (usually rodents) to test how their minds respond to different stimuli and conditions.

reward: (In animal behavior) A stimulus, such as a tasty food pellet, that is offered to an animal or person to get them to change their behavior or to learn a task.

sea: An ocean (or region that is part of an ocean). Unlike lakes and streams, seawater — or ocean water — is salty.

seaweed: Large algae growing in the sea or on rocks below the high-water mark.

social: (adj.) Relating to gatherings of people; a term for animals (or people) that prefer to exist in groups.

species: A group of similar organisms capable of producing offspring that can survive and reproduce.

stress: (in biology) A factor — such as unusual temperatures, movements, moisture or pollution — that affects the health of a species or ecosystem. (in psychology) A mental, physical, emotional or behavioral reaction to an event or circumstance (stressor) that disturbs a person or animal’s usual state of being or places increased demands on a person or animal; psychological stress can be either positive or negative.

subjective: (in psychology) An adjective for an assessment that is based (at least in part) on someone’s own feelings, opinions or preferences.

tool: An object that a person or other animal makes or obtains and then uses to carry out some purpose such as reaching food, defending itself or grooming.

wave: A disturbance or variation that travels through space and matter in a regular, oscillating fashion.

weather: Conditions in the atmosphere at a localized place and a particular time. It is usually described in terms of particular features, such as air pressure, humidity, moisture, any precipitation (rain, snow or ice), temperature and wind speed. Weather constitutes the actual conditions that occur at any time and place. It’s different from climate, which is a description of the conditions that tend to occur in some general region during a particular month or season.

Western: (n. the West)  An adjective describing nations in Western Europe and North America (from Mexico northward). These nations tend to be fairly industrialized and to share generally similar lifestyles; levels of economic development (incomes); and attitudes toward work, education, social issues and government.

zoologist: An expert in the study of animals and their habitats.