Many people are against using food and treats in a training program. They call it bribery and maintain that the dog won't do what they want unless we have a pocketful of treats ready at all times.
Yes, this can be absolutely true, but if it is true - then you're doing it wrong.
Food is a primary reinforcer. Primary reinforcers are things that the animal needs to survive: food, water, air, reproduction.
Under normal circumstances we all love food! Water and air are pretty good too, but we would never withold these necessities of life in the name of training. Some have, eg. hanging or 'stringing up', but that sort of activity is reprehensible! This is an article on Cesar Millan stringing up a Husky named Shadow.
Back to food.
Food heightens a response in the dopamine system which drives the brains pleasure centre.
Once the dopamine system is activated, the dog associates the activity, and what's happening in its environment, to be a good thing. When we are rewarded for doing something, we are more likely to repeat that action or activity. If someone even says thanks (a reward) I'm likely going to repeat whatever I did to get another thank-you. Rewards can also create addictions. Think slot machines or getting a 'Like' on your facebook page. These rewards drive us to repeat an activity more and more and more - just for that tiny rush of dopamine to our brains pleasure centre.
Need more information to convince you, read on. It has been shown that our dogs' brains and systems work very much like ours.
This article from the Icahn School of Medicine at Mount Sinai, Neuroscience Department tells us that, the most important reward pathway in the brain is the mesolimbic dopamine system (VTA-NAc). This circuit is a key detector of a rewarding stimulus. Under normal conditions, the circuit controls an individual's response to natural rewards, such as food, sex, and social interactions, and is, therefore, an important determinant of motivation and reward. It also tells the memory centers in the brain to pay particular attention to all features of that rewarding experience, so it can be repeated in the future. Not surprisingly, it is a very old pathway from an evolutionary point of view. The use of dopamine neurons to mediate behavioral responses to natural rewards is seen in worms and flies, which evolved 1 - 2 billion years ago.
This pathway is a part of a series of parallel, integrated circuits, which involve several other key brain regions. The VTA is the site of dopaminergic neurons, which tell the organism whether an environmental stimulus (natural reward, drug of abuse, stress) is rewarding or aversive.
The amygdala is particularly important for conditioned forms of learning. It helps an organism establish associations between environmental cues and whether or not that particular experience was rewarding or aversive, for example, remembering what accompanied finding food or fleeing a predator.
It also interacts eith the VTA-NAc pathway to determine the rewarding or aversive value of an environmental stimulus.
The hippocampus is critical for declarative memory, the memory of persons, places, or things. Along with the amygdala, it establishes memories of experiences which are important mediators of repetitivness.
The hypothalamus is important for coordinating an individual's interest in rewards with the body's physiological state. This region integrates brain function with the physiological needs of the organism.
Probably the most important, but least understood, are frontal regions of cerebral cortex, such as medial prefrontal cortex, anterior cingulate cortex, and orbitofrontal cortex, which provide executive control over choices made in the environment (for example, whether to seek a reward).
The locus coeruleus is the primary site of noradrenergic neurons in the brain, which pervasively modulate brain bunction to regulate the state of activation and mood of the organism.
The dorsal raphe is the primary site of serotonergic neurons in the brain, which, like noradrenergic neurons, pervasively modulate brain function to regulate the state of activation and mood of the organism.
Of course, these various brain regions, and many more, do not function separately. Rather they function in a highly inter-related manner and mediate an individual's responses to a range of environmental stimuli.
Other articles of interest on using reinforcements in training:
Using Secondary Reinforcers - Wisdom from Ken Ramirez
Dog Training Treats - How Do They Work by Canine Principles
Reactive Dog - Treat Training for Success by Canine Principles