Biological area: Sperry (1968) and Casey et al. (2011)

Psychology - H167 · Cambridge OCR AS Level · 6 min read · Updated: Aug 27, 2026

Biological Area: Regions of the Brain (Sperry, 1968 & Casey et al., 2011)

Welcome to your revision guide for the Biological Area! In this section of Component 02: Psychological themes through core studies, we look at the key theme "Regions of the brain." We will explore two landmark studies:

• Sperry (1968): The classic study exploring split-brain patients and hemisphere lateralisation.
• Casey et al. (2011): The contemporary study looking at delay of gratification, impulse control, and neural activity.

Don't worry if brain biology seems tricky at first! We will break down every concept step-by-step with clear explanations, memory tricks, and exam warnings.

Part 1: The Basics of Brain Structure

Before diving into the studies, let's establish how the brain is organised:

• Two Hemispheres: The human brain is split into two halves: the Left Hemisphere and the Right Hemisphere.
• Corpus Callosum: A thick bridge of nerve fibres that connects the two hemispheres and allows them to talk to each other.
• Contralateral Control (The "Cross-Over" Rule): The left hemisphere controls and receives sensory input from the right side of the body. The right hemisphere controls and receives sensory input from the left side of the body.

Analogy: Imagine two separate offices in a company (the Left and Right hemispheres). The corpus callosum is the telephone line between them. If the telephone line is cut, both offices can still work, but they can no longer share information!

Part 2: Classic Study — Sperry (1968)

Hemisphere deconnection and unity in conscious awareness

1. Background and Aim

In patients with severe epilepsy, surgeons sometimes perform a procedure called a commissurotomy, cutting through the corpus callosum to prevent seizures from spreading across the brain. Sperry wanted to investigate the effects of hemisphere deconnection (split-brain) and find out whether each hemisphere has specialized functions (lateralisation).

2. Sample and Method

• Sample: 11 "split-brain" patients who had undergone a commissurotomy.
• Method: A quasi-experiment (the independent variable—having a severed corpus callosum—was naturally occurring, not manipulated by Sperry).
• Apparatus: A tachistoscope. This device flashed visual stimuli onto a screen for only 0.1 seconds. Why 0.1 seconds? This is too fast for the eye to move, ensuring the image was received only by the intended visual field.

3. The Visual and Tactile Tests (The Rules of the Brain)

Understanding the cross-over rule is the secret to mastering Sperry:

Visual Testing:
• Right Visual Field (RVF) \(\rightarrow\) Left Hemisphere: Language centres live in the left hemisphere! Therefore, when an image was flashed to the RVF, the participant could describe the object in speech or writing.
• Left Visual Field (LVF) \(\rightarrow\) Right Hemisphere: The right hemisphere is non-verbal. When an image was flashed to the LVF, the participant claimed they saw nothing (or just a flash). However, they could point to a matching object with their left hand!

Tactile (Touch) Testing:
• Object in Right Hand \(\rightarrow\) Left Hemisphere: The participant could name the object verbally.
• Object in Left Hand \(\rightarrow\) Right Hemisphere: The participant could not name the object, but could find it by touch among a bag of items using their left hand.

4. Key Conclusions

• The two hemispheres operate independently when the corpus callosum is severed.
• Left Hemisphere: Specialises in language and logic.
• Right Hemisphere: Specialises in spatial tasks, non-verbal processing, and creative tasks.

Memory Trick: Left = Language & Logic. Right = Recognition & Spatial.

Common Examiner Trap to Avoid: Never confuse the eye with the visual field! It is not "left eye vs. right eye." Information from the Left Visual Field (LVF) goes to the Right Hemisphere, and information from the Right Visual Field (RVF) goes to the Left Hemisphere.

Section Takeaway: Sperry proved that brain functions are lateralised, and that without the corpus callosum, the two hemispheres have independent streams of awareness.

Part 3: Contemporary Study — Casey et al. (2011)

Behavioural and neural correlates of delay of gratification 40 years later

1. Background and Aim

Can childhood self-control predict adult willpower and brain activity? Casey et al. followed up participants from the famous 1960s/1970s "Marshmallow Test" (where young children tried to delay gratification to get a bigger treat) to see if delay ability is stable across the lifespan and how specific brain regions are involved.

2. Sample and Method

• Design: Longitudinal study, quasi-experiment, and laboratory experiment with fMRI (functional Magnetic Resonance Imaging).
• Original Cohort: 562 children tested in the 1960s and 1970s.
• Experiment 1 Sample: 59 adults (32 high delayers, 27 low delayers).
• Experiment 2 Sample: 26 adults (15 high delayers, 11 low delayers) scanned using fMRI.

3. The Tasks: "Cool" vs. "Hot"

Participants performed a computerized Go/No-Go task where they had to press a button when a target appeared ("Go") and resist pressing when a non-target appeared ("No-Go"):
• "Cool" Task: Neutral faces (e.g., Male vs. Female). One gender was "Go", the other was "No-Go".
• "Hot" Task: Emotional faces (e.g., Happy vs. Fearful). Resisting a happy, alluring face requires emotional impulse control.

4. Key Findings

• Behavioural Results: Both high and low delayers performed well on the "cool" tasks. However, low delayers made significantly more errors on "hot" tasks when trying to resist alluring (happy) faces.
• Neural Results (fMRI):
1. High Delayers: Showed greater activity in the Right Inferior Frontal Gyrus (part of the Prefrontal Cortex) during No-Go trials. This area handles cognitive control and restraint.
2. Low Delayers: Showed greater activity in the Ventral Striatum when trying to resist happy faces. This area is the brain's reward centre.

Memory Trick:
• PFC (Prefrontal Cortex / Inferior Frontal Gyrus): The Police of the brain — stops you and maintains control.
• Ventral Striatum: The Sweet Shop of the brain — seeks immediate rewards!

5. Key Conclusions

• The ability to delay gratification is a stable trait across 40 years.
• Resistance to temptation involves an interplay between brain regions: cognitive control from the prefrontal cortex vs. reward sensitivity from the ventral striatum.

Section Takeaway: Casey et al. showed that willpower is linked to distinct brain regions: the Prefrontal Cortex suppresses impulses, while the Ventral Striatum drives reward-seeking.

Part 4: Linking the Studies to the Key Theme

Key Theme: "Regions of the Brain"

OCR exams frequently ask how the contemporary study (Casey et al.) changes or extends our understanding compared to the classic study (Sperry):

• Sperry (1968) showed THAT the brain is divided: Sperry demonstrated lateralisation of function across the two large cerebral hemispheres (left vs. right) connected by the corpus callosum.
• Casey et al. (2011) showed HOW specific localized networks interact: Casey et al. used modern fMRI technology to look inside the intact brain, showing how specific subcortical and cortical regions (Ventral Striatum and Inferior Frontal Gyrus) interact to regulate complex human behaviours like self-control.

Quick Review Summary Table

Sperry (1968)
• Theme: Regions of the Brain (Lateralisation)
• Sample: 11 split-brain patients (commissurotomy)
• Apparatus: Tachistoscope (0.1s presentation)
• Key Brain Areas: Left Hemisphere (Language), Right Hemisphere (Spatial/Non-verbal), Corpus Callosum
• Core Finding: Severing the corpus callosum creates two independent streams of conscious awareness.

Casey et al. (2011)
• Theme: Regions of the Brain (Delay of Gratification / Neural Correlates)
• Sample: Longitudinal follow-up; Exp 1 (\(N = 59\)), Exp 2 (\(N = 26\))
• Apparatus: Go/No-Go tasks, fMRI scanner
• Key Brain Areas: Right Inferior Frontal Gyrus (Control), Ventral Striatum (Reward)
• Core Finding: Low delayers have higher Ventral Striatum activity; High delayers use the Inferior Frontal Gyrus to resist temptation.

Quick check

Can you answer these now?

Open each question to check the key ideas from this chapter.

What is the function of the corpus callosum and the principle of contralateral control in the human brain?

The corpus callosum is a thick band of nerve fibres allowing communication between hemispheres, while contralateral control means each hemisphere processes sensory input and controls motor output for the opposite side of the body.

What was the primary aim and sample characteristics of Sperry's (1968) study?

Sperry aimed to investigate the effects of hemisphere deconnection and lateralisation of function in 11 patients who had undergone a commissurotomy to treat severe epilepsy.

Why did Sperry use a tachistoscope to flash visual stimuli for only 0.1 seconds?

Flashing stimuli for 0.1 seconds ensured the image was presented strictly to the intended visual field before the participant's eyes could move to scan it.

How did split-brain patients respond when visual stimuli were presented to their Left Visual Field (LVF) versus their Right Visual Field (RVF)?

Stimuli in the RVF (processed by the left hemisphere) were described verbally, whereas stimuli in the LVF (processed by the non-verbal right hemisphere) could not be spoken but could be identified by pointing with the left hand.

What did tactile testing in Sperry's study reveal about hemispheric specialisation?

Objects placed in the right hand could be named verbally, whereas objects in the left hand could not be named but could be retrieved by touch using the left hand.

What were the main conclusions of Sperry (1968)?

The two hemispheres operate with independent streams of awareness when disconnected, with the left hemisphere specializing in language and logic and the right hemisphere in spatial and non-verbal tasks.

What was the primary aim and research design of Casey et al. (2011)?

Casey et al. aimed to test whether childhood delay of gratification remains stable into adulthood and to identify the neural correlates of self-control using a longitudinal follow-up and fMRI scans.

How did Go/No-Go performance differ between high and low delayers on 'cool' versus 'hot' tasks in Casey et al. (2011)?

Both groups performed equally well on 'cool' (neutral) tasks, but low delayers made significantly more false alarms on 'hot' (emotional/happy) No-Go trials.

What distinct neural activation patterns did fMRI reveal for high delayers versus low delayers in Casey et al. (2011)?

High delayers exhibited greater activation in the right inferior frontal gyrus during No-Go trials, whereas low delayers showed heightened activity in the ventral striatum during alluring trials.

How does Casey et al. (2011) extend our understanding of the 'Regions of the Brain' theme compared to Sperry (1968)?

While Sperry showed broad macro-level lateralisation between the two cerebral hemispheres, Casey et al. identified specific micro-level neural circuits and interactions between cortical and subcortical brain regions in an intact brain.

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